Index: projects/clang1100-import/contrib/llvm-project/clang/lib/AST/ExprConstant.cpp
===================================================================
--- projects/clang1100-import/contrib/llvm-project/clang/lib/AST/ExprConstant.cpp	(revision 363976)
+++ projects/clang1100-import/contrib/llvm-project/clang/lib/AST/ExprConstant.cpp	(revision 363977)
@@ -1,15113 +1,15120 @@
 //===--- ExprConstant.cpp - Expression Constant Evaluator -----------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the Expr constant evaluator.
 //
 // Constant expression evaluation produces four main results:
 //
 //  * A success/failure flag indicating whether constant folding was successful.
 //    This is the 'bool' return value used by most of the code in this file. A
 //    'false' return value indicates that constant folding has failed, and any
 //    appropriate diagnostic has already been produced.
 //
 //  * An evaluated result, valid only if constant folding has not failed.
 //
 //  * A flag indicating if evaluation encountered (unevaluated) side-effects.
 //    These arise in cases such as (sideEffect(), 0) and (sideEffect() || 1),
 //    where it is possible to determine the evaluated result regardless.
 //
 //  * A set of notes indicating why the evaluation was not a constant expression
 //    (under the C++11 / C++1y rules only, at the moment), or, if folding failed
 //    too, why the expression could not be folded.
 //
 // If we are checking for a potential constant expression, failure to constant
 // fold a potential constant sub-expression will be indicated by a 'false'
 // return value (the expression could not be folded) and no diagnostic (the
 // expression is not necessarily non-constant).
 //
 //===----------------------------------------------------------------------===//
 
 #include "Interp/Context.h"
 #include "Interp/Frame.h"
 #include "Interp/State.h"
 #include "clang/AST/APValue.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTDiagnostic.h"
 #include "clang/AST/ASTLambda.h"
 #include "clang/AST/Attr.h"
 #include "clang/AST/CXXInheritance.h"
 #include "clang/AST/CharUnits.h"
 #include "clang/AST/CurrentSourceLocExprScope.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/OSLog.h"
 #include "clang/AST/OptionalDiagnostic.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/AST/TypeLoc.h"
 #include "clang/Basic/Builtins.h"
 #include "clang/Basic/FixedPoint.h"
 #include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallBitVector.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstring>
 #include <functional>
 
 #define DEBUG_TYPE "exprconstant"
 
 using namespace clang;
 using llvm::APInt;
 using llvm::APSInt;
 using llvm::APFloat;
 using llvm::Optional;
 
 namespace {
   struct LValue;
   class CallStackFrame;
   class EvalInfo;
 
   using SourceLocExprScopeGuard =
       CurrentSourceLocExprScope::SourceLocExprScopeGuard;
 
   static QualType getType(APValue::LValueBase B) {
     if (!B) return QualType();
     if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
       // FIXME: It's unclear where we're supposed to take the type from, and
       // this actually matters for arrays of unknown bound. Eg:
       //
       // extern int arr[]; void f() { extern int arr[3]; };
       // constexpr int *p = &arr[1]; // valid?
       //
       // For now, we take the array bound from the most recent declaration.
       for (auto *Redecl = cast<ValueDecl>(D->getMostRecentDecl()); Redecl;
            Redecl = cast_or_null<ValueDecl>(Redecl->getPreviousDecl())) {
         QualType T = Redecl->getType();
         if (!T->isIncompleteArrayType())
           return T;
       }
       return D->getType();
     }
 
     if (B.is<TypeInfoLValue>())
       return B.getTypeInfoType();
 
     if (B.is<DynamicAllocLValue>())
       return B.getDynamicAllocType();
 
     const Expr *Base = B.get<const Expr*>();
 
     // For a materialized temporary, the type of the temporary we materialized
     // may not be the type of the expression.
     if (const MaterializeTemporaryExpr *MTE =
             dyn_cast<MaterializeTemporaryExpr>(Base)) {
       SmallVector<const Expr *, 2> CommaLHSs;
       SmallVector<SubobjectAdjustment, 2> Adjustments;
       const Expr *Temp = MTE->getSubExpr();
       const Expr *Inner = Temp->skipRValueSubobjectAdjustments(CommaLHSs,
                                                                Adjustments);
       // Keep any cv-qualifiers from the reference if we generated a temporary
       // for it directly. Otherwise use the type after adjustment.
       if (!Adjustments.empty())
         return Inner->getType();
     }
 
     return Base->getType();
   }
 
   /// Get an LValue path entry, which is known to not be an array index, as a
   /// field declaration.
   static const FieldDecl *getAsField(APValue::LValuePathEntry E) {
     return dyn_cast_or_null<FieldDecl>(E.getAsBaseOrMember().getPointer());
   }
   /// Get an LValue path entry, which is known to not be an array index, as a
   /// base class declaration.
   static const CXXRecordDecl *getAsBaseClass(APValue::LValuePathEntry E) {
     return dyn_cast_or_null<CXXRecordDecl>(E.getAsBaseOrMember().getPointer());
   }
   /// Determine whether this LValue path entry for a base class names a virtual
   /// base class.
   static bool isVirtualBaseClass(APValue::LValuePathEntry E) {
     return E.getAsBaseOrMember().getInt();
   }
 
   /// Given an expression, determine the type used to store the result of
   /// evaluating that expression.
   static QualType getStorageType(const ASTContext &Ctx, const Expr *E) {
     if (E->isRValue())
       return E->getType();
     return Ctx.getLValueReferenceType(E->getType());
   }
 
   /// Given a CallExpr, try to get the alloc_size attribute. May return null.
   static const AllocSizeAttr *getAllocSizeAttr(const CallExpr *CE) {
     const FunctionDecl *Callee = CE->getDirectCallee();
     return Callee ? Callee->getAttr<AllocSizeAttr>() : nullptr;
   }
 
   /// Attempts to unwrap a CallExpr (with an alloc_size attribute) from an Expr.
   /// This will look through a single cast.
   ///
   /// Returns null if we couldn't unwrap a function with alloc_size.
   static const CallExpr *tryUnwrapAllocSizeCall(const Expr *E) {
     if (!E->getType()->isPointerType())
       return nullptr;
 
     E = E->IgnoreParens();
     // If we're doing a variable assignment from e.g. malloc(N), there will
     // probably be a cast of some kind. In exotic cases, we might also see a
     // top-level ExprWithCleanups. Ignore them either way.
     if (const auto *FE = dyn_cast<FullExpr>(E))
       E = FE->getSubExpr()->IgnoreParens();
 
     if (const auto *Cast = dyn_cast<CastExpr>(E))
       E = Cast->getSubExpr()->IgnoreParens();
 
     if (const auto *CE = dyn_cast<CallExpr>(E))
       return getAllocSizeAttr(CE) ? CE : nullptr;
     return nullptr;
   }
 
   /// Determines whether or not the given Base contains a call to a function
   /// with the alloc_size attribute.
   static bool isBaseAnAllocSizeCall(APValue::LValueBase Base) {
     const auto *E = Base.dyn_cast<const Expr *>();
     return E && E->getType()->isPointerType() && tryUnwrapAllocSizeCall(E);
   }
 
   /// The bound to claim that an array of unknown bound has.
   /// The value in MostDerivedArraySize is undefined in this case. So, set it
   /// to an arbitrary value that's likely to loudly break things if it's used.
   static const uint64_t AssumedSizeForUnsizedArray =
       std::numeric_limits<uint64_t>::max() / 2;
 
   /// Determines if an LValue with the given LValueBase will have an unsized
   /// array in its designator.
   /// Find the path length and type of the most-derived subobject in the given
   /// path, and find the size of the containing array, if any.
   static unsigned
   findMostDerivedSubobject(ASTContext &Ctx, APValue::LValueBase Base,
                            ArrayRef<APValue::LValuePathEntry> Path,
                            uint64_t &ArraySize, QualType &Type, bool &IsArray,
                            bool &FirstEntryIsUnsizedArray) {
     // This only accepts LValueBases from APValues, and APValues don't support
     // arrays that lack size info.
     assert(!isBaseAnAllocSizeCall(Base) &&
            "Unsized arrays shouldn't appear here");
     unsigned MostDerivedLength = 0;
     Type = getType(Base);
 
     for (unsigned I = 0, N = Path.size(); I != N; ++I) {
       if (Type->isArrayType()) {
         const ArrayType *AT = Ctx.getAsArrayType(Type);
         Type = AT->getElementType();
         MostDerivedLength = I + 1;
         IsArray = true;
 
         if (auto *CAT = dyn_cast<ConstantArrayType>(AT)) {
           ArraySize = CAT->getSize().getZExtValue();
         } else {
           assert(I == 0 && "unexpected unsized array designator");
           FirstEntryIsUnsizedArray = true;
           ArraySize = AssumedSizeForUnsizedArray;
         }
       } else if (Type->isAnyComplexType()) {
         const ComplexType *CT = Type->castAs<ComplexType>();
         Type = CT->getElementType();
         ArraySize = 2;
         MostDerivedLength = I + 1;
         IsArray = true;
       } else if (const FieldDecl *FD = getAsField(Path[I])) {
         Type = FD->getType();
         ArraySize = 0;
         MostDerivedLength = I + 1;
         IsArray = false;
       } else {
         // Path[I] describes a base class.
         ArraySize = 0;
         IsArray = false;
       }
     }
     return MostDerivedLength;
   }
 
   /// A path from a glvalue to a subobject of that glvalue.
   struct SubobjectDesignator {
     /// True if the subobject was named in a manner not supported by C++11. Such
     /// lvalues can still be folded, but they are not core constant expressions
     /// and we cannot perform lvalue-to-rvalue conversions on them.
     unsigned Invalid : 1;
 
     /// Is this a pointer one past the end of an object?
     unsigned IsOnePastTheEnd : 1;
 
     /// Indicator of whether the first entry is an unsized array.
     unsigned FirstEntryIsAnUnsizedArray : 1;
 
     /// Indicator of whether the most-derived object is an array element.
     unsigned MostDerivedIsArrayElement : 1;
 
     /// The length of the path to the most-derived object of which this is a
     /// subobject.
     unsigned MostDerivedPathLength : 28;
 
     /// The size of the array of which the most-derived object is an element.
     /// This will always be 0 if the most-derived object is not an array
     /// element. 0 is not an indicator of whether or not the most-derived object
     /// is an array, however, because 0-length arrays are allowed.
     ///
     /// If the current array is an unsized array, the value of this is
     /// undefined.
     uint64_t MostDerivedArraySize;
 
     /// The type of the most derived object referred to by this address.
     QualType MostDerivedType;
 
     typedef APValue::LValuePathEntry PathEntry;
 
     /// The entries on the path from the glvalue to the designated subobject.
     SmallVector<PathEntry, 8> Entries;
 
     SubobjectDesignator() : Invalid(true) {}
 
     explicit SubobjectDesignator(QualType T)
         : Invalid(false), IsOnePastTheEnd(false),
           FirstEntryIsAnUnsizedArray(false), MostDerivedIsArrayElement(false),
           MostDerivedPathLength(0), MostDerivedArraySize(0),
           MostDerivedType(T) {}
 
     SubobjectDesignator(ASTContext &Ctx, const APValue &V)
         : Invalid(!V.isLValue() || !V.hasLValuePath()), IsOnePastTheEnd(false),
           FirstEntryIsAnUnsizedArray(false), MostDerivedIsArrayElement(false),
           MostDerivedPathLength(0), MostDerivedArraySize(0) {
       assert(V.isLValue() && "Non-LValue used to make an LValue designator?");
       if (!Invalid) {
         IsOnePastTheEnd = V.isLValueOnePastTheEnd();
         ArrayRef<PathEntry> VEntries = V.getLValuePath();
         Entries.insert(Entries.end(), VEntries.begin(), VEntries.end());
         if (V.getLValueBase()) {
           bool IsArray = false;
           bool FirstIsUnsizedArray = false;
           MostDerivedPathLength = findMostDerivedSubobject(
               Ctx, V.getLValueBase(), V.getLValuePath(), MostDerivedArraySize,
               MostDerivedType, IsArray, FirstIsUnsizedArray);
           MostDerivedIsArrayElement = IsArray;
           FirstEntryIsAnUnsizedArray = FirstIsUnsizedArray;
         }
       }
     }
 
     void truncate(ASTContext &Ctx, APValue::LValueBase Base,
                   unsigned NewLength) {
       if (Invalid)
         return;
 
       assert(Base && "cannot truncate path for null pointer");
       assert(NewLength <= Entries.size() && "not a truncation");
 
       if (NewLength == Entries.size())
         return;
       Entries.resize(NewLength);
 
       bool IsArray = false;
       bool FirstIsUnsizedArray = false;
       MostDerivedPathLength = findMostDerivedSubobject(
           Ctx, Base, Entries, MostDerivedArraySize, MostDerivedType, IsArray,
           FirstIsUnsizedArray);
       MostDerivedIsArrayElement = IsArray;
       FirstEntryIsAnUnsizedArray = FirstIsUnsizedArray;
     }
 
     void setInvalid() {
       Invalid = true;
       Entries.clear();
     }
 
     /// Determine whether the most derived subobject is an array without a
     /// known bound.
     bool isMostDerivedAnUnsizedArray() const {
       assert(!Invalid && "Calling this makes no sense on invalid designators");
       return Entries.size() == 1 && FirstEntryIsAnUnsizedArray;
     }
 
     /// Determine what the most derived array's size is. Results in an assertion
     /// failure if the most derived array lacks a size.
     uint64_t getMostDerivedArraySize() const {
       assert(!isMostDerivedAnUnsizedArray() && "Unsized array has no size");
       return MostDerivedArraySize;
     }
 
     /// Determine whether this is a one-past-the-end pointer.
     bool isOnePastTheEnd() const {
       assert(!Invalid);
       if (IsOnePastTheEnd)
         return true;
       if (!isMostDerivedAnUnsizedArray() && MostDerivedIsArrayElement &&
           Entries[MostDerivedPathLength - 1].getAsArrayIndex() ==
               MostDerivedArraySize)
         return true;
       return false;
     }
 
     /// Get the range of valid index adjustments in the form
     ///   {maximum value that can be subtracted from this pointer,
     ///    maximum value that can be added to this pointer}
     std::pair<uint64_t, uint64_t> validIndexAdjustments() {
       if (Invalid || isMostDerivedAnUnsizedArray())
         return {0, 0};
 
       // [expr.add]p4: For the purposes of these operators, a pointer to a
       // nonarray object behaves the same as a pointer to the first element of
       // an array of length one with the type of the object as its element type.
       bool IsArray = MostDerivedPathLength == Entries.size() &&
                      MostDerivedIsArrayElement;
       uint64_t ArrayIndex = IsArray ? Entries.back().getAsArrayIndex()
                                     : (uint64_t)IsOnePastTheEnd;
       uint64_t ArraySize =
           IsArray ? getMostDerivedArraySize() : (uint64_t)1;
       return {ArrayIndex, ArraySize - ArrayIndex};
     }
 
     /// Check that this refers to a valid subobject.
     bool isValidSubobject() const {
       if (Invalid)
         return false;
       return !isOnePastTheEnd();
     }
     /// Check that this refers to a valid subobject, and if not, produce a
     /// relevant diagnostic and set the designator as invalid.
     bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK);
 
     /// Get the type of the designated object.
     QualType getType(ASTContext &Ctx) const {
       assert(!Invalid && "invalid designator has no subobject type");
       return MostDerivedPathLength == Entries.size()
                  ? MostDerivedType
                  : Ctx.getRecordType(getAsBaseClass(Entries.back()));
     }
 
     /// Update this designator to refer to the first element within this array.
     void addArrayUnchecked(const ConstantArrayType *CAT) {
       Entries.push_back(PathEntry::ArrayIndex(0));
 
       // This is a most-derived object.
       MostDerivedType = CAT->getElementType();
       MostDerivedIsArrayElement = true;
       MostDerivedArraySize = CAT->getSize().getZExtValue();
       MostDerivedPathLength = Entries.size();
     }
     /// Update this designator to refer to the first element within the array of
     /// elements of type T. This is an array of unknown size.
     void addUnsizedArrayUnchecked(QualType ElemTy) {
       Entries.push_back(PathEntry::ArrayIndex(0));
 
       MostDerivedType = ElemTy;
       MostDerivedIsArrayElement = true;
       // The value in MostDerivedArraySize is undefined in this case. So, set it
       // to an arbitrary value that's likely to loudly break things if it's
       // used.
       MostDerivedArraySize = AssumedSizeForUnsizedArray;
       MostDerivedPathLength = Entries.size();
     }
     /// Update this designator to refer to the given base or member of this
     /// object.
     void addDeclUnchecked(const Decl *D, bool Virtual = false) {
       Entries.push_back(APValue::BaseOrMemberType(D, Virtual));
 
       // If this isn't a base class, it's a new most-derived object.
       if (const FieldDecl *FD = dyn_cast<FieldDecl>(D)) {
         MostDerivedType = FD->getType();
         MostDerivedIsArrayElement = false;
         MostDerivedArraySize = 0;
         MostDerivedPathLength = Entries.size();
       }
     }
     /// Update this designator to refer to the given complex component.
     void addComplexUnchecked(QualType EltTy, bool Imag) {
       Entries.push_back(PathEntry::ArrayIndex(Imag));
 
       // This is technically a most-derived object, though in practice this
       // is unlikely to matter.
       MostDerivedType = EltTy;
       MostDerivedIsArrayElement = true;
       MostDerivedArraySize = 2;
       MostDerivedPathLength = Entries.size();
     }
     void diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info, const Expr *E);
     void diagnosePointerArithmetic(EvalInfo &Info, const Expr *E,
                                    const APSInt &N);
     /// Add N to the address of this subobject.
     void adjustIndex(EvalInfo &Info, const Expr *E, APSInt N) {
       if (Invalid || !N) return;
       uint64_t TruncatedN = N.extOrTrunc(64).getZExtValue();
       if (isMostDerivedAnUnsizedArray()) {
         diagnoseUnsizedArrayPointerArithmetic(Info, E);
         // Can't verify -- trust that the user is doing the right thing (or if
         // not, trust that the caller will catch the bad behavior).
         // FIXME: Should we reject if this overflows, at least?
         Entries.back() = PathEntry::ArrayIndex(
             Entries.back().getAsArrayIndex() + TruncatedN);
         return;
       }
 
       // [expr.add]p4: For the purposes of these operators, a pointer to a
       // nonarray object behaves the same as a pointer to the first element of
       // an array of length one with the type of the object as its element type.
       bool IsArray = MostDerivedPathLength == Entries.size() &&
                      MostDerivedIsArrayElement;
       uint64_t ArrayIndex = IsArray ? Entries.back().getAsArrayIndex()
                                     : (uint64_t)IsOnePastTheEnd;
       uint64_t ArraySize =
           IsArray ? getMostDerivedArraySize() : (uint64_t)1;
 
       if (N < -(int64_t)ArrayIndex || N > ArraySize - ArrayIndex) {
         // Calculate the actual index in a wide enough type, so we can include
         // it in the note.
         N = N.extend(std::max<unsigned>(N.getBitWidth() + 1, 65));
         (llvm::APInt&)N += ArrayIndex;
         assert(N.ugt(ArraySize) && "bounds check failed for in-bounds index");
         diagnosePointerArithmetic(Info, E, N);
         setInvalid();
         return;
       }
 
       ArrayIndex += TruncatedN;
       assert(ArrayIndex <= ArraySize &&
              "bounds check succeeded for out-of-bounds index");
 
       if (IsArray)
         Entries.back() = PathEntry::ArrayIndex(ArrayIndex);
       else
         IsOnePastTheEnd = (ArrayIndex != 0);
     }
   };
 
   /// A stack frame in the constexpr call stack.
   class CallStackFrame : public interp::Frame {
   public:
     EvalInfo &Info;
 
     /// Parent - The caller of this stack frame.
     CallStackFrame *Caller;
 
     /// Callee - The function which was called.
     const FunctionDecl *Callee;
 
     /// This - The binding for the this pointer in this call, if any.
     const LValue *This;
 
     /// Arguments - Parameter bindings for this function call, indexed by
     /// parameters' function scope indices.
     APValue *Arguments;
 
     /// Source location information about the default argument or default
     /// initializer expression we're evaluating, if any.
     CurrentSourceLocExprScope CurSourceLocExprScope;
 
     // Note that we intentionally use std::map here so that references to
     // values are stable.
     typedef std::pair<const void *, unsigned> MapKeyTy;
     typedef std::map<MapKeyTy, APValue> MapTy;
     /// Temporaries - Temporary lvalues materialized within this stack frame.
     MapTy Temporaries;
 
     /// CallLoc - The location of the call expression for this call.
     SourceLocation CallLoc;
 
     /// Index - The call index of this call.
     unsigned Index;
 
     /// The stack of integers for tracking version numbers for temporaries.
     SmallVector<unsigned, 2> TempVersionStack = {1};
     unsigned CurTempVersion = TempVersionStack.back();
 
     unsigned getTempVersion() const { return TempVersionStack.back(); }
 
     void pushTempVersion() {
       TempVersionStack.push_back(++CurTempVersion);
     }
 
     void popTempVersion() {
       TempVersionStack.pop_back();
     }
 
     // FIXME: Adding this to every 'CallStackFrame' may have a nontrivial impact
     // on the overall stack usage of deeply-recursing constexpr evaluations.
     // (We should cache this map rather than recomputing it repeatedly.)
     // But let's try this and see how it goes; we can look into caching the map
     // as a later change.
 
     /// LambdaCaptureFields - Mapping from captured variables/this to
     /// corresponding data members in the closure class.
     llvm::DenseMap<const VarDecl *, FieldDecl *> LambdaCaptureFields;
     FieldDecl *LambdaThisCaptureField;
 
     CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
                    const FunctionDecl *Callee, const LValue *This,
                    APValue *Arguments);
     ~CallStackFrame();
 
     // Return the temporary for Key whose version number is Version.
     APValue *getTemporary(const void *Key, unsigned Version) {
       MapKeyTy KV(Key, Version);
       auto LB = Temporaries.lower_bound(KV);
       if (LB != Temporaries.end() && LB->first == KV)
         return &LB->second;
       // Pair (Key,Version) wasn't found in the map. Check that no elements
       // in the map have 'Key' as their key.
       assert((LB == Temporaries.end() || LB->first.first != Key) &&
              (LB == Temporaries.begin() || std::prev(LB)->first.first != Key) &&
              "Element with key 'Key' found in map");
       return nullptr;
     }
 
     // Return the current temporary for Key in the map.
     APValue *getCurrentTemporary(const void *Key) {
       auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX));
       if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
         return &std::prev(UB)->second;
       return nullptr;
     }
 
     // Return the version number of the current temporary for Key.
     unsigned getCurrentTemporaryVersion(const void *Key) const {
       auto UB = Temporaries.upper_bound(MapKeyTy(Key, UINT_MAX));
       if (UB != Temporaries.begin() && std::prev(UB)->first.first == Key)
         return std::prev(UB)->first.second;
       return 0;
     }
 
     /// Allocate storage for an object of type T in this stack frame.
     /// Populates LV with a handle to the created object. Key identifies
     /// the temporary within the stack frame, and must not be reused without
     /// bumping the temporary version number.
     template<typename KeyT>
     APValue &createTemporary(const KeyT *Key, QualType T,
                              bool IsLifetimeExtended, LValue &LV);
 
     void describe(llvm::raw_ostream &OS) override;
 
     Frame *getCaller() const override { return Caller; }
     SourceLocation getCallLocation() const override { return CallLoc; }
     const FunctionDecl *getCallee() const override { return Callee; }
 
     bool isStdFunction() const {
       for (const DeclContext *DC = Callee; DC; DC = DC->getParent())
         if (DC->isStdNamespace())
           return true;
       return false;
     }
   };
 
   /// Temporarily override 'this'.
   class ThisOverrideRAII {
   public:
     ThisOverrideRAII(CallStackFrame &Frame, const LValue *NewThis, bool Enable)
         : Frame(Frame), OldThis(Frame.This) {
       if (Enable)
         Frame.This = NewThis;
     }
     ~ThisOverrideRAII() {
       Frame.This = OldThis;
     }
   private:
     CallStackFrame &Frame;
     const LValue *OldThis;
   };
 }
 
 static bool HandleDestruction(EvalInfo &Info, const Expr *E,
                               const LValue &This, QualType ThisType);
 static bool HandleDestruction(EvalInfo &Info, SourceLocation Loc,
                               APValue::LValueBase LVBase, APValue &Value,
                               QualType T);
 
 namespace {
   /// A cleanup, and a flag indicating whether it is lifetime-extended.
   class Cleanup {
     llvm::PointerIntPair<APValue*, 1, bool> Value;
     APValue::LValueBase Base;
     QualType T;
 
   public:
     Cleanup(APValue *Val, APValue::LValueBase Base, QualType T,
             bool IsLifetimeExtended)
         : Value(Val, IsLifetimeExtended), Base(Base), T(T) {}
 
     bool isLifetimeExtended() const { return Value.getInt(); }
     bool endLifetime(EvalInfo &Info, bool RunDestructors) {
       if (RunDestructors) {
         SourceLocation Loc;
         if (const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>())
           Loc = VD->getLocation();
         else if (const Expr *E = Base.dyn_cast<const Expr*>())
           Loc = E->getExprLoc();
         return HandleDestruction(Info, Loc, Base, *Value.getPointer(), T);
       }
       *Value.getPointer() = APValue();
       return true;
     }
 
     bool hasSideEffect() {
       return T.isDestructedType();
     }
   };
 
   /// A reference to an object whose construction we are currently evaluating.
   struct ObjectUnderConstruction {
     APValue::LValueBase Base;
     ArrayRef<APValue::LValuePathEntry> Path;
     friend bool operator==(const ObjectUnderConstruction &LHS,
                            const ObjectUnderConstruction &RHS) {
       return LHS.Base == RHS.Base && LHS.Path == RHS.Path;
     }
     friend llvm::hash_code hash_value(const ObjectUnderConstruction &Obj) {
       return llvm::hash_combine(Obj.Base, Obj.Path);
     }
   };
   enum class ConstructionPhase {
     None,
     Bases,
     AfterBases,
     AfterFields,
     Destroying,
     DestroyingBases
   };
 }
 
 namespace llvm {
 template<> struct DenseMapInfo<ObjectUnderConstruction> {
   using Base = DenseMapInfo<APValue::LValueBase>;
   static ObjectUnderConstruction getEmptyKey() {
     return {Base::getEmptyKey(), {}}; }
   static ObjectUnderConstruction getTombstoneKey() {
     return {Base::getTombstoneKey(), {}};
   }
   static unsigned getHashValue(const ObjectUnderConstruction &Object) {
     return hash_value(Object);
   }
   static bool isEqual(const ObjectUnderConstruction &LHS,
                       const ObjectUnderConstruction &RHS) {
     return LHS == RHS;
   }
 };
 }
 
 namespace {
   /// A dynamically-allocated heap object.
   struct DynAlloc {
     /// The value of this heap-allocated object.
     APValue Value;
     /// The allocating expression; used for diagnostics. Either a CXXNewExpr
     /// or a CallExpr (the latter is for direct calls to operator new inside
     /// std::allocator<T>::allocate).
     const Expr *AllocExpr = nullptr;
 
     enum Kind {
       New,
       ArrayNew,
       StdAllocator
     };
 
     /// Get the kind of the allocation. This must match between allocation
     /// and deallocation.
     Kind getKind() const {
       if (auto *NE = dyn_cast<CXXNewExpr>(AllocExpr))
         return NE->isArray() ? ArrayNew : New;
       assert(isa<CallExpr>(AllocExpr));
       return StdAllocator;
     }
   };
 
   struct DynAllocOrder {
     bool operator()(DynamicAllocLValue L, DynamicAllocLValue R) const {
       return L.getIndex() < R.getIndex();
     }
   };
 
   /// EvalInfo - This is a private struct used by the evaluator to capture
   /// information about a subexpression as it is folded.  It retains information
   /// about the AST context, but also maintains information about the folded
   /// expression.
   ///
   /// If an expression could be evaluated, it is still possible it is not a C
   /// "integer constant expression" or constant expression.  If not, this struct
   /// captures information about how and why not.
   ///
   /// One bit of information passed *into* the request for constant folding
   /// indicates whether the subexpression is "evaluated" or not according to C
   /// rules.  For example, the RHS of (0 && foo()) is not evaluated.  We can
   /// evaluate the expression regardless of what the RHS is, but C only allows
   /// certain things in certain situations.
   class EvalInfo : public interp::State {
   public:
     ASTContext &Ctx;
 
     /// EvalStatus - Contains information about the evaluation.
     Expr::EvalStatus &EvalStatus;
 
     /// CurrentCall - The top of the constexpr call stack.
     CallStackFrame *CurrentCall;
 
     /// CallStackDepth - The number of calls in the call stack right now.
     unsigned CallStackDepth;
 
     /// NextCallIndex - The next call index to assign.
     unsigned NextCallIndex;
 
     /// StepsLeft - The remaining number of evaluation steps we're permitted
     /// to perform. This is essentially a limit for the number of statements
     /// we will evaluate.
     unsigned StepsLeft;
 
     /// Enable the experimental new constant interpreter. If an expression is
     /// not supported by the interpreter, an error is triggered.
     bool EnableNewConstInterp;
 
     /// BottomFrame - The frame in which evaluation started. This must be
     /// initialized after CurrentCall and CallStackDepth.
     CallStackFrame BottomFrame;
 
     /// A stack of values whose lifetimes end at the end of some surrounding
     /// evaluation frame.
     llvm::SmallVector<Cleanup, 16> CleanupStack;
 
     /// EvaluatingDecl - This is the declaration whose initializer is being
     /// evaluated, if any.
     APValue::LValueBase EvaluatingDecl;
 
     enum class EvaluatingDeclKind {
       None,
       /// We're evaluating the construction of EvaluatingDecl.
       Ctor,
       /// We're evaluating the destruction of EvaluatingDecl.
       Dtor,
     };
     EvaluatingDeclKind IsEvaluatingDecl = EvaluatingDeclKind::None;
 
     /// EvaluatingDeclValue - This is the value being constructed for the
     /// declaration whose initializer is being evaluated, if any.
     APValue *EvaluatingDeclValue;
 
     /// Set of objects that are currently being constructed.
     llvm::DenseMap<ObjectUnderConstruction, ConstructionPhase>
         ObjectsUnderConstruction;
 
     /// Current heap allocations, along with the location where each was
     /// allocated. We use std::map here because we need stable addresses
     /// for the stored APValues.
     std::map<DynamicAllocLValue, DynAlloc, DynAllocOrder> HeapAllocs;
 
     /// The number of heap allocations performed so far in this evaluation.
     unsigned NumHeapAllocs = 0;
 
     struct EvaluatingConstructorRAII {
       EvalInfo &EI;
       ObjectUnderConstruction Object;
       bool DidInsert;
       EvaluatingConstructorRAII(EvalInfo &EI, ObjectUnderConstruction Object,
                                 bool HasBases)
           : EI(EI), Object(Object) {
         DidInsert =
             EI.ObjectsUnderConstruction
                 .insert({Object, HasBases ? ConstructionPhase::Bases
                                           : ConstructionPhase::AfterBases})
                 .second;
       }
       void finishedConstructingBases() {
         EI.ObjectsUnderConstruction[Object] = ConstructionPhase::AfterBases;
       }
       void finishedConstructingFields() {
         EI.ObjectsUnderConstruction[Object] = ConstructionPhase::AfterFields;
       }
       ~EvaluatingConstructorRAII() {
         if (DidInsert) EI.ObjectsUnderConstruction.erase(Object);
       }
     };
 
     struct EvaluatingDestructorRAII {
       EvalInfo &EI;
       ObjectUnderConstruction Object;
       bool DidInsert;
       EvaluatingDestructorRAII(EvalInfo &EI, ObjectUnderConstruction Object)
           : EI(EI), Object(Object) {
         DidInsert = EI.ObjectsUnderConstruction
                         .insert({Object, ConstructionPhase::Destroying})
                         .second;
       }
       void startedDestroyingBases() {
         EI.ObjectsUnderConstruction[Object] =
             ConstructionPhase::DestroyingBases;
       }
       ~EvaluatingDestructorRAII() {
         if (DidInsert)
           EI.ObjectsUnderConstruction.erase(Object);
       }
     };
 
     ConstructionPhase
     isEvaluatingCtorDtor(APValue::LValueBase Base,
                          ArrayRef<APValue::LValuePathEntry> Path) {
       return ObjectsUnderConstruction.lookup({Base, Path});
     }
 
     /// If we're currently speculatively evaluating, the outermost call stack
     /// depth at which we can mutate state, otherwise 0.
     unsigned SpeculativeEvaluationDepth = 0;
 
     /// The current array initialization index, if we're performing array
     /// initialization.
     uint64_t ArrayInitIndex = -1;
 
     /// HasActiveDiagnostic - Was the previous diagnostic stored? If so, further
     /// notes attached to it will also be stored, otherwise they will not be.
     bool HasActiveDiagnostic;
 
     /// Have we emitted a diagnostic explaining why we couldn't constant
     /// fold (not just why it's not strictly a constant expression)?
     bool HasFoldFailureDiagnostic;
 
     /// Whether or not we're in a context where the front end requires a
     /// constant value.
     bool InConstantContext;
 
     /// Whether we're checking that an expression is a potential constant
     /// expression. If so, do not fail on constructs that could become constant
     /// later on (such as a use of an undefined global).
     bool CheckingPotentialConstantExpression = false;
 
     /// Whether we're checking for an expression that has undefined behavior.
     /// If so, we will produce warnings if we encounter an operation that is
     /// always undefined.
     bool CheckingForUndefinedBehavior = false;
 
     enum EvaluationMode {
       /// Evaluate as a constant expression. Stop if we find that the expression
       /// is not a constant expression.
       EM_ConstantExpression,
 
       /// Evaluate as a constant expression. Stop if we find that the expression
       /// is not a constant expression. Some expressions can be retried in the
       /// optimizer if we don't constant fold them here, but in an unevaluated
       /// context we try to fold them immediately since the optimizer never
       /// gets a chance to look at it.
       EM_ConstantExpressionUnevaluated,
 
       /// Fold the expression to a constant. Stop if we hit a side-effect that
       /// we can't model.
       EM_ConstantFold,
 
       /// Evaluate in any way we know how. Don't worry about side-effects that
       /// can't be modeled.
       EM_IgnoreSideEffects,
     } EvalMode;
 
     /// Are we checking whether the expression is a potential constant
     /// expression?
     bool checkingPotentialConstantExpression() const override  {
       return CheckingPotentialConstantExpression;
     }
 
     /// Are we checking an expression for overflow?
     // FIXME: We should check for any kind of undefined or suspicious behavior
     // in such constructs, not just overflow.
     bool checkingForUndefinedBehavior() const override {
       return CheckingForUndefinedBehavior;
     }
 
     EvalInfo(const ASTContext &C, Expr::EvalStatus &S, EvaluationMode Mode)
         : Ctx(const_cast<ASTContext &>(C)), EvalStatus(S), CurrentCall(nullptr),
           CallStackDepth(0), NextCallIndex(1),
           StepsLeft(C.getLangOpts().ConstexprStepLimit),
           EnableNewConstInterp(C.getLangOpts().EnableNewConstInterp),
           BottomFrame(*this, SourceLocation(), nullptr, nullptr, nullptr),
           EvaluatingDecl((const ValueDecl *)nullptr),
           EvaluatingDeclValue(nullptr), HasActiveDiagnostic(false),
           HasFoldFailureDiagnostic(false), InConstantContext(false),
           EvalMode(Mode) {}
 
     ~EvalInfo() {
       discardCleanups();
     }
 
     void setEvaluatingDecl(APValue::LValueBase Base, APValue &Value,
                            EvaluatingDeclKind EDK = EvaluatingDeclKind::Ctor) {
       EvaluatingDecl = Base;
       IsEvaluatingDecl = EDK;
       EvaluatingDeclValue = &Value;
     }
 
     bool CheckCallLimit(SourceLocation Loc) {
       // Don't perform any constexpr calls (other than the call we're checking)
       // when checking a potential constant expression.
       if (checkingPotentialConstantExpression() && CallStackDepth > 1)
         return false;
       if (NextCallIndex == 0) {
         // NextCallIndex has wrapped around.
         FFDiag(Loc, diag::note_constexpr_call_limit_exceeded);
         return false;
       }
       if (CallStackDepth <= getLangOpts().ConstexprCallDepth)
         return true;
       FFDiag(Loc, diag::note_constexpr_depth_limit_exceeded)
         << getLangOpts().ConstexprCallDepth;
       return false;
     }
 
     std::pair<CallStackFrame *, unsigned>
     getCallFrameAndDepth(unsigned CallIndex) {
       assert(CallIndex && "no call index in getCallFrameAndDepth");
       // We will eventually hit BottomFrame, which has Index 1, so Frame can't
       // be null in this loop.
       unsigned Depth = CallStackDepth;
       CallStackFrame *Frame = CurrentCall;
       while (Frame->Index > CallIndex) {
         Frame = Frame->Caller;
         --Depth;
       }
       if (Frame->Index == CallIndex)
         return {Frame, Depth};
       return {nullptr, 0};
     }
 
     bool nextStep(const Stmt *S) {
       if (!StepsLeft) {
         FFDiag(S->getBeginLoc(), diag::note_constexpr_step_limit_exceeded);
         return false;
       }
       --StepsLeft;
       return true;
     }
 
     APValue *createHeapAlloc(const Expr *E, QualType T, LValue &LV);
 
     Optional<DynAlloc*> lookupDynamicAlloc(DynamicAllocLValue DA) {
       Optional<DynAlloc*> Result;
       auto It = HeapAllocs.find(DA);
       if (It != HeapAllocs.end())
         Result = &It->second;
       return Result;
     }
 
     /// Information about a stack frame for std::allocator<T>::[de]allocate.
     struct StdAllocatorCaller {
       unsigned FrameIndex;
       QualType ElemType;
       explicit operator bool() const { return FrameIndex != 0; };
     };
 
     StdAllocatorCaller getStdAllocatorCaller(StringRef FnName) const {
       for (const CallStackFrame *Call = CurrentCall; Call != &BottomFrame;
            Call = Call->Caller) {
         const auto *MD = dyn_cast_or_null<CXXMethodDecl>(Call->Callee);
         if (!MD)
           continue;
         const IdentifierInfo *FnII = MD->getIdentifier();
         if (!FnII || !FnII->isStr(FnName))
           continue;
 
         const auto *CTSD =
             dyn_cast<ClassTemplateSpecializationDecl>(MD->getParent());
         if (!CTSD)
           continue;
 
         const IdentifierInfo *ClassII = CTSD->getIdentifier();
         const TemplateArgumentList &TAL = CTSD->getTemplateArgs();
         if (CTSD->isInStdNamespace() && ClassII &&
             ClassII->isStr("allocator") && TAL.size() >= 1 &&
             TAL[0].getKind() == TemplateArgument::Type)
           return {Call->Index, TAL[0].getAsType()};
       }
 
       return {};
     }
 
     void performLifetimeExtension() {
       // Disable the cleanups for lifetime-extended temporaries.
       CleanupStack.erase(
           std::remove_if(CleanupStack.begin(), CleanupStack.end(),
                          [](Cleanup &C) { return C.isLifetimeExtended(); }),
           CleanupStack.end());
      }
 
     /// Throw away any remaining cleanups at the end of evaluation. If any
     /// cleanups would have had a side-effect, note that as an unmodeled
     /// side-effect and return false. Otherwise, return true.
     bool discardCleanups() {
       for (Cleanup &C : CleanupStack) {
         if (C.hasSideEffect() && !noteSideEffect()) {
           CleanupStack.clear();
           return false;
         }
       }
       CleanupStack.clear();
       return true;
     }
 
   private:
     interp::Frame *getCurrentFrame() override { return CurrentCall; }
     const interp::Frame *getBottomFrame() const override { return &BottomFrame; }
 
     bool hasActiveDiagnostic() override { return HasActiveDiagnostic; }
     void setActiveDiagnostic(bool Flag) override { HasActiveDiagnostic = Flag; }
 
     void setFoldFailureDiagnostic(bool Flag) override {
       HasFoldFailureDiagnostic = Flag;
     }
 
     Expr::EvalStatus &getEvalStatus() const override { return EvalStatus; }
 
     ASTContext &getCtx() const override { return Ctx; }
 
     // If we have a prior diagnostic, it will be noting that the expression
     // isn't a constant expression. This diagnostic is more important,
     // unless we require this evaluation to produce a constant expression.
     //
     // FIXME: We might want to show both diagnostics to the user in
     // EM_ConstantFold mode.
     bool hasPriorDiagnostic() override {
       if (!EvalStatus.Diag->empty()) {
         switch (EvalMode) {
         case EM_ConstantFold:
         case EM_IgnoreSideEffects:
           if (!HasFoldFailureDiagnostic)
             break;
           // We've already failed to fold something. Keep that diagnostic.
           LLVM_FALLTHROUGH;
         case EM_ConstantExpression:
         case EM_ConstantExpressionUnevaluated:
           setActiveDiagnostic(false);
           return true;
         }
       }
       return false;
     }
 
     unsigned getCallStackDepth() override { return CallStackDepth; }
 
   public:
     /// Should we continue evaluation after encountering a side-effect that we
     /// couldn't model?
     bool keepEvaluatingAfterSideEffect() {
       switch (EvalMode) {
       case EM_IgnoreSideEffects:
         return true;
 
       case EM_ConstantExpression:
       case EM_ConstantExpressionUnevaluated:
       case EM_ConstantFold:
         // By default, assume any side effect might be valid in some other
         // evaluation of this expression from a different context.
         return checkingPotentialConstantExpression() ||
                checkingForUndefinedBehavior();
       }
       llvm_unreachable("Missed EvalMode case");
     }
 
     /// Note that we have had a side-effect, and determine whether we should
     /// keep evaluating.
     bool noteSideEffect() {
       EvalStatus.HasSideEffects = true;
       return keepEvaluatingAfterSideEffect();
     }
 
     /// Should we continue evaluation after encountering undefined behavior?
     bool keepEvaluatingAfterUndefinedBehavior() {
       switch (EvalMode) {
       case EM_IgnoreSideEffects:
       case EM_ConstantFold:
         return true;
 
       case EM_ConstantExpression:
       case EM_ConstantExpressionUnevaluated:
         return checkingForUndefinedBehavior();
       }
       llvm_unreachable("Missed EvalMode case");
     }
 
     /// Note that we hit something that was technically undefined behavior, but
     /// that we can evaluate past it (such as signed overflow or floating-point
     /// division by zero.)
     bool noteUndefinedBehavior() override {
       EvalStatus.HasUndefinedBehavior = true;
       return keepEvaluatingAfterUndefinedBehavior();
     }
 
     /// Should we continue evaluation as much as possible after encountering a
     /// construct which can't be reduced to a value?
     bool keepEvaluatingAfterFailure() const override {
       if (!StepsLeft)
         return false;
 
       switch (EvalMode) {
       case EM_ConstantExpression:
       case EM_ConstantExpressionUnevaluated:
       case EM_ConstantFold:
       case EM_IgnoreSideEffects:
         return checkingPotentialConstantExpression() ||
                checkingForUndefinedBehavior();
       }
       llvm_unreachable("Missed EvalMode case");
     }
 
     /// Notes that we failed to evaluate an expression that other expressions
     /// directly depend on, and determine if we should keep evaluating. This
     /// should only be called if we actually intend to keep evaluating.
     ///
     /// Call noteSideEffect() instead if we may be able to ignore the value that
     /// we failed to evaluate, e.g. if we failed to evaluate Foo() in:
     ///
     /// (Foo(), 1)      // use noteSideEffect
     /// (Foo() || true) // use noteSideEffect
     /// Foo() + 1       // use noteFailure
     LLVM_NODISCARD bool noteFailure() {
       // Failure when evaluating some expression often means there is some
       // subexpression whose evaluation was skipped. Therefore, (because we
       // don't track whether we skipped an expression when unwinding after an
       // evaluation failure) every evaluation failure that bubbles up from a
       // subexpression implies that a side-effect has potentially happened. We
       // skip setting the HasSideEffects flag to true until we decide to
       // continue evaluating after that point, which happens here.
       bool KeepGoing = keepEvaluatingAfterFailure();
       EvalStatus.HasSideEffects |= KeepGoing;
       return KeepGoing;
     }
 
     class ArrayInitLoopIndex {
       EvalInfo &Info;
       uint64_t OuterIndex;
 
     public:
       ArrayInitLoopIndex(EvalInfo &Info)
           : Info(Info), OuterIndex(Info.ArrayInitIndex) {
         Info.ArrayInitIndex = 0;
       }
       ~ArrayInitLoopIndex() { Info.ArrayInitIndex = OuterIndex; }
 
       operator uint64_t&() { return Info.ArrayInitIndex; }
     };
   };
 
   /// Object used to treat all foldable expressions as constant expressions.
   struct FoldConstant {
     EvalInfo &Info;
     bool Enabled;
     bool HadNoPriorDiags;
     EvalInfo::EvaluationMode OldMode;
 
     explicit FoldConstant(EvalInfo &Info, bool Enabled)
       : Info(Info),
         Enabled(Enabled),
         HadNoPriorDiags(Info.EvalStatus.Diag &&
                         Info.EvalStatus.Diag->empty() &&
                         !Info.EvalStatus.HasSideEffects),
         OldMode(Info.EvalMode) {
       if (Enabled)
         Info.EvalMode = EvalInfo::EM_ConstantFold;
     }
     void keepDiagnostics() { Enabled = false; }
     ~FoldConstant() {
       if (Enabled && HadNoPriorDiags && !Info.EvalStatus.Diag->empty() &&
           !Info.EvalStatus.HasSideEffects)
         Info.EvalStatus.Diag->clear();
       Info.EvalMode = OldMode;
     }
   };
 
   /// RAII object used to set the current evaluation mode to ignore
   /// side-effects.
   struct IgnoreSideEffectsRAII {
     EvalInfo &Info;
     EvalInfo::EvaluationMode OldMode;
     explicit IgnoreSideEffectsRAII(EvalInfo &Info)
         : Info(Info), OldMode(Info.EvalMode) {
       Info.EvalMode = EvalInfo::EM_IgnoreSideEffects;
     }
 
     ~IgnoreSideEffectsRAII() { Info.EvalMode = OldMode; }
   };
 
   /// RAII object used to optionally suppress diagnostics and side-effects from
   /// a speculative evaluation.
   class SpeculativeEvaluationRAII {
     EvalInfo *Info = nullptr;
     Expr::EvalStatus OldStatus;
     unsigned OldSpeculativeEvaluationDepth;
 
     void moveFromAndCancel(SpeculativeEvaluationRAII &&Other) {
       Info = Other.Info;
       OldStatus = Other.OldStatus;
       OldSpeculativeEvaluationDepth = Other.OldSpeculativeEvaluationDepth;
       Other.Info = nullptr;
     }
 
     void maybeRestoreState() {
       if (!Info)
         return;
 
       Info->EvalStatus = OldStatus;
       Info->SpeculativeEvaluationDepth = OldSpeculativeEvaluationDepth;
     }
 
   public:
     SpeculativeEvaluationRAII() = default;
 
     SpeculativeEvaluationRAII(
         EvalInfo &Info, SmallVectorImpl<PartialDiagnosticAt> *NewDiag = nullptr)
         : Info(&Info), OldStatus(Info.EvalStatus),
           OldSpeculativeEvaluationDepth(Info.SpeculativeEvaluationDepth) {
       Info.EvalStatus.Diag = NewDiag;
       Info.SpeculativeEvaluationDepth = Info.CallStackDepth + 1;
     }
 
     SpeculativeEvaluationRAII(const SpeculativeEvaluationRAII &Other) = delete;
     SpeculativeEvaluationRAII(SpeculativeEvaluationRAII &&Other) {
       moveFromAndCancel(std::move(Other));
     }
 
     SpeculativeEvaluationRAII &operator=(SpeculativeEvaluationRAII &&Other) {
       maybeRestoreState();
       moveFromAndCancel(std::move(Other));
       return *this;
     }
 
     ~SpeculativeEvaluationRAII() { maybeRestoreState(); }
   };
 
   /// RAII object wrapping a full-expression or block scope, and handling
   /// the ending of the lifetime of temporaries created within it.
   template<bool IsFullExpression>
   class ScopeRAII {
     EvalInfo &Info;
     unsigned OldStackSize;
   public:
     ScopeRAII(EvalInfo &Info)
         : Info(Info), OldStackSize(Info.CleanupStack.size()) {
       // Push a new temporary version. This is needed to distinguish between
       // temporaries created in different iterations of a loop.
       Info.CurrentCall->pushTempVersion();
     }
     bool destroy(bool RunDestructors = true) {
       bool OK = cleanup(Info, RunDestructors, OldStackSize);
       OldStackSize = -1U;
       return OK;
     }
     ~ScopeRAII() {
       if (OldStackSize != -1U)
         destroy(false);
       // Body moved to a static method to encourage the compiler to inline away
       // instances of this class.
       Info.CurrentCall->popTempVersion();
     }
   private:
     static bool cleanup(EvalInfo &Info, bool RunDestructors,
                         unsigned OldStackSize) {
       assert(OldStackSize <= Info.CleanupStack.size() &&
              "running cleanups out of order?");
 
       // Run all cleanups for a block scope, and non-lifetime-extended cleanups
       // for a full-expression scope.
       bool Success = true;
       for (unsigned I = Info.CleanupStack.size(); I > OldStackSize; --I) {
         if (!(IsFullExpression &&
               Info.CleanupStack[I - 1].isLifetimeExtended())) {
           if (!Info.CleanupStack[I - 1].endLifetime(Info, RunDestructors)) {
             Success = false;
             break;
           }
         }
       }
 
       // Compact lifetime-extended cleanups.
       auto NewEnd = Info.CleanupStack.begin() + OldStackSize;
       if (IsFullExpression)
         NewEnd =
             std::remove_if(NewEnd, Info.CleanupStack.end(),
                            [](Cleanup &C) { return !C.isLifetimeExtended(); });
       Info.CleanupStack.erase(NewEnd, Info.CleanupStack.end());
       return Success;
     }
   };
   typedef ScopeRAII<false> BlockScopeRAII;
   typedef ScopeRAII<true> FullExpressionRAII;
 }
 
 bool SubobjectDesignator::checkSubobject(EvalInfo &Info, const Expr *E,
                                          CheckSubobjectKind CSK) {
   if (Invalid)
     return false;
   if (isOnePastTheEnd()) {
     Info.CCEDiag(E, diag::note_constexpr_past_end_subobject)
       << CSK;
     setInvalid();
     return false;
   }
   // Note, we do not diagnose if isMostDerivedAnUnsizedArray(), because there
   // must actually be at least one array element; even a VLA cannot have a
   // bound of zero. And if our index is nonzero, we already had a CCEDiag.
   return true;
 }
 
 void SubobjectDesignator::diagnoseUnsizedArrayPointerArithmetic(EvalInfo &Info,
                                                                 const Expr *E) {
   Info.CCEDiag(E, diag::note_constexpr_unsized_array_indexed);
   // Do not set the designator as invalid: we can represent this situation,
   // and correct handling of __builtin_object_size requires us to do so.
 }
 
 void SubobjectDesignator::diagnosePointerArithmetic(EvalInfo &Info,
                                                     const Expr *E,
                                                     const APSInt &N) {
   // If we're complaining, we must be able to statically determine the size of
   // the most derived array.
   if (MostDerivedPathLength == Entries.size() && MostDerivedIsArrayElement)
     Info.CCEDiag(E, diag::note_constexpr_array_index)
       << N << /*array*/ 0
       << static_cast<unsigned>(getMostDerivedArraySize());
   else
     Info.CCEDiag(E, diag::note_constexpr_array_index)
       << N << /*non-array*/ 1;
   setInvalid();
 }
 
 CallStackFrame::CallStackFrame(EvalInfo &Info, SourceLocation CallLoc,
                                const FunctionDecl *Callee, const LValue *This,
                                APValue *Arguments)
     : Info(Info), Caller(Info.CurrentCall), Callee(Callee), This(This),
       Arguments(Arguments), CallLoc(CallLoc), Index(Info.NextCallIndex++) {
   Info.CurrentCall = this;
   ++Info.CallStackDepth;
 }
 
 CallStackFrame::~CallStackFrame() {
   assert(Info.CurrentCall == this && "calls retired out of order");
   --Info.CallStackDepth;
   Info.CurrentCall = Caller;
 }
 
 static bool isRead(AccessKinds AK) {
   return AK == AK_Read || AK == AK_ReadObjectRepresentation;
 }
 
 static bool isModification(AccessKinds AK) {
   switch (AK) {
   case AK_Read:
   case AK_ReadObjectRepresentation:
   case AK_MemberCall:
   case AK_DynamicCast:
   case AK_TypeId:
     return false;
   case AK_Assign:
   case AK_Increment:
   case AK_Decrement:
   case AK_Construct:
   case AK_Destroy:
     return true;
   }
   llvm_unreachable("unknown access kind");
 }
 
 static bool isAnyAccess(AccessKinds AK) {
   return isRead(AK) || isModification(AK);
 }
 
 /// Is this an access per the C++ definition?
 static bool isFormalAccess(AccessKinds AK) {
   return isAnyAccess(AK) && AK != AK_Construct && AK != AK_Destroy;
 }
 
 /// Is this kind of axcess valid on an indeterminate object value?
 static bool isValidIndeterminateAccess(AccessKinds AK) {
   switch (AK) {
   case AK_Read:
   case AK_Increment:
   case AK_Decrement:
     // These need the object's value.
     return false;
 
   case AK_ReadObjectRepresentation:
   case AK_Assign:
   case AK_Construct:
   case AK_Destroy:
     // Construction and destruction don't need the value.
     return true;
 
   case AK_MemberCall:
   case AK_DynamicCast:
   case AK_TypeId:
     // These aren't really meaningful on scalars.
     return true;
   }
   llvm_unreachable("unknown access kind");
 }
 
 namespace {
   struct ComplexValue {
   private:
     bool IsInt;
 
   public:
     APSInt IntReal, IntImag;
     APFloat FloatReal, FloatImag;
 
     ComplexValue() : FloatReal(APFloat::Bogus()), FloatImag(APFloat::Bogus()) {}
 
     void makeComplexFloat() { IsInt = false; }
     bool isComplexFloat() const { return !IsInt; }
     APFloat &getComplexFloatReal() { return FloatReal; }
     APFloat &getComplexFloatImag() { return FloatImag; }
 
     void makeComplexInt() { IsInt = true; }
     bool isComplexInt() const { return IsInt; }
     APSInt &getComplexIntReal() { return IntReal; }
     APSInt &getComplexIntImag() { return IntImag; }
 
     void moveInto(APValue &v) const {
       if (isComplexFloat())
         v = APValue(FloatReal, FloatImag);
       else
         v = APValue(IntReal, IntImag);
     }
     void setFrom(const APValue &v) {
       assert(v.isComplexFloat() || v.isComplexInt());
       if (v.isComplexFloat()) {
         makeComplexFloat();
         FloatReal = v.getComplexFloatReal();
         FloatImag = v.getComplexFloatImag();
       } else {
         makeComplexInt();
         IntReal = v.getComplexIntReal();
         IntImag = v.getComplexIntImag();
       }
     }
   };
 
   struct LValue {
     APValue::LValueBase Base;
     CharUnits Offset;
     SubobjectDesignator Designator;
     bool IsNullPtr : 1;
     bool InvalidBase : 1;
 
     const APValue::LValueBase getLValueBase() const { return Base; }
     CharUnits &getLValueOffset() { return Offset; }
     const CharUnits &getLValueOffset() const { return Offset; }
     SubobjectDesignator &getLValueDesignator() { return Designator; }
     const SubobjectDesignator &getLValueDesignator() const { return Designator;}
     bool isNullPointer() const { return IsNullPtr;}
 
     unsigned getLValueCallIndex() const { return Base.getCallIndex(); }
     unsigned getLValueVersion() const { return Base.getVersion(); }
 
     void moveInto(APValue &V) const {
       if (Designator.Invalid)
         V = APValue(Base, Offset, APValue::NoLValuePath(), IsNullPtr);
       else {
         assert(!InvalidBase && "APValues can't handle invalid LValue bases");
         V = APValue(Base, Offset, Designator.Entries,
                     Designator.IsOnePastTheEnd, IsNullPtr);
       }
     }
     void setFrom(ASTContext &Ctx, const APValue &V) {
       assert(V.isLValue() && "Setting LValue from a non-LValue?");
       Base = V.getLValueBase();
       Offset = V.getLValueOffset();
       InvalidBase = false;
       Designator = SubobjectDesignator(Ctx, V);
       IsNullPtr = V.isNullPointer();
     }
 
     void set(APValue::LValueBase B, bool BInvalid = false) {
 #ifndef NDEBUG
       // We only allow a few types of invalid bases. Enforce that here.
       if (BInvalid) {
         const auto *E = B.get<const Expr *>();
         assert((isa<MemberExpr>(E) || tryUnwrapAllocSizeCall(E)) &&
                "Unexpected type of invalid base");
       }
 #endif
 
       Base = B;
       Offset = CharUnits::fromQuantity(0);
       InvalidBase = BInvalid;
       Designator = SubobjectDesignator(getType(B));
       IsNullPtr = false;
     }
 
     void setNull(ASTContext &Ctx, QualType PointerTy) {
       Base = (Expr *)nullptr;
       Offset =
           CharUnits::fromQuantity(Ctx.getTargetNullPointerValue(PointerTy));
       InvalidBase = false;
       Designator = SubobjectDesignator(PointerTy->getPointeeType());
       IsNullPtr = true;
     }
 
     void setInvalid(APValue::LValueBase B, unsigned I = 0) {
       set(B, true);
     }
 
     std::string toString(ASTContext &Ctx, QualType T) const {
       APValue Printable;
       moveInto(Printable);
       return Printable.getAsString(Ctx, T);
     }
 
   private:
     // Check that this LValue is not based on a null pointer. If it is, produce
     // a diagnostic and mark the designator as invalid.
     template <typename GenDiagType>
     bool checkNullPointerDiagnosingWith(const GenDiagType &GenDiag) {
       if (Designator.Invalid)
         return false;
       if (IsNullPtr) {
         GenDiag();
         Designator.setInvalid();
         return false;
       }
       return true;
     }
 
   public:
     bool checkNullPointer(EvalInfo &Info, const Expr *E,
                           CheckSubobjectKind CSK) {
       return checkNullPointerDiagnosingWith([&Info, E, CSK] {
         Info.CCEDiag(E, diag::note_constexpr_null_subobject) << CSK;
       });
     }
 
     bool checkNullPointerForFoldAccess(EvalInfo &Info, const Expr *E,
                                        AccessKinds AK) {
       return checkNullPointerDiagnosingWith([&Info, E, AK] {
         Info.FFDiag(E, diag::note_constexpr_access_null) << AK;
       });
     }
 
     // Check this LValue refers to an object. If not, set the designator to be
     // invalid and emit a diagnostic.
     bool checkSubobject(EvalInfo &Info, const Expr *E, CheckSubobjectKind CSK) {
       return (CSK == CSK_ArrayToPointer || checkNullPointer(Info, E, CSK)) &&
              Designator.checkSubobject(Info, E, CSK);
     }
 
     void addDecl(EvalInfo &Info, const Expr *E,
                  const Decl *D, bool Virtual = false) {
       if (checkSubobject(Info, E, isa<FieldDecl>(D) ? CSK_Field : CSK_Base))
         Designator.addDeclUnchecked(D, Virtual);
     }
     void addUnsizedArray(EvalInfo &Info, const Expr *E, QualType ElemTy) {
       if (!Designator.Entries.empty()) {
         Info.CCEDiag(E, diag::note_constexpr_unsupported_unsized_array);
         Designator.setInvalid();
         return;
       }
       if (checkSubobject(Info, E, CSK_ArrayToPointer)) {
         assert(getType(Base)->isPointerType() || getType(Base)->isArrayType());
         Designator.FirstEntryIsAnUnsizedArray = true;
         Designator.addUnsizedArrayUnchecked(ElemTy);
       }
     }
     void addArray(EvalInfo &Info, const Expr *E, const ConstantArrayType *CAT) {
       if (checkSubobject(Info, E, CSK_ArrayToPointer))
         Designator.addArrayUnchecked(CAT);
     }
     void addComplex(EvalInfo &Info, const Expr *E, QualType EltTy, bool Imag) {
       if (checkSubobject(Info, E, Imag ? CSK_Imag : CSK_Real))
         Designator.addComplexUnchecked(EltTy, Imag);
     }
     void clearIsNullPointer() {
       IsNullPtr = false;
     }
     void adjustOffsetAndIndex(EvalInfo &Info, const Expr *E,
                               const APSInt &Index, CharUnits ElementSize) {
       // An index of 0 has no effect. (In C, adding 0 to a null pointer is UB,
       // but we're not required to diagnose it and it's valid in C++.)
       if (!Index)
         return;
 
       // Compute the new offset in the appropriate width, wrapping at 64 bits.
       // FIXME: When compiling for a 32-bit target, we should use 32-bit
       // offsets.
       uint64_t Offset64 = Offset.getQuantity();
       uint64_t ElemSize64 = ElementSize.getQuantity();
       uint64_t Index64 = Index.extOrTrunc(64).getZExtValue();
       Offset = CharUnits::fromQuantity(Offset64 + ElemSize64 * Index64);
 
       if (checkNullPointer(Info, E, CSK_ArrayIndex))
         Designator.adjustIndex(Info, E, Index);
       clearIsNullPointer();
     }
     void adjustOffset(CharUnits N) {
       Offset += N;
       if (N.getQuantity())
         clearIsNullPointer();
     }
   };
 
   struct MemberPtr {
     MemberPtr() {}
     explicit MemberPtr(const ValueDecl *Decl) :
       DeclAndIsDerivedMember(Decl, false), Path() {}
 
     /// The member or (direct or indirect) field referred to by this member
     /// pointer, or 0 if this is a null member pointer.
     const ValueDecl *getDecl() const {
       return DeclAndIsDerivedMember.getPointer();
     }
     /// Is this actually a member of some type derived from the relevant class?
     bool isDerivedMember() const {
       return DeclAndIsDerivedMember.getInt();
     }
     /// Get the class which the declaration actually lives in.
     const CXXRecordDecl *getContainingRecord() const {
       return cast<CXXRecordDecl>(
           DeclAndIsDerivedMember.getPointer()->getDeclContext());
     }
 
     void moveInto(APValue &V) const {
       V = APValue(getDecl(), isDerivedMember(), Path);
     }
     void setFrom(const APValue &V) {
       assert(V.isMemberPointer());
       DeclAndIsDerivedMember.setPointer(V.getMemberPointerDecl());
       DeclAndIsDerivedMember.setInt(V.isMemberPointerToDerivedMember());
       Path.clear();
       ArrayRef<const CXXRecordDecl*> P = V.getMemberPointerPath();
       Path.insert(Path.end(), P.begin(), P.end());
     }
 
     /// DeclAndIsDerivedMember - The member declaration, and a flag indicating
     /// whether the member is a member of some class derived from the class type
     /// of the member pointer.
     llvm::PointerIntPair<const ValueDecl*, 1, bool> DeclAndIsDerivedMember;
     /// Path - The path of base/derived classes from the member declaration's
     /// class (exclusive) to the class type of the member pointer (inclusive).
     SmallVector<const CXXRecordDecl*, 4> Path;
 
     /// Perform a cast towards the class of the Decl (either up or down the
     /// hierarchy).
     bool castBack(const CXXRecordDecl *Class) {
       assert(!Path.empty());
       const CXXRecordDecl *Expected;
       if (Path.size() >= 2)
         Expected = Path[Path.size() - 2];
       else
         Expected = getContainingRecord();
       if (Expected->getCanonicalDecl() != Class->getCanonicalDecl()) {
         // C++11 [expr.static.cast]p12: In a conversion from (D::*) to (B::*),
         // if B does not contain the original member and is not a base or
         // derived class of the class containing the original member, the result
         // of the cast is undefined.
         // C++11 [conv.mem]p2 does not cover this case for a cast from (B::*) to
         // (D::*). We consider that to be a language defect.
         return false;
       }
       Path.pop_back();
       return true;
     }
     /// Perform a base-to-derived member pointer cast.
     bool castToDerived(const CXXRecordDecl *Derived) {
       if (!getDecl())
         return true;
       if (!isDerivedMember()) {
         Path.push_back(Derived);
         return true;
       }
       if (!castBack(Derived))
         return false;
       if (Path.empty())
         DeclAndIsDerivedMember.setInt(false);
       return true;
     }
     /// Perform a derived-to-base member pointer cast.
     bool castToBase(const CXXRecordDecl *Base) {
       if (!getDecl())
         return true;
       if (Path.empty())
         DeclAndIsDerivedMember.setInt(true);
       if (isDerivedMember()) {
         Path.push_back(Base);
         return true;
       }
       return castBack(Base);
     }
   };
 
   /// Compare two member pointers, which are assumed to be of the same type.
   static bool operator==(const MemberPtr &LHS, const MemberPtr &RHS) {
     if (!LHS.getDecl() || !RHS.getDecl())
       return !LHS.getDecl() && !RHS.getDecl();
     if (LHS.getDecl()->getCanonicalDecl() != RHS.getDecl()->getCanonicalDecl())
       return false;
     return LHS.Path == RHS.Path;
   }
 }
 
 static bool Evaluate(APValue &Result, EvalInfo &Info, const Expr *E);
 static bool EvaluateInPlace(APValue &Result, EvalInfo &Info,
                             const LValue &This, const Expr *E,
                             bool AllowNonLiteralTypes = false);
 static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info,
                            bool InvalidBaseOK = false);
 static bool EvaluatePointer(const Expr *E, LValue &Result, EvalInfo &Info,
                             bool InvalidBaseOK = false);
 static bool EvaluateMemberPointer(const Expr *E, MemberPtr &Result,
                                   EvalInfo &Info);
 static bool EvaluateTemporary(const Expr *E, LValue &Result, EvalInfo &Info);
 static bool EvaluateInteger(const Expr *E, APSInt &Result, EvalInfo &Info);
 static bool EvaluateIntegerOrLValue(const Expr *E, APValue &Result,
                                     EvalInfo &Info);
 static bool EvaluateFloat(const Expr *E, APFloat &Result, EvalInfo &Info);
 static bool EvaluateComplex(const Expr *E, ComplexValue &Res, EvalInfo &Info);
 static bool EvaluateAtomic(const Expr *E, const LValue *This, APValue &Result,
                            EvalInfo &Info);
 static bool EvaluateAsRValue(EvalInfo &Info, const Expr *E, APValue &Result);
 
 /// Evaluate an integer or fixed point expression into an APResult.
 static bool EvaluateFixedPointOrInteger(const Expr *E, APFixedPoint &Result,
                                         EvalInfo &Info);
 
 /// Evaluate only a fixed point expression into an APResult.
 static bool EvaluateFixedPoint(const Expr *E, APFixedPoint &Result,
                                EvalInfo &Info);
 
 //===----------------------------------------------------------------------===//
 // Misc utilities
 //===----------------------------------------------------------------------===//
 
 /// Negate an APSInt in place, converting it to a signed form if necessary, and
 /// preserving its value (by extending by up to one bit as needed).
 static void negateAsSigned(APSInt &Int) {
   if (Int.isUnsigned() || Int.isMinSignedValue()) {
     Int = Int.extend(Int.getBitWidth() + 1);
     Int.setIsSigned(true);
   }
   Int = -Int;
 }
 
 template<typename KeyT>
 APValue &CallStackFrame::createTemporary(const KeyT *Key, QualType T,
                                          bool IsLifetimeExtended, LValue &LV) {
   unsigned Version = getTempVersion();
   APValue::LValueBase Base(Key, Index, Version);
   LV.set(Base);
   APValue &Result = Temporaries[MapKeyTy(Key, Version)];
   assert(Result.isAbsent() && "temporary created multiple times");
 
   // If we're creating a temporary immediately in the operand of a speculative
   // evaluation, don't register a cleanup to be run outside the speculative
   // evaluation context, since we won't actually be able to initialize this
   // object.
   if (Index <= Info.SpeculativeEvaluationDepth) {
     if (T.isDestructedType())
       Info.noteSideEffect();
   } else {
     Info.CleanupStack.push_back(Cleanup(&Result, Base, T, IsLifetimeExtended));
   }
   return Result;
 }
 
 APValue *EvalInfo::createHeapAlloc(const Expr *E, QualType T, LValue &LV) {
   if (NumHeapAllocs > DynamicAllocLValue::getMaxIndex()) {
     FFDiag(E, diag::note_constexpr_heap_alloc_limit_exceeded);
     return nullptr;
   }
 
   DynamicAllocLValue DA(NumHeapAllocs++);
   LV.set(APValue::LValueBase::getDynamicAlloc(DA, T));
   auto Result = HeapAllocs.emplace(std::piecewise_construct,
                                    std::forward_as_tuple(DA), std::tuple<>());
   assert(Result.second && "reused a heap alloc index?");
   Result.first->second.AllocExpr = E;
   return &Result.first->second.Value;
 }
 
 /// Produce a string describing the given constexpr call.
 void CallStackFrame::describe(raw_ostream &Out) {
   unsigned ArgIndex = 0;
   bool IsMemberCall = isa<CXXMethodDecl>(Callee) &&
                       !isa<CXXConstructorDecl>(Callee) &&
                       cast<CXXMethodDecl>(Callee)->isInstance();
 
   if (!IsMemberCall)
     Out << *Callee << '(';
 
   if (This && IsMemberCall) {
     APValue Val;
     This->moveInto(Val);
     Val.printPretty(Out, Info.Ctx,
                     This->Designator.MostDerivedType);
     // FIXME: Add parens around Val if needed.
     Out << "->" << *Callee << '(';
     IsMemberCall = false;
   }
 
   for (FunctionDecl::param_const_iterator I = Callee->param_begin(),
        E = Callee->param_end(); I != E; ++I, ++ArgIndex) {
     if (ArgIndex > (unsigned)IsMemberCall)
       Out << ", ";
 
     const ParmVarDecl *Param = *I;
     const APValue &Arg = Arguments[ArgIndex];
     Arg.printPretty(Out, Info.Ctx, Param->getType());
 
     if (ArgIndex == 0 && IsMemberCall)
       Out << "->" << *Callee << '(';
   }
 
   Out << ')';
 }
 
 /// Evaluate an expression to see if it had side-effects, and discard its
 /// result.
 /// \return \c true if the caller should keep evaluating.
 static bool EvaluateIgnoredValue(EvalInfo &Info, const Expr *E) {
   APValue Scratch;
   if (!Evaluate(Scratch, Info, E))
     // We don't need the value, but we might have skipped a side effect here.
     return Info.noteSideEffect();
   return true;
 }
 
 /// Should this call expression be treated as a string literal?
 static bool IsStringLiteralCall(const CallExpr *E) {
   unsigned Builtin = E->getBuiltinCallee();
   return (Builtin == Builtin::BI__builtin___CFStringMakeConstantString ||
           Builtin == Builtin::BI__builtin___NSStringMakeConstantString);
 }
 
 static bool IsGlobalLValue(APValue::LValueBase B) {
   // C++11 [expr.const]p3 An address constant expression is a prvalue core
   // constant expression of pointer type that evaluates to...
 
   // ... a null pointer value, or a prvalue core constant expression of type
   // std::nullptr_t.
   if (!B) return true;
 
   if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
     // ... the address of an object with static storage duration,
     if (const VarDecl *VD = dyn_cast<VarDecl>(D))
       return VD->hasGlobalStorage();
     // ... the address of a function,
     // ... the address of a GUID [MS extension],
     return isa<FunctionDecl>(D) || isa<MSGuidDecl>(D);
   }
 
   if (B.is<TypeInfoLValue>() || B.is<DynamicAllocLValue>())
     return true;
 
   const Expr *E = B.get<const Expr*>();
   switch (E->getStmtClass()) {
   default:
     return false;
   case Expr::CompoundLiteralExprClass: {
     const CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
     return CLE->isFileScope() && CLE->isLValue();
   }
   case Expr::MaterializeTemporaryExprClass:
     // A materialized temporary might have been lifetime-extended to static
     // storage duration.
     return cast<MaterializeTemporaryExpr>(E)->getStorageDuration() == SD_Static;
   // A string literal has static storage duration.
   case Expr::StringLiteralClass:
   case Expr::PredefinedExprClass:
   case Expr::ObjCStringLiteralClass:
   case Expr::ObjCEncodeExprClass:
     return true;
   case Expr::ObjCBoxedExprClass:
     return cast<ObjCBoxedExpr>(E)->isExpressibleAsConstantInitializer();
   case Expr::CallExprClass:
     return IsStringLiteralCall(cast<CallExpr>(E));
   // For GCC compatibility, &&label has static storage duration.
   case Expr::AddrLabelExprClass:
     return true;
   // A Block literal expression may be used as the initialization value for
   // Block variables at global or local static scope.
   case Expr::BlockExprClass:
     return !cast<BlockExpr>(E)->getBlockDecl()->hasCaptures();
   case Expr::ImplicitValueInitExprClass:
     // FIXME:
     // We can never form an lvalue with an implicit value initialization as its
     // base through expression evaluation, so these only appear in one case: the
     // implicit variable declaration we invent when checking whether a constexpr
     // constructor can produce a constant expression. We must assume that such
     // an expression might be a global lvalue.
     return true;
   }
 }
 
 static const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
   return LVal.Base.dyn_cast<const ValueDecl*>();
 }
 
 static bool IsLiteralLValue(const LValue &Value) {
   if (Value.getLValueCallIndex())
     return false;
   const Expr *E = Value.Base.dyn_cast<const Expr*>();
   return E && !isa<MaterializeTemporaryExpr>(E);
 }
 
 static bool IsWeakLValue(const LValue &Value) {
   const ValueDecl *Decl = GetLValueBaseDecl(Value);
   return Decl && Decl->isWeak();
 }
 
 static bool isZeroSized(const LValue &Value) {
   const ValueDecl *Decl = GetLValueBaseDecl(Value);
   if (Decl && isa<VarDecl>(Decl)) {
     QualType Ty = Decl->getType();
     if (Ty->isArrayType())
       return Ty->isIncompleteType() ||
              Decl->getASTContext().getTypeSize(Ty) == 0;
   }
   return false;
 }
 
 static bool HasSameBase(const LValue &A, const LValue &B) {
   if (!A.getLValueBase())
     return !B.getLValueBase();
   if (!B.getLValueBase())
     return false;
 
   if (A.getLValueBase().getOpaqueValue() !=
       B.getLValueBase().getOpaqueValue()) {
     const Decl *ADecl = GetLValueBaseDecl(A);
     if (!ADecl)
       return false;
     const Decl *BDecl = GetLValueBaseDecl(B);
     if (!BDecl || ADecl->getCanonicalDecl() != BDecl->getCanonicalDecl())
       return false;
   }
 
   return IsGlobalLValue(A.getLValueBase()) ||
          (A.getLValueCallIndex() == B.getLValueCallIndex() &&
           A.getLValueVersion() == B.getLValueVersion());
 }
 
 static void NoteLValueLocation(EvalInfo &Info, APValue::LValueBase Base) {
   assert(Base && "no location for a null lvalue");
   const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
   if (VD)
     Info.Note(VD->getLocation(), diag::note_declared_at);
   else if (const Expr *E = Base.dyn_cast<const Expr*>())
     Info.Note(E->getExprLoc(), diag::note_constexpr_temporary_here);
   else if (DynamicAllocLValue DA = Base.dyn_cast<DynamicAllocLValue>()) {
     // FIXME: Produce a note for dangling pointers too.
     if (Optional<DynAlloc*> Alloc = Info.lookupDynamicAlloc(DA))
       Info.Note((*Alloc)->AllocExpr->getExprLoc(),
                 diag::note_constexpr_dynamic_alloc_here);
   }
   // We have no information to show for a typeid(T) object.
 }
 
 enum class CheckEvaluationResultKind {
   ConstantExpression,
   FullyInitialized,
 };
 
 /// Materialized temporaries that we've already checked to determine if they're
 /// initializsed by a constant expression.
 using CheckedTemporaries =
     llvm::SmallPtrSet<const MaterializeTemporaryExpr *, 8>;
 
 static bool CheckEvaluationResult(CheckEvaluationResultKind CERK,
                                   EvalInfo &Info, SourceLocation DiagLoc,
                                   QualType Type, const APValue &Value,
                                   Expr::ConstExprUsage Usage,
                                   SourceLocation SubobjectLoc,
                                   CheckedTemporaries &CheckedTemps);
 
 /// Check that this reference or pointer core constant expression is a valid
 /// value for an address or reference constant expression. Return true if we
 /// can fold this expression, whether or not it's a constant expression.
 static bool CheckLValueConstantExpression(EvalInfo &Info, SourceLocation Loc,
                                           QualType Type, const LValue &LVal,
                                           Expr::ConstExprUsage Usage,
                                           CheckedTemporaries &CheckedTemps) {
   bool IsReferenceType = Type->isReferenceType();
 
   APValue::LValueBase Base = LVal.getLValueBase();
   const SubobjectDesignator &Designator = LVal.getLValueDesignator();
 
   if (auto *VD = LVal.getLValueBase().dyn_cast<const ValueDecl *>()) {
     if (auto *FD = dyn_cast<FunctionDecl>(VD)) {
       if (FD->isConsteval()) {
         Info.FFDiag(Loc, diag::note_consteval_address_accessible)
             << !Type->isAnyPointerType();
         Info.Note(FD->getLocation(), diag::note_declared_at);
         return false;
       }
     }
   }
 
   // Check that the object is a global. Note that the fake 'this' object we
   // manufacture when checking potential constant expressions is conservatively
   // assumed to be global here.
   if (!IsGlobalLValue(Base)) {
     if (Info.getLangOpts().CPlusPlus11) {
       const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
       Info.FFDiag(Loc, diag::note_constexpr_non_global, 1)
         << IsReferenceType << !Designator.Entries.empty()
         << !!VD << VD;
       NoteLValueLocation(Info, Base);
     } else {
       Info.FFDiag(Loc);
     }
     // Don't allow references to temporaries to escape.
     return false;
   }
   assert((Info.checkingPotentialConstantExpression() ||
           LVal.getLValueCallIndex() == 0) &&
          "have call index for global lvalue");
 
   if (Base.is<DynamicAllocLValue>()) {
     Info.FFDiag(Loc, diag::note_constexpr_dynamic_alloc)
         << IsReferenceType << !Designator.Entries.empty();
     NoteLValueLocation(Info, Base);
     return false;
   }
 
   if (const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>()) {
     if (const VarDecl *Var = dyn_cast<const VarDecl>(VD)) {
       // Check if this is a thread-local variable.
       if (Var->getTLSKind())
         // FIXME: Diagnostic!
         return false;
 
       // A dllimport variable never acts like a constant.
       if (Usage == Expr::EvaluateForCodeGen && Var->hasAttr<DLLImportAttr>())
         // FIXME: Diagnostic!
         return false;
     }
     if (const auto *FD = dyn_cast<const FunctionDecl>(VD)) {
       // __declspec(dllimport) must be handled very carefully:
       // We must never initialize an expression with the thunk in C++.
       // Doing otherwise would allow the same id-expression to yield
       // different addresses for the same function in different translation
       // units.  However, this means that we must dynamically initialize the
       // expression with the contents of the import address table at runtime.
       //
       // The C language has no notion of ODR; furthermore, it has no notion of
       // dynamic initialization.  This means that we are permitted to
       // perform initialization with the address of the thunk.
       if (Info.getLangOpts().CPlusPlus && Usage == Expr::EvaluateForCodeGen &&
           FD->hasAttr<DLLImportAttr>())
         // FIXME: Diagnostic!
         return false;
     }
   } else if (const auto *MTE = dyn_cast_or_null<MaterializeTemporaryExpr>(
                  Base.dyn_cast<const Expr *>())) {
     if (CheckedTemps.insert(MTE).second) {
       QualType TempType = getType(Base);
       if (TempType.isDestructedType()) {
         Info.FFDiag(MTE->getExprLoc(),
                     diag::note_constexpr_unsupported_tempoarary_nontrivial_dtor)
             << TempType;
         return false;
       }
 
       APValue *V = MTE->getOrCreateValue(false);
       assert(V && "evasluation result refers to uninitialised temporary");
       if (!CheckEvaluationResult(CheckEvaluationResultKind::ConstantExpression,
                                  Info, MTE->getExprLoc(), TempType, *V,
                                  Usage, SourceLocation(), CheckedTemps))
         return false;
     }
   }
 
   // Allow address constant expressions to be past-the-end pointers. This is
   // an extension: the standard requires them to point to an object.
   if (!IsReferenceType)
     return true;
 
   // A reference constant expression must refer to an object.
   if (!Base) {
     // FIXME: diagnostic
     Info.CCEDiag(Loc);
     return true;
   }
 
   // Does this refer one past the end of some object?
   if (!Designator.Invalid && Designator.isOnePastTheEnd()) {
     const ValueDecl *VD = Base.dyn_cast<const ValueDecl*>();
     Info.FFDiag(Loc, diag::note_constexpr_past_end, 1)
       << !Designator.Entries.empty() << !!VD << VD;
     NoteLValueLocation(Info, Base);
   }
 
   return true;
 }
 
 /// Member pointers are constant expressions unless they point to a
 /// non-virtual dllimport member function.
 static bool CheckMemberPointerConstantExpression(EvalInfo &Info,
                                                  SourceLocation Loc,
                                                  QualType Type,
                                                  const APValue &Value,
                                                  Expr::ConstExprUsage Usage) {
   const ValueDecl *Member = Value.getMemberPointerDecl();
   const auto *FD = dyn_cast_or_null<CXXMethodDecl>(Member);
   if (!FD)
     return true;
   if (FD->isConsteval()) {
     Info.FFDiag(Loc, diag::note_consteval_address_accessible) << /*pointer*/ 0;
     Info.Note(FD->getLocation(), diag::note_declared_at);
     return false;
   }
   return Usage == Expr::EvaluateForMangling || FD->isVirtual() ||
          !FD->hasAttr<DLLImportAttr>();
 }
 
 /// Check that this core constant expression is of literal type, and if not,
 /// produce an appropriate diagnostic.
 static bool CheckLiteralType(EvalInfo &Info, const Expr *E,
                              const LValue *This = nullptr) {
   if (!E->isRValue() || E->getType()->isLiteralType(Info.Ctx))
     return true;
 
   // C++1y: A constant initializer for an object o [...] may also invoke
   // constexpr constructors for o and its subobjects even if those objects
   // are of non-literal class types.
   //
   // C++11 missed this detail for aggregates, so classes like this:
   //   struct foo_t { union { int i; volatile int j; } u; };
   // are not (obviously) initializable like so:
   //   __attribute__((__require_constant_initialization__))
   //   static const foo_t x = {{0}};
   // because "i" is a subobject with non-literal initialization (due to the
   // volatile member of the union). See:
   //   http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1677
   // Therefore, we use the C++1y behavior.
   if (This && Info.EvaluatingDecl == This->getLValueBase())
     return true;
 
   // Prvalue constant expressions must be of literal types.
   if (Info.getLangOpts().CPlusPlus11)
     Info.FFDiag(E, diag::note_constexpr_nonliteral)
       << E->getType();
   else
     Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
   return false;
 }
 
 static bool CheckEvaluationResult(CheckEvaluationResultKind CERK,
                                   EvalInfo &Info, SourceLocation DiagLoc,
                                   QualType Type, const APValue &Value,
                                   Expr::ConstExprUsage Usage,
                                   SourceLocation SubobjectLoc,
                                   CheckedTemporaries &CheckedTemps) {
   if (!Value.hasValue()) {
     Info.FFDiag(DiagLoc, diag::note_constexpr_uninitialized)
       << true << Type;
     if (SubobjectLoc.isValid())
       Info.Note(SubobjectLoc, diag::note_constexpr_subobject_declared_here);
     return false;
   }
 
   // We allow _Atomic(T) to be initialized from anything that T can be
   // initialized from.
   if (const AtomicType *AT = Type->getAs<AtomicType>())
     Type = AT->getValueType();
 
   // Core issue 1454: For a literal constant expression of array or class type,
   // each subobject of its value shall have been initialized by a constant
   // expression.
   if (Value.isArray()) {
     QualType EltTy = Type->castAsArrayTypeUnsafe()->getElementType();
     for (unsigned I = 0, N = Value.getArrayInitializedElts(); I != N; ++I) {
       if (!CheckEvaluationResult(CERK, Info, DiagLoc, EltTy,
                                  Value.getArrayInitializedElt(I), Usage,
                                  SubobjectLoc, CheckedTemps))
         return false;
     }
     if (!Value.hasArrayFiller())
       return true;
     return CheckEvaluationResult(CERK, Info, DiagLoc, EltTy,
                                  Value.getArrayFiller(), Usage, SubobjectLoc,
                                  CheckedTemps);
   }
   if (Value.isUnion() && Value.getUnionField()) {
     return CheckEvaluationResult(
         CERK, Info, DiagLoc, Value.getUnionField()->getType(),
         Value.getUnionValue(), Usage, Value.getUnionField()->getLocation(),
         CheckedTemps);
   }
   if (Value.isStruct()) {
     RecordDecl *RD = Type->castAs<RecordType>()->getDecl();
     if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
       unsigned BaseIndex = 0;
       for (const CXXBaseSpecifier &BS : CD->bases()) {
         if (!CheckEvaluationResult(CERK, Info, DiagLoc, BS.getType(),
                                    Value.getStructBase(BaseIndex), Usage,
                                    BS.getBeginLoc(), CheckedTemps))
           return false;
         ++BaseIndex;
       }
     }
     for (const auto *I : RD->fields()) {
       if (I->isUnnamedBitfield())
         continue;
 
       if (!CheckEvaluationResult(CERK, Info, DiagLoc, I->getType(),
                                  Value.getStructField(I->getFieldIndex()),
                                  Usage, I->getLocation(), CheckedTemps))
         return false;
     }
   }
 
   if (Value.isLValue() &&
       CERK == CheckEvaluationResultKind::ConstantExpression) {
     LValue LVal;
     LVal.setFrom(Info.Ctx, Value);
     return CheckLValueConstantExpression(Info, DiagLoc, Type, LVal, Usage,
                                          CheckedTemps);
   }
 
   if (Value.isMemberPointer() &&
       CERK == CheckEvaluationResultKind::ConstantExpression)
     return CheckMemberPointerConstantExpression(Info, DiagLoc, Type, Value, Usage);
 
   // Everything else is fine.
   return true;
 }
 
 /// Check that this core constant expression value is a valid value for a
 /// constant expression. If not, report an appropriate diagnostic. Does not
 /// check that the expression is of literal type.
 static bool
 CheckConstantExpression(EvalInfo &Info, SourceLocation DiagLoc, QualType Type,
                         const APValue &Value,
                         Expr::ConstExprUsage Usage = Expr::EvaluateForCodeGen) {
   CheckedTemporaries CheckedTemps;
   return CheckEvaluationResult(CheckEvaluationResultKind::ConstantExpression,
                                Info, DiagLoc, Type, Value, Usage,
                                SourceLocation(), CheckedTemps);
 }
 
 /// Check that this evaluated value is fully-initialized and can be loaded by
 /// an lvalue-to-rvalue conversion.
 static bool CheckFullyInitialized(EvalInfo &Info, SourceLocation DiagLoc,
                                   QualType Type, const APValue &Value) {
   CheckedTemporaries CheckedTemps;
   return CheckEvaluationResult(
       CheckEvaluationResultKind::FullyInitialized, Info, DiagLoc, Type, Value,
       Expr::EvaluateForCodeGen, SourceLocation(), CheckedTemps);
 }
 
 /// Enforce C++2a [expr.const]/4.17, which disallows new-expressions unless
 /// "the allocated storage is deallocated within the evaluation".
 static bool CheckMemoryLeaks(EvalInfo &Info) {
   if (!Info.HeapAllocs.empty()) {
     // We can still fold to a constant despite a compile-time memory leak,
     // so long as the heap allocation isn't referenced in the result (we check
     // that in CheckConstantExpression).
     Info.CCEDiag(Info.HeapAllocs.begin()->second.AllocExpr,
                  diag::note_constexpr_memory_leak)
         << unsigned(Info.HeapAllocs.size() - 1);
   }
   return true;
 }
 
 static bool EvalPointerValueAsBool(const APValue &Value, bool &Result) {
   // A null base expression indicates a null pointer.  These are always
   // evaluatable, and they are false unless the offset is zero.
   if (!Value.getLValueBase()) {
     Result = !Value.getLValueOffset().isZero();
     return true;
   }
 
   // We have a non-null base.  These are generally known to be true, but if it's
   // a weak declaration it can be null at runtime.
   Result = true;
   const ValueDecl *Decl = Value.getLValueBase().dyn_cast<const ValueDecl*>();
   return !Decl || !Decl->isWeak();
 }
 
 static bool HandleConversionToBool(const APValue &Val, bool &Result) {
   switch (Val.getKind()) {
   case APValue::None:
   case APValue::Indeterminate:
     return false;
   case APValue::Int:
     Result = Val.getInt().getBoolValue();
     return true;
   case APValue::FixedPoint:
     Result = Val.getFixedPoint().getBoolValue();
     return true;
   case APValue::Float:
     Result = !Val.getFloat().isZero();
     return true;
   case APValue::ComplexInt:
     Result = Val.getComplexIntReal().getBoolValue() ||
              Val.getComplexIntImag().getBoolValue();
     return true;
   case APValue::ComplexFloat:
     Result = !Val.getComplexFloatReal().isZero() ||
              !Val.getComplexFloatImag().isZero();
     return true;
   case APValue::LValue:
     return EvalPointerValueAsBool(Val, Result);
   case APValue::MemberPointer:
     Result = Val.getMemberPointerDecl();
     return true;
   case APValue::Vector:
   case APValue::Array:
   case APValue::Struct:
   case APValue::Union:
   case APValue::AddrLabelDiff:
     return false;
   }
 
   llvm_unreachable("unknown APValue kind");
 }
 
 static bool EvaluateAsBooleanCondition(const Expr *E, bool &Result,
                                        EvalInfo &Info) {
   assert(E->isRValue() && "missing lvalue-to-rvalue conv in bool condition");
   APValue Val;
   if (!Evaluate(Val, Info, E))
     return false;
   return HandleConversionToBool(Val, Result);
 }
 
 template<typename T>
 static bool HandleOverflow(EvalInfo &Info, const Expr *E,
                            const T &SrcValue, QualType DestType) {
   Info.CCEDiag(E, diag::note_constexpr_overflow)
     << SrcValue << DestType;
   return Info.noteUndefinedBehavior();
 }
 
 static bool HandleFloatToIntCast(EvalInfo &Info, const Expr *E,
                                  QualType SrcType, const APFloat &Value,
                                  QualType DestType, APSInt &Result) {
   unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
   // Determine whether we are converting to unsigned or signed.
   bool DestSigned = DestType->isSignedIntegerOrEnumerationType();
 
   Result = APSInt(DestWidth, !DestSigned);
   bool ignored;
   if (Value.convertToInteger(Result, llvm::APFloat::rmTowardZero, &ignored)
       & APFloat::opInvalidOp)
     return HandleOverflow(Info, E, Value, DestType);
   return true;
 }
 
 static bool HandleFloatToFloatCast(EvalInfo &Info, const Expr *E,
                                    QualType SrcType, QualType DestType,
                                    APFloat &Result) {
   APFloat Value = Result;
   bool ignored;
   Result.convert(Info.Ctx.getFloatTypeSemantics(DestType),
                  APFloat::rmNearestTiesToEven, &ignored);
   return true;
 }
 
 static APSInt HandleIntToIntCast(EvalInfo &Info, const Expr *E,
                                  QualType DestType, QualType SrcType,
                                  const APSInt &Value) {
   unsigned DestWidth = Info.Ctx.getIntWidth(DestType);
   // Figure out if this is a truncate, extend or noop cast.
   // If the input is signed, do a sign extend, noop, or truncate.
   APSInt Result = Value.extOrTrunc(DestWidth);
   Result.setIsUnsigned(DestType->isUnsignedIntegerOrEnumerationType());
   if (DestType->isBooleanType())
     Result = Value.getBoolValue();
   return Result;
 }
 
 static bool HandleIntToFloatCast(EvalInfo &Info, const Expr *E,
                                  QualType SrcType, const APSInt &Value,
                                  QualType DestType, APFloat &Result) {
   Result = APFloat(Info.Ctx.getFloatTypeSemantics(DestType), 1);
   Result.convertFromAPInt(Value, Value.isSigned(),
                           APFloat::rmNearestTiesToEven);
   return true;
 }
 
 static bool truncateBitfieldValue(EvalInfo &Info, const Expr *E,
                                   APValue &Value, const FieldDecl *FD) {
   assert(FD->isBitField() && "truncateBitfieldValue on non-bitfield");
 
   if (!Value.isInt()) {
     // Trying to store a pointer-cast-to-integer into a bitfield.
     // FIXME: In this case, we should provide the diagnostic for casting
     // a pointer to an integer.
     assert(Value.isLValue() && "integral value neither int nor lvalue?");
     Info.FFDiag(E);
     return false;
   }
 
   APSInt &Int = Value.getInt();
   unsigned OldBitWidth = Int.getBitWidth();
   unsigned NewBitWidth = FD->getBitWidthValue(Info.Ctx);
   if (NewBitWidth < OldBitWidth)
     Int = Int.trunc(NewBitWidth).extend(OldBitWidth);
   return true;
 }
 
 static bool EvalAndBitcastToAPInt(EvalInfo &Info, const Expr *E,
                                   llvm::APInt &Res) {
   APValue SVal;
   if (!Evaluate(SVal, Info, E))
     return false;
   if (SVal.isInt()) {
     Res = SVal.getInt();
     return true;
   }
   if (SVal.isFloat()) {
     Res = SVal.getFloat().bitcastToAPInt();
     return true;
   }
   if (SVal.isVector()) {
     QualType VecTy = E->getType();
     unsigned VecSize = Info.Ctx.getTypeSize(VecTy);
     QualType EltTy = VecTy->castAs<VectorType>()->getElementType();
     unsigned EltSize = Info.Ctx.getTypeSize(EltTy);
     bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
     Res = llvm::APInt::getNullValue(VecSize);
     for (unsigned i = 0; i < SVal.getVectorLength(); i++) {
       APValue &Elt = SVal.getVectorElt(i);
       llvm::APInt EltAsInt;
       if (Elt.isInt()) {
         EltAsInt = Elt.getInt();
       } else if (Elt.isFloat()) {
         EltAsInt = Elt.getFloat().bitcastToAPInt();
       } else {
         // Don't try to handle vectors of anything other than int or float
         // (not sure if it's possible to hit this case).
         Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
         return false;
       }
       unsigned BaseEltSize = EltAsInt.getBitWidth();
       if (BigEndian)
         Res |= EltAsInt.zextOrTrunc(VecSize).rotr(i*EltSize+BaseEltSize);
       else
         Res |= EltAsInt.zextOrTrunc(VecSize).rotl(i*EltSize);
     }
     return true;
   }
   // Give up if the input isn't an int, float, or vector.  For example, we
   // reject "(v4i16)(intptr_t)&a".
   Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
   return false;
 }
 
 /// Perform the given integer operation, which is known to need at most BitWidth
 /// bits, and check for overflow in the original type (if that type was not an
 /// unsigned type).
 template<typename Operation>
 static bool CheckedIntArithmetic(EvalInfo &Info, const Expr *E,
                                  const APSInt &LHS, const APSInt &RHS,
                                  unsigned BitWidth, Operation Op,
                                  APSInt &Result) {
   if (LHS.isUnsigned()) {
     Result = Op(LHS, RHS);
     return true;
   }
 
   APSInt Value(Op(LHS.extend(BitWidth), RHS.extend(BitWidth)), false);
   Result = Value.trunc(LHS.getBitWidth());
   if (Result.extend(BitWidth) != Value) {
     if (Info.checkingForUndefinedBehavior())
       Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
                                        diag::warn_integer_constant_overflow)
           << Result.toString(10) << E->getType();
     else
       return HandleOverflow(Info, E, Value, E->getType());
   }
   return true;
 }
 
 /// Perform the given binary integer operation.
 static bool handleIntIntBinOp(EvalInfo &Info, const Expr *E, const APSInt &LHS,
                               BinaryOperatorKind Opcode, APSInt RHS,
                               APSInt &Result) {
   switch (Opcode) {
   default:
     Info.FFDiag(E);
     return false;
   case BO_Mul:
     return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() * 2,
                                 std::multiplies<APSInt>(), Result);
   case BO_Add:
     return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
                                 std::plus<APSInt>(), Result);
   case BO_Sub:
     return CheckedIntArithmetic(Info, E, LHS, RHS, LHS.getBitWidth() + 1,
                                 std::minus<APSInt>(), Result);
   case BO_And: Result = LHS & RHS; return true;
   case BO_Xor: Result = LHS ^ RHS; return true;
   case BO_Or:  Result = LHS | RHS; return true;
   case BO_Div:
   case BO_Rem:
     if (RHS == 0) {
       Info.FFDiag(E, diag::note_expr_divide_by_zero);
       return false;
     }
     Result = (Opcode == BO_Rem ? LHS % RHS : LHS / RHS);
     // Check for overflow case: INT_MIN / -1 or INT_MIN % -1. APSInt supports
     // this operation and gives the two's complement result.
     if (RHS.isNegative() && RHS.isAllOnesValue() &&
         LHS.isSigned() && LHS.isMinSignedValue())
       return HandleOverflow(Info, E, -LHS.extend(LHS.getBitWidth() + 1),
                             E->getType());
     return true;
   case BO_Shl: {
     if (Info.getLangOpts().OpenCL)
       // OpenCL 6.3j: shift values are effectively % word size of LHS.
       RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
                     static_cast<uint64_t>(LHS.getBitWidth() - 1)),
                     RHS.isUnsigned());
     else if (RHS.isSigned() && RHS.isNegative()) {
       // During constant-folding, a negative shift is an opposite shift. Such
       // a shift is not a constant expression.
       Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
       RHS = -RHS;
       goto shift_right;
     }
   shift_left:
     // C++11 [expr.shift]p1: Shift width must be less than the bit width of
     // the shifted type.
     unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
     if (SA != RHS) {
       Info.CCEDiag(E, diag::note_constexpr_large_shift)
         << RHS << E->getType() << LHS.getBitWidth();
     } else if (LHS.isSigned() && !Info.getLangOpts().CPlusPlus20) {
       // C++11 [expr.shift]p2: A signed left shift must have a non-negative
       // operand, and must not overflow the corresponding unsigned type.
       // C++2a [expr.shift]p2: E1 << E2 is the unique value congruent to
       // E1 x 2^E2 module 2^N.
       if (LHS.isNegative())
         Info.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS;
       else if (LHS.countLeadingZeros() < SA)
         Info.CCEDiag(E, diag::note_constexpr_lshift_discards);
     }
     Result = LHS << SA;
     return true;
   }
   case BO_Shr: {
     if (Info.getLangOpts().OpenCL)
       // OpenCL 6.3j: shift values are effectively % word size of LHS.
       RHS &= APSInt(llvm::APInt(RHS.getBitWidth(),
                     static_cast<uint64_t>(LHS.getBitWidth() - 1)),
                     RHS.isUnsigned());
     else if (RHS.isSigned() && RHS.isNegative()) {
       // During constant-folding, a negative shift is an opposite shift. Such a
       // shift is not a constant expression.
       Info.CCEDiag(E, diag::note_constexpr_negative_shift) << RHS;
       RHS = -RHS;
       goto shift_left;
     }
   shift_right:
     // C++11 [expr.shift]p1: Shift width must be less than the bit width of the
     // shifted type.
     unsigned SA = (unsigned) RHS.getLimitedValue(LHS.getBitWidth()-1);
     if (SA != RHS)
       Info.CCEDiag(E, diag::note_constexpr_large_shift)
         << RHS << E->getType() << LHS.getBitWidth();
     Result = LHS >> SA;
     return true;
   }
 
   case BO_LT: Result = LHS < RHS; return true;
   case BO_GT: Result = LHS > RHS; return true;
   case BO_LE: Result = LHS <= RHS; return true;
   case BO_GE: Result = LHS >= RHS; return true;
   case BO_EQ: Result = LHS == RHS; return true;
   case BO_NE: Result = LHS != RHS; return true;
   case BO_Cmp:
     llvm_unreachable("BO_Cmp should be handled elsewhere");
   }
 }
 
 /// Perform the given binary floating-point operation, in-place, on LHS.
 static bool handleFloatFloatBinOp(EvalInfo &Info, const Expr *E,
                                   APFloat &LHS, BinaryOperatorKind Opcode,
                                   const APFloat &RHS) {
   switch (Opcode) {
   default:
     Info.FFDiag(E);
     return false;
   case BO_Mul:
     LHS.multiply(RHS, APFloat::rmNearestTiesToEven);
     break;
   case BO_Add:
     LHS.add(RHS, APFloat::rmNearestTiesToEven);
     break;
   case BO_Sub:
     LHS.subtract(RHS, APFloat::rmNearestTiesToEven);
     break;
   case BO_Div:
     // [expr.mul]p4:
     //   If the second operand of / or % is zero the behavior is undefined.
     if (RHS.isZero())
       Info.CCEDiag(E, diag::note_expr_divide_by_zero);
     LHS.divide(RHS, APFloat::rmNearestTiesToEven);
     break;
   }
 
   // [expr.pre]p4:
   //   If during the evaluation of an expression, the result is not
   //   mathematically defined [...], the behavior is undefined.
   // FIXME: C++ rules require us to not conform to IEEE 754 here.
   if (LHS.isNaN()) {
     Info.CCEDiag(E, diag::note_constexpr_float_arithmetic) << LHS.isNaN();
     return Info.noteUndefinedBehavior();
   }
   return true;
 }
 
 static bool handleLogicalOpForVector(const APInt &LHSValue,
                                      BinaryOperatorKind Opcode,
                                      const APInt &RHSValue, APInt &Result) {
   bool LHS = (LHSValue != 0);
   bool RHS = (RHSValue != 0);
 
   if (Opcode == BO_LAnd)
     Result = LHS && RHS;
   else
     Result = LHS || RHS;
   return true;
 }
 static bool handleLogicalOpForVector(const APFloat &LHSValue,
                                      BinaryOperatorKind Opcode,
                                      const APFloat &RHSValue, APInt &Result) {
   bool LHS = !LHSValue.isZero();
   bool RHS = !RHSValue.isZero();
 
   if (Opcode == BO_LAnd)
     Result = LHS && RHS;
   else
     Result = LHS || RHS;
   return true;
 }
 
 static bool handleLogicalOpForVector(const APValue &LHSValue,
                                      BinaryOperatorKind Opcode,
                                      const APValue &RHSValue, APInt &Result) {
   // The result is always an int type, however operands match the first.
   if (LHSValue.getKind() == APValue::Int)
     return handleLogicalOpForVector(LHSValue.getInt(), Opcode,
                                     RHSValue.getInt(), Result);
   assert(LHSValue.getKind() == APValue::Float && "Should be no other options");
   return handleLogicalOpForVector(LHSValue.getFloat(), Opcode,
                                   RHSValue.getFloat(), Result);
 }
 
 template <typename APTy>
 static bool
 handleCompareOpForVectorHelper(const APTy &LHSValue, BinaryOperatorKind Opcode,
                                const APTy &RHSValue, APInt &Result) {
   switch (Opcode) {
   default:
     llvm_unreachable("unsupported binary operator");
   case BO_EQ:
     Result = (LHSValue == RHSValue);
     break;
   case BO_NE:
     Result = (LHSValue != RHSValue);
     break;
   case BO_LT:
     Result = (LHSValue < RHSValue);
     break;
   case BO_GT:
     Result = (LHSValue > RHSValue);
     break;
   case BO_LE:
     Result = (LHSValue <= RHSValue);
     break;
   case BO_GE:
     Result = (LHSValue >= RHSValue);
     break;
   }
 
   return true;
 }
 
 static bool handleCompareOpForVector(const APValue &LHSValue,
                                      BinaryOperatorKind Opcode,
                                      const APValue &RHSValue, APInt &Result) {
   // The result is always an int type, however operands match the first.
   if (LHSValue.getKind() == APValue::Int)
     return handleCompareOpForVectorHelper(LHSValue.getInt(), Opcode,
                                           RHSValue.getInt(), Result);
   assert(LHSValue.getKind() == APValue::Float && "Should be no other options");
   return handleCompareOpForVectorHelper(LHSValue.getFloat(), Opcode,
                                         RHSValue.getFloat(), Result);
 }
 
 // Perform binary operations for vector types, in place on the LHS.
 static bool handleVectorVectorBinOp(EvalInfo &Info, const Expr *E,
                                     BinaryOperatorKind Opcode,
                                     APValue &LHSValue,
                                     const APValue &RHSValue) {
   assert(Opcode != BO_PtrMemD && Opcode != BO_PtrMemI &&
          "Operation not supported on vector types");
 
   const auto *VT = E->getType()->castAs<VectorType>();
   unsigned NumElements = VT->getNumElements();
   QualType EltTy = VT->getElementType();
 
   // In the cases (typically C as I've observed) where we aren't evaluating
   // constexpr but are checking for cases where the LHS isn't yet evaluatable,
   // just give up.
   if (!LHSValue.isVector()) {
     assert(LHSValue.isLValue() &&
            "A vector result that isn't a vector OR uncalculated LValue");
     Info.FFDiag(E);
     return false;
   }
 
   assert(LHSValue.getVectorLength() == NumElements &&
          RHSValue.getVectorLength() == NumElements && "Different vector sizes");
 
   SmallVector<APValue, 4> ResultElements;
 
   for (unsigned EltNum = 0; EltNum < NumElements; ++EltNum) {
     APValue LHSElt = LHSValue.getVectorElt(EltNum);
     APValue RHSElt = RHSValue.getVectorElt(EltNum);
 
     if (EltTy->isIntegerType()) {
       APSInt EltResult{Info.Ctx.getIntWidth(EltTy),
                        EltTy->isUnsignedIntegerType()};
       bool Success = true;
 
       if (BinaryOperator::isLogicalOp(Opcode))
         Success = handleLogicalOpForVector(LHSElt, Opcode, RHSElt, EltResult);
       else if (BinaryOperator::isComparisonOp(Opcode))
         Success = handleCompareOpForVector(LHSElt, Opcode, RHSElt, EltResult);
       else
         Success = handleIntIntBinOp(Info, E, LHSElt.getInt(), Opcode,
                                     RHSElt.getInt(), EltResult);
 
       if (!Success) {
         Info.FFDiag(E);
         return false;
       }
       ResultElements.emplace_back(EltResult);
 
     } else if (EltTy->isFloatingType()) {
       assert(LHSElt.getKind() == APValue::Float &&
              RHSElt.getKind() == APValue::Float &&
              "Mismatched LHS/RHS/Result Type");
       APFloat LHSFloat = LHSElt.getFloat();
 
       if (!handleFloatFloatBinOp(Info, E, LHSFloat, Opcode,
                                  RHSElt.getFloat())) {
         Info.FFDiag(E);
         return false;
       }
 
       ResultElements.emplace_back(LHSFloat);
     }
   }
 
   LHSValue = APValue(ResultElements.data(), ResultElements.size());
   return true;
 }
 
 /// Cast an lvalue referring to a base subobject to a derived class, by
 /// truncating the lvalue's path to the given length.
 static bool CastToDerivedClass(EvalInfo &Info, const Expr *E, LValue &Result,
                                const RecordDecl *TruncatedType,
                                unsigned TruncatedElements) {
   SubobjectDesignator &D = Result.Designator;
 
   // Check we actually point to a derived class object.
   if (TruncatedElements == D.Entries.size())
     return true;
   assert(TruncatedElements >= D.MostDerivedPathLength &&
          "not casting to a derived class");
   if (!Result.checkSubobject(Info, E, CSK_Derived))
     return false;
 
   // Truncate the path to the subobject, and remove any derived-to-base offsets.
   const RecordDecl *RD = TruncatedType;
   for (unsigned I = TruncatedElements, N = D.Entries.size(); I != N; ++I) {
     if (RD->isInvalidDecl()) return false;
     const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
     const CXXRecordDecl *Base = getAsBaseClass(D.Entries[I]);
     if (isVirtualBaseClass(D.Entries[I]))
       Result.Offset -= Layout.getVBaseClassOffset(Base);
     else
       Result.Offset -= Layout.getBaseClassOffset(Base);
     RD = Base;
   }
   D.Entries.resize(TruncatedElements);
   return true;
 }
 
 static bool HandleLValueDirectBase(EvalInfo &Info, const Expr *E, LValue &Obj,
                                    const CXXRecordDecl *Derived,
                                    const CXXRecordDecl *Base,
                                    const ASTRecordLayout *RL = nullptr) {
   if (!RL) {
     if (Derived->isInvalidDecl()) return false;
     RL = &Info.Ctx.getASTRecordLayout(Derived);
   }
 
   Obj.getLValueOffset() += RL->getBaseClassOffset(Base);
   Obj.addDecl(Info, E, Base, /*Virtual*/ false);
   return true;
 }
 
 static bool HandleLValueBase(EvalInfo &Info, const Expr *E, LValue &Obj,
                              const CXXRecordDecl *DerivedDecl,
                              const CXXBaseSpecifier *Base) {
   const CXXRecordDecl *BaseDecl = Base->getType()->getAsCXXRecordDecl();
 
   if (!Base->isVirtual())
     return HandleLValueDirectBase(Info, E, Obj, DerivedDecl, BaseDecl);
 
   SubobjectDesignator &D = Obj.Designator;
   if (D.Invalid)
     return false;
 
   // Extract most-derived object and corresponding type.
   DerivedDecl = D.MostDerivedType->getAsCXXRecordDecl();
   if (!CastToDerivedClass(Info, E, Obj, DerivedDecl, D.MostDerivedPathLength))
     return false;
 
   // Find the virtual base class.
   if (DerivedDecl->isInvalidDecl()) return false;
   const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(DerivedDecl);
   Obj.getLValueOffset() += Layout.getVBaseClassOffset(BaseDecl);
   Obj.addDecl(Info, E, BaseDecl, /*Virtual*/ true);
   return true;
 }
 
 static bool HandleLValueBasePath(EvalInfo &Info, const CastExpr *E,
                                  QualType Type, LValue &Result) {
   for (CastExpr::path_const_iterator PathI = E->path_begin(),
                                      PathE = E->path_end();
        PathI != PathE; ++PathI) {
     if (!HandleLValueBase(Info, E, Result, Type->getAsCXXRecordDecl(),
                           *PathI))
       return false;
     Type = (*PathI)->getType();
   }
   return true;
 }
 
 /// Cast an lvalue referring to a derived class to a known base subobject.
 static bool CastToBaseClass(EvalInfo &Info, const Expr *E, LValue &Result,
                             const CXXRecordDecl *DerivedRD,
                             const CXXRecordDecl *BaseRD) {
   CXXBasePaths Paths(/*FindAmbiguities=*/false,
                      /*RecordPaths=*/true, /*DetectVirtual=*/false);
   if (!DerivedRD->isDerivedFrom(BaseRD, Paths))
     llvm_unreachable("Class must be derived from the passed in base class!");
 
   for (CXXBasePathElement &Elem : Paths.front())
     if (!HandleLValueBase(Info, E, Result, Elem.Class, Elem.Base))
       return false;
   return true;
 }
 
 /// Update LVal to refer to the given field, which must be a member of the type
 /// currently described by LVal.
 static bool HandleLValueMember(EvalInfo &Info, const Expr *E, LValue &LVal,
                                const FieldDecl *FD,
                                const ASTRecordLayout *RL = nullptr) {
   if (!RL) {
     if (FD->getParent()->isInvalidDecl()) return false;
     RL = &Info.Ctx.getASTRecordLayout(FD->getParent());
   }
 
   unsigned I = FD->getFieldIndex();
   LVal.adjustOffset(Info.Ctx.toCharUnitsFromBits(RL->getFieldOffset(I)));
   LVal.addDecl(Info, E, FD);
   return true;
 }
 
 /// Update LVal to refer to the given indirect field.
 static bool HandleLValueIndirectMember(EvalInfo &Info, const Expr *E,
                                        LValue &LVal,
                                        const IndirectFieldDecl *IFD) {
   for (const auto *C : IFD->chain())
     if (!HandleLValueMember(Info, E, LVal, cast<FieldDecl>(C)))
       return false;
   return true;
 }
 
 /// Get the size of the given type in char units.
 static bool HandleSizeof(EvalInfo &Info, SourceLocation Loc,
                          QualType Type, CharUnits &Size) {
   // sizeof(void), __alignof__(void), sizeof(function) = 1 as a gcc
   // extension.
   if (Type->isVoidType() || Type->isFunctionType()) {
     Size = CharUnits::One();
     return true;
   }
 
   if (Type->isDependentType()) {
     Info.FFDiag(Loc);
     return false;
   }
 
   if (!Type->isConstantSizeType()) {
     // sizeof(vla) is not a constantexpr: C99 6.5.3.4p2.
     // FIXME: Better diagnostic.
     Info.FFDiag(Loc);
     return false;
   }
 
   Size = Info.Ctx.getTypeSizeInChars(Type);
   return true;
 }
 
 /// Update a pointer value to model pointer arithmetic.
 /// \param Info - Information about the ongoing evaluation.
 /// \param E - The expression being evaluated, for diagnostic purposes.
 /// \param LVal - The pointer value to be updated.
 /// \param EltTy - The pointee type represented by LVal.
 /// \param Adjustment - The adjustment, in objects of type EltTy, to add.
 static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
                                         LValue &LVal, QualType EltTy,
                                         APSInt Adjustment) {
   CharUnits SizeOfPointee;
   if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfPointee))
     return false;
 
   LVal.adjustOffsetAndIndex(Info, E, Adjustment, SizeOfPointee);
   return true;
 }
 
 static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
                                         LValue &LVal, QualType EltTy,
                                         int64_t Adjustment) {
   return HandleLValueArrayAdjustment(Info, E, LVal, EltTy,
                                      APSInt::get(Adjustment));
 }
 
 /// Update an lvalue to refer to a component of a complex number.
 /// \param Info - Information about the ongoing evaluation.
 /// \param LVal - The lvalue to be updated.
 /// \param EltTy - The complex number's component type.
 /// \param Imag - False for the real component, true for the imaginary.
 static bool HandleLValueComplexElement(EvalInfo &Info, const Expr *E,
                                        LValue &LVal, QualType EltTy,
                                        bool Imag) {
   if (Imag) {
     CharUnits SizeOfComponent;
     if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfComponent))
       return false;
     LVal.Offset += SizeOfComponent;
   }
   LVal.addComplex(Info, E, EltTy, Imag);
   return true;
 }
 
 /// Try to evaluate the initializer for a variable declaration.
 ///
 /// \param Info   Information about the ongoing evaluation.
 /// \param E      An expression to be used when printing diagnostics.
 /// \param VD     The variable whose initializer should be obtained.
 /// \param Frame  The frame in which the variable was created. Must be null
 ///               if this variable is not local to the evaluation.
 /// \param Result Filled in with a pointer to the value of the variable.
 static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
                                 const VarDecl *VD, CallStackFrame *Frame,
                                 APValue *&Result, const LValue *LVal) {
 
   // If this is a parameter to an active constexpr function call, perform
   // argument substitution.
   if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(VD)) {
     // Assume arguments of a potential constant expression are unknown
     // constant expressions.
     if (Info.checkingPotentialConstantExpression())
       return false;
     if (!Frame || !Frame->Arguments) {
       Info.FFDiag(E, diag::note_constexpr_function_param_value_unknown) << VD;
       return false;
     }
     Result = &Frame->Arguments[PVD->getFunctionScopeIndex()];
     return true;
   }
 
   // If this is a local variable, dig out its value.
   if (Frame) {
     Result = LVal ? Frame->getTemporary(VD, LVal->getLValueVersion())
                   : Frame->getCurrentTemporary(VD);
     if (!Result) {
       // Assume variables referenced within a lambda's call operator that were
       // not declared within the call operator are captures and during checking
       // of a potential constant expression, assume they are unknown constant
       // expressions.
       assert(isLambdaCallOperator(Frame->Callee) &&
              (VD->getDeclContext() != Frame->Callee || VD->isInitCapture()) &&
              "missing value for local variable");
       if (Info.checkingPotentialConstantExpression())
         return false;
       // FIXME: implement capture evaluation during constant expr evaluation.
       Info.FFDiag(E->getBeginLoc(),
                   diag::note_unimplemented_constexpr_lambda_feature_ast)
           << "captures not currently allowed";
       return false;
     }
     return true;
   }
 
   // Dig out the initializer, and use the declaration which it's attached to.
   // FIXME: We should eventually check whether the variable has a reachable
   // initializing declaration.
   const Expr *Init = VD->getAnyInitializer(VD);
   if (!Init) {
     // Don't diagnose during potential constant expression checking; an
     // initializer might be added later.
     if (!Info.checkingPotentialConstantExpression()) {
       Info.FFDiag(E, diag::note_constexpr_var_init_unknown, 1)
         << VD;
       Info.Note(VD->getLocation(), diag::note_declared_at);
     }
     return false;
   }
 
   if (Init->isValueDependent()) {
     // The DeclRefExpr is not value-dependent, but the variable it refers to
     // has a value-dependent initializer. This should only happen in
     // constant-folding cases, where the variable is not actually of a suitable
     // type for use in a constant expression (otherwise the DeclRefExpr would
     // have been value-dependent too), so diagnose that.
     assert(!VD->mightBeUsableInConstantExpressions(Info.Ctx));
     if (!Info.checkingPotentialConstantExpression()) {
       Info.FFDiag(E, Info.getLangOpts().CPlusPlus11
                          ? diag::note_constexpr_ltor_non_constexpr
                          : diag::note_constexpr_ltor_non_integral, 1)
           << VD << VD->getType();
       Info.Note(VD->getLocation(), diag::note_declared_at);
     }
     return false;
   }
 
   // If we're currently evaluating the initializer of this declaration, use that
   // in-flight value.
   if (Info.EvaluatingDecl.dyn_cast<const ValueDecl*>() == VD) {
     Result = Info.EvaluatingDeclValue;
     return true;
   }
 
   // Check that we can fold the initializer. In C++, we will have already done
   // this in the cases where it matters for conformance.
   SmallVector<PartialDiagnosticAt, 8> Notes;
   if (!VD->evaluateValue(Notes)) {
     Info.FFDiag(E, diag::note_constexpr_var_init_non_constant,
               Notes.size() + 1) << VD;
     Info.Note(VD->getLocation(), diag::note_declared_at);
     Info.addNotes(Notes);
     return false;
   }
 
   // Check that the variable is actually usable in constant expressions.
   if (!VD->checkInitIsICE()) {
     Info.CCEDiag(E, diag::note_constexpr_var_init_non_constant,
                  Notes.size() + 1) << VD;
     Info.Note(VD->getLocation(), diag::note_declared_at);
     Info.addNotes(Notes);
   }
 
   // Never use the initializer of a weak variable, not even for constant
   // folding. We can't be sure that this is the definition that will be used.
   if (VD->isWeak()) {
     Info.FFDiag(E, diag::note_constexpr_var_init_weak) << VD;
     Info.Note(VD->getLocation(), diag::note_declared_at);
     return false;
   }
 
   Result = VD->getEvaluatedValue();
   return true;
 }
 
 static bool IsConstNonVolatile(QualType T) {
   Qualifiers Quals = T.getQualifiers();
   return Quals.hasConst() && !Quals.hasVolatile();
 }
 
 /// Get the base index of the given base class within an APValue representing
 /// the given derived class.
 static unsigned getBaseIndex(const CXXRecordDecl *Derived,
                              const CXXRecordDecl *Base) {
   Base = Base->getCanonicalDecl();
   unsigned Index = 0;
   for (CXXRecordDecl::base_class_const_iterator I = Derived->bases_begin(),
          E = Derived->bases_end(); I != E; ++I, ++Index) {
     if (I->getType()->getAsCXXRecordDecl()->getCanonicalDecl() == Base)
       return Index;
   }
 
   llvm_unreachable("base class missing from derived class's bases list");
 }
 
 /// Extract the value of a character from a string literal.
 static APSInt extractStringLiteralCharacter(EvalInfo &Info, const Expr *Lit,
                                             uint64_t Index) {
   assert(!isa<SourceLocExpr>(Lit) &&
          "SourceLocExpr should have already been converted to a StringLiteral");
 
   // FIXME: Support MakeStringConstant
   if (const auto *ObjCEnc = dyn_cast<ObjCEncodeExpr>(Lit)) {
     std::string Str;
     Info.Ctx.getObjCEncodingForType(ObjCEnc->getEncodedType(), Str);
     assert(Index <= Str.size() && "Index too large");
     return APSInt::getUnsigned(Str.c_str()[Index]);
   }
 
   if (auto PE = dyn_cast<PredefinedExpr>(Lit))
     Lit = PE->getFunctionName();
   const StringLiteral *S = cast<StringLiteral>(Lit);
   const ConstantArrayType *CAT =
       Info.Ctx.getAsConstantArrayType(S->getType());
   assert(CAT && "string literal isn't an array");
   QualType CharType = CAT->getElementType();
   assert(CharType->isIntegerType() && "unexpected character type");
 
   APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
                CharType->isUnsignedIntegerType());
   if (Index < S->getLength())
     Value = S->getCodeUnit(Index);
   return Value;
 }
 
 // Expand a string literal into an array of characters.
 //
 // FIXME: This is inefficient; we should probably introduce something similar
 // to the LLVM ConstantDataArray to make this cheaper.
 static void expandStringLiteral(EvalInfo &Info, const StringLiteral *S,
                                 APValue &Result,
                                 QualType AllocType = QualType()) {
   const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(
       AllocType.isNull() ? S->getType() : AllocType);
   assert(CAT && "string literal isn't an array");
   QualType CharType = CAT->getElementType();
   assert(CharType->isIntegerType() && "unexpected character type");
 
   unsigned Elts = CAT->getSize().getZExtValue();
   Result = APValue(APValue::UninitArray(),
                    std::min(S->getLength(), Elts), Elts);
   APSInt Value(S->getCharByteWidth() * Info.Ctx.getCharWidth(),
                CharType->isUnsignedIntegerType());
   if (Result.hasArrayFiller())
     Result.getArrayFiller() = APValue(Value);
   for (unsigned I = 0, N = Result.getArrayInitializedElts(); I != N; ++I) {
     Value = S->getCodeUnit(I);
     Result.getArrayInitializedElt(I) = APValue(Value);
   }
 }
 
 // Expand an array so that it has more than Index filled elements.
 static void expandArray(APValue &Array, unsigned Index) {
   unsigned Size = Array.getArraySize();
   assert(Index < Size);
 
   // Always at least double the number of elements for which we store a value.
   unsigned OldElts = Array.getArrayInitializedElts();
   unsigned NewElts = std::max(Index+1, OldElts * 2);
   NewElts = std::min(Size, std::max(NewElts, 8u));
 
   // Copy the data across.
   APValue NewValue(APValue::UninitArray(), NewElts, Size);
   for (unsigned I = 0; I != OldElts; ++I)
     NewValue.getArrayInitializedElt(I).swap(Array.getArrayInitializedElt(I));
   for (unsigned I = OldElts; I != NewElts; ++I)
     NewValue.getArrayInitializedElt(I) = Array.getArrayFiller();
   if (NewValue.hasArrayFiller())
     NewValue.getArrayFiller() = Array.getArrayFiller();
   Array.swap(NewValue);
 }
 
 /// Determine whether a type would actually be read by an lvalue-to-rvalue
 /// conversion. If it's of class type, we may assume that the copy operation
 /// is trivial. Note that this is never true for a union type with fields
 /// (because the copy always "reads" the active member) and always true for
 /// a non-class type.
 static bool isReadByLvalueToRvalueConversion(const CXXRecordDecl *RD);
 static bool isReadByLvalueToRvalueConversion(QualType T) {
   CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
   return !RD || isReadByLvalueToRvalueConversion(RD);
 }
 static bool isReadByLvalueToRvalueConversion(const CXXRecordDecl *RD) {
   // FIXME: A trivial copy of a union copies the object representation, even if
   // the union is empty.
   if (RD->isUnion())
     return !RD->field_empty();
   if (RD->isEmpty())
     return false;
 
   for (auto *Field : RD->fields())
     if (!Field->isUnnamedBitfield() &&
         isReadByLvalueToRvalueConversion(Field->getType()))
       return true;
 
   for (auto &BaseSpec : RD->bases())
     if (isReadByLvalueToRvalueConversion(BaseSpec.getType()))
       return true;
 
   return false;
 }
 
 /// Diagnose an attempt to read from any unreadable field within the specified
 /// type, which might be a class type.
 static bool diagnoseMutableFields(EvalInfo &Info, const Expr *E, AccessKinds AK,
                                   QualType T) {
   CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
   if (!RD)
     return false;
 
   if (!RD->hasMutableFields())
     return false;
 
   for (auto *Field : RD->fields()) {
     // If we're actually going to read this field in some way, then it can't
     // be mutable. If we're in a union, then assigning to a mutable field
     // (even an empty one) can change the active member, so that's not OK.
     // FIXME: Add core issue number for the union case.
     if (Field->isMutable() &&
         (RD->isUnion() || isReadByLvalueToRvalueConversion(Field->getType()))) {
       Info.FFDiag(E, diag::note_constexpr_access_mutable, 1) << AK << Field;
       Info.Note(Field->getLocation(), diag::note_declared_at);
       return true;
     }
 
     if (diagnoseMutableFields(Info, E, AK, Field->getType()))
       return true;
   }
 
   for (auto &BaseSpec : RD->bases())
     if (diagnoseMutableFields(Info, E, AK, BaseSpec.getType()))
       return true;
 
   // All mutable fields were empty, and thus not actually read.
   return false;
 }
 
 static bool lifetimeStartedInEvaluation(EvalInfo &Info,
                                         APValue::LValueBase Base,
                                         bool MutableSubobject = false) {
   // A temporary we created.
   if (Base.getCallIndex())
     return true;
 
   auto *Evaluating = Info.EvaluatingDecl.dyn_cast<const ValueDecl*>();
   if (!Evaluating)
     return false;
 
   auto *BaseD = Base.dyn_cast<const ValueDecl*>();
 
   switch (Info.IsEvaluatingDecl) {
   case EvalInfo::EvaluatingDeclKind::None:
     return false;
 
   case EvalInfo::EvaluatingDeclKind::Ctor:
     // The variable whose initializer we're evaluating.
     if (BaseD)
       return declaresSameEntity(Evaluating, BaseD);
 
     // A temporary lifetime-extended by the variable whose initializer we're
     // evaluating.
     if (auto *BaseE = Base.dyn_cast<const Expr *>())
       if (auto *BaseMTE = dyn_cast<MaterializeTemporaryExpr>(BaseE))
         return declaresSameEntity(BaseMTE->getExtendingDecl(), Evaluating);
     return false;
 
   case EvalInfo::EvaluatingDeclKind::Dtor:
     // C++2a [expr.const]p6:
     //   [during constant destruction] the lifetime of a and its non-mutable
     //   subobjects (but not its mutable subobjects) [are] considered to start
     //   within e.
     //
     // FIXME: We can meaningfully extend this to cover non-const objects, but
     // we will need special handling: we should be able to access only
     // subobjects of such objects that are themselves declared const.
     if (!BaseD ||
         !(BaseD->getType().isConstQualified() ||
           BaseD->getType()->isReferenceType()) ||
         MutableSubobject)
       return false;
     return declaresSameEntity(Evaluating, BaseD);
   }
 
   llvm_unreachable("unknown evaluating decl kind");
 }
 
 namespace {
 /// A handle to a complete object (an object that is not a subobject of
 /// another object).
 struct CompleteObject {
   /// The identity of the object.
   APValue::LValueBase Base;
   /// The value of the complete object.
   APValue *Value;
   /// The type of the complete object.
   QualType Type;
 
   CompleteObject() : Value(nullptr) {}
   CompleteObject(APValue::LValueBase Base, APValue *Value, QualType Type)
       : Base(Base), Value(Value), Type(Type) {}
 
   bool mayAccessMutableMembers(EvalInfo &Info, AccessKinds AK) const {
     // If this isn't a "real" access (eg, if it's just accessing the type
     // info), allow it. We assume the type doesn't change dynamically for
     // subobjects of constexpr objects (even though we'd hit UB here if it
     // did). FIXME: Is this right?
     if (!isAnyAccess(AK))
       return true;
 
     // In C++14 onwards, it is permitted to read a mutable member whose
     // lifetime began within the evaluation.
     // FIXME: Should we also allow this in C++11?
     if (!Info.getLangOpts().CPlusPlus14)
       return false;
     return lifetimeStartedInEvaluation(Info, Base, /*MutableSubobject*/true);
   }
 
   explicit operator bool() const { return !Type.isNull(); }
 };
 } // end anonymous namespace
 
 static QualType getSubobjectType(QualType ObjType, QualType SubobjType,
                                  bool IsMutable = false) {
   // C++ [basic.type.qualifier]p1:
   // - A const object is an object of type const T or a non-mutable subobject
   //   of a const object.
   if (ObjType.isConstQualified() && !IsMutable)
     SubobjType.addConst();
   // - A volatile object is an object of type const T or a subobject of a
   //   volatile object.
   if (ObjType.isVolatileQualified())
     SubobjType.addVolatile();
   return SubobjType;
 }
 
 /// Find the designated sub-object of an rvalue.
 template<typename SubobjectHandler>
 typename SubobjectHandler::result_type
 findSubobject(EvalInfo &Info, const Expr *E, const CompleteObject &Obj,
               const SubobjectDesignator &Sub, SubobjectHandler &handler) {
   if (Sub.Invalid)
     // A diagnostic will have already been produced.
     return handler.failed();
   if (Sub.isOnePastTheEnd() || Sub.isMostDerivedAnUnsizedArray()) {
     if (Info.getLangOpts().CPlusPlus11)
       Info.FFDiag(E, Sub.isOnePastTheEnd()
                          ? diag::note_constexpr_access_past_end
                          : diag::note_constexpr_access_unsized_array)
           << handler.AccessKind;
     else
       Info.FFDiag(E);
     return handler.failed();
   }
 
   APValue *O = Obj.Value;
   QualType ObjType = Obj.Type;
   const FieldDecl *LastField = nullptr;
   const FieldDecl *VolatileField = nullptr;
 
   // Walk the designator's path to find the subobject.
   for (unsigned I = 0, N = Sub.Entries.size(); /**/; ++I) {
     // Reading an indeterminate value is undefined, but assigning over one is OK.
     if ((O->isAbsent() && !(handler.AccessKind == AK_Construct && I == N)) ||
         (O->isIndeterminate() &&
          !isValidIndeterminateAccess(handler.AccessKind))) {
       if (!Info.checkingPotentialConstantExpression())
         Info.FFDiag(E, diag::note_constexpr_access_uninit)
             << handler.AccessKind << O->isIndeterminate();
       return handler.failed();
     }
 
     // C++ [class.ctor]p5, C++ [class.dtor]p5:
     //    const and volatile semantics are not applied on an object under
     //    {con,de}struction.
     if ((ObjType.isConstQualified() || ObjType.isVolatileQualified()) &&
         ObjType->isRecordType() &&
         Info.isEvaluatingCtorDtor(
             Obj.Base, llvm::makeArrayRef(Sub.Entries.begin(),
                                          Sub.Entries.begin() + I)) !=
                           ConstructionPhase::None) {
       ObjType = Info.Ctx.getCanonicalType(ObjType);
       ObjType.removeLocalConst();
       ObjType.removeLocalVolatile();
     }
 
     // If this is our last pass, check that the final object type is OK.
     if (I == N || (I == N - 1 && ObjType->isAnyComplexType())) {
       // Accesses to volatile objects are prohibited.
       if (ObjType.isVolatileQualified() && isFormalAccess(handler.AccessKind)) {
         if (Info.getLangOpts().CPlusPlus) {
           int DiagKind;
           SourceLocation Loc;
           const NamedDecl *Decl = nullptr;
           if (VolatileField) {
             DiagKind = 2;
             Loc = VolatileField->getLocation();
             Decl = VolatileField;
           } else if (auto *VD = Obj.Base.dyn_cast<const ValueDecl*>()) {
             DiagKind = 1;
             Loc = VD->getLocation();
             Decl = VD;
           } else {
             DiagKind = 0;
             if (auto *E = Obj.Base.dyn_cast<const Expr *>())
               Loc = E->getExprLoc();
           }
           Info.FFDiag(E, diag::note_constexpr_access_volatile_obj, 1)
               << handler.AccessKind << DiagKind << Decl;
           Info.Note(Loc, diag::note_constexpr_volatile_here) << DiagKind;
         } else {
           Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
         }
         return handler.failed();
       }
 
       // If we are reading an object of class type, there may still be more
       // things we need to check: if there are any mutable subobjects, we
       // cannot perform this read. (This only happens when performing a trivial
       // copy or assignment.)
       if (ObjType->isRecordType() &&
           !Obj.mayAccessMutableMembers(Info, handler.AccessKind) &&
           diagnoseMutableFields(Info, E, handler.AccessKind, ObjType))
         return handler.failed();
     }
 
     if (I == N) {
       if (!handler.found(*O, ObjType))
         return false;
 
       // If we modified a bit-field, truncate it to the right width.
       if (isModification(handler.AccessKind) &&
           LastField && LastField->isBitField() &&
           !truncateBitfieldValue(Info, E, *O, LastField))
         return false;
 
       return true;
     }
 
     LastField = nullptr;
     if (ObjType->isArrayType()) {
       // Next subobject is an array element.
       const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(ObjType);
       assert(CAT && "vla in literal type?");
       uint64_t Index = Sub.Entries[I].getAsArrayIndex();
       if (CAT->getSize().ule(Index)) {
         // Note, it should not be possible to form a pointer with a valid
         // designator which points more than one past the end of the array.
         if (Info.getLangOpts().CPlusPlus11)
           Info.FFDiag(E, diag::note_constexpr_access_past_end)
             << handler.AccessKind;
         else
           Info.FFDiag(E);
         return handler.failed();
       }
 
       ObjType = CAT->getElementType();
 
       if (O->getArrayInitializedElts() > Index)
         O = &O->getArrayInitializedElt(Index);
       else if (!isRead(handler.AccessKind)) {
         expandArray(*O, Index);
         O = &O->getArrayInitializedElt(Index);
       } else
         O = &O->getArrayFiller();
     } else if (ObjType->isAnyComplexType()) {
       // Next subobject is a complex number.
       uint64_t Index = Sub.Entries[I].getAsArrayIndex();
       if (Index > 1) {
         if (Info.getLangOpts().CPlusPlus11)
           Info.FFDiag(E, diag::note_constexpr_access_past_end)
             << handler.AccessKind;
         else
           Info.FFDiag(E);
         return handler.failed();
       }
 
       ObjType = getSubobjectType(
           ObjType, ObjType->castAs<ComplexType>()->getElementType());
 
       assert(I == N - 1 && "extracting subobject of scalar?");
       if (O->isComplexInt()) {
         return handler.found(Index ? O->getComplexIntImag()
                                    : O->getComplexIntReal(), ObjType);
       } else {
         assert(O->isComplexFloat());
         return handler.found(Index ? O->getComplexFloatImag()
                                    : O->getComplexFloatReal(), ObjType);
       }
     } else if (const FieldDecl *Field = getAsField(Sub.Entries[I])) {
       if (Field->isMutable() &&
           !Obj.mayAccessMutableMembers(Info, handler.AccessKind)) {
         Info.FFDiag(E, diag::note_constexpr_access_mutable, 1)
           << handler.AccessKind << Field;
         Info.Note(Field->getLocation(), diag::note_declared_at);
         return handler.failed();
       }
 
       // Next subobject is a class, struct or union field.
       RecordDecl *RD = ObjType->castAs<RecordType>()->getDecl();
       if (RD->isUnion()) {
         const FieldDecl *UnionField = O->getUnionField();
         if (!UnionField ||
             UnionField->getCanonicalDecl() != Field->getCanonicalDecl()) {
           if (I == N - 1 && handler.AccessKind == AK_Construct) {
             // Placement new onto an inactive union member makes it active.
             O->setUnion(Field, APValue());
           } else {
             // FIXME: If O->getUnionValue() is absent, report that there's no
             // active union member rather than reporting the prior active union
             // member. We'll need to fix nullptr_t to not use APValue() as its
             // representation first.
             Info.FFDiag(E, diag::note_constexpr_access_inactive_union_member)
                 << handler.AccessKind << Field << !UnionField << UnionField;
             return handler.failed();
           }
         }
         O = &O->getUnionValue();
       } else
         O = &O->getStructField(Field->getFieldIndex());
 
       ObjType = getSubobjectType(ObjType, Field->getType(), Field->isMutable());
       LastField = Field;
       if (Field->getType().isVolatileQualified())
         VolatileField = Field;
     } else {
       // Next subobject is a base class.
       const CXXRecordDecl *Derived = ObjType->getAsCXXRecordDecl();
       const CXXRecordDecl *Base = getAsBaseClass(Sub.Entries[I]);
       O = &O->getStructBase(getBaseIndex(Derived, Base));
 
       ObjType = getSubobjectType(ObjType, Info.Ctx.getRecordType(Base));
     }
   }
 }
 
 namespace {
 struct ExtractSubobjectHandler {
   EvalInfo &Info;
   const Expr *E;
   APValue &Result;
   const AccessKinds AccessKind;
 
   typedef bool result_type;
   bool failed() { return false; }
   bool found(APValue &Subobj, QualType SubobjType) {
     Result = Subobj;
     if (AccessKind == AK_ReadObjectRepresentation)
       return true;
     return CheckFullyInitialized(Info, E->getExprLoc(), SubobjType, Result);
   }
   bool found(APSInt &Value, QualType SubobjType) {
     Result = APValue(Value);
     return true;
   }
   bool found(APFloat &Value, QualType SubobjType) {
     Result = APValue(Value);
     return true;
   }
 };
 } // end anonymous namespace
 
 /// Extract the designated sub-object of an rvalue.
 static bool extractSubobject(EvalInfo &Info, const Expr *E,
                              const CompleteObject &Obj,
                              const SubobjectDesignator &Sub, APValue &Result,
                              AccessKinds AK = AK_Read) {
   assert(AK == AK_Read || AK == AK_ReadObjectRepresentation);
   ExtractSubobjectHandler Handler = {Info, E, Result, AK};
   return findSubobject(Info, E, Obj, Sub, Handler);
 }
 
 namespace {
 struct ModifySubobjectHandler {
   EvalInfo &Info;
   APValue &NewVal;
   const Expr *E;
 
   typedef bool result_type;
   static const AccessKinds AccessKind = AK_Assign;
 
   bool checkConst(QualType QT) {
     // Assigning to a const object has undefined behavior.
     if (QT.isConstQualified()) {
       Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
       return false;
     }
     return true;
   }
 
   bool failed() { return false; }
   bool found(APValue &Subobj, QualType SubobjType) {
     if (!checkConst(SubobjType))
       return false;
     // We've been given ownership of NewVal, so just swap it in.
     Subobj.swap(NewVal);
     return true;
   }
   bool found(APSInt &Value, QualType SubobjType) {
     if (!checkConst(SubobjType))
       return false;
     if (!NewVal.isInt()) {
       // Maybe trying to write a cast pointer value into a complex?
       Info.FFDiag(E);
       return false;
     }
     Value = NewVal.getInt();
     return true;
   }
   bool found(APFloat &Value, QualType SubobjType) {
     if (!checkConst(SubobjType))
       return false;
     Value = NewVal.getFloat();
     return true;
   }
 };
 } // end anonymous namespace
 
 const AccessKinds ModifySubobjectHandler::AccessKind;
 
 /// Update the designated sub-object of an rvalue to the given value.
 static bool modifySubobject(EvalInfo &Info, const Expr *E,
                             const CompleteObject &Obj,
                             const SubobjectDesignator &Sub,
                             APValue &NewVal) {
   ModifySubobjectHandler Handler = { Info, NewVal, E };
   return findSubobject(Info, E, Obj, Sub, Handler);
 }
 
 /// Find the position where two subobject designators diverge, or equivalently
 /// the length of the common initial subsequence.
 static unsigned FindDesignatorMismatch(QualType ObjType,
                                        const SubobjectDesignator &A,
                                        const SubobjectDesignator &B,
                                        bool &WasArrayIndex) {
   unsigned I = 0, N = std::min(A.Entries.size(), B.Entries.size());
   for (/**/; I != N; ++I) {
     if (!ObjType.isNull() &&
         (ObjType->isArrayType() || ObjType->isAnyComplexType())) {
       // Next subobject is an array element.
       if (A.Entries[I].getAsArrayIndex() != B.Entries[I].getAsArrayIndex()) {
         WasArrayIndex = true;
         return I;
       }
       if (ObjType->isAnyComplexType())
         ObjType = ObjType->castAs<ComplexType>()->getElementType();
       else
         ObjType = ObjType->castAsArrayTypeUnsafe()->getElementType();
     } else {
       if (A.Entries[I].getAsBaseOrMember() !=
           B.Entries[I].getAsBaseOrMember()) {
         WasArrayIndex = false;
         return I;
       }
       if (const FieldDecl *FD = getAsField(A.Entries[I]))
         // Next subobject is a field.
         ObjType = FD->getType();
       else
         // Next subobject is a base class.
         ObjType = QualType();
     }
   }
   WasArrayIndex = false;
   return I;
 }
 
 /// Determine whether the given subobject designators refer to elements of the
 /// same array object.
 static bool AreElementsOfSameArray(QualType ObjType,
                                    const SubobjectDesignator &A,
                                    const SubobjectDesignator &B) {
   if (A.Entries.size() != B.Entries.size())
     return false;
 
   bool IsArray = A.MostDerivedIsArrayElement;
   if (IsArray && A.MostDerivedPathLength != A.Entries.size())
     // A is a subobject of the array element.
     return false;
 
   // If A (and B) designates an array element, the last entry will be the array
   // index. That doesn't have to match. Otherwise, we're in the 'implicit array
   // of length 1' case, and the entire path must match.
   bool WasArrayIndex;
   unsigned CommonLength = FindDesignatorMismatch(ObjType, A, B, WasArrayIndex);
   return CommonLength >= A.Entries.size() - IsArray;
 }
 
 /// Find the complete object to which an LValue refers.
 static CompleteObject findCompleteObject(EvalInfo &Info, const Expr *E,
                                          AccessKinds AK, const LValue &LVal,
                                          QualType LValType) {
   if (LVal.InvalidBase) {
     Info.FFDiag(E);
     return CompleteObject();
   }
 
   if (!LVal.Base) {
     Info.FFDiag(E, diag::note_constexpr_access_null) << AK;
     return CompleteObject();
   }
 
   CallStackFrame *Frame = nullptr;
   unsigned Depth = 0;
   if (LVal.getLValueCallIndex()) {
     std::tie(Frame, Depth) =
         Info.getCallFrameAndDepth(LVal.getLValueCallIndex());
     if (!Frame) {
       Info.FFDiag(E, diag::note_constexpr_lifetime_ended, 1)
         << AK << LVal.Base.is<const ValueDecl*>();
       NoteLValueLocation(Info, LVal.Base);
       return CompleteObject();
     }
   }
 
   bool IsAccess = isAnyAccess(AK);
 
   // C++11 DR1311: An lvalue-to-rvalue conversion on a volatile-qualified type
   // is not a constant expression (even if the object is non-volatile). We also
   // apply this rule to C++98, in order to conform to the expected 'volatile'
   // semantics.
   if (isFormalAccess(AK) && LValType.isVolatileQualified()) {
     if (Info.getLangOpts().CPlusPlus)
       Info.FFDiag(E, diag::note_constexpr_access_volatile_type)
         << AK << LValType;
     else
       Info.FFDiag(E);
     return CompleteObject();
   }
 
   // Compute value storage location and type of base object.
   APValue *BaseVal = nullptr;
   QualType BaseType = getType(LVal.Base);
 
   if (const ConstantExpr *CE =
           dyn_cast_or_null<ConstantExpr>(LVal.Base.dyn_cast<const Expr *>())) {
     /// Nested immediate invocation have been previously removed so if we found
     /// a ConstantExpr it can only be the EvaluatingDecl.
     assert(CE->isImmediateInvocation() && CE == Info.EvaluatingDecl);
     (void)CE;
     BaseVal = Info.EvaluatingDeclValue;
   } else if (const ValueDecl *D = LVal.Base.dyn_cast<const ValueDecl *>()) {
     // Allow reading from a GUID declaration.
     if (auto *GD = dyn_cast<MSGuidDecl>(D)) {
       if (isModification(AK)) {
         // All the remaining cases do not permit modification of the object.
         Info.FFDiag(E, diag::note_constexpr_modify_global);
         return CompleteObject();
       }
       APValue &V = GD->getAsAPValue();
       if (V.isAbsent()) {
         Info.FFDiag(E, diag::note_constexpr_unsupported_layout)
             << GD->getType();
         return CompleteObject();
       }
       return CompleteObject(LVal.Base, &V, GD->getType());
     }
 
     // In C++98, const, non-volatile integers initialized with ICEs are ICEs.
     // In C++11, constexpr, non-volatile variables initialized with constant
     // expressions are constant expressions too. Inside constexpr functions,
     // parameters are constant expressions even if they're non-const.
     // In C++1y, objects local to a constant expression (those with a Frame) are
     // both readable and writable inside constant expressions.
     // In C, such things can also be folded, although they are not ICEs.
     const VarDecl *VD = dyn_cast<VarDecl>(D);
     if (VD) {
       if (const VarDecl *VDef = VD->getDefinition(Info.Ctx))
         VD = VDef;
     }
     if (!VD || VD->isInvalidDecl()) {
       Info.FFDiag(E);
       return CompleteObject();
     }
 
     // In OpenCL if a variable is in constant address space it is a const value.
     bool IsConstant = BaseType.isConstQualified() ||
                       (Info.getLangOpts().OpenCL &&
                        BaseType.getAddressSpace() == LangAS::opencl_constant);
 
     // Unless we're looking at a local variable or argument in a constexpr call,
     // the variable we're reading must be const.
     if (!Frame) {
       if (Info.getLangOpts().CPlusPlus14 &&
           lifetimeStartedInEvaluation(Info, LVal.Base)) {
         // OK, we can read and modify an object if we're in the process of
         // evaluating its initializer, because its lifetime began in this
         // evaluation.
       } else if (isModification(AK)) {
         // All the remaining cases do not permit modification of the object.
         Info.FFDiag(E, diag::note_constexpr_modify_global);
         return CompleteObject();
       } else if (VD->isConstexpr()) {
         // OK, we can read this variable.
       } else if (BaseType->isIntegralOrEnumerationType()) {
         // In OpenCL if a variable is in constant address space it is a const
         // value.
         if (!IsConstant) {
           if (!IsAccess)
             return CompleteObject(LVal.getLValueBase(), nullptr, BaseType);
           if (Info.getLangOpts().CPlusPlus) {
             Info.FFDiag(E, diag::note_constexpr_ltor_non_const_int, 1) << VD;
             Info.Note(VD->getLocation(), diag::note_declared_at);
           } else {
             Info.FFDiag(E);
           }
           return CompleteObject();
         }
       } else if (!IsAccess) {
         return CompleteObject(LVal.getLValueBase(), nullptr, BaseType);
       } else if (IsConstant && Info.checkingPotentialConstantExpression() &&
                  BaseType->isLiteralType(Info.Ctx) && !VD->hasDefinition()) {
         // This variable might end up being constexpr. Don't diagnose it yet.
       } else if (IsConstant) {
         // Keep evaluating to see what we can do. In particular, we support
         // folding of const floating-point types, in order to make static const
         // data members of such types (supported as an extension) more useful.
         if (Info.getLangOpts().CPlusPlus) {
           Info.CCEDiag(E, Info.getLangOpts().CPlusPlus11
                               ? diag::note_constexpr_ltor_non_constexpr
                               : diag::note_constexpr_ltor_non_integral, 1)
               << VD << BaseType;
           Info.Note(VD->getLocation(), diag::note_declared_at);
         } else {
           Info.CCEDiag(E);
         }
       } else {
         // Never allow reading a non-const value.
         if (Info.getLangOpts().CPlusPlus) {
           Info.FFDiag(E, Info.getLangOpts().CPlusPlus11
                              ? diag::note_constexpr_ltor_non_constexpr
                              : diag::note_constexpr_ltor_non_integral, 1)
               << VD << BaseType;
           Info.Note(VD->getLocation(), diag::note_declared_at);
         } else {
           Info.FFDiag(E);
         }
         return CompleteObject();
       }
     }
 
     if (!evaluateVarDeclInit(Info, E, VD, Frame, BaseVal, &LVal))
       return CompleteObject();
   } else if (DynamicAllocLValue DA = LVal.Base.dyn_cast<DynamicAllocLValue>()) {
     Optional<DynAlloc*> Alloc = Info.lookupDynamicAlloc(DA);
     if (!Alloc) {
       Info.FFDiag(E, diag::note_constexpr_access_deleted_object) << AK;
       return CompleteObject();
     }
     return CompleteObject(LVal.Base, &(*Alloc)->Value,
                           LVal.Base.getDynamicAllocType());
   } else {
     const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
 
     if (!Frame) {
       if (const MaterializeTemporaryExpr *MTE =
               dyn_cast_or_null<MaterializeTemporaryExpr>(Base)) {
         assert(MTE->getStorageDuration() == SD_Static &&
                "should have a frame for a non-global materialized temporary");
 
         // Per C++1y [expr.const]p2:
         //  an lvalue-to-rvalue conversion [is not allowed unless it applies to]
         //   - a [...] glvalue of integral or enumeration type that refers to
         //     a non-volatile const object [...]
         //   [...]
         //   - a [...] glvalue of literal type that refers to a non-volatile
         //     object whose lifetime began within the evaluation of e.
         //
         // C++11 misses the 'began within the evaluation of e' check and
         // instead allows all temporaries, including things like:
         //   int &&r = 1;
         //   int x = ++r;
         //   constexpr int k = r;
         // Therefore we use the C++14 rules in C++11 too.
         //
         // Note that temporaries whose lifetimes began while evaluating a
         // variable's constructor are not usable while evaluating the
         // corresponding destructor, not even if they're of const-qualified
         // types.
         if (!(BaseType.isConstQualified() &&
               BaseType->isIntegralOrEnumerationType()) &&
             !lifetimeStartedInEvaluation(Info, LVal.Base)) {
           if (!IsAccess)
             return CompleteObject(LVal.getLValueBase(), nullptr, BaseType);
           Info.FFDiag(E, diag::note_constexpr_access_static_temporary, 1) << AK;
           Info.Note(MTE->getExprLoc(), diag::note_constexpr_temporary_here);
           return CompleteObject();
         }
 
         BaseVal = MTE->getOrCreateValue(false);
         assert(BaseVal && "got reference to unevaluated temporary");
       } else {
         if (!IsAccess)
           return CompleteObject(LVal.getLValueBase(), nullptr, BaseType);
         APValue Val;
         LVal.moveInto(Val);
         Info.FFDiag(E, diag::note_constexpr_access_unreadable_object)
             << AK
             << Val.getAsString(Info.Ctx,
                                Info.Ctx.getLValueReferenceType(LValType));
         NoteLValueLocation(Info, LVal.Base);
         return CompleteObject();
       }
     } else {
       BaseVal = Frame->getTemporary(Base, LVal.Base.getVersion());
       assert(BaseVal && "missing value for temporary");
     }
   }
 
   // In C++14, we can't safely access any mutable state when we might be
   // evaluating after an unmodeled side effect.
   //
   // FIXME: Not all local state is mutable. Allow local constant subobjects
   // to be read here (but take care with 'mutable' fields).
   if ((Frame && Info.getLangOpts().CPlusPlus14 &&
        Info.EvalStatus.HasSideEffects) ||
       (isModification(AK) && Depth < Info.SpeculativeEvaluationDepth))
     return CompleteObject();
 
   return CompleteObject(LVal.getLValueBase(), BaseVal, BaseType);
 }
 
 /// Perform an lvalue-to-rvalue conversion on the given glvalue. This
 /// can also be used for 'lvalue-to-lvalue' conversions for looking up the
 /// glvalue referred to by an entity of reference type.
 ///
 /// \param Info - Information about the ongoing evaluation.
 /// \param Conv - The expression for which we are performing the conversion.
 ///               Used for diagnostics.
 /// \param Type - The type of the glvalue (before stripping cv-qualifiers in the
 ///               case of a non-class type).
 /// \param LVal - The glvalue on which we are attempting to perform this action.
 /// \param RVal - The produced value will be placed here.
 /// \param WantObjectRepresentation - If true, we're looking for the object
 ///               representation rather than the value, and in particular,
 ///               there is no requirement that the result be fully initialized.
 static bool
 handleLValueToRValueConversion(EvalInfo &Info, const Expr *Conv, QualType Type,
                                const LValue &LVal, APValue &RVal,
                                bool WantObjectRepresentation = false) {
   if (LVal.Designator.Invalid)
     return false;
 
   // Check for special cases where there is no existing APValue to look at.
   const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
 
   AccessKinds AK =
       WantObjectRepresentation ? AK_ReadObjectRepresentation : AK_Read;
 
   if (Base && !LVal.getLValueCallIndex() && !Type.isVolatileQualified()) {
     if (const CompoundLiteralExpr *CLE = dyn_cast<CompoundLiteralExpr>(Base)) {
       // In C99, a CompoundLiteralExpr is an lvalue, and we defer evaluating the
       // initializer until now for such expressions. Such an expression can't be
       // an ICE in C, so this only matters for fold.
       if (Type.isVolatileQualified()) {
         Info.FFDiag(Conv);
         return false;
       }
       APValue Lit;
       if (!Evaluate(Lit, Info, CLE->getInitializer()))
         return false;
       CompleteObject LitObj(LVal.Base, &Lit, Base->getType());
       return extractSubobject(Info, Conv, LitObj, LVal.Designator, RVal, AK);
     } else if (isa<StringLiteral>(Base) || isa<PredefinedExpr>(Base)) {
       // Special-case character extraction so we don't have to construct an
       // APValue for the whole string.
       assert(LVal.Designator.Entries.size() <= 1 &&
              "Can only read characters from string literals");
       if (LVal.Designator.Entries.empty()) {
         // Fail for now for LValue to RValue conversion of an array.
         // (This shouldn't show up in C/C++, but it could be triggered by a
         // weird EvaluateAsRValue call from a tool.)
         Info.FFDiag(Conv);
         return false;
       }
       if (LVal.Designator.isOnePastTheEnd()) {
         if (Info.getLangOpts().CPlusPlus11)
           Info.FFDiag(Conv, diag::note_constexpr_access_past_end) << AK;
         else
           Info.FFDiag(Conv);
         return false;
       }
       uint64_t CharIndex = LVal.Designator.Entries[0].getAsArrayIndex();
       RVal = APValue(extractStringLiteralCharacter(Info, Base, CharIndex));
       return true;
     }
   }
 
   CompleteObject Obj = findCompleteObject(Info, Conv, AK, LVal, Type);
   return Obj && extractSubobject(Info, Conv, Obj, LVal.Designator, RVal, AK);
 }
 
 /// Perform an assignment of Val to LVal. Takes ownership of Val.
 static bool handleAssignment(EvalInfo &Info, const Expr *E, const LValue &LVal,
                              QualType LValType, APValue &Val) {
   if (LVal.Designator.Invalid)
     return false;
 
   if (!Info.getLangOpts().CPlusPlus14) {
     Info.FFDiag(E);
     return false;
   }
 
   CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
   return Obj && modifySubobject(Info, E, Obj, LVal.Designator, Val);
 }
 
 namespace {
 struct CompoundAssignSubobjectHandler {
   EvalInfo &Info;
   const Expr *E;
   QualType PromotedLHSType;
   BinaryOperatorKind Opcode;
   const APValue &RHS;
 
   static const AccessKinds AccessKind = AK_Assign;
 
   typedef bool result_type;
 
   bool checkConst(QualType QT) {
     // Assigning to a const object has undefined behavior.
     if (QT.isConstQualified()) {
       Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
       return false;
     }
     return true;
   }
 
   bool failed() { return false; }
   bool found(APValue &Subobj, QualType SubobjType) {
     switch (Subobj.getKind()) {
     case APValue::Int:
       return found(Subobj.getInt(), SubobjType);
     case APValue::Float:
       return found(Subobj.getFloat(), SubobjType);
     case APValue::ComplexInt:
     case APValue::ComplexFloat:
       // FIXME: Implement complex compound assignment.
       Info.FFDiag(E);
       return false;
     case APValue::LValue:
       return foundPointer(Subobj, SubobjType);
     case APValue::Vector:
       return foundVector(Subobj, SubobjType);
     default:
       // FIXME: can this happen?
       Info.FFDiag(E);
       return false;
     }
   }
 
   bool foundVector(APValue &Value, QualType SubobjType) {
     if (!checkConst(SubobjType))
       return false;
 
     if (!SubobjType->isVectorType()) {
       Info.FFDiag(E);
       return false;
     }
     return handleVectorVectorBinOp(Info, E, Opcode, Value, RHS);
   }
 
   bool found(APSInt &Value, QualType SubobjType) {
     if (!checkConst(SubobjType))
       return false;
 
     if (!SubobjType->isIntegerType()) {
       // We don't support compound assignment on integer-cast-to-pointer
       // values.
       Info.FFDiag(E);
       return false;
     }
 
     if (RHS.isInt()) {
       APSInt LHS =
           HandleIntToIntCast(Info, E, PromotedLHSType, SubobjType, Value);
       if (!handleIntIntBinOp(Info, E, LHS, Opcode, RHS.getInt(), LHS))
         return false;
       Value = HandleIntToIntCast(Info, E, SubobjType, PromotedLHSType, LHS);
       return true;
     } else if (RHS.isFloat()) {
       APFloat FValue(0.0);
       return HandleIntToFloatCast(Info, E, SubobjType, Value, PromotedLHSType,
                                   FValue) &&
              handleFloatFloatBinOp(Info, E, FValue, Opcode, RHS.getFloat()) &&
              HandleFloatToIntCast(Info, E, PromotedLHSType, FValue, SubobjType,
                                   Value);
     }
 
     Info.FFDiag(E);
     return false;
   }
   bool found(APFloat &Value, QualType SubobjType) {
     return checkConst(SubobjType) &&
            HandleFloatToFloatCast(Info, E, SubobjType, PromotedLHSType,
                                   Value) &&
            handleFloatFloatBinOp(Info, E, Value, Opcode, RHS.getFloat()) &&
            HandleFloatToFloatCast(Info, E, PromotedLHSType, SubobjType, Value);
   }
   bool foundPointer(APValue &Subobj, QualType SubobjType) {
     if (!checkConst(SubobjType))
       return false;
 
     QualType PointeeType;
     if (const PointerType *PT = SubobjType->getAs<PointerType>())
       PointeeType = PT->getPointeeType();
 
     if (PointeeType.isNull() || !RHS.isInt() ||
         (Opcode != BO_Add && Opcode != BO_Sub)) {
       Info.FFDiag(E);
       return false;
     }
 
     APSInt Offset = RHS.getInt();
     if (Opcode == BO_Sub)
       negateAsSigned(Offset);
 
     LValue LVal;
     LVal.setFrom(Info.Ctx, Subobj);
     if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType, Offset))
       return false;
     LVal.moveInto(Subobj);
     return true;
   }
 };
 } // end anonymous namespace
 
 const AccessKinds CompoundAssignSubobjectHandler::AccessKind;
 
 /// Perform a compound assignment of LVal <op>= RVal.
 static bool handleCompoundAssignment(
     EvalInfo &Info, const Expr *E,
     const LValue &LVal, QualType LValType, QualType PromotedLValType,
     BinaryOperatorKind Opcode, const APValue &RVal) {
   if (LVal.Designator.Invalid)
     return false;
 
   if (!Info.getLangOpts().CPlusPlus14) {
     Info.FFDiag(E);
     return false;
   }
 
   CompleteObject Obj = findCompleteObject(Info, E, AK_Assign, LVal, LValType);
   CompoundAssignSubobjectHandler Handler = { Info, E, PromotedLValType, Opcode,
                                              RVal };
   return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
 }
 
 namespace {
 struct IncDecSubobjectHandler {
   EvalInfo &Info;
   const UnaryOperator *E;
   AccessKinds AccessKind;
   APValue *Old;
 
   typedef bool result_type;
 
   bool checkConst(QualType QT) {
     // Assigning to a const object has undefined behavior.
     if (QT.isConstQualified()) {
       Info.FFDiag(E, diag::note_constexpr_modify_const_type) << QT;
       return false;
     }
     return true;
   }
 
   bool failed() { return false; }
   bool found(APValue &Subobj, QualType SubobjType) {
     // Stash the old value. Also clear Old, so we don't clobber it later
     // if we're post-incrementing a complex.
     if (Old) {
       *Old = Subobj;
       Old = nullptr;
     }
 
     switch (Subobj.getKind()) {
     case APValue::Int:
       return found(Subobj.getInt(), SubobjType);
     case APValue::Float:
       return found(Subobj.getFloat(), SubobjType);
     case APValue::ComplexInt:
       return found(Subobj.getComplexIntReal(),
                    SubobjType->castAs<ComplexType>()->getElementType()
                      .withCVRQualifiers(SubobjType.getCVRQualifiers()));
     case APValue::ComplexFloat:
       return found(Subobj.getComplexFloatReal(),
                    SubobjType->castAs<ComplexType>()->getElementType()
                      .withCVRQualifiers(SubobjType.getCVRQualifiers()));
     case APValue::LValue:
       return foundPointer(Subobj, SubobjType);
     default:
       // FIXME: can this happen?
       Info.FFDiag(E);
       return false;
     }
   }
   bool found(APSInt &Value, QualType SubobjType) {
     if (!checkConst(SubobjType))
       return false;
 
     if (!SubobjType->isIntegerType()) {
       // We don't support increment / decrement on integer-cast-to-pointer
       // values.
       Info.FFDiag(E);
       return false;
     }
 
     if (Old) *Old = APValue(Value);
 
     // bool arithmetic promotes to int, and the conversion back to bool
     // doesn't reduce mod 2^n, so special-case it.
     if (SubobjType->isBooleanType()) {
       if (AccessKind == AK_Increment)
         Value = 1;
       else
         Value = !Value;
       return true;
     }
 
     bool WasNegative = Value.isNegative();
     if (AccessKind == AK_Increment) {
       ++Value;
 
       if (!WasNegative && Value.isNegative() && E->canOverflow()) {
         APSInt ActualValue(Value, /*IsUnsigned*/true);
         return HandleOverflow(Info, E, ActualValue, SubobjType);
       }
     } else {
       --Value;
 
       if (WasNegative && !Value.isNegative() && E->canOverflow()) {
         unsigned BitWidth = Value.getBitWidth();
         APSInt ActualValue(Value.sext(BitWidth + 1), /*IsUnsigned*/false);
         ActualValue.setBit(BitWidth);
         return HandleOverflow(Info, E, ActualValue, SubobjType);
       }
     }
     return true;
   }
   bool found(APFloat &Value, QualType SubobjType) {
     if (!checkConst(SubobjType))
       return false;
 
     if (Old) *Old = APValue(Value);
 
     APFloat One(Value.getSemantics(), 1);
     if (AccessKind == AK_Increment)
       Value.add(One, APFloat::rmNearestTiesToEven);
     else
       Value.subtract(One, APFloat::rmNearestTiesToEven);
     return true;
   }
   bool foundPointer(APValue &Subobj, QualType SubobjType) {
     if (!checkConst(SubobjType))
       return false;
 
     QualType PointeeType;
     if (const PointerType *PT = SubobjType->getAs<PointerType>())
       PointeeType = PT->getPointeeType();
     else {
       Info.FFDiag(E);
       return false;
     }
 
     LValue LVal;
     LVal.setFrom(Info.Ctx, Subobj);
     if (!HandleLValueArrayAdjustment(Info, E, LVal, PointeeType,
                                      AccessKind == AK_Increment ? 1 : -1))
       return false;
     LVal.moveInto(Subobj);
     return true;
   }
 };
 } // end anonymous namespace
 
 /// Perform an increment or decrement on LVal.
 static bool handleIncDec(EvalInfo &Info, const Expr *E, const LValue &LVal,
                          QualType LValType, bool IsIncrement, APValue *Old) {
   if (LVal.Designator.Invalid)
     return false;
 
   if (!Info.getLangOpts().CPlusPlus14) {
     Info.FFDiag(E);
     return false;
   }
 
   AccessKinds AK = IsIncrement ? AK_Increment : AK_Decrement;
   CompleteObject Obj = findCompleteObject(Info, E, AK, LVal, LValType);
   IncDecSubobjectHandler Handler = {Info, cast<UnaryOperator>(E), AK, Old};
   return Obj && findSubobject(Info, E, Obj, LVal.Designator, Handler);
 }
 
 /// Build an lvalue for the object argument of a member function call.
 static bool EvaluateObjectArgument(EvalInfo &Info, const Expr *Object,
                                    LValue &This) {
   if (Object->getType()->isPointerType() && Object->isRValue())
     return EvaluatePointer(Object, This, Info);
 
   if (Object->isGLValue())
     return EvaluateLValue(Object, This, Info);
 
   if (Object->getType()->isLiteralType(Info.Ctx))
     return EvaluateTemporary(Object, This, Info);
 
   Info.FFDiag(Object, diag::note_constexpr_nonliteral) << Object->getType();
   return false;
 }
 
 /// HandleMemberPointerAccess - Evaluate a member access operation and build an
 /// lvalue referring to the result.
 ///
 /// \param Info - Information about the ongoing evaluation.
 /// \param LV - An lvalue referring to the base of the member pointer.
 /// \param RHS - The member pointer expression.
 /// \param IncludeMember - Specifies whether the member itself is included in
 ///        the resulting LValue subobject designator. This is not possible when
 ///        creating a bound member function.
 /// \return The field or method declaration to which the member pointer refers,
 ///         or 0 if evaluation fails.
 static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
                                                   QualType LVType,
                                                   LValue &LV,
                                                   const Expr *RHS,
                                                   bool IncludeMember = true) {
   MemberPtr MemPtr;
   if (!EvaluateMemberPointer(RHS, MemPtr, Info))
     return nullptr;
 
   // C++11 [expr.mptr.oper]p6: If the second operand is the null pointer to
   // member value, the behavior is undefined.
   if (!MemPtr.getDecl()) {
     // FIXME: Specific diagnostic.
     Info.FFDiag(RHS);
     return nullptr;
   }
 
   if (MemPtr.isDerivedMember()) {
     // This is a member of some derived class. Truncate LV appropriately.
     // The end of the derived-to-base path for the base object must match the
     // derived-to-base path for the member pointer.
     if (LV.Designator.MostDerivedPathLength + MemPtr.Path.size() >
         LV.Designator.Entries.size()) {
       Info.FFDiag(RHS);
       return nullptr;
     }
     unsigned PathLengthToMember =
         LV.Designator.Entries.size() - MemPtr.Path.size();
     for (unsigned I = 0, N = MemPtr.Path.size(); I != N; ++I) {
       const CXXRecordDecl *LVDecl = getAsBaseClass(
           LV.Designator.Entries[PathLengthToMember + I]);
       const CXXRecordDecl *MPDecl = MemPtr.Path[I];
       if (LVDecl->getCanonicalDecl() != MPDecl->getCanonicalDecl()) {
         Info.FFDiag(RHS);
         return nullptr;
       }
     }
 
     // Truncate the lvalue to the appropriate derived class.
     if (!CastToDerivedClass(Info, RHS, LV, MemPtr.getContainingRecord(),
                             PathLengthToMember))
       return nullptr;
   } else if (!MemPtr.Path.empty()) {
     // Extend the LValue path with the member pointer's path.
     LV.Designator.Entries.reserve(LV.Designator.Entries.size() +
                                   MemPtr.Path.size() + IncludeMember);
 
     // Walk down to the appropriate base class.
     if (const PointerType *PT = LVType->getAs<PointerType>())
       LVType = PT->getPointeeType();
     const CXXRecordDecl *RD = LVType->getAsCXXRecordDecl();
     assert(RD && "member pointer access on non-class-type expression");
     // The first class in the path is that of the lvalue.
     for (unsigned I = 1, N = MemPtr.Path.size(); I != N; ++I) {
       const CXXRecordDecl *Base = MemPtr.Path[N - I - 1];
       if (!HandleLValueDirectBase(Info, RHS, LV, RD, Base))
         return nullptr;
       RD = Base;
     }
     // Finally cast to the class containing the member.
     if (!HandleLValueDirectBase(Info, RHS, LV, RD,
                                 MemPtr.getContainingRecord()))
       return nullptr;
   }
 
   // Add the member. Note that we cannot build bound member functions here.
   if (IncludeMember) {
     if (const FieldDecl *FD = dyn_cast<FieldDecl>(MemPtr.getDecl())) {
       if (!HandleLValueMember(Info, RHS, LV, FD))
         return nullptr;
     } else if (const IndirectFieldDecl *IFD =
                  dyn_cast<IndirectFieldDecl>(MemPtr.getDecl())) {
       if (!HandleLValueIndirectMember(Info, RHS, LV, IFD))
         return nullptr;
     } else {
       llvm_unreachable("can't construct reference to bound member function");
     }
   }
 
   return MemPtr.getDecl();
 }
 
 static const ValueDecl *HandleMemberPointerAccess(EvalInfo &Info,
                                                   const BinaryOperator *BO,
                                                   LValue &LV,
                                                   bool IncludeMember = true) {
   assert(BO->getOpcode() == BO_PtrMemD || BO->getOpcode() == BO_PtrMemI);
 
   if (!EvaluateObjectArgument(Info, BO->getLHS(), LV)) {
     if (Info.noteFailure()) {
       MemberPtr MemPtr;
       EvaluateMemberPointer(BO->getRHS(), MemPtr, Info);
     }
     return nullptr;
   }
 
   return HandleMemberPointerAccess(Info, BO->getLHS()->getType(), LV,
                                    BO->getRHS(), IncludeMember);
 }
 
 /// HandleBaseToDerivedCast - Apply the given base-to-derived cast operation on
 /// the provided lvalue, which currently refers to the base object.
 static bool HandleBaseToDerivedCast(EvalInfo &Info, const CastExpr *E,
                                     LValue &Result) {
   SubobjectDesignator &D = Result.Designator;
   if (D.Invalid || !Result.checkNullPointer(Info, E, CSK_Derived))
     return false;
 
   QualType TargetQT = E->getType();
   if (const PointerType *PT = TargetQT->getAs<PointerType>())
     TargetQT = PT->getPointeeType();
 
   // Check this cast lands within the final derived-to-base subobject path.
   if (D.MostDerivedPathLength + E->path_size() > D.Entries.size()) {
     Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
       << D.MostDerivedType << TargetQT;
     return false;
   }
 
   // Check the type of the final cast. We don't need to check the path,
   // since a cast can only be formed if the path is unique.
   unsigned NewEntriesSize = D.Entries.size() - E->path_size();
   const CXXRecordDecl *TargetType = TargetQT->getAsCXXRecordDecl();
   const CXXRecordDecl *FinalType;
   if (NewEntriesSize == D.MostDerivedPathLength)
     FinalType = D.MostDerivedType->getAsCXXRecordDecl();
   else
     FinalType = getAsBaseClass(D.Entries[NewEntriesSize - 1]);
   if (FinalType->getCanonicalDecl() != TargetType->getCanonicalDecl()) {
     Info.CCEDiag(E, diag::note_constexpr_invalid_downcast)
       << D.MostDerivedType << TargetQT;
     return false;
   }
 
   // Truncate the lvalue to the appropriate derived class.
   return CastToDerivedClass(Info, E, Result, TargetType, NewEntriesSize);
 }
 
 /// Get the value to use for a default-initialized object of type T.
 /// Return false if it encounters something invalid.
 static bool getDefaultInitValue(QualType T, APValue &Result) {
   bool Success = true;
   if (auto *RD = T->getAsCXXRecordDecl()) {
     if (RD->isInvalidDecl()) {
       Result = APValue();
       return false;
     }
     if (RD->isUnion()) {
       Result = APValue((const FieldDecl *)nullptr);
       return true;
     }
     Result = APValue(APValue::UninitStruct(), RD->getNumBases(),
                      std::distance(RD->field_begin(), RD->field_end()));
 
     unsigned Index = 0;
     for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
                                                   End = RD->bases_end();
          I != End; ++I, ++Index)
       Success &= getDefaultInitValue(I->getType(), Result.getStructBase(Index));
 
     for (const auto *I : RD->fields()) {
       if (I->isUnnamedBitfield())
         continue;
       Success &= getDefaultInitValue(I->getType(),
                                      Result.getStructField(I->getFieldIndex()));
     }
     return Success;
   }
 
   if (auto *AT =
           dyn_cast_or_null<ConstantArrayType>(T->getAsArrayTypeUnsafe())) {
     Result = APValue(APValue::UninitArray(), 0, AT->getSize().getZExtValue());
     if (Result.hasArrayFiller())
       Success &=
           getDefaultInitValue(AT->getElementType(), Result.getArrayFiller());
 
     return Success;
   }
 
   Result = APValue::IndeterminateValue();
   return true;
 }
 
 namespace {
 enum EvalStmtResult {
   /// Evaluation failed.
   ESR_Failed,
   /// Hit a 'return' statement.
   ESR_Returned,
   /// Evaluation succeeded.
   ESR_Succeeded,
   /// Hit a 'continue' statement.
   ESR_Continue,
   /// Hit a 'break' statement.
   ESR_Break,
   /// Still scanning for 'case' or 'default' statement.
   ESR_CaseNotFound
 };
 }
 
 static bool EvaluateVarDecl(EvalInfo &Info, const VarDecl *VD) {
   // We don't need to evaluate the initializer for a static local.
   if (!VD->hasLocalStorage())
     return true;
 
   LValue Result;
   APValue &Val =
       Info.CurrentCall->createTemporary(VD, VD->getType(), true, Result);
 
   const Expr *InitE = VD->getInit();
   if (!InitE)
     return getDefaultInitValue(VD->getType(), Val);
 
   if (InitE->isValueDependent())
     return false;
 
   if (!EvaluateInPlace(Val, Info, Result, InitE)) {
     // Wipe out any partially-computed value, to allow tracking that this
     // evaluation failed.
     Val = APValue();
     return false;
   }
 
   return true;
 }
 
 static bool EvaluateDecl(EvalInfo &Info, const Decl *D) {
   bool OK = true;
 
   if (const VarDecl *VD = dyn_cast<VarDecl>(D))
     OK &= EvaluateVarDecl(Info, VD);
 
   if (const DecompositionDecl *DD = dyn_cast<DecompositionDecl>(D))
     for (auto *BD : DD->bindings())
       if (auto *VD = BD->getHoldingVar())
         OK &= EvaluateDecl(Info, VD);
 
   return OK;
 }
 
 
 /// Evaluate a condition (either a variable declaration or an expression).
 static bool EvaluateCond(EvalInfo &Info, const VarDecl *CondDecl,
                          const Expr *Cond, bool &Result) {
   FullExpressionRAII Scope(Info);
   if (CondDecl && !EvaluateDecl(Info, CondDecl))
     return false;
   if (!EvaluateAsBooleanCondition(Cond, Result, Info))
     return false;
   return Scope.destroy();
 }
 
 namespace {
 /// A location where the result (returned value) of evaluating a
 /// statement should be stored.
 struct StmtResult {
   /// The APValue that should be filled in with the returned value.
   APValue &Value;
   /// The location containing the result, if any (used to support RVO).
   const LValue *Slot;
 };
 
 struct TempVersionRAII {
   CallStackFrame &Frame;
 
   TempVersionRAII(CallStackFrame &Frame) : Frame(Frame) {
     Frame.pushTempVersion();
   }
 
   ~TempVersionRAII() {
     Frame.popTempVersion();
   }
 };
 
 }
 
 static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
                                    const Stmt *S,
                                    const SwitchCase *SC = nullptr);
 
 /// Evaluate the body of a loop, and translate the result as appropriate.
 static EvalStmtResult EvaluateLoopBody(StmtResult &Result, EvalInfo &Info,
                                        const Stmt *Body,
                                        const SwitchCase *Case = nullptr) {
   BlockScopeRAII Scope(Info);
 
   EvalStmtResult ESR = EvaluateStmt(Result, Info, Body, Case);
   if (ESR != ESR_Failed && ESR != ESR_CaseNotFound && !Scope.destroy())
     ESR = ESR_Failed;
 
   switch (ESR) {
   case ESR_Break:
     return ESR_Succeeded;
   case ESR_Succeeded:
   case ESR_Continue:
     return ESR_Continue;
   case ESR_Failed:
   case ESR_Returned:
   case ESR_CaseNotFound:
     return ESR;
   }
   llvm_unreachable("Invalid EvalStmtResult!");
 }
 
 /// Evaluate a switch statement.
 static EvalStmtResult EvaluateSwitch(StmtResult &Result, EvalInfo &Info,
                                      const SwitchStmt *SS) {
   BlockScopeRAII Scope(Info);
 
   // Evaluate the switch condition.
   APSInt Value;
   {
     if (const Stmt *Init = SS->getInit()) {
       EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
       if (ESR != ESR_Succeeded) {
         if (ESR != ESR_Failed && !Scope.destroy())
           ESR = ESR_Failed;
         return ESR;
       }
     }
 
     FullExpressionRAII CondScope(Info);
     if (SS->getConditionVariable() &&
         !EvaluateDecl(Info, SS->getConditionVariable()))
       return ESR_Failed;
     if (!EvaluateInteger(SS->getCond(), Value, Info))
       return ESR_Failed;
     if (!CondScope.destroy())
       return ESR_Failed;
   }
 
   // Find the switch case corresponding to the value of the condition.
   // FIXME: Cache this lookup.
   const SwitchCase *Found = nullptr;
   for (const SwitchCase *SC = SS->getSwitchCaseList(); SC;
        SC = SC->getNextSwitchCase()) {
     if (isa<DefaultStmt>(SC)) {
       Found = SC;
       continue;
     }
 
     const CaseStmt *CS = cast<CaseStmt>(SC);
     APSInt LHS = CS->getLHS()->EvaluateKnownConstInt(Info.Ctx);
     APSInt RHS = CS->getRHS() ? CS->getRHS()->EvaluateKnownConstInt(Info.Ctx)
                               : LHS;
     if (LHS <= Value && Value <= RHS) {
       Found = SC;
       break;
     }
   }
 
   if (!Found)
     return Scope.destroy() ? ESR_Succeeded : ESR_Failed;
 
   // Search the switch body for the switch case and evaluate it from there.
   EvalStmtResult ESR = EvaluateStmt(Result, Info, SS->getBody(), Found);
   if (ESR != ESR_Failed && ESR != ESR_CaseNotFound && !Scope.destroy())
     return ESR_Failed;
 
   switch (ESR) {
   case ESR_Break:
     return ESR_Succeeded;
   case ESR_Succeeded:
   case ESR_Continue:
   case ESR_Failed:
   case ESR_Returned:
     return ESR;
   case ESR_CaseNotFound:
     // This can only happen if the switch case is nested within a statement
     // expression. We have no intention of supporting that.
     Info.FFDiag(Found->getBeginLoc(),
                 diag::note_constexpr_stmt_expr_unsupported);
     return ESR_Failed;
   }
   llvm_unreachable("Invalid EvalStmtResult!");
 }
 
 // Evaluate a statement.
 static EvalStmtResult EvaluateStmt(StmtResult &Result, EvalInfo &Info,
                                    const Stmt *S, const SwitchCase *Case) {
   if (!Info.nextStep(S))
     return ESR_Failed;
 
   // If we're hunting down a 'case' or 'default' label, recurse through
   // substatements until we hit the label.
   if (Case) {
     switch (S->getStmtClass()) {
     case Stmt::CompoundStmtClass:
       // FIXME: Precompute which substatement of a compound statement we
       // would jump to, and go straight there rather than performing a
       // linear scan each time.
     case Stmt::LabelStmtClass:
     case Stmt::AttributedStmtClass:
     case Stmt::DoStmtClass:
       break;
 
     case Stmt::CaseStmtClass:
     case Stmt::DefaultStmtClass:
       if (Case == S)
         Case = nullptr;
       break;
 
     case Stmt::IfStmtClass: {
       // FIXME: Precompute which side of an 'if' we would jump to, and go
       // straight there rather than scanning both sides.
       const IfStmt *IS = cast<IfStmt>(S);
 
       // Wrap the evaluation in a block scope, in case it's a DeclStmt
       // preceded by our switch label.
       BlockScopeRAII Scope(Info);
 
       // Step into the init statement in case it brings an (uninitialized)
       // variable into scope.
       if (const Stmt *Init = IS->getInit()) {
         EvalStmtResult ESR = EvaluateStmt(Result, Info, Init, Case);
         if (ESR != ESR_CaseNotFound) {
           assert(ESR != ESR_Succeeded);
           return ESR;
         }
       }
 
       // Condition variable must be initialized if it exists.
       // FIXME: We can skip evaluating the body if there's a condition
       // variable, as there can't be any case labels within it.
       // (The same is true for 'for' statements.)
 
       EvalStmtResult ESR = EvaluateStmt(Result, Info, IS->getThen(), Case);
       if (ESR == ESR_Failed)
         return ESR;
       if (ESR != ESR_CaseNotFound)
         return Scope.destroy() ? ESR : ESR_Failed;
       if (!IS->getElse())
         return ESR_CaseNotFound;
 
       ESR = EvaluateStmt(Result, Info, IS->getElse(), Case);
       if (ESR == ESR_Failed)
         return ESR;
       if (ESR != ESR_CaseNotFound)
         return Scope.destroy() ? ESR : ESR_Failed;
       return ESR_CaseNotFound;
     }
 
     case Stmt::WhileStmtClass: {
       EvalStmtResult ESR =
           EvaluateLoopBody(Result, Info, cast<WhileStmt>(S)->getBody(), Case);
       if (ESR != ESR_Continue)
         return ESR;
       break;
     }
 
     case Stmt::ForStmtClass: {
       const ForStmt *FS = cast<ForStmt>(S);
       BlockScopeRAII Scope(Info);
 
       // Step into the init statement in case it brings an (uninitialized)
       // variable into scope.
       if (const Stmt *Init = FS->getInit()) {
         EvalStmtResult ESR = EvaluateStmt(Result, Info, Init, Case);
         if (ESR != ESR_CaseNotFound) {
           assert(ESR != ESR_Succeeded);
           return ESR;
         }
       }
 
       EvalStmtResult ESR =
           EvaluateLoopBody(Result, Info, FS->getBody(), Case);
       if (ESR != ESR_Continue)
         return ESR;
       if (FS->getInc()) {
         FullExpressionRAII IncScope(Info);
         if (!EvaluateIgnoredValue(Info, FS->getInc()) || !IncScope.destroy())
           return ESR_Failed;
       }
       break;
     }
 
     case Stmt::DeclStmtClass: {
       // Start the lifetime of any uninitialized variables we encounter. They
       // might be used by the selected branch of the switch.
       const DeclStmt *DS = cast<DeclStmt>(S);
       for (const auto *D : DS->decls()) {
         if (const auto *VD = dyn_cast<VarDecl>(D)) {
           if (VD->hasLocalStorage() && !VD->getInit())
             if (!EvaluateVarDecl(Info, VD))
               return ESR_Failed;
           // FIXME: If the variable has initialization that can't be jumped
           // over, bail out of any immediately-surrounding compound-statement
           // too. There can't be any case labels here.
         }
       }
       return ESR_CaseNotFound;
     }
 
     default:
       return ESR_CaseNotFound;
     }
   }
 
   switch (S->getStmtClass()) {
   default:
     if (const Expr *E = dyn_cast<Expr>(S)) {
       // Don't bother evaluating beyond an expression-statement which couldn't
       // be evaluated.
       // FIXME: Do we need the FullExpressionRAII object here?
       // VisitExprWithCleanups should create one when necessary.
       FullExpressionRAII Scope(Info);
       if (!EvaluateIgnoredValue(Info, E) || !Scope.destroy())
         return ESR_Failed;
       return ESR_Succeeded;
     }
 
     Info.FFDiag(S->getBeginLoc());
     return ESR_Failed;
 
   case Stmt::NullStmtClass:
     return ESR_Succeeded;
 
   case Stmt::DeclStmtClass: {
     const DeclStmt *DS = cast<DeclStmt>(S);
     for (const auto *D : DS->decls()) {
       // Each declaration initialization is its own full-expression.
       FullExpressionRAII Scope(Info);
       if (!EvaluateDecl(Info, D) && !Info.noteFailure())
         return ESR_Failed;
       if (!Scope.destroy())
         return ESR_Failed;
     }
     return ESR_Succeeded;
   }
 
   case Stmt::ReturnStmtClass: {
     const Expr *RetExpr = cast<ReturnStmt>(S)->getRetValue();
     FullExpressionRAII Scope(Info);
     if (RetExpr &&
         !(Result.Slot
               ? EvaluateInPlace(Result.Value, Info, *Result.Slot, RetExpr)
               : Evaluate(Result.Value, Info, RetExpr)))
       return ESR_Failed;
     return Scope.destroy() ? ESR_Returned : ESR_Failed;
   }
 
   case Stmt::CompoundStmtClass: {
     BlockScopeRAII Scope(Info);
 
     const CompoundStmt *CS = cast<CompoundStmt>(S);
     for (const auto *BI : CS->body()) {
       EvalStmtResult ESR = EvaluateStmt(Result, Info, BI, Case);
       if (ESR == ESR_Succeeded)
         Case = nullptr;
       else if (ESR != ESR_CaseNotFound) {
         if (ESR != ESR_Failed && !Scope.destroy())
           return ESR_Failed;
         return ESR;
       }
     }
     if (Case)
       return ESR_CaseNotFound;
     return Scope.destroy() ? ESR_Succeeded : ESR_Failed;
   }
 
   case Stmt::IfStmtClass: {
     const IfStmt *IS = cast<IfStmt>(S);
 
     // Evaluate the condition, as either a var decl or as an expression.
     BlockScopeRAII Scope(Info);
     if (const Stmt *Init = IS->getInit()) {
       EvalStmtResult ESR = EvaluateStmt(Result, Info, Init);
       if (ESR != ESR_Succeeded) {
         if (ESR != ESR_Failed && !Scope.destroy())
           return ESR_Failed;
         return ESR;
       }
     }
     bool Cond;
     if (!EvaluateCond(Info, IS->getConditionVariable(), IS->getCond(), Cond))
       return ESR_Failed;
 
     if (const Stmt *SubStmt = Cond ? IS->getThen() : IS->getElse()) {
       EvalStmtResult ESR = EvaluateStmt(Result, Info, SubStmt);
       if (ESR != ESR_Succeeded) {
         if (ESR != ESR_Failed && !Scope.destroy())
           return ESR_Failed;
         return ESR;
       }
     }
     return Scope.destroy() ? ESR_Succeeded : ESR_Failed;
   }
 
   case Stmt::WhileStmtClass: {
     const WhileStmt *WS = cast<WhileStmt>(S);
     while (true) {
       BlockScopeRAII Scope(Info);
       bool Continue;
       if (!EvaluateCond(Info, WS->getConditionVariable(), WS->getCond(),
                         Continue))
         return ESR_Failed;
       if (!Continue)
         break;
 
       EvalStmtResult ESR = EvaluateLoopBody(Result, Info, WS->getBody());
       if (ESR != ESR_Continue) {
         if (ESR != ESR_Failed && !Scope.destroy())
           return ESR_Failed;
         return ESR;
       }
       if (!Scope.destroy())
         return ESR_Failed;
     }
     return ESR_Succeeded;
   }
 
   case Stmt::DoStmtClass: {
     const DoStmt *DS = cast<DoStmt>(S);
     bool Continue;
     do {
       EvalStmtResult ESR = EvaluateLoopBody(Result, Info, DS->getBody(), Case);
       if (ESR != ESR_Continue)
         return ESR;
       Case = nullptr;
 
       FullExpressionRAII CondScope(Info);
       if (!EvaluateAsBooleanCondition(DS->getCond(), Continue, Info) ||
           !CondScope.destroy())
         return ESR_Failed;
     } while (Continue);
     return ESR_Succeeded;
   }
 
   case Stmt::ForStmtClass: {
     const ForStmt *FS = cast<ForStmt>(S);
     BlockScopeRAII ForScope(Info);
     if (FS->getInit()) {
       EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getInit());
       if (ESR != ESR_Succeeded) {
         if (ESR != ESR_Failed && !ForScope.destroy())
           return ESR_Failed;
         return ESR;
       }
     }
     while (true) {
       BlockScopeRAII IterScope(Info);
       bool Continue = true;
       if (FS->getCond() && !EvaluateCond(Info, FS->getConditionVariable(),
                                          FS->getCond(), Continue))
         return ESR_Failed;
       if (!Continue)
         break;
 
       EvalStmtResult ESR = EvaluateLoopBody(Result, Info, FS->getBody());
       if (ESR != ESR_Continue) {
         if (ESR != ESR_Failed && (!IterScope.destroy() || !ForScope.destroy()))
           return ESR_Failed;
         return ESR;
       }
 
       if (FS->getInc()) {
         FullExpressionRAII IncScope(Info);
         if (!EvaluateIgnoredValue(Info, FS->getInc()) || !IncScope.destroy())
           return ESR_Failed;
       }
 
       if (!IterScope.destroy())
         return ESR_Failed;
     }
     return ForScope.destroy() ? ESR_Succeeded : ESR_Failed;
   }
 
   case Stmt::CXXForRangeStmtClass: {
     const CXXForRangeStmt *FS = cast<CXXForRangeStmt>(S);
     BlockScopeRAII Scope(Info);
 
     // Evaluate the init-statement if present.
     if (FS->getInit()) {
       EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getInit());
       if (ESR != ESR_Succeeded) {
         if (ESR != ESR_Failed && !Scope.destroy())
           return ESR_Failed;
         return ESR;
       }
     }
 
     // Initialize the __range variable.
     EvalStmtResult ESR = EvaluateStmt(Result, Info, FS->getRangeStmt());
     if (ESR != ESR_Succeeded) {
       if (ESR != ESR_Failed && !Scope.destroy())
         return ESR_Failed;
       return ESR;
     }
 
     // Create the __begin and __end iterators.
     ESR = EvaluateStmt(Result, Info, FS->getBeginStmt());
     if (ESR != ESR_Succeeded) {
       if (ESR != ESR_Failed && !Scope.destroy())
         return ESR_Failed;
       return ESR;
     }
     ESR = EvaluateStmt(Result, Info, FS->getEndStmt());
     if (ESR != ESR_Succeeded) {
       if (ESR != ESR_Failed && !Scope.destroy())
         return ESR_Failed;
       return ESR;
     }
 
     while (true) {
       // Condition: __begin != __end.
       {
         bool Continue = true;
         FullExpressionRAII CondExpr(Info);
         if (!EvaluateAsBooleanCondition(FS->getCond(), Continue, Info))
           return ESR_Failed;
         if (!Continue)
           break;
       }
 
       // User's variable declaration, initialized by *__begin.
       BlockScopeRAII InnerScope(Info);
       ESR = EvaluateStmt(Result, Info, FS->getLoopVarStmt());
       if (ESR != ESR_Succeeded) {
         if (ESR != ESR_Failed && (!InnerScope.destroy() || !Scope.destroy()))
           return ESR_Failed;
         return ESR;
       }
 
       // Loop body.
       ESR = EvaluateLoopBody(Result, Info, FS->getBody());
       if (ESR != ESR_Continue) {
         if (ESR != ESR_Failed && (!InnerScope.destroy() || !Scope.destroy()))
           return ESR_Failed;
         return ESR;
       }
 
       // Increment: ++__begin
       if (!EvaluateIgnoredValue(Info, FS->getInc()))
         return ESR_Failed;
 
       if (!InnerScope.destroy())
         return ESR_Failed;
     }
 
     return Scope.destroy() ? ESR_Succeeded : ESR_Failed;
   }
 
   case Stmt::SwitchStmtClass:
     return EvaluateSwitch(Result, Info, cast<SwitchStmt>(S));
 
   case Stmt::ContinueStmtClass:
     return ESR_Continue;
 
   case Stmt::BreakStmtClass:
     return ESR_Break;
 
   case Stmt::LabelStmtClass:
     return EvaluateStmt(Result, Info, cast<LabelStmt>(S)->getSubStmt(), Case);
 
   case Stmt::AttributedStmtClass:
     // As a general principle, C++11 attributes can be ignored without
     // any semantic impact.
     return EvaluateStmt(Result, Info, cast<AttributedStmt>(S)->getSubStmt(),
                         Case);
 
   case Stmt::CaseStmtClass:
   case Stmt::DefaultStmtClass:
     return EvaluateStmt(Result, Info, cast<SwitchCase>(S)->getSubStmt(), Case);
   case Stmt::CXXTryStmtClass:
     // Evaluate try blocks by evaluating all sub statements.
     return EvaluateStmt(Result, Info, cast<CXXTryStmt>(S)->getTryBlock(), Case);
   }
 }
 
 /// CheckTrivialDefaultConstructor - Check whether a constructor is a trivial
 /// default constructor. If so, we'll fold it whether or not it's marked as
 /// constexpr. If it is marked as constexpr, we will never implicitly define it,
 /// so we need special handling.
 static bool CheckTrivialDefaultConstructor(EvalInfo &Info, SourceLocation Loc,
                                            const CXXConstructorDecl *CD,
                                            bool IsValueInitialization) {
   if (!CD->isTrivial() || !CD->isDefaultConstructor())
     return false;
 
   // Value-initialization does not call a trivial default constructor, so such a
   // call is a core constant expression whether or not the constructor is
   // constexpr.
   if (!CD->isConstexpr() && !IsValueInitialization) {
     if (Info.getLangOpts().CPlusPlus11) {
       // FIXME: If DiagDecl is an implicitly-declared special member function,
       // we should be much more explicit about why it's not constexpr.
       Info.CCEDiag(Loc, diag::note_constexpr_invalid_function, 1)
         << /*IsConstexpr*/0 << /*IsConstructor*/1 << CD;
       Info.Note(CD->getLocation(), diag::note_declared_at);
     } else {
       Info.CCEDiag(Loc, diag::note_invalid_subexpr_in_const_expr);
     }
   }
   return true;
 }
 
 /// CheckConstexprFunction - Check that a function can be called in a constant
 /// expression.
 static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
                                    const FunctionDecl *Declaration,
                                    const FunctionDecl *Definition,
                                    const Stmt *Body) {
   // Potential constant expressions can contain calls to declared, but not yet
   // defined, constexpr functions.
   if (Info.checkingPotentialConstantExpression() && !Definition &&
       Declaration->isConstexpr())
     return false;
 
   // Bail out if the function declaration itself is invalid.  We will
   // have produced a relevant diagnostic while parsing it, so just
   // note the problematic sub-expression.
   if (Declaration->isInvalidDecl()) {
     Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
     return false;
   }
 
   // DR1872: An instantiated virtual constexpr function can't be called in a
   // constant expression (prior to C++20). We can still constant-fold such a
   // call.
   if (!Info.Ctx.getLangOpts().CPlusPlus20 && isa<CXXMethodDecl>(Declaration) &&
       cast<CXXMethodDecl>(Declaration)->isVirtual())
     Info.CCEDiag(CallLoc, diag::note_constexpr_virtual_call);
 
   if (Definition && Definition->isInvalidDecl()) {
     Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
     return false;
   }
 
   if (const auto *CtorDecl = dyn_cast_or_null<CXXConstructorDecl>(Definition)) {
     for (const auto *InitExpr : CtorDecl->inits()) {
       if (InitExpr->getInit() && InitExpr->getInit()->containsErrors())
         return false;
     }
   }
 
   // Can we evaluate this function call?
   if (Definition && Definition->isConstexpr() && Body)
     return true;
 
   if (Info.getLangOpts().CPlusPlus11) {
     const FunctionDecl *DiagDecl = Definition ? Definition : Declaration;
 
     // If this function is not constexpr because it is an inherited
     // non-constexpr constructor, diagnose that directly.
     auto *CD = dyn_cast<CXXConstructorDecl>(DiagDecl);
     if (CD && CD->isInheritingConstructor()) {
       auto *Inherited = CD->getInheritedConstructor().getConstructor();
       if (!Inherited->isConstexpr())
         DiagDecl = CD = Inherited;
     }
 
     // FIXME: If DiagDecl is an implicitly-declared special member function
     // or an inheriting constructor, we should be much more explicit about why
     // it's not constexpr.
     if (CD && CD->isInheritingConstructor())
       Info.FFDiag(CallLoc, diag::note_constexpr_invalid_inhctor, 1)
         << CD->getInheritedConstructor().getConstructor()->getParent();
     else
       Info.FFDiag(CallLoc, diag::note_constexpr_invalid_function, 1)
         << DiagDecl->isConstexpr() << (bool)CD << DiagDecl;
     Info.Note(DiagDecl->getLocation(), diag::note_declared_at);
   } else {
     Info.FFDiag(CallLoc, diag::note_invalid_subexpr_in_const_expr);
   }
   return false;
 }
 
 namespace {
 struct CheckDynamicTypeHandler {
   AccessKinds AccessKind;
   typedef bool result_type;
   bool failed() { return false; }
   bool found(APValue &Subobj, QualType SubobjType) { return true; }
   bool found(APSInt &Value, QualType SubobjType) { return true; }
   bool found(APFloat &Value, QualType SubobjType) { return true; }
 };
 } // end anonymous namespace
 
 /// Check that we can access the notional vptr of an object / determine its
 /// dynamic type.
 static bool checkDynamicType(EvalInfo &Info, const Expr *E, const LValue &This,
                              AccessKinds AK, bool Polymorphic) {
   if (This.Designator.Invalid)
     return false;
 
   CompleteObject Obj = findCompleteObject(Info, E, AK, This, QualType());
 
   if (!Obj)
     return false;
 
   if (!Obj.Value) {
     // The object is not usable in constant expressions, so we can't inspect
     // its value to see if it's in-lifetime or what the active union members
     // are. We can still check for a one-past-the-end lvalue.
     if (This.Designator.isOnePastTheEnd() ||
         This.Designator.isMostDerivedAnUnsizedArray()) {
       Info.FFDiag(E, This.Designator.isOnePastTheEnd()
                          ? diag::note_constexpr_access_past_end
                          : diag::note_constexpr_access_unsized_array)
           << AK;
       return false;
     } else if (Polymorphic) {
       // Conservatively refuse to perform a polymorphic operation if we would
       // not be able to read a notional 'vptr' value.
       APValue Val;
       This.moveInto(Val);
       QualType StarThisType =
           Info.Ctx.getLValueReferenceType(This.Designator.getType(Info.Ctx));
       Info.FFDiag(E, diag::note_constexpr_polymorphic_unknown_dynamic_type)
           << AK << Val.getAsString(Info.Ctx, StarThisType);
       return false;
     }
     return true;
   }
 
   CheckDynamicTypeHandler Handler{AK};
   return Obj && findSubobject(Info, E, Obj, This.Designator, Handler);
 }
 
 /// Check that the pointee of the 'this' pointer in a member function call is
 /// either within its lifetime or in its period of construction or destruction.
 static bool
 checkNonVirtualMemberCallThisPointer(EvalInfo &Info, const Expr *E,
                                      const LValue &This,
                                      const CXXMethodDecl *NamedMember) {
   return checkDynamicType(
       Info, E, This,
       isa<CXXDestructorDecl>(NamedMember) ? AK_Destroy : AK_MemberCall, false);
 }
 
 struct DynamicType {
   /// The dynamic class type of the object.
   const CXXRecordDecl *Type;
   /// The corresponding path length in the lvalue.
   unsigned PathLength;
 };
 
 static const CXXRecordDecl *getBaseClassType(SubobjectDesignator &Designator,
                                              unsigned PathLength) {
   assert(PathLength >= Designator.MostDerivedPathLength && PathLength <=
       Designator.Entries.size() && "invalid path length");
   return (PathLength == Designator.MostDerivedPathLength)
              ? Designator.MostDerivedType->getAsCXXRecordDecl()
              : getAsBaseClass(Designator.Entries[PathLength - 1]);
 }
 
 /// Determine the dynamic type of an object.
 static Optional<DynamicType> ComputeDynamicType(EvalInfo &Info, const Expr *E,
                                                 LValue &This, AccessKinds AK) {
   // If we don't have an lvalue denoting an object of class type, there is no
   // meaningful dynamic type. (We consider objects of non-class type to have no
   // dynamic type.)
   if (!checkDynamicType(Info, E, This, AK, true))
     return None;
 
   // Refuse to compute a dynamic type in the presence of virtual bases. This
   // shouldn't happen other than in constant-folding situations, since literal
   // types can't have virtual bases.
   //
   // Note that consumers of DynamicType assume that the type has no virtual
   // bases, and will need modifications if this restriction is relaxed.
   const CXXRecordDecl *Class =
       This.Designator.MostDerivedType->getAsCXXRecordDecl();
   if (!Class || Class->getNumVBases()) {
     Info.FFDiag(E);
     return None;
   }
 
   // FIXME: For very deep class hierarchies, it might be beneficial to use a
   // binary search here instead. But the overwhelmingly common case is that
   // we're not in the middle of a constructor, so it probably doesn't matter
   // in practice.
   ArrayRef<APValue::LValuePathEntry> Path = This.Designator.Entries;
   for (unsigned PathLength = This.Designator.MostDerivedPathLength;
        PathLength <= Path.size(); ++PathLength) {
     switch (Info.isEvaluatingCtorDtor(This.getLValueBase(),
                                       Path.slice(0, PathLength))) {
     case ConstructionPhase::Bases:
     case ConstructionPhase::DestroyingBases:
       // We're constructing or destroying a base class. This is not the dynamic
       // type.
       break;
 
     case ConstructionPhase::None:
     case ConstructionPhase::AfterBases:
     case ConstructionPhase::AfterFields:
     case ConstructionPhase::Destroying:
       // We've finished constructing the base classes and not yet started
       // destroying them again, so this is the dynamic type.
       return DynamicType{getBaseClassType(This.Designator, PathLength),
                          PathLength};
     }
   }
 
   // CWG issue 1517: we're constructing a base class of the object described by
   // 'This', so that object has not yet begun its period of construction and
   // any polymorphic operation on it results in undefined behavior.
   Info.FFDiag(E);
   return None;
 }
 
 /// Perform virtual dispatch.
 static const CXXMethodDecl *HandleVirtualDispatch(
     EvalInfo &Info, const Expr *E, LValue &This, const CXXMethodDecl *Found,
     llvm::SmallVectorImpl<QualType> &CovariantAdjustmentPath) {
   Optional<DynamicType> DynType = ComputeDynamicType(
       Info, E, This,
       isa<CXXDestructorDecl>(Found) ? AK_Destroy : AK_MemberCall);
   if (!DynType)
     return nullptr;
 
   // Find the final overrider. It must be declared in one of the classes on the
   // path from the dynamic type to the static type.
   // FIXME: If we ever allow literal types to have virtual base classes, that
   // won't be true.
   const CXXMethodDecl *Callee = Found;
   unsigned PathLength = DynType->PathLength;
   for (/**/; PathLength <= This.Designator.Entries.size(); ++PathLength) {
     const CXXRecordDecl *Class = getBaseClassType(This.Designator, PathLength);
     const CXXMethodDecl *Overrider =
         Found->getCorrespondingMethodDeclaredInClass(Class, false);
     if (Overrider) {
       Callee = Overrider;
       break;
     }
   }
 
   // C++2a [class.abstract]p6:
   //   the effect of making a virtual call to a pure virtual function [...] is
   //   undefined
   if (Callee->isPure()) {
     Info.FFDiag(E, diag::note_constexpr_pure_virtual_call, 1) << Callee;
     Info.Note(Callee->getLocation(), diag::note_declared_at);
     return nullptr;
   }
 
   // If necessary, walk the rest of the path to determine the sequence of
   // covariant adjustment steps to apply.
   if (!Info.Ctx.hasSameUnqualifiedType(Callee->getReturnType(),
                                        Found->getReturnType())) {
     CovariantAdjustmentPath.push_back(Callee->getReturnType());
     for (unsigned CovariantPathLength = PathLength + 1;
          CovariantPathLength != This.Designator.Entries.size();
          ++CovariantPathLength) {
       const CXXRecordDecl *NextClass =
           getBaseClassType(This.Designator, CovariantPathLength);
       const CXXMethodDecl *Next =
           Found->getCorrespondingMethodDeclaredInClass(NextClass, false);
       if (Next && !Info.Ctx.hasSameUnqualifiedType(
                       Next->getReturnType(), CovariantAdjustmentPath.back()))
         CovariantAdjustmentPath.push_back(Next->getReturnType());
     }
     if (!Info.Ctx.hasSameUnqualifiedType(Found->getReturnType(),
                                          CovariantAdjustmentPath.back()))
       CovariantAdjustmentPath.push_back(Found->getReturnType());
   }
 
   // Perform 'this' adjustment.
   if (!CastToDerivedClass(Info, E, This, Callee->getParent(), PathLength))
     return nullptr;
 
   return Callee;
 }
 
 /// Perform the adjustment from a value returned by a virtual function to
 /// a value of the statically expected type, which may be a pointer or
 /// reference to a base class of the returned type.
 static bool HandleCovariantReturnAdjustment(EvalInfo &Info, const Expr *E,
                                             APValue &Result,
                                             ArrayRef<QualType> Path) {
   assert(Result.isLValue() &&
          "unexpected kind of APValue for covariant return");
   if (Result.isNullPointer())
     return true;
 
   LValue LVal;
   LVal.setFrom(Info.Ctx, Result);
 
   const CXXRecordDecl *OldClass = Path[0]->getPointeeCXXRecordDecl();
   for (unsigned I = 1; I != Path.size(); ++I) {
     const CXXRecordDecl *NewClass = Path[I]->getPointeeCXXRecordDecl();
     assert(OldClass && NewClass && "unexpected kind of covariant return");
     if (OldClass != NewClass &&
         !CastToBaseClass(Info, E, LVal, OldClass, NewClass))
       return false;
     OldClass = NewClass;
   }
 
   LVal.moveInto(Result);
   return true;
 }
 
 /// Determine whether \p Base, which is known to be a direct base class of
 /// \p Derived, is a public base class.
 static bool isBaseClassPublic(const CXXRecordDecl *Derived,
                               const CXXRecordDecl *Base) {
   for (const CXXBaseSpecifier &BaseSpec : Derived->bases()) {
     auto *BaseClass = BaseSpec.getType()->getAsCXXRecordDecl();
     if (BaseClass && declaresSameEntity(BaseClass, Base))
       return BaseSpec.getAccessSpecifier() == AS_public;
   }
   llvm_unreachable("Base is not a direct base of Derived");
 }
 
 /// Apply the given dynamic cast operation on the provided lvalue.
 ///
 /// This implements the hard case of dynamic_cast, requiring a "runtime check"
 /// to find a suitable target subobject.
 static bool HandleDynamicCast(EvalInfo &Info, const ExplicitCastExpr *E,
                               LValue &Ptr) {
   // We can't do anything with a non-symbolic pointer value.
   SubobjectDesignator &D = Ptr.Designator;
   if (D.Invalid)
     return false;
 
   // C++ [expr.dynamic.cast]p6:
   //   If v is a null pointer value, the result is a null pointer value.
   if (Ptr.isNullPointer() && !E->isGLValue())
     return true;
 
   // For all the other cases, we need the pointer to point to an object within
   // its lifetime / period of construction / destruction, and we need to know
   // its dynamic type.
   Optional<DynamicType> DynType =
       ComputeDynamicType(Info, E, Ptr, AK_DynamicCast);
   if (!DynType)
     return false;
 
   // C++ [expr.dynamic.cast]p7:
   //   If T is "pointer to cv void", then the result is a pointer to the most
   //   derived object
   if (E->getType()->isVoidPointerType())
     return CastToDerivedClass(Info, E, Ptr, DynType->Type, DynType->PathLength);
 
   const CXXRecordDecl *C = E->getTypeAsWritten()->getPointeeCXXRecordDecl();
   assert(C && "dynamic_cast target is not void pointer nor class");
   CanQualType CQT = Info.Ctx.getCanonicalType(Info.Ctx.getRecordType(C));
 
   auto RuntimeCheckFailed = [&] (CXXBasePaths *Paths) {
     // C++ [expr.dynamic.cast]p9:
     if (!E->isGLValue()) {
       //   The value of a failed cast to pointer type is the null pointer value
       //   of the required result type.
       Ptr.setNull(Info.Ctx, E->getType());
       return true;
     }
 
     //   A failed cast to reference type throws [...] std::bad_cast.
     unsigned DiagKind;
     if (!Paths && (declaresSameEntity(DynType->Type, C) ||
                    DynType->Type->isDerivedFrom(C)))
       DiagKind = 0;
     else if (!Paths || Paths->begin() == Paths->end())
       DiagKind = 1;
     else if (Paths->isAmbiguous(CQT))
       DiagKind = 2;
     else {
       assert(Paths->front().Access != AS_public && "why did the cast fail?");
       DiagKind = 3;
     }
     Info.FFDiag(E, diag::note_constexpr_dynamic_cast_to_reference_failed)
         << DiagKind << Ptr.Designator.getType(Info.Ctx)
         << Info.Ctx.getRecordType(DynType->Type)
         << E->getType().getUnqualifiedType();
     return false;
   };
 
   // Runtime check, phase 1:
   //   Walk from the base subobject towards the derived object looking for the
   //   target type.
   for (int PathLength = Ptr.Designator.Entries.size();
        PathLength >= (int)DynType->PathLength; --PathLength) {
     const CXXRecordDecl *Class = getBaseClassType(Ptr.Designator, PathLength);
     if (declaresSameEntity(Class, C))
       return CastToDerivedClass(Info, E, Ptr, Class, PathLength);
     // We can only walk across public inheritance edges.
     if (PathLength > (int)DynType->PathLength &&
         !isBaseClassPublic(getBaseClassType(Ptr.Designator, PathLength - 1),
                            Class))
       return RuntimeCheckFailed(nullptr);
   }
 
   // Runtime check, phase 2:
   //   Search the dynamic type for an unambiguous public base of type C.
   CXXBasePaths Paths(/*FindAmbiguities=*/true,
                      /*RecordPaths=*/true, /*DetectVirtual=*/false);
   if (DynType->Type->isDerivedFrom(C, Paths) && !Paths.isAmbiguous(CQT) &&
       Paths.front().Access == AS_public) {
     // Downcast to the dynamic type...
     if (!CastToDerivedClass(Info, E, Ptr, DynType->Type, DynType->PathLength))
       return false;
     // ... then upcast to the chosen base class subobject.
     for (CXXBasePathElement &Elem : Paths.front())
       if (!HandleLValueBase(Info, E, Ptr, Elem.Class, Elem.Base))
         return false;
     return true;
   }
 
   // Otherwise, the runtime check fails.
   return RuntimeCheckFailed(&Paths);
 }
 
 namespace {
 struct StartLifetimeOfUnionMemberHandler {
   EvalInfo &Info;
   const Expr *LHSExpr;
   const FieldDecl *Field;
   bool DuringInit;
   bool Failed = false;
   static const AccessKinds AccessKind = AK_Assign;
 
   typedef bool result_type;
   bool failed() { return Failed; }
   bool found(APValue &Subobj, QualType SubobjType) {
     // We are supposed to perform no initialization but begin the lifetime of
     // the object. We interpret that as meaning to do what default
     // initialization of the object would do if all constructors involved were
     // trivial:
     //  * All base, non-variant member, and array element subobjects' lifetimes
     //    begin
     //  * No variant members' lifetimes begin
     //  * All scalar subobjects whose lifetimes begin have indeterminate values
     assert(SubobjType->isUnionType());
     if (declaresSameEntity(Subobj.getUnionField(), Field)) {
       // This union member is already active. If it's also in-lifetime, there's
       // nothing to do.
       if (Subobj.getUnionValue().hasValue())
         return true;
     } else if (DuringInit) {
       // We're currently in the process of initializing a different union
       // member.  If we carried on, that initialization would attempt to
       // store to an inactive union member, resulting in undefined behavior.
       Info.FFDiag(LHSExpr,
                   diag::note_constexpr_union_member_change_during_init);
       return false;
     }
     APValue Result;
     Failed = !getDefaultInitValue(Field->getType(), Result);
     Subobj.setUnion(Field, Result);
     return true;
   }
   bool found(APSInt &Value, QualType SubobjType) {
     llvm_unreachable("wrong value kind for union object");
   }
   bool found(APFloat &Value, QualType SubobjType) {
     llvm_unreachable("wrong value kind for union object");
   }
 };
 } // end anonymous namespace
 
 const AccessKinds StartLifetimeOfUnionMemberHandler::AccessKind;
 
 /// Handle a builtin simple-assignment or a call to a trivial assignment
 /// operator whose left-hand side might involve a union member access. If it
 /// does, implicitly start the lifetime of any accessed union elements per
 /// C++20 [class.union]5.
 static bool HandleUnionActiveMemberChange(EvalInfo &Info, const Expr *LHSExpr,
                                           const LValue &LHS) {
   if (LHS.InvalidBase || LHS.Designator.Invalid)
     return false;
 
   llvm::SmallVector<std::pair<unsigned, const FieldDecl*>, 4> UnionPathLengths;
   // C++ [class.union]p5:
   //   define the set S(E) of subexpressions of E as follows:
   unsigned PathLength = LHS.Designator.Entries.size();
   for (const Expr *E = LHSExpr; E != nullptr;) {
     //   -- If E is of the form A.B, S(E) contains the elements of S(A)...
     if (auto *ME = dyn_cast<MemberExpr>(E)) {
       auto *FD = dyn_cast<FieldDecl>(ME->getMemberDecl());
       // Note that we can't implicitly start the lifetime of a reference,
       // so we don't need to proceed any further if we reach one.
       if (!FD || FD->getType()->isReferenceType())
         break;
 
       //    ... and also contains A.B if B names a union member ...
       if (FD->getParent()->isUnion()) {
         //    ... of a non-class, non-array type, or of a class type with a
         //    trivial default constructor that is not deleted, or an array of
         //    such types.
         auto *RD =
             FD->getType()->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
         if (!RD || RD->hasTrivialDefaultConstructor())
           UnionPathLengths.push_back({PathLength - 1, FD});
       }
 
       E = ME->getBase();
       --PathLength;
       assert(declaresSameEntity(FD,
                                 LHS.Designator.Entries[PathLength]
                                     .getAsBaseOrMember().getPointer()));
 
       //   -- If E is of the form A[B] and is interpreted as a built-in array
       //      subscripting operator, S(E) is [S(the array operand, if any)].
     } else if (auto *ASE = dyn_cast<ArraySubscriptExpr>(E)) {
       // Step over an ArrayToPointerDecay implicit cast.
       auto *Base = ASE->getBase()->IgnoreImplicit();
       if (!Base->getType()->isArrayType())
         break;
 
       E = Base;
       --PathLength;
 
     } else if (auto *ICE = dyn_cast<ImplicitCastExpr>(E)) {
       // Step over a derived-to-base conversion.
       E = ICE->getSubExpr();
       if (ICE->getCastKind() == CK_NoOp)
         continue;
       if (ICE->getCastKind() != CK_DerivedToBase &&
           ICE->getCastKind() != CK_UncheckedDerivedToBase)
         break;
       // Walk path backwards as we walk up from the base to the derived class.
       for (const CXXBaseSpecifier *Elt : llvm::reverse(ICE->path())) {
         --PathLength;
         (void)Elt;
         assert(declaresSameEntity(Elt->getType()->getAsCXXRecordDecl(),
                                   LHS.Designator.Entries[PathLength]
                                       .getAsBaseOrMember().getPointer()));
       }
 
     //   -- Otherwise, S(E) is empty.
     } else {
       break;
     }
   }
 
   // Common case: no unions' lifetimes are started.
   if (UnionPathLengths.empty())
     return true;
 
   //   if modification of X [would access an inactive union member], an object
   //   of the type of X is implicitly created
   CompleteObject Obj =
       findCompleteObject(Info, LHSExpr, AK_Assign, LHS, LHSExpr->getType());
   if (!Obj)
     return false;
   for (std::pair<unsigned, const FieldDecl *> LengthAndField :
            llvm::reverse(UnionPathLengths)) {
     // Form a designator for the union object.
     SubobjectDesignator D = LHS.Designator;
     D.truncate(Info.Ctx, LHS.Base, LengthAndField.first);
 
     bool DuringInit = Info.isEvaluatingCtorDtor(LHS.Base, D.Entries) ==
                       ConstructionPhase::AfterBases;
     StartLifetimeOfUnionMemberHandler StartLifetime{
         Info, LHSExpr, LengthAndField.second, DuringInit};
     if (!findSubobject(Info, LHSExpr, Obj, D, StartLifetime))
       return false;
   }
 
   return true;
 }
 
 namespace {
 typedef SmallVector<APValue, 8> ArgVector;
 }
 
 /// EvaluateArgs - Evaluate the arguments to a function call.
 static bool EvaluateArgs(ArrayRef<const Expr *> Args, ArgVector &ArgValues,
                          EvalInfo &Info, const FunctionDecl *Callee) {
   bool Success = true;
   llvm::SmallBitVector ForbiddenNullArgs;
   if (Callee->hasAttr<NonNullAttr>()) {
     ForbiddenNullArgs.resize(Args.size());
     for (const auto *Attr : Callee->specific_attrs<NonNullAttr>()) {
       if (!Attr->args_size()) {
         ForbiddenNullArgs.set();
         break;
       } else
         for (auto Idx : Attr->args()) {
           unsigned ASTIdx = Idx.getASTIndex();
           if (ASTIdx >= Args.size())
             continue;
           ForbiddenNullArgs[ASTIdx] = 1;
         }
     }
   }
   // FIXME: This is the wrong evaluation order for an assignment operator
   // called via operator syntax.
   for (unsigned Idx = 0; Idx < Args.size(); Idx++) {
     if (!Evaluate(ArgValues[Idx], Info, Args[Idx])) {
       // If we're checking for a potential constant expression, evaluate all
       // initializers even if some of them fail.
       if (!Info.noteFailure())
         return false;
       Success = false;
     } else if (!ForbiddenNullArgs.empty() &&
                ForbiddenNullArgs[Idx] &&
                ArgValues[Idx].isLValue() &&
                ArgValues[Idx].isNullPointer()) {
       Info.CCEDiag(Args[Idx], diag::note_non_null_attribute_failed);
       if (!Info.noteFailure())
         return false;
       Success = false;
     }
   }
   return Success;
 }
 
 /// Evaluate a function call.
 static bool HandleFunctionCall(SourceLocation CallLoc,
                                const FunctionDecl *Callee, const LValue *This,
                                ArrayRef<const Expr*> Args, const Stmt *Body,
                                EvalInfo &Info, APValue &Result,
                                const LValue *ResultSlot) {
   ArgVector ArgValues(Args.size());
   if (!EvaluateArgs(Args, ArgValues, Info, Callee))
     return false;
 
   if (!Info.CheckCallLimit(CallLoc))
     return false;
 
   CallStackFrame Frame(Info, CallLoc, Callee, This, ArgValues.data());
 
   // For a trivial copy or move assignment, perform an APValue copy. This is
   // essential for unions, where the operations performed by the assignment
   // operator cannot be represented as statements.
   //
   // Skip this for non-union classes with no fields; in that case, the defaulted
   // copy/move does not actually read the object.
   const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Callee);
   if (MD && MD->isDefaulted() &&
       (MD->getParent()->isUnion() ||
        (MD->isTrivial() &&
         isReadByLvalueToRvalueConversion(MD->getParent())))) {
     assert(This &&
            (MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator()));
     LValue RHS;
     RHS.setFrom(Info.Ctx, ArgValues[0]);
     APValue RHSValue;
     if (!handleLValueToRValueConversion(Info, Args[0], Args[0]->getType(), RHS,
                                         RHSValue, MD->getParent()->isUnion()))
       return false;
     if (Info.getLangOpts().CPlusPlus20 && MD->isTrivial() &&
         !HandleUnionActiveMemberChange(Info, Args[0], *This))
       return false;
     if (!handleAssignment(Info, Args[0], *This, MD->getThisType(),
                           RHSValue))
       return false;
     This->moveInto(Result);
     return true;
   } else if (MD && isLambdaCallOperator(MD)) {
     // We're in a lambda; determine the lambda capture field maps unless we're
     // just constexpr checking a lambda's call operator. constexpr checking is
     // done before the captures have been added to the closure object (unless
     // we're inferring constexpr-ness), so we don't have access to them in this
     // case. But since we don't need the captures to constexpr check, we can
     // just ignore them.
     if (!Info.checkingPotentialConstantExpression())
       MD->getParent()->getCaptureFields(Frame.LambdaCaptureFields,
                                         Frame.LambdaThisCaptureField);
   }
 
   StmtResult Ret = {Result, ResultSlot};
   EvalStmtResult ESR = EvaluateStmt(Ret, Info, Body);
   if (ESR == ESR_Succeeded) {
     if (Callee->getReturnType()->isVoidType())
       return true;
     Info.FFDiag(Callee->getEndLoc(), diag::note_constexpr_no_return);
   }
   return ESR == ESR_Returned;
 }
 
 /// Evaluate a constructor call.
 static bool HandleConstructorCall(const Expr *E, const LValue &This,
                                   APValue *ArgValues,
                                   const CXXConstructorDecl *Definition,
                                   EvalInfo &Info, APValue &Result) {
   SourceLocation CallLoc = E->getExprLoc();
   if (!Info.CheckCallLimit(CallLoc))
     return false;
 
   const CXXRecordDecl *RD = Definition->getParent();
   if (RD->getNumVBases()) {
     Info.FFDiag(CallLoc, diag::note_constexpr_virtual_base) << RD;
     return false;
   }
 
   EvalInfo::EvaluatingConstructorRAII EvalObj(
       Info,
       ObjectUnderConstruction{This.getLValueBase(), This.Designator.Entries},
       RD->getNumBases());
   CallStackFrame Frame(Info, CallLoc, Definition, &This, ArgValues);
 
   // FIXME: Creating an APValue just to hold a nonexistent return value is
   // wasteful.
   APValue RetVal;
   StmtResult Ret = {RetVal, nullptr};
 
   // If it's a delegating constructor, delegate.
   if (Definition->isDelegatingConstructor()) {
     CXXConstructorDecl::init_const_iterator I = Definition->init_begin();
     {
       FullExpressionRAII InitScope(Info);
       if (!EvaluateInPlace(Result, Info, This, (*I)->getInit()) ||
           !InitScope.destroy())
         return false;
     }
     return EvaluateStmt(Ret, Info, Definition->getBody()) != ESR_Failed;
   }
 
   // For a trivial copy or move constructor, perform an APValue copy. This is
   // essential for unions (or classes with anonymous union members), where the
   // operations performed by the constructor cannot be represented by
   // ctor-initializers.
   //
   // Skip this for empty non-union classes; we should not perform an
   // lvalue-to-rvalue conversion on them because their copy constructor does not
   // actually read them.
   if (Definition->isDefaulted() && Definition->isCopyOrMoveConstructor() &&
       (Definition->getParent()->isUnion() ||
        (Definition->isTrivial() &&
         isReadByLvalueToRvalueConversion(Definition->getParent())))) {
     LValue RHS;
     RHS.setFrom(Info.Ctx, ArgValues[0]);
     return handleLValueToRValueConversion(
         Info, E, Definition->getParamDecl(0)->getType().getNonReferenceType(),
         RHS, Result, Definition->getParent()->isUnion());
   }
 
   // Reserve space for the struct members.
   if (!Result.hasValue()) {
     if (!RD->isUnion())
       Result = APValue(APValue::UninitStruct(), RD->getNumBases(),
                        std::distance(RD->field_begin(), RD->field_end()));
     else
       // A union starts with no active member.
       Result = APValue((const FieldDecl*)nullptr);
   }
 
   if (RD->isInvalidDecl()) return false;
   const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
 
   // A scope for temporaries lifetime-extended by reference members.
   BlockScopeRAII LifetimeExtendedScope(Info);
 
   bool Success = true;
   unsigned BasesSeen = 0;
 #ifndef NDEBUG
   CXXRecordDecl::base_class_const_iterator BaseIt = RD->bases_begin();
 #endif
   CXXRecordDecl::field_iterator FieldIt = RD->field_begin();
   auto SkipToField = [&](FieldDecl *FD, bool Indirect) {
     // We might be initializing the same field again if this is an indirect
     // field initialization.
     if (FieldIt == RD->field_end() ||
         FieldIt->getFieldIndex() > FD->getFieldIndex()) {
       assert(Indirect && "fields out of order?");
       return;
     }
 
     // Default-initialize any fields with no explicit initializer.
     for (; !declaresSameEntity(*FieldIt, FD); ++FieldIt) {
       assert(FieldIt != RD->field_end() && "missing field?");
       if (!FieldIt->isUnnamedBitfield())
         Success &= getDefaultInitValue(
             FieldIt->getType(),
             Result.getStructField(FieldIt->getFieldIndex()));
     }
     ++FieldIt;
   };
   for (const auto *I : Definition->inits()) {
     LValue Subobject = This;
     LValue SubobjectParent = This;
     APValue *Value = &Result;
 
     // Determine the subobject to initialize.
     FieldDecl *FD = nullptr;
     if (I->isBaseInitializer()) {
       QualType BaseType(I->getBaseClass(), 0);
 #ifndef NDEBUG
       // Non-virtual base classes are initialized in the order in the class
       // definition. We have already checked for virtual base classes.
       assert(!BaseIt->isVirtual() && "virtual base for literal type");
       assert(Info.Ctx.hasSameType(BaseIt->getType(), BaseType) &&
              "base class initializers not in expected order");
       ++BaseIt;
 #endif
       if (!HandleLValueDirectBase(Info, I->getInit(), Subobject, RD,
                                   BaseType->getAsCXXRecordDecl(), &Layout))
         return false;
       Value = &Result.getStructBase(BasesSeen++);
     } else if ((FD = I->getMember())) {
       if (!HandleLValueMember(Info, I->getInit(), Subobject, FD, &Layout))
         return false;
       if (RD->isUnion()) {
         Result = APValue(FD);
         Value = &Result.getUnionValue();
       } else {
         SkipToField(FD, false);
         Value = &Result.getStructField(FD->getFieldIndex());
       }
     } else if (IndirectFieldDecl *IFD = I->getIndirectMember()) {
       // Walk the indirect field decl's chain to find the object to initialize,
       // and make sure we've initialized every step along it.
       auto IndirectFieldChain = IFD->chain();
       for (auto *C : IndirectFieldChain) {
         FD = cast<FieldDecl>(C);
         CXXRecordDecl *CD = cast<CXXRecordDecl>(FD->getParent());
         // Switch the union field if it differs. This happens if we had
         // preceding zero-initialization, and we're now initializing a union
         // subobject other than the first.
         // FIXME: In this case, the values of the other subobjects are
         // specified, since zero-initialization sets all padding bits to zero.
         if (!Value->hasValue() ||
             (Value->isUnion() && Value->getUnionField() != FD)) {
           if (CD->isUnion())
             *Value = APValue(FD);
           else
             // FIXME: This immediately starts the lifetime of all members of
             // an anonymous struct. It would be preferable to strictly start
             // member lifetime in initialization order.
             Success &= getDefaultInitValue(Info.Ctx.getRecordType(CD), *Value);
         }
         // Store Subobject as its parent before updating it for the last element
         // in the chain.
         if (C == IndirectFieldChain.back())
           SubobjectParent = Subobject;
         if (!HandleLValueMember(Info, I->getInit(), Subobject, FD))
           return false;
         if (CD->isUnion())
           Value = &Value->getUnionValue();
         else {
           if (C == IndirectFieldChain.front() && !RD->isUnion())
             SkipToField(FD, true);
           Value = &Value->getStructField(FD->getFieldIndex());
         }
       }
     } else {
       llvm_unreachable("unknown base initializer kind");
     }
 
     // Need to override This for implicit field initializers as in this case
     // This refers to innermost anonymous struct/union containing initializer,
     // not to currently constructed class.
     const Expr *Init = I->getInit();
     ThisOverrideRAII ThisOverride(*Info.CurrentCall, &SubobjectParent,
                                   isa<CXXDefaultInitExpr>(Init));
     FullExpressionRAII InitScope(Info);
     if (!EvaluateInPlace(*Value, Info, Subobject, Init) ||
         (FD && FD->isBitField() &&
          !truncateBitfieldValue(Info, Init, *Value, FD))) {
       // If we're checking for a potential constant expression, evaluate all
       // initializers even if some of them fail.
       if (!Info.noteFailure())
         return false;
       Success = false;
     }
 
     // This is the point at which the dynamic type of the object becomes this
     // class type.
     if (I->isBaseInitializer() && BasesSeen == RD->getNumBases())
       EvalObj.finishedConstructingBases();
   }
 
   // Default-initialize any remaining fields.
   if (!RD->isUnion()) {
     for (; FieldIt != RD->field_end(); ++FieldIt) {
       if (!FieldIt->isUnnamedBitfield())
         Success &= getDefaultInitValue(
             FieldIt->getType(),
             Result.getStructField(FieldIt->getFieldIndex()));
     }
   }
 
   EvalObj.finishedConstructingFields();
 
   return Success &&
          EvaluateStmt(Ret, Info, Definition->getBody()) != ESR_Failed &&
          LifetimeExtendedScope.destroy();
 }
 
 static bool HandleConstructorCall(const Expr *E, const LValue &This,
                                   ArrayRef<const Expr*> Args,
                                   const CXXConstructorDecl *Definition,
                                   EvalInfo &Info, APValue &Result) {
   ArgVector ArgValues(Args.size());
   if (!EvaluateArgs(Args, ArgValues, Info, Definition))
     return false;
 
   return HandleConstructorCall(E, This, ArgValues.data(), Definition,
                                Info, Result);
 }
 
 static bool HandleDestructionImpl(EvalInfo &Info, SourceLocation CallLoc,
                                   const LValue &This, APValue &Value,
                                   QualType T) {
   // Objects can only be destroyed while they're within their lifetimes.
   // FIXME: We have no representation for whether an object of type nullptr_t
   // is in its lifetime; it usually doesn't matter. Perhaps we should model it
   // as indeterminate instead?
   if (Value.isAbsent() && !T->isNullPtrType()) {
     APValue Printable;
     This.moveInto(Printable);
     Info.FFDiag(CallLoc, diag::note_constexpr_destroy_out_of_lifetime)
       << Printable.getAsString(Info.Ctx, Info.Ctx.getLValueReferenceType(T));
     return false;
   }
 
   // Invent an expression for location purposes.
   // FIXME: We shouldn't need to do this.
   OpaqueValueExpr LocE(CallLoc, Info.Ctx.IntTy, VK_RValue);
 
   // For arrays, destroy elements right-to-left.
   if (const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(T)) {
     uint64_t Size = CAT->getSize().getZExtValue();
     QualType ElemT = CAT->getElementType();
 
     LValue ElemLV = This;
     ElemLV.addArray(Info, &LocE, CAT);
     if (!HandleLValueArrayAdjustment(Info, &LocE, ElemLV, ElemT, Size))
       return false;
 
     // Ensure that we have actual array elements available to destroy; the
     // destructors might mutate the value, so we can't run them on the array
     // filler.
     if (Size && Size > Value.getArrayInitializedElts())
       expandArray(Value, Value.getArraySize() - 1);
 
     for (; Size != 0; --Size) {
       APValue &Elem = Value.getArrayInitializedElt(Size - 1);
       if (!HandleLValueArrayAdjustment(Info, &LocE, ElemLV, ElemT, -1) ||
           !HandleDestructionImpl(Info, CallLoc, ElemLV, Elem, ElemT))
         return false;
     }
 
     // End the lifetime of this array now.
     Value = APValue();
     return true;
   }
 
   const CXXRecordDecl *RD = T->getAsCXXRecordDecl();
   if (!RD) {
     if (T.isDestructedType()) {
       Info.FFDiag(CallLoc, diag::note_constexpr_unsupported_destruction) << T;
       return false;
     }
 
     Value = APValue();
     return true;
   }
 
   if (RD->getNumVBases()) {
     Info.FFDiag(CallLoc, diag::note_constexpr_virtual_base) << RD;
     return false;
   }
 
   const CXXDestructorDecl *DD = RD->getDestructor();
   if (!DD && !RD->hasTrivialDestructor()) {
     Info.FFDiag(CallLoc);
     return false;
   }
 
   if (!DD || DD->isTrivial() ||
       (RD->isAnonymousStructOrUnion() && RD->isUnion())) {
     // A trivial destructor just ends the lifetime of the object. Check for
     // this case before checking for a body, because we might not bother
     // building a body for a trivial destructor. Note that it doesn't matter
     // whether the destructor is constexpr in this case; all trivial
     // destructors are constexpr.
     //
     // If an anonymous union would be destroyed, some enclosing destructor must
     // have been explicitly defined, and the anonymous union destruction should
     // have no effect.
     Value = APValue();
     return true;
   }
 
   if (!Info.CheckCallLimit(CallLoc))
     return false;
 
   const FunctionDecl *Definition = nullptr;
   const Stmt *Body = DD->getBody(Definition);
 
   if (!CheckConstexprFunction(Info, CallLoc, DD, Definition, Body))
     return false;
 
   CallStackFrame Frame(Info, CallLoc, Definition, &This, nullptr);
 
   // We're now in the period of destruction of this object.
   unsigned BasesLeft = RD->getNumBases();
   EvalInfo::EvaluatingDestructorRAII EvalObj(
       Info,
       ObjectUnderConstruction{This.getLValueBase(), This.Designator.Entries});
   if (!EvalObj.DidInsert) {
     // C++2a [class.dtor]p19:
     //   the behavior is undefined if the destructor is invoked for an object
     //   whose lifetime has ended
     // (Note that formally the lifetime ends when the period of destruction
     // begins, even though certain uses of the object remain valid until the
     // period of destruction ends.)
     Info.FFDiag(CallLoc, diag::note_constexpr_double_destroy);
     return false;
   }
 
   // FIXME: Creating an APValue just to hold a nonexistent return value is
   // wasteful.
   APValue RetVal;
   StmtResult Ret = {RetVal, nullptr};
   if (EvaluateStmt(Ret, Info, Definition->getBody()) == ESR_Failed)
     return false;
 
   // A union destructor does not implicitly destroy its members.
   if (RD->isUnion())
     return true;
 
   const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
 
   // We don't have a good way to iterate fields in reverse, so collect all the
   // fields first and then walk them backwards.
   SmallVector<FieldDecl*, 16> Fields(RD->field_begin(), RD->field_end());
   for (const FieldDecl *FD : llvm::reverse(Fields)) {
     if (FD->isUnnamedBitfield())
       continue;
 
     LValue Subobject = This;
     if (!HandleLValueMember(Info, &LocE, Subobject, FD, &Layout))
       return false;
 
     APValue *SubobjectValue = &Value.getStructField(FD->getFieldIndex());
     if (!HandleDestructionImpl(Info, CallLoc, Subobject, *SubobjectValue,
                                FD->getType()))
       return false;
   }
 
   if (BasesLeft != 0)
     EvalObj.startedDestroyingBases();
 
   // Destroy base classes in reverse order.
   for (const CXXBaseSpecifier &Base : llvm::reverse(RD->bases())) {
     --BasesLeft;
 
     QualType BaseType = Base.getType();
     LValue Subobject = This;
     if (!HandleLValueDirectBase(Info, &LocE, Subobject, RD,
                                 BaseType->getAsCXXRecordDecl(), &Layout))
       return false;
 
     APValue *SubobjectValue = &Value.getStructBase(BasesLeft);
     if (!HandleDestructionImpl(Info, CallLoc, Subobject, *SubobjectValue,
                                BaseType))
       return false;
   }
   assert(BasesLeft == 0 && "NumBases was wrong?");
 
   // The period of destruction ends now. The object is gone.
   Value = APValue();
   return true;
 }
 
 namespace {
 struct DestroyObjectHandler {
   EvalInfo &Info;
   const Expr *E;
   const LValue &This;
   const AccessKinds AccessKind;
 
   typedef bool result_type;
   bool failed() { return false; }
   bool found(APValue &Subobj, QualType SubobjType) {
     return HandleDestructionImpl(Info, E->getExprLoc(), This, Subobj,
                                  SubobjType);
   }
   bool found(APSInt &Value, QualType SubobjType) {
     Info.FFDiag(E, diag::note_constexpr_destroy_complex_elem);
     return false;
   }
   bool found(APFloat &Value, QualType SubobjType) {
     Info.FFDiag(E, diag::note_constexpr_destroy_complex_elem);
     return false;
   }
 };
 }
 
 /// Perform a destructor or pseudo-destructor call on the given object, which
 /// might in general not be a complete object.
 static bool HandleDestruction(EvalInfo &Info, const Expr *E,
                               const LValue &This, QualType ThisType) {
   CompleteObject Obj = findCompleteObject(Info, E, AK_Destroy, This, ThisType);
   DestroyObjectHandler Handler = {Info, E, This, AK_Destroy};
   return Obj && findSubobject(Info, E, Obj, This.Designator, Handler);
 }
 
 /// Destroy and end the lifetime of the given complete object.
 static bool HandleDestruction(EvalInfo &Info, SourceLocation Loc,
                               APValue::LValueBase LVBase, APValue &Value,
                               QualType T) {
   // If we've had an unmodeled side-effect, we can't rely on mutable state
   // (such as the object we're about to destroy) being correct.
   if (Info.EvalStatus.HasSideEffects)
     return false;
 
   LValue LV;
   LV.set({LVBase});
   return HandleDestructionImpl(Info, Loc, LV, Value, T);
 }
 
 /// Perform a call to 'perator new' or to `__builtin_operator_new'.
 static bool HandleOperatorNewCall(EvalInfo &Info, const CallExpr *E,
                                   LValue &Result) {
   if (Info.checkingPotentialConstantExpression() ||
       Info.SpeculativeEvaluationDepth)
     return false;
 
   // This is permitted only within a call to std::allocator<T>::allocate.
   auto Caller = Info.getStdAllocatorCaller("allocate");
   if (!Caller) {
     Info.FFDiag(E->getExprLoc(), Info.getLangOpts().CPlusPlus20
                                      ? diag::note_constexpr_new_untyped
                                      : diag::note_constexpr_new);
     return false;
   }
 
   QualType ElemType = Caller.ElemType;
   if (ElemType->isIncompleteType() || ElemType->isFunctionType()) {
     Info.FFDiag(E->getExprLoc(),
                 diag::note_constexpr_new_not_complete_object_type)
         << (ElemType->isIncompleteType() ? 0 : 1) << ElemType;
     return false;
   }
 
   APSInt ByteSize;
   if (!EvaluateInteger(E->getArg(0), ByteSize, Info))
     return false;
   bool IsNothrow = false;
   for (unsigned I = 1, N = E->getNumArgs(); I != N; ++I) {
     EvaluateIgnoredValue(Info, E->getArg(I));
     IsNothrow |= E->getType()->isNothrowT();
   }
 
   CharUnits ElemSize;
   if (!HandleSizeof(Info, E->getExprLoc(), ElemType, ElemSize))
     return false;
   APInt Size, Remainder;
   APInt ElemSizeAP(ByteSize.getBitWidth(), ElemSize.getQuantity());
   APInt::udivrem(ByteSize, ElemSizeAP, Size, Remainder);
   if (Remainder != 0) {
     // This likely indicates a bug in the implementation of 'std::allocator'.
     Info.FFDiag(E->getExprLoc(), diag::note_constexpr_operator_new_bad_size)
         << ByteSize << APSInt(ElemSizeAP, true) << ElemType;
     return false;
   }
 
   if (ByteSize.getActiveBits() > ConstantArrayType::getMaxSizeBits(Info.Ctx)) {
     if (IsNothrow) {
       Result.setNull(Info.Ctx, E->getType());
       return true;
     }
 
     Info.FFDiag(E, diag::note_constexpr_new_too_large) << APSInt(Size, true);
     return false;
   }
 
   QualType AllocType = Info.Ctx.getConstantArrayType(ElemType, Size, nullptr,
                                                      ArrayType::Normal, 0);
   APValue *Val = Info.createHeapAlloc(E, AllocType, Result);
   *Val = APValue(APValue::UninitArray(), 0, Size.getZExtValue());
   Result.addArray(Info, E, cast<ConstantArrayType>(AllocType));
   return true;
 }
 
 static bool hasVirtualDestructor(QualType T) {
   if (CXXRecordDecl *RD = T->getAsCXXRecordDecl())
     if (CXXDestructorDecl *DD = RD->getDestructor())
       return DD->isVirtual();
   return false;
 }
 
 static const FunctionDecl *getVirtualOperatorDelete(QualType T) {
   if (CXXRecordDecl *RD = T->getAsCXXRecordDecl())
     if (CXXDestructorDecl *DD = RD->getDestructor())
       return DD->isVirtual() ? DD->getOperatorDelete() : nullptr;
   return nullptr;
 }
 
 /// Check that the given object is a suitable pointer to a heap allocation that
 /// still exists and is of the right kind for the purpose of a deletion.
 ///
 /// On success, returns the heap allocation to deallocate. On failure, produces
 /// a diagnostic and returns None.
 static Optional<DynAlloc *> CheckDeleteKind(EvalInfo &Info, const Expr *E,
                                             const LValue &Pointer,
                                             DynAlloc::Kind DeallocKind) {
   auto PointerAsString = [&] {
     return Pointer.toString(Info.Ctx, Info.Ctx.VoidPtrTy);
   };
 
   DynamicAllocLValue DA = Pointer.Base.dyn_cast<DynamicAllocLValue>();
   if (!DA) {
     Info.FFDiag(E, diag::note_constexpr_delete_not_heap_alloc)
         << PointerAsString();
     if (Pointer.Base)
       NoteLValueLocation(Info, Pointer.Base);
     return None;
   }
 
   Optional<DynAlloc *> Alloc = Info.lookupDynamicAlloc(DA);
   if (!Alloc) {
     Info.FFDiag(E, diag::note_constexpr_double_delete);
     return None;
   }
 
   QualType AllocType = Pointer.Base.getDynamicAllocType();
   if (DeallocKind != (*Alloc)->getKind()) {
     Info.FFDiag(E, diag::note_constexpr_new_delete_mismatch)
         << DeallocKind << (*Alloc)->getKind() << AllocType;
     NoteLValueLocation(Info, Pointer.Base);
     return None;
   }
 
   bool Subobject = false;
   if (DeallocKind == DynAlloc::New) {
     Subobject = Pointer.Designator.MostDerivedPathLength != 0 ||
                 Pointer.Designator.isOnePastTheEnd();
   } else {
     Subobject = Pointer.Designator.Entries.size() != 1 ||
                 Pointer.Designator.Entries[0].getAsArrayIndex() != 0;
   }
   if (Subobject) {
     Info.FFDiag(E, diag::note_constexpr_delete_subobject)
         << PointerAsString() << Pointer.Designator.isOnePastTheEnd();
     return None;
   }
 
   return Alloc;
 }
 
 // Perform a call to 'operator delete' or '__builtin_operator_delete'.
 bool HandleOperatorDeleteCall(EvalInfo &Info, const CallExpr *E) {
   if (Info.checkingPotentialConstantExpression() ||
       Info.SpeculativeEvaluationDepth)
     return false;
 
   // This is permitted only within a call to std::allocator<T>::deallocate.
   if (!Info.getStdAllocatorCaller("deallocate")) {
     Info.FFDiag(E->getExprLoc());
     return true;
   }
 
   LValue Pointer;
   if (!EvaluatePointer(E->getArg(0), Pointer, Info))
     return false;
   for (unsigned I = 1, N = E->getNumArgs(); I != N; ++I)
     EvaluateIgnoredValue(Info, E->getArg(I));
 
   if (Pointer.Designator.Invalid)
     return false;
 
   // Deleting a null pointer has no effect.
   if (Pointer.isNullPointer())
     return true;
 
   if (!CheckDeleteKind(Info, E, Pointer, DynAlloc::StdAllocator))
     return false;
 
   Info.HeapAllocs.erase(Pointer.Base.get<DynamicAllocLValue>());
   return true;
 }
 
 //===----------------------------------------------------------------------===//
 // Generic Evaluation
 //===----------------------------------------------------------------------===//
 namespace {
 
 class BitCastBuffer {
   // FIXME: We're going to need bit-level granularity when we support
   // bit-fields.
   // FIXME: Its possible under the C++ standard for 'char' to not be 8 bits, but
   // we don't support a host or target where that is the case. Still, we should
   // use a more generic type in case we ever do.
   SmallVector<Optional<unsigned char>, 32> Bytes;
 
   static_assert(std::numeric_limits<unsigned char>::digits >= 8,
                 "Need at least 8 bit unsigned char");
 
   bool TargetIsLittleEndian;
 
 public:
   BitCastBuffer(CharUnits Width, bool TargetIsLittleEndian)
       : Bytes(Width.getQuantity()),
         TargetIsLittleEndian(TargetIsLittleEndian) {}
 
   LLVM_NODISCARD
   bool readObject(CharUnits Offset, CharUnits Width,
                   SmallVectorImpl<unsigned char> &Output) const {
     for (CharUnits I = Offset, E = Offset + Width; I != E; ++I) {
       // If a byte of an integer is uninitialized, then the whole integer is
       // uninitalized.
       if (!Bytes[I.getQuantity()])
         return false;
       Output.push_back(*Bytes[I.getQuantity()]);
     }
     if (llvm::sys::IsLittleEndianHost != TargetIsLittleEndian)
       std::reverse(Output.begin(), Output.end());
     return true;
   }
 
   void writeObject(CharUnits Offset, SmallVectorImpl<unsigned char> &Input) {
     if (llvm::sys::IsLittleEndianHost != TargetIsLittleEndian)
       std::reverse(Input.begin(), Input.end());
 
     size_t Index = 0;
     for (unsigned char Byte : Input) {
       assert(!Bytes[Offset.getQuantity() + Index] && "overwriting a byte?");
       Bytes[Offset.getQuantity() + Index] = Byte;
       ++Index;
     }
   }
 
   size_t size() { return Bytes.size(); }
 };
 
 /// Traverse an APValue to produce an BitCastBuffer, emulating how the current
 /// target would represent the value at runtime.
 class APValueToBufferConverter {
   EvalInfo &Info;
   BitCastBuffer Buffer;
   const CastExpr *BCE;
 
   APValueToBufferConverter(EvalInfo &Info, CharUnits ObjectWidth,
                            const CastExpr *BCE)
       : Info(Info),
         Buffer(ObjectWidth, Info.Ctx.getTargetInfo().isLittleEndian()),
         BCE(BCE) {}
 
   bool visit(const APValue &Val, QualType Ty) {
     return visit(Val, Ty, CharUnits::fromQuantity(0));
   }
 
   // Write out Val with type Ty into Buffer starting at Offset.
   bool visit(const APValue &Val, QualType Ty, CharUnits Offset) {
     assert((size_t)Offset.getQuantity() <= Buffer.size());
 
     // As a special case, nullptr_t has an indeterminate value.
     if (Ty->isNullPtrType())
       return true;
 
     // Dig through Src to find the byte at SrcOffset.
     switch (Val.getKind()) {
     case APValue::Indeterminate:
     case APValue::None:
       return true;
 
     case APValue::Int:
       return visitInt(Val.getInt(), Ty, Offset);
     case APValue::Float:
       return visitFloat(Val.getFloat(), Ty, Offset);
     case APValue::Array:
       return visitArray(Val, Ty, Offset);
     case APValue::Struct:
       return visitRecord(Val, Ty, Offset);
 
     case APValue::ComplexInt:
     case APValue::ComplexFloat:
     case APValue::Vector:
     case APValue::FixedPoint:
       // FIXME: We should support these.
 
     case APValue::Union:
     case APValue::MemberPointer:
     case APValue::AddrLabelDiff: {
       Info.FFDiag(BCE->getBeginLoc(),
                   diag::note_constexpr_bit_cast_unsupported_type)
           << Ty;
       return false;
     }
 
     case APValue::LValue:
       llvm_unreachable("LValue subobject in bit_cast?");
     }
     llvm_unreachable("Unhandled APValue::ValueKind");
   }
 
   bool visitRecord(const APValue &Val, QualType Ty, CharUnits Offset) {
     const RecordDecl *RD = Ty->getAsRecordDecl();
     const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
 
     // Visit the base classes.
     if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD)) {
       for (size_t I = 0, E = CXXRD->getNumBases(); I != E; ++I) {
         const CXXBaseSpecifier &BS = CXXRD->bases_begin()[I];
         CXXRecordDecl *BaseDecl = BS.getType()->getAsCXXRecordDecl();
 
         if (!visitRecord(Val.getStructBase(I), BS.getType(),
                          Layout.getBaseClassOffset(BaseDecl) + Offset))
           return false;
       }
     }
 
     // Visit the fields.
     unsigned FieldIdx = 0;
     for (FieldDecl *FD : RD->fields()) {
       if (FD->isBitField()) {
         Info.FFDiag(BCE->getBeginLoc(),
                     diag::note_constexpr_bit_cast_unsupported_bitfield);
         return false;
       }
 
       uint64_t FieldOffsetBits = Layout.getFieldOffset(FieldIdx);
 
       assert(FieldOffsetBits % Info.Ctx.getCharWidth() == 0 &&
              "only bit-fields can have sub-char alignment");
       CharUnits FieldOffset =
           Info.Ctx.toCharUnitsFromBits(FieldOffsetBits) + Offset;
       QualType FieldTy = FD->getType();
       if (!visit(Val.getStructField(FieldIdx), FieldTy, FieldOffset))
         return false;
       ++FieldIdx;
     }
 
     return true;
   }
 
   bool visitArray(const APValue &Val, QualType Ty, CharUnits Offset) {
     const auto *CAT =
         dyn_cast_or_null<ConstantArrayType>(Ty->getAsArrayTypeUnsafe());
     if (!CAT)
       return false;
 
     CharUnits ElemWidth = Info.Ctx.getTypeSizeInChars(CAT->getElementType());
     unsigned NumInitializedElts = Val.getArrayInitializedElts();
     unsigned ArraySize = Val.getArraySize();
     // First, initialize the initialized elements.
     for (unsigned I = 0; I != NumInitializedElts; ++I) {
       const APValue &SubObj = Val.getArrayInitializedElt(I);
       if (!visit(SubObj, CAT->getElementType(), Offset + I * ElemWidth))
         return false;
     }
 
     // Next, initialize the rest of the array using the filler.
     if (Val.hasArrayFiller()) {
       const APValue &Filler = Val.getArrayFiller();
       for (unsigned I = NumInitializedElts; I != ArraySize; ++I) {
         if (!visit(Filler, CAT->getElementType(), Offset + I * ElemWidth))
           return false;
       }
     }
 
     return true;
   }
 
   bool visitInt(const APSInt &Val, QualType Ty, CharUnits Offset) {
     CharUnits Width = Info.Ctx.getTypeSizeInChars(Ty);
     SmallVector<unsigned char, 8> Bytes(Width.getQuantity());
     llvm::StoreIntToMemory(Val, &*Bytes.begin(), Width.getQuantity());
     Buffer.writeObject(Offset, Bytes);
     return true;
   }
 
   bool visitFloat(const APFloat &Val, QualType Ty, CharUnits Offset) {
     APSInt AsInt(Val.bitcastToAPInt());
     return visitInt(AsInt, Ty, Offset);
   }
 
 public:
   static Optional<BitCastBuffer> convert(EvalInfo &Info, const APValue &Src,
                                          const CastExpr *BCE) {
     CharUnits DstSize = Info.Ctx.getTypeSizeInChars(BCE->getType());
     APValueToBufferConverter Converter(Info, DstSize, BCE);
     if (!Converter.visit(Src, BCE->getSubExpr()->getType()))
       return None;
     return Converter.Buffer;
   }
 };
 
 /// Write an BitCastBuffer into an APValue.
 class BufferToAPValueConverter {
   EvalInfo &Info;
   const BitCastBuffer &Buffer;
   const CastExpr *BCE;
 
   BufferToAPValueConverter(EvalInfo &Info, const BitCastBuffer &Buffer,
                            const CastExpr *BCE)
       : Info(Info), Buffer(Buffer), BCE(BCE) {}
 
   // Emit an unsupported bit_cast type error. Sema refuses to build a bit_cast
   // with an invalid type, so anything left is a deficiency on our part (FIXME).
   // Ideally this will be unreachable.
   llvm::NoneType unsupportedType(QualType Ty) {
     Info.FFDiag(BCE->getBeginLoc(),
                 diag::note_constexpr_bit_cast_unsupported_type)
         << Ty;
     return None;
   }
 
   Optional<APValue> visit(const BuiltinType *T, CharUnits Offset,
                           const EnumType *EnumSugar = nullptr) {
     if (T->isNullPtrType()) {
       uint64_t NullValue = Info.Ctx.getTargetNullPointerValue(QualType(T, 0));
       return APValue((Expr *)nullptr,
                      /*Offset=*/CharUnits::fromQuantity(NullValue),
                      APValue::NoLValuePath{}, /*IsNullPtr=*/true);
     }
 
     CharUnits SizeOf = Info.Ctx.getTypeSizeInChars(T);
     SmallVector<uint8_t, 8> Bytes;
     if (!Buffer.readObject(Offset, SizeOf, Bytes)) {
       // If this is std::byte or unsigned char, then its okay to store an
       // indeterminate value.
       bool IsStdByte = EnumSugar && EnumSugar->isStdByteType();
       bool IsUChar =
           !EnumSugar && (T->isSpecificBuiltinType(BuiltinType::UChar) ||
                          T->isSpecificBuiltinType(BuiltinType::Char_U));
       if (!IsStdByte && !IsUChar) {
         QualType DisplayType(EnumSugar ? (const Type *)EnumSugar : T, 0);
         Info.FFDiag(BCE->getExprLoc(),
                     diag::note_constexpr_bit_cast_indet_dest)
             << DisplayType << Info.Ctx.getLangOpts().CharIsSigned;
         return None;
       }
 
       return APValue::IndeterminateValue();
     }
 
     APSInt Val(SizeOf.getQuantity() * Info.Ctx.getCharWidth(), true);
     llvm::LoadIntFromMemory(Val, &*Bytes.begin(), Bytes.size());
 
     if (T->isIntegralOrEnumerationType()) {
       Val.setIsSigned(T->isSignedIntegerOrEnumerationType());
       return APValue(Val);
     }
 
     if (T->isRealFloatingType()) {
       const llvm::fltSemantics &Semantics =
           Info.Ctx.getFloatTypeSemantics(QualType(T, 0));
       return APValue(APFloat(Semantics, Val));
     }
 
     return unsupportedType(QualType(T, 0));
   }
 
   Optional<APValue> visit(const RecordType *RTy, CharUnits Offset) {
     const RecordDecl *RD = RTy->getAsRecordDecl();
     const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
 
     unsigned NumBases = 0;
     if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
       NumBases = CXXRD->getNumBases();
 
     APValue ResultVal(APValue::UninitStruct(), NumBases,
                       std::distance(RD->field_begin(), RD->field_end()));
 
     // Visit the base classes.
     if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD)) {
       for (size_t I = 0, E = CXXRD->getNumBases(); I != E; ++I) {
         const CXXBaseSpecifier &BS = CXXRD->bases_begin()[I];
         CXXRecordDecl *BaseDecl = BS.getType()->getAsCXXRecordDecl();
         if (BaseDecl->isEmpty() ||
             Info.Ctx.getASTRecordLayout(BaseDecl).getNonVirtualSize().isZero())
           continue;
 
         Optional<APValue> SubObj = visitType(
             BS.getType(), Layout.getBaseClassOffset(BaseDecl) + Offset);
         if (!SubObj)
           return None;
         ResultVal.getStructBase(I) = *SubObj;
       }
     }
 
     // Visit the fields.
     unsigned FieldIdx = 0;
     for (FieldDecl *FD : RD->fields()) {
       // FIXME: We don't currently support bit-fields. A lot of the logic for
       // this is in CodeGen, so we need to factor it around.
       if (FD->isBitField()) {
         Info.FFDiag(BCE->getBeginLoc(),
                     diag::note_constexpr_bit_cast_unsupported_bitfield);
         return None;
       }
 
       uint64_t FieldOffsetBits = Layout.getFieldOffset(FieldIdx);
       assert(FieldOffsetBits % Info.Ctx.getCharWidth() == 0);
 
       CharUnits FieldOffset =
           CharUnits::fromQuantity(FieldOffsetBits / Info.Ctx.getCharWidth()) +
           Offset;
       QualType FieldTy = FD->getType();
       Optional<APValue> SubObj = visitType(FieldTy, FieldOffset);
       if (!SubObj)
         return None;
       ResultVal.getStructField(FieldIdx) = *SubObj;
       ++FieldIdx;
     }
 
     return ResultVal;
   }
 
   Optional<APValue> visit(const EnumType *Ty, CharUnits Offset) {
     QualType RepresentationType = Ty->getDecl()->getIntegerType();
     assert(!RepresentationType.isNull() &&
            "enum forward decl should be caught by Sema");
     const auto *AsBuiltin =
         RepresentationType.getCanonicalType()->castAs<BuiltinType>();
     // Recurse into the underlying type. Treat std::byte transparently as
     // unsigned char.
     return visit(AsBuiltin, Offset, /*EnumTy=*/Ty);
   }
 
   Optional<APValue> visit(const ConstantArrayType *Ty, CharUnits Offset) {
     size_t Size = Ty->getSize().getLimitedValue();
     CharUnits ElementWidth = Info.Ctx.getTypeSizeInChars(Ty->getElementType());
 
     APValue ArrayValue(APValue::UninitArray(), Size, Size);
     for (size_t I = 0; I != Size; ++I) {
       Optional<APValue> ElementValue =
           visitType(Ty->getElementType(), Offset + I * ElementWidth);
       if (!ElementValue)
         return None;
       ArrayValue.getArrayInitializedElt(I) = std::move(*ElementValue);
     }
 
     return ArrayValue;
   }
 
   Optional<APValue> visit(const Type *Ty, CharUnits Offset) {
     return unsupportedType(QualType(Ty, 0));
   }
 
   Optional<APValue> visitType(QualType Ty, CharUnits Offset) {
     QualType Can = Ty.getCanonicalType();
 
     switch (Can->getTypeClass()) {
 #define TYPE(Class, Base)                                                      \
   case Type::Class:                                                            \
     return visit(cast<Class##Type>(Can.getTypePtr()), Offset);
 #define ABSTRACT_TYPE(Class, Base)
 #define NON_CANONICAL_TYPE(Class, Base)                                        \
   case Type::Class:                                                            \
     llvm_unreachable("non-canonical type should be impossible!");
 #define DEPENDENT_TYPE(Class, Base)                                            \
   case Type::Class:                                                            \
     llvm_unreachable(                                                          \
         "dependent types aren't supported in the constant evaluator!");
 #define NON_CANONICAL_UNLESS_DEPENDENT(Class, Base)                            \
   case Type::Class:                                                            \
     llvm_unreachable("either dependent or not canonical!");
 #include "clang/AST/TypeNodes.inc"
     }
     llvm_unreachable("Unhandled Type::TypeClass");
   }
 
 public:
   // Pull out a full value of type DstType.
   static Optional<APValue> convert(EvalInfo &Info, BitCastBuffer &Buffer,
                                    const CastExpr *BCE) {
     BufferToAPValueConverter Converter(Info, Buffer, BCE);
     return Converter.visitType(BCE->getType(), CharUnits::fromQuantity(0));
   }
 };
 
 static bool checkBitCastConstexprEligibilityType(SourceLocation Loc,
                                                  QualType Ty, EvalInfo *Info,
                                                  const ASTContext &Ctx,
                                                  bool CheckingDest) {
   Ty = Ty.getCanonicalType();
 
   auto diag = [&](int Reason) {
     if (Info)
       Info->FFDiag(Loc, diag::note_constexpr_bit_cast_invalid_type)
           << CheckingDest << (Reason == 4) << Reason;
     return false;
   };
   auto note = [&](int Construct, QualType NoteTy, SourceLocation NoteLoc) {
     if (Info)
       Info->Note(NoteLoc, diag::note_constexpr_bit_cast_invalid_subtype)
           << NoteTy << Construct << Ty;
     return false;
   };
 
   if (Ty->isUnionType())
     return diag(0);
   if (Ty->isPointerType())
     return diag(1);
   if (Ty->isMemberPointerType())
     return diag(2);
   if (Ty.isVolatileQualified())
     return diag(3);
 
   if (RecordDecl *Record = Ty->getAsRecordDecl()) {
     if (auto *CXXRD = dyn_cast<CXXRecordDecl>(Record)) {
       for (CXXBaseSpecifier &BS : CXXRD->bases())
         if (!checkBitCastConstexprEligibilityType(Loc, BS.getType(), Info, Ctx,
                                                   CheckingDest))
           return note(1, BS.getType(), BS.getBeginLoc());
     }
     for (FieldDecl *FD : Record->fields()) {
       if (FD->getType()->isReferenceType())
         return diag(4);
       if (!checkBitCastConstexprEligibilityType(Loc, FD->getType(), Info, Ctx,
                                                 CheckingDest))
         return note(0, FD->getType(), FD->getBeginLoc());
     }
   }
 
   if (Ty->isArrayType() &&
       !checkBitCastConstexprEligibilityType(Loc, Ctx.getBaseElementType(Ty),
                                             Info, Ctx, CheckingDest))
     return false;
 
   return true;
 }
 
 static bool checkBitCastConstexprEligibility(EvalInfo *Info,
                                              const ASTContext &Ctx,
                                              const CastExpr *BCE) {
   bool DestOK = checkBitCastConstexprEligibilityType(
       BCE->getBeginLoc(), BCE->getType(), Info, Ctx, true);
   bool SourceOK = DestOK && checkBitCastConstexprEligibilityType(
                                 BCE->getBeginLoc(),
                                 BCE->getSubExpr()->getType(), Info, Ctx, false);
   return SourceOK;
 }
 
 static bool handleLValueToRValueBitCast(EvalInfo &Info, APValue &DestValue,
                                         APValue &SourceValue,
                                         const CastExpr *BCE) {
   assert(CHAR_BIT == 8 && Info.Ctx.getTargetInfo().getCharWidth() == 8 &&
          "no host or target supports non 8-bit chars");
   assert(SourceValue.isLValue() &&
          "LValueToRValueBitcast requires an lvalue operand!");
 
   if (!checkBitCastConstexprEligibility(&Info, Info.Ctx, BCE))
     return false;
 
   LValue SourceLValue;
   APValue SourceRValue;
   SourceLValue.setFrom(Info.Ctx, SourceValue);
   if (!handleLValueToRValueConversion(
           Info, BCE, BCE->getSubExpr()->getType().withConst(), SourceLValue,
           SourceRValue, /*WantObjectRepresentation=*/true))
     return false;
 
   // Read out SourceValue into a char buffer.
   Optional<BitCastBuffer> Buffer =
       APValueToBufferConverter::convert(Info, SourceRValue, BCE);
   if (!Buffer)
     return false;
 
   // Write out the buffer into a new APValue.
   Optional<APValue> MaybeDestValue =
       BufferToAPValueConverter::convert(Info, *Buffer, BCE);
   if (!MaybeDestValue)
     return false;
 
   DestValue = std::move(*MaybeDestValue);
   return true;
 }
 
 template <class Derived>
 class ExprEvaluatorBase
   : public ConstStmtVisitor<Derived, bool> {
 private:
   Derived &getDerived() { return static_cast<Derived&>(*this); }
   bool DerivedSuccess(const APValue &V, const Expr *E) {
     return getDerived().Success(V, E);
   }
   bool DerivedZeroInitialization(const Expr *E) {
     return getDerived().ZeroInitialization(E);
   }
 
   // Check whether a conditional operator with a non-constant condition is a
   // potential constant expression. If neither arm is a potential constant
   // expression, then the conditional operator is not either.
   template<typename ConditionalOperator>
   void CheckPotentialConstantConditional(const ConditionalOperator *E) {
     assert(Info.checkingPotentialConstantExpression());
 
     // Speculatively evaluate both arms.
     SmallVector<PartialDiagnosticAt, 8> Diag;
     {
       SpeculativeEvaluationRAII Speculate(Info, &Diag);
       StmtVisitorTy::Visit(E->getFalseExpr());
       if (Diag.empty())
         return;
     }
 
     {
       SpeculativeEvaluationRAII Speculate(Info, &Diag);
       Diag.clear();
       StmtVisitorTy::Visit(E->getTrueExpr());
       if (Diag.empty())
         return;
     }
 
     Error(E, diag::note_constexpr_conditional_never_const);
   }
 
 
   template<typename ConditionalOperator>
   bool HandleConditionalOperator(const ConditionalOperator *E) {
     bool BoolResult;
     if (!EvaluateAsBooleanCondition(E->getCond(), BoolResult, Info)) {
       if (Info.checkingPotentialConstantExpression() && Info.noteFailure()) {
         CheckPotentialConstantConditional(E);
         return false;
       }
       if (Info.noteFailure()) {
         StmtVisitorTy::Visit(E->getTrueExpr());
         StmtVisitorTy::Visit(E->getFalseExpr());
       }
       return false;
     }
 
     Expr *EvalExpr = BoolResult ? E->getTrueExpr() : E->getFalseExpr();
     return StmtVisitorTy::Visit(EvalExpr);
   }
 
 protected:
   EvalInfo &Info;
   typedef ConstStmtVisitor<Derived, bool> StmtVisitorTy;
   typedef ExprEvaluatorBase ExprEvaluatorBaseTy;
 
   OptionalDiagnostic CCEDiag(const Expr *E, diag::kind D) {
     return Info.CCEDiag(E, D);
   }
 
   bool ZeroInitialization(const Expr *E) { return Error(E); }
 
 public:
   ExprEvaluatorBase(EvalInfo &Info) : Info(Info) {}
 
   EvalInfo &getEvalInfo() { return Info; }
 
   /// Report an evaluation error. This should only be called when an error is
   /// first discovered. When propagating an error, just return false.
   bool Error(const Expr *E, diag::kind D) {
     Info.FFDiag(E, D);
     return false;
   }
   bool Error(const Expr *E) {
     return Error(E, diag::note_invalid_subexpr_in_const_expr);
   }
 
   bool VisitStmt(const Stmt *) {
     llvm_unreachable("Expression evaluator should not be called on stmts");
   }
   bool VisitExpr(const Expr *E) {
     return Error(E);
   }
 
   bool VisitConstantExpr(const ConstantExpr *E) {
     if (E->hasAPValueResult())
       return DerivedSuccess(E->getAPValueResult(), E);
 
     return StmtVisitorTy::Visit(E->getSubExpr());
   }
 
   bool VisitParenExpr(const ParenExpr *E)
     { return StmtVisitorTy::Visit(E->getSubExpr()); }
   bool VisitUnaryExtension(const UnaryOperator *E)
     { return StmtVisitorTy::Visit(E->getSubExpr()); }
   bool VisitUnaryPlus(const UnaryOperator *E)
     { return StmtVisitorTy::Visit(E->getSubExpr()); }
   bool VisitChooseExpr(const ChooseExpr *E)
     { return StmtVisitorTy::Visit(E->getChosenSubExpr()); }
   bool VisitGenericSelectionExpr(const GenericSelectionExpr *E)
     { return StmtVisitorTy::Visit(E->getResultExpr()); }
   bool VisitSubstNonTypeTemplateParmExpr(const SubstNonTypeTemplateParmExpr *E)
     { return StmtVisitorTy::Visit(E->getReplacement()); }
   bool VisitCXXDefaultArgExpr(const CXXDefaultArgExpr *E) {
     TempVersionRAII RAII(*Info.CurrentCall);
     SourceLocExprScopeGuard Guard(E, Info.CurrentCall->CurSourceLocExprScope);
     return StmtVisitorTy::Visit(E->getExpr());
   }
   bool VisitCXXDefaultInitExpr(const CXXDefaultInitExpr *E) {
     TempVersionRAII RAII(*Info.CurrentCall);
     // The initializer may not have been parsed yet, or might be erroneous.
     if (!E->getExpr())
       return Error(E);
     SourceLocExprScopeGuard Guard(E, Info.CurrentCall->CurSourceLocExprScope);
     return StmtVisitorTy::Visit(E->getExpr());
   }
 
   bool VisitExprWithCleanups(const ExprWithCleanups *E) {
     FullExpressionRAII Scope(Info);
     return StmtVisitorTy::Visit(E->getSubExpr()) && Scope.destroy();
   }
 
   // Temporaries are registered when created, so we don't care about
   // CXXBindTemporaryExpr.
   bool VisitCXXBindTemporaryExpr(const CXXBindTemporaryExpr *E) {
     return StmtVisitorTy::Visit(E->getSubExpr());
   }
 
   bool VisitCXXReinterpretCastExpr(const CXXReinterpretCastExpr *E) {
     CCEDiag(E, diag::note_constexpr_invalid_cast) << 0;
     return static_cast<Derived*>(this)->VisitCastExpr(E);
   }
   bool VisitCXXDynamicCastExpr(const CXXDynamicCastExpr *E) {
     if (!Info.Ctx.getLangOpts().CPlusPlus20)
       CCEDiag(E, diag::note_constexpr_invalid_cast) << 1;
     return static_cast<Derived*>(this)->VisitCastExpr(E);
   }
   bool VisitBuiltinBitCastExpr(const BuiltinBitCastExpr *E) {
     return static_cast<Derived*>(this)->VisitCastExpr(E);
   }
 
   bool VisitBinaryOperator(const BinaryOperator *E) {
     switch (E->getOpcode()) {
     default:
       return Error(E);
 
     case BO_Comma:
       VisitIgnoredValue(E->getLHS());
       return StmtVisitorTy::Visit(E->getRHS());
 
     case BO_PtrMemD:
     case BO_PtrMemI: {
       LValue Obj;
       if (!HandleMemberPointerAccess(Info, E, Obj))
         return false;
       APValue Result;
       if (!handleLValueToRValueConversion(Info, E, E->getType(), Obj, Result))
         return false;
       return DerivedSuccess(Result, E);
     }
     }
   }
 
   bool VisitCXXRewrittenBinaryOperator(const CXXRewrittenBinaryOperator *E) {
     return StmtVisitorTy::Visit(E->getSemanticForm());
   }
 
   bool VisitBinaryConditionalOperator(const BinaryConditionalOperator *E) {
     // Evaluate and cache the common expression. We treat it as a temporary,
     // even though it's not quite the same thing.
     LValue CommonLV;
     if (!Evaluate(Info.CurrentCall->createTemporary(
                       E->getOpaqueValue(),
                       getStorageType(Info.Ctx, E->getOpaqueValue()), false,
                       CommonLV),
                   Info, E->getCommon()))
       return false;
 
     return HandleConditionalOperator(E);
   }
 
   bool VisitConditionalOperator(const ConditionalOperator *E) {
     bool IsBcpCall = false;
     // If the condition (ignoring parens) is a __builtin_constant_p call,
     // the result is a constant expression if it can be folded without
     // side-effects. This is an important GNU extension. See GCC PR38377
     // for discussion.
     if (const CallExpr *CallCE =
           dyn_cast<CallExpr>(E->getCond()->IgnoreParenCasts()))
       if (CallCE->getBuiltinCallee() == Builtin::BI__builtin_constant_p)
         IsBcpCall = true;
 
     // Always assume __builtin_constant_p(...) ? ... : ... is a potential
     // constant expression; we can't check whether it's potentially foldable.
     // FIXME: We should instead treat __builtin_constant_p as non-constant if
     // it would return 'false' in this mode.
     if (Info.checkingPotentialConstantExpression() && IsBcpCall)
       return false;
 
     FoldConstant Fold(Info, IsBcpCall);
     if (!HandleConditionalOperator(E)) {
       Fold.keepDiagnostics();
       return false;
     }
 
     return true;
   }
 
   bool VisitOpaqueValueExpr(const OpaqueValueExpr *E) {
     if (APValue *Value = Info.CurrentCall->getCurrentTemporary(E))
       return DerivedSuccess(*Value, E);
 
     const Expr *Source = E->getSourceExpr();
     if (!Source)
       return Error(E);
     if (Source == E) { // sanity checking.
       assert(0 && "OpaqueValueExpr recursively refers to itself");
       return Error(E);
     }
     return StmtVisitorTy::Visit(Source);
   }
 
   bool VisitPseudoObjectExpr(const PseudoObjectExpr *E) {
     for (const Expr *SemE : E->semantics()) {
       if (auto *OVE = dyn_cast<OpaqueValueExpr>(SemE)) {
         // FIXME: We can't handle the case where an OpaqueValueExpr is also the
         // result expression: there could be two different LValues that would
         // refer to the same object in that case, and we can't model that.
         if (SemE == E->getResultExpr())
           return Error(E);
 
         // Unique OVEs get evaluated if and when we encounter them when
         // emitting the rest of the semantic form, rather than eagerly.
         if (OVE->isUnique())
           continue;
 
         LValue LV;
         if (!Evaluate(Info.CurrentCall->createTemporary(
                           OVE, getStorageType(Info.Ctx, OVE), false, LV),
                       Info, OVE->getSourceExpr()))
           return false;
       } else if (SemE == E->getResultExpr()) {
         if (!StmtVisitorTy::Visit(SemE))
           return false;
       } else {
         if (!EvaluateIgnoredValue(Info, SemE))
           return false;
       }
     }
     return true;
   }
 
   bool VisitCallExpr(const CallExpr *E) {
     APValue Result;
     if (!handleCallExpr(E, Result, nullptr))
       return false;
     return DerivedSuccess(Result, E);
   }
 
   bool handleCallExpr(const CallExpr *E, APValue &Result,
                      const LValue *ResultSlot) {
     const Expr *Callee = E->getCallee()->IgnoreParens();
     QualType CalleeType = Callee->getType();
 
     const FunctionDecl *FD = nullptr;
     LValue *This = nullptr, ThisVal;
     auto Args = llvm::makeArrayRef(E->getArgs(), E->getNumArgs());
     bool HasQualifier = false;
 
     // Extract function decl and 'this' pointer from the callee.
     if (CalleeType->isSpecificBuiltinType(BuiltinType::BoundMember)) {
       const CXXMethodDecl *Member = nullptr;
       if (const MemberExpr *ME = dyn_cast<MemberExpr>(Callee)) {
         // Explicit bound member calls, such as x.f() or p->g();
         if (!EvaluateObjectArgument(Info, ME->getBase(), ThisVal))
           return false;
         Member = dyn_cast<CXXMethodDecl>(ME->getMemberDecl());
         if (!Member)
           return Error(Callee);
         This = &ThisVal;
         HasQualifier = ME->hasQualifier();
       } else if (const BinaryOperator *BE = dyn_cast<BinaryOperator>(Callee)) {
         // Indirect bound member calls ('.*' or '->*').
         const ValueDecl *D =
             HandleMemberPointerAccess(Info, BE, ThisVal, false);
         if (!D)
           return false;
         Member = dyn_cast<CXXMethodDecl>(D);
         if (!Member)
           return Error(Callee);
         This = &ThisVal;
       } else if (const auto *PDE = dyn_cast<CXXPseudoDestructorExpr>(Callee)) {
         if (!Info.getLangOpts().CPlusPlus20)
           Info.CCEDiag(PDE, diag::note_constexpr_pseudo_destructor);
         return EvaluateObjectArgument(Info, PDE->getBase(), ThisVal) &&
                HandleDestruction(Info, PDE, ThisVal, PDE->getDestroyedType());
       } else
         return Error(Callee);
       FD = Member;
     } else if (CalleeType->isFunctionPointerType()) {
       LValue Call;
       if (!EvaluatePointer(Callee, Call, Info))
         return false;
 
       if (!Call.getLValueOffset().isZero())
         return Error(Callee);
       FD = dyn_cast_or_null<FunctionDecl>(
                              Call.getLValueBase().dyn_cast<const ValueDecl*>());
       if (!FD)
         return Error(Callee);
       // Don't call function pointers which have been cast to some other type.
       // Per DR (no number yet), the caller and callee can differ in noexcept.
       if (!Info.Ctx.hasSameFunctionTypeIgnoringExceptionSpec(
         CalleeType->getPointeeType(), FD->getType())) {
         return Error(E);
       }
 
       // Overloaded operator calls to member functions are represented as normal
       // calls with '*this' as the first argument.
       const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
       if (MD && !MD->isStatic()) {
         // FIXME: When selecting an implicit conversion for an overloaded
         // operator delete, we sometimes try to evaluate calls to conversion
         // operators without a 'this' parameter!
         if (Args.empty())
           return Error(E);
 
         if (!EvaluateObjectArgument(Info, Args[0], ThisVal))
           return false;
         This = &ThisVal;
         Args = Args.slice(1);
       } else if (MD && MD->isLambdaStaticInvoker()) {
         // Map the static invoker for the lambda back to the call operator.
         // Conveniently, we don't have to slice out the 'this' argument (as is
         // being done for the non-static case), since a static member function
         // doesn't have an implicit argument passed in.
         const CXXRecordDecl *ClosureClass = MD->getParent();
         assert(
             ClosureClass->captures_begin() == ClosureClass->captures_end() &&
             "Number of captures must be zero for conversion to function-ptr");
 
         const CXXMethodDecl *LambdaCallOp =
             ClosureClass->getLambdaCallOperator();
 
         // Set 'FD', the function that will be called below, to the call
         // operator.  If the closure object represents a generic lambda, find
         // the corresponding specialization of the call operator.
 
         if (ClosureClass->isGenericLambda()) {
           assert(MD->isFunctionTemplateSpecialization() &&
                  "A generic lambda's static-invoker function must be a "
                  "template specialization");
           const TemplateArgumentList *TAL = MD->getTemplateSpecializationArgs();
           FunctionTemplateDecl *CallOpTemplate =
               LambdaCallOp->getDescribedFunctionTemplate();
           void *InsertPos = nullptr;
           FunctionDecl *CorrespondingCallOpSpecialization =
               CallOpTemplate->findSpecialization(TAL->asArray(), InsertPos);
           assert(CorrespondingCallOpSpecialization &&
                  "We must always have a function call operator specialization "
                  "that corresponds to our static invoker specialization");
           FD = cast<CXXMethodDecl>(CorrespondingCallOpSpecialization);
         } else
           FD = LambdaCallOp;
       } else if (FD->isReplaceableGlobalAllocationFunction()) {
         if (FD->getDeclName().getCXXOverloadedOperator() == OO_New ||
             FD->getDeclName().getCXXOverloadedOperator() == OO_Array_New) {
           LValue Ptr;
           if (!HandleOperatorNewCall(Info, E, Ptr))
             return false;
           Ptr.moveInto(Result);
           return true;
         } else {
           return HandleOperatorDeleteCall(Info, E);
         }
       }
     } else
       return Error(E);
 
     SmallVector<QualType, 4> CovariantAdjustmentPath;
     if (This) {
       auto *NamedMember = dyn_cast<CXXMethodDecl>(FD);
       if (NamedMember && NamedMember->isVirtual() && !HasQualifier) {
         // Perform virtual dispatch, if necessary.
         FD = HandleVirtualDispatch(Info, E, *This, NamedMember,
                                    CovariantAdjustmentPath);
         if (!FD)
           return false;
       } else {
         // Check that the 'this' pointer points to an object of the right type.
         // FIXME: If this is an assignment operator call, we may need to change
         // the active union member before we check this.
         if (!checkNonVirtualMemberCallThisPointer(Info, E, *This, NamedMember))
           return false;
       }
     }
 
     // Destructor calls are different enough that they have their own codepath.
     if (auto *DD = dyn_cast<CXXDestructorDecl>(FD)) {
       assert(This && "no 'this' pointer for destructor call");
       return HandleDestruction(Info, E, *This,
                                Info.Ctx.getRecordType(DD->getParent()));
     }
 
     const FunctionDecl *Definition = nullptr;
     Stmt *Body = FD->getBody(Definition);
 
     if (!CheckConstexprFunction(Info, E->getExprLoc(), FD, Definition, Body) ||
         !HandleFunctionCall(E->getExprLoc(), Definition, This, Args, Body, Info,
                             Result, ResultSlot))
       return false;
 
     if (!CovariantAdjustmentPath.empty() &&
         !HandleCovariantReturnAdjustment(Info, E, Result,
                                          CovariantAdjustmentPath))
       return false;
 
     return true;
   }
 
   bool VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
     return StmtVisitorTy::Visit(E->getInitializer());
   }
   bool VisitInitListExpr(const InitListExpr *E) {
     if (E->getNumInits() == 0)
       return DerivedZeroInitialization(E);
     if (E->getNumInits() == 1)
       return StmtVisitorTy::Visit(E->getInit(0));
     return Error(E);
   }
   bool VisitImplicitValueInitExpr(const ImplicitValueInitExpr *E) {
     return DerivedZeroInitialization(E);
   }
   bool VisitCXXScalarValueInitExpr(const CXXScalarValueInitExpr *E) {
     return DerivedZeroInitialization(E);
   }
   bool VisitCXXNullPtrLiteralExpr(const CXXNullPtrLiteralExpr *E) {
     return DerivedZeroInitialization(E);
   }
 
   /// A member expression where the object is a prvalue is itself a prvalue.
   bool VisitMemberExpr(const MemberExpr *E) {
     assert(!Info.Ctx.getLangOpts().CPlusPlus11 &&
            "missing temporary materialization conversion");
     assert(!E->isArrow() && "missing call to bound member function?");
 
     APValue Val;
     if (!Evaluate(Val, Info, E->getBase()))
       return false;
 
     QualType BaseTy = E->getBase()->getType();
 
     const FieldDecl *FD = dyn_cast<FieldDecl>(E->getMemberDecl());
     if (!FD) return Error(E);
     assert(!FD->getType()->isReferenceType() && "prvalue reference?");
     assert(BaseTy->castAs<RecordType>()->getDecl()->getCanonicalDecl() ==
            FD->getParent()->getCanonicalDecl() && "record / field mismatch");
 
     // Note: there is no lvalue base here. But this case should only ever
     // happen in C or in C++98, where we cannot be evaluating a constexpr
     // constructor, which is the only case the base matters.
     CompleteObject Obj(APValue::LValueBase(), &Val, BaseTy);
     SubobjectDesignator Designator(BaseTy);
     Designator.addDeclUnchecked(FD);
 
     APValue Result;
     return extractSubobject(Info, E, Obj, Designator, Result) &&
            DerivedSuccess(Result, E);
   }
 
   bool VisitExtVectorElementExpr(const ExtVectorElementExpr *E) {
     APValue Val;
     if (!Evaluate(Val, Info, E->getBase()))
       return false;
 
     if (Val.isVector()) {
       SmallVector<uint32_t, 4> Indices;
       E->getEncodedElementAccess(Indices);
       if (Indices.size() == 1) {
         // Return scalar.
         return DerivedSuccess(Val.getVectorElt(Indices[0]), E);
       } else {
         // Construct new APValue vector.
         SmallVector<APValue, 4> Elts;
         for (unsigned I = 0; I < Indices.size(); ++I) {
           Elts.push_back(Val.getVectorElt(Indices[I]));
         }
         APValue VecResult(Elts.data(), Indices.size());
         return DerivedSuccess(VecResult, E);
       }
     }
 
     return false;
   }
 
   bool VisitCastExpr(const CastExpr *E) {
     switch (E->getCastKind()) {
     default:
       break;
 
     case CK_AtomicToNonAtomic: {
       APValue AtomicVal;
       // This does not need to be done in place even for class/array types:
       // atomic-to-non-atomic conversion implies copying the object
       // representation.
       if (!Evaluate(AtomicVal, Info, E->getSubExpr()))
         return false;
       return DerivedSuccess(AtomicVal, E);
     }
 
     case CK_NoOp:
     case CK_UserDefinedConversion:
       return StmtVisitorTy::Visit(E->getSubExpr());
 
     case CK_LValueToRValue: {
       LValue LVal;
       if (!EvaluateLValue(E->getSubExpr(), LVal, Info))
         return false;
       APValue RVal;
       // Note, we use the subexpression's type in order to retain cv-qualifiers.
       if (!handleLValueToRValueConversion(Info, E, E->getSubExpr()->getType(),
                                           LVal, RVal))
         return false;
       return DerivedSuccess(RVal, E);
     }
     case CK_LValueToRValueBitCast: {
       APValue DestValue, SourceValue;
       if (!Evaluate(SourceValue, Info, E->getSubExpr()))
         return false;
       if (!handleLValueToRValueBitCast(Info, DestValue, SourceValue, E))
         return false;
       return DerivedSuccess(DestValue, E);
     }
 
     case CK_AddressSpaceConversion: {
       APValue Value;
       if (!Evaluate(Value, Info, E->getSubExpr()))
         return false;
       return DerivedSuccess(Value, E);
     }
     }
 
     return Error(E);
   }
 
   bool VisitUnaryPostInc(const UnaryOperator *UO) {
     return VisitUnaryPostIncDec(UO);
   }
   bool VisitUnaryPostDec(const UnaryOperator *UO) {
     return VisitUnaryPostIncDec(UO);
   }
   bool VisitUnaryPostIncDec(const UnaryOperator *UO) {
     if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
       return Error(UO);
 
     LValue LVal;
     if (!EvaluateLValue(UO->getSubExpr(), LVal, Info))
       return false;
     APValue RVal;
     if (!handleIncDec(this->Info, UO, LVal, UO->getSubExpr()->getType(),
                       UO->isIncrementOp(), &RVal))
       return false;
     return DerivedSuccess(RVal, UO);
   }
 
   bool VisitStmtExpr(const StmtExpr *E) {
     // We will have checked the full-expressions inside the statement expression
     // when they were completed, and don't need to check them again now.
     if (Info.checkingForUndefinedBehavior())
       return Error(E);
 
     const CompoundStmt *CS = E->getSubStmt();
     if (CS->body_empty())
       return true;
 
     BlockScopeRAII Scope(Info);
     for (CompoundStmt::const_body_iterator BI = CS->body_begin(),
                                            BE = CS->body_end();
          /**/; ++BI) {
       if (BI + 1 == BE) {
         const Expr *FinalExpr = dyn_cast<Expr>(*BI);
         if (!FinalExpr) {
           Info.FFDiag((*BI)->getBeginLoc(),
                       diag::note_constexpr_stmt_expr_unsupported);
           return false;
         }
         return this->Visit(FinalExpr) && Scope.destroy();
       }
 
       APValue ReturnValue;
       StmtResult Result = { ReturnValue, nullptr };
       EvalStmtResult ESR = EvaluateStmt(Result, Info, *BI);
       if (ESR != ESR_Succeeded) {
         // FIXME: If the statement-expression terminated due to 'return',
         // 'break', or 'continue', it would be nice to propagate that to
         // the outer statement evaluation rather than bailing out.
         if (ESR != ESR_Failed)
           Info.FFDiag((*BI)->getBeginLoc(),
                       diag::note_constexpr_stmt_expr_unsupported);
         return false;
       }
     }
 
     llvm_unreachable("Return from function from the loop above.");
   }
 
   /// Visit a value which is evaluated, but whose value is ignored.
   void VisitIgnoredValue(const Expr *E) {
     EvaluateIgnoredValue(Info, E);
   }
 
   /// Potentially visit a MemberExpr's base expression.
   void VisitIgnoredBaseExpression(const Expr *E) {
     // While MSVC doesn't evaluate the base expression, it does diagnose the
     // presence of side-effecting behavior.
     if (Info.getLangOpts().MSVCCompat && !E->HasSideEffects(Info.Ctx))
       return;
     VisitIgnoredValue(E);
   }
 };
 
 } // namespace
 
 //===----------------------------------------------------------------------===//
 // Common base class for lvalue and temporary evaluation.
 //===----------------------------------------------------------------------===//
 namespace {
 template<class Derived>
 class LValueExprEvaluatorBase
   : public ExprEvaluatorBase<Derived> {
 protected:
   LValue &Result;
   bool InvalidBaseOK;
   typedef LValueExprEvaluatorBase LValueExprEvaluatorBaseTy;
   typedef ExprEvaluatorBase<Derived> ExprEvaluatorBaseTy;
 
   bool Success(APValue::LValueBase B) {
     Result.set(B);
     return true;
   }
 
   bool evaluatePointer(const Expr *E, LValue &Result) {
     return EvaluatePointer(E, Result, this->Info, InvalidBaseOK);
   }
 
 public:
   LValueExprEvaluatorBase(EvalInfo &Info, LValue &Result, bool InvalidBaseOK)
       : ExprEvaluatorBaseTy(Info), Result(Result),
         InvalidBaseOK(InvalidBaseOK) {}
 
   bool Success(const APValue &V, const Expr *E) {
     Result.setFrom(this->Info.Ctx, V);
     return true;
   }
 
   bool VisitMemberExpr(const MemberExpr *E) {
     // Handle non-static data members.
     QualType BaseTy;
     bool EvalOK;
     if (E->isArrow()) {
       EvalOK = evaluatePointer(E->getBase(), Result);
       BaseTy = E->getBase()->getType()->castAs<PointerType>()->getPointeeType();
     } else if (E->getBase()->isRValue()) {
       assert(E->getBase()->getType()->isRecordType());
       EvalOK = EvaluateTemporary(E->getBase(), Result, this->Info);
       BaseTy = E->getBase()->getType();
     } else {
       EvalOK = this->Visit(E->getBase());
       BaseTy = E->getBase()->getType();
     }
     if (!EvalOK) {
       if (!InvalidBaseOK)
         return false;
       Result.setInvalid(E);
       return true;
     }
 
     const ValueDecl *MD = E->getMemberDecl();
     if (const FieldDecl *FD = dyn_cast<FieldDecl>(E->getMemberDecl())) {
       assert(BaseTy->castAs<RecordType>()->getDecl()->getCanonicalDecl() ==
              FD->getParent()->getCanonicalDecl() && "record / field mismatch");
       (void)BaseTy;
       if (!HandleLValueMember(this->Info, E, Result, FD))
         return false;
     } else if (const IndirectFieldDecl *IFD = dyn_cast<IndirectFieldDecl>(MD)) {
       if (!HandleLValueIndirectMember(this->Info, E, Result, IFD))
         return false;
     } else
       return this->Error(E);
 
     if (MD->getType()->isReferenceType()) {
       APValue RefValue;
       if (!handleLValueToRValueConversion(this->Info, E, MD->getType(), Result,
                                           RefValue))
         return false;
       return Success(RefValue, E);
     }
     return true;
   }
 
   bool VisitBinaryOperator(const BinaryOperator *E) {
     switch (E->getOpcode()) {
     default:
       return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
 
     case BO_PtrMemD:
     case BO_PtrMemI:
       return HandleMemberPointerAccess(this->Info, E, Result);
     }
   }
 
   bool VisitCastExpr(const CastExpr *E) {
     switch (E->getCastKind()) {
     default:
       return ExprEvaluatorBaseTy::VisitCastExpr(E);
 
     case CK_DerivedToBase:
     case CK_UncheckedDerivedToBase:
       if (!this->Visit(E->getSubExpr()))
         return false;
 
       // Now figure out the necessary offset to add to the base LV to get from
       // the derived class to the base class.
       return HandleLValueBasePath(this->Info, E, E->getSubExpr()->getType(),
                                   Result);
     }
   }
 };
 }
 
 //===----------------------------------------------------------------------===//
 // LValue Evaluation
 //
 // This is used for evaluating lvalues (in C and C++), xvalues (in C++11),
 // function designators (in C), decl references to void objects (in C), and
 // temporaries (if building with -Wno-address-of-temporary).
 //
 // LValue evaluation produces values comprising a base expression of one of the
 // following types:
 // - Declarations
 //  * VarDecl
 //  * FunctionDecl
 // - Literals
 //  * CompoundLiteralExpr in C (and in global scope in C++)
 //  * StringLiteral
 //  * PredefinedExpr
 //  * ObjCStringLiteralExpr
 //  * ObjCEncodeExpr
 //  * AddrLabelExpr
 //  * BlockExpr
 //  * CallExpr for a MakeStringConstant builtin
 // - typeid(T) expressions, as TypeInfoLValues
 // - Locals and temporaries
 //  * MaterializeTemporaryExpr
 //  * Any Expr, with a CallIndex indicating the function in which the temporary
 //    was evaluated, for cases where the MaterializeTemporaryExpr is missing
 //    from the AST (FIXME).
 //  * A MaterializeTemporaryExpr that has static storage duration, with no
 //    CallIndex, for a lifetime-extended temporary.
 //  * The ConstantExpr that is currently being evaluated during evaluation of an
 //    immediate invocation.
 // plus an offset in bytes.
 //===----------------------------------------------------------------------===//
 namespace {
 class LValueExprEvaluator
   : public LValueExprEvaluatorBase<LValueExprEvaluator> {
 public:
   LValueExprEvaluator(EvalInfo &Info, LValue &Result, bool InvalidBaseOK) :
     LValueExprEvaluatorBaseTy(Info, Result, InvalidBaseOK) {}
 
   bool VisitVarDecl(const Expr *E, const VarDecl *VD);
   bool VisitUnaryPreIncDec(const UnaryOperator *UO);
 
   bool VisitDeclRefExpr(const DeclRefExpr *E);
   bool VisitPredefinedExpr(const PredefinedExpr *E) { return Success(E); }
   bool VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *E);
   bool VisitCompoundLiteralExpr(const CompoundLiteralExpr *E);
   bool VisitMemberExpr(const MemberExpr *E);
   bool VisitStringLiteral(const StringLiteral *E) { return Success(E); }
   bool VisitObjCEncodeExpr(const ObjCEncodeExpr *E) { return Success(E); }
   bool VisitCXXTypeidExpr(const CXXTypeidExpr *E);
   bool VisitCXXUuidofExpr(const CXXUuidofExpr *E);
   bool VisitArraySubscriptExpr(const ArraySubscriptExpr *E);
   bool VisitUnaryDeref(const UnaryOperator *E);
   bool VisitUnaryReal(const UnaryOperator *E);
   bool VisitUnaryImag(const UnaryOperator *E);
   bool VisitUnaryPreInc(const UnaryOperator *UO) {
     return VisitUnaryPreIncDec(UO);
   }
   bool VisitUnaryPreDec(const UnaryOperator *UO) {
     return VisitUnaryPreIncDec(UO);
   }
   bool VisitBinAssign(const BinaryOperator *BO);
   bool VisitCompoundAssignOperator(const CompoundAssignOperator *CAO);
 
   bool VisitCastExpr(const CastExpr *E) {
     switch (E->getCastKind()) {
     default:
       return LValueExprEvaluatorBaseTy::VisitCastExpr(E);
 
     case CK_LValueBitCast:
       this->CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
       if (!Visit(E->getSubExpr()))
         return false;
       Result.Designator.setInvalid();
       return true;
 
     case CK_BaseToDerived:
       if (!Visit(E->getSubExpr()))
         return false;
       return HandleBaseToDerivedCast(Info, E, Result);
 
     case CK_Dynamic:
       if (!Visit(E->getSubExpr()))
         return false;
       return HandleDynamicCast(Info, cast<ExplicitCastExpr>(E), Result);
     }
   }
 };
 } // end anonymous namespace
 
 /// Evaluate an expression as an lvalue. This can be legitimately called on
 /// expressions which are not glvalues, in three cases:
 ///  * function designators in C, and
 ///  * "extern void" objects
 ///  * @selector() expressions in Objective-C
 static bool EvaluateLValue(const Expr *E, LValue &Result, EvalInfo &Info,
                            bool InvalidBaseOK) {
   assert(E->isGLValue() || E->getType()->isFunctionType() ||
          E->getType()->isVoidType() || isa<ObjCSelectorExpr>(E));
   return LValueExprEvaluator(Info, Result, InvalidBaseOK).Visit(E);
 }
 
 bool LValueExprEvaluator::VisitDeclRefExpr(const DeclRefExpr *E) {
   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(E->getDecl()))
     return Success(FD);
   if (const VarDecl *VD = dyn_cast<VarDecl>(E->getDecl()))
     return VisitVarDecl(E, VD);
   if (const BindingDecl *BD = dyn_cast<BindingDecl>(E->getDecl()))
     return Visit(BD->getBinding());
   if (const MSGuidDecl *GD = dyn_cast<MSGuidDecl>(E->getDecl()))
     return Success(GD);
   return Error(E);
 }
 
 
 bool LValueExprEvaluator::VisitVarDecl(const Expr *E, const VarDecl *VD) {
 
   // If we are within a lambda's call operator, check whether the 'VD' referred
   // to within 'E' actually represents a lambda-capture that maps to a
   // data-member/field within the closure object, and if so, evaluate to the
   // field or what the field refers to.
   if (Info.CurrentCall && isLambdaCallOperator(Info.CurrentCall->Callee) &&
       isa<DeclRefExpr>(E) &&
       cast<DeclRefExpr>(E)->refersToEnclosingVariableOrCapture()) {
     // We don't always have a complete capture-map when checking or inferring if
     // the function call operator meets the requirements of a constexpr function
     // - but we don't need to evaluate the captures to determine constexprness
     // (dcl.constexpr C++17).
     if (Info.checkingPotentialConstantExpression())
       return false;
 
     if (auto *FD = Info.CurrentCall->LambdaCaptureFields.lookup(VD)) {
       // Start with 'Result' referring to the complete closure object...
       Result = *Info.CurrentCall->This;
       // ... then update it to refer to the field of the closure object
       // that represents the capture.
       if (!HandleLValueMember(Info, E, Result, FD))
         return false;
       // And if the field is of reference type, update 'Result' to refer to what
       // the field refers to.
       if (FD->getType()->isReferenceType()) {
         APValue RVal;
         if (!handleLValueToRValueConversion(Info, E, FD->getType(), Result,
                                             RVal))
           return false;
         Result.setFrom(Info.Ctx, RVal);
       }
       return true;
     }
   }
   CallStackFrame *Frame = nullptr;
   if (VD->hasLocalStorage() && Info.CurrentCall->Index > 1) {
     // Only if a local variable was declared in the function currently being
     // evaluated, do we expect to be able to find its value in the current
     // frame. (Otherwise it was likely declared in an enclosing context and
     // could either have a valid evaluatable value (for e.g. a constexpr
     // variable) or be ill-formed (and trigger an appropriate evaluation
     // diagnostic)).
     if (Info.CurrentCall->Callee &&
         Info.CurrentCall->Callee->Equals(VD->getDeclContext())) {
       Frame = Info.CurrentCall;
     }
   }
 
   if (!VD->getType()->isReferenceType()) {
     if (Frame) {
       Result.set({VD, Frame->Index,
                   Info.CurrentCall->getCurrentTemporaryVersion(VD)});
       return true;
     }
     return Success(VD);
   }
 
   APValue *V;
   if (!evaluateVarDeclInit(Info, E, VD, Frame, V, nullptr))
     return false;
   if (!V->hasValue()) {
     // FIXME: Is it possible for V to be indeterminate here? If so, we should
     // adjust the diagnostic to say that.
     if (!Info.checkingPotentialConstantExpression())
       Info.FFDiag(E, diag::note_constexpr_use_uninit_reference);
     return false;
   }
   return Success(*V, E);
 }
 
 bool LValueExprEvaluator::VisitMaterializeTemporaryExpr(
     const MaterializeTemporaryExpr *E) {
   // Walk through the expression to find the materialized temporary itself.
   SmallVector<const Expr *, 2> CommaLHSs;
   SmallVector<SubobjectAdjustment, 2> Adjustments;
   const Expr *Inner =
       E->getSubExpr()->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments);
 
   // If we passed any comma operators, evaluate their LHSs.
   for (unsigned I = 0, N = CommaLHSs.size(); I != N; ++I)
     if (!EvaluateIgnoredValue(Info, CommaLHSs[I]))
       return false;
 
   // A materialized temporary with static storage duration can appear within the
   // result of a constant expression evaluation, so we need to preserve its
   // value for use outside this evaluation.
   APValue *Value;
   if (E->getStorageDuration() == SD_Static) {
     Value = E->getOrCreateValue(true);
     *Value = APValue();
     Result.set(E);
   } else {
     Value = &Info.CurrentCall->createTemporary(
         E, E->getType(), E->getStorageDuration() == SD_Automatic, Result);
   }
 
   QualType Type = Inner->getType();
 
   // Materialize the temporary itself.
   if (!EvaluateInPlace(*Value, Info, Result, Inner)) {
     *Value = APValue();
     return false;
   }
 
   // Adjust our lvalue to refer to the desired subobject.
   for (unsigned I = Adjustments.size(); I != 0; /**/) {
     --I;
     switch (Adjustments[I].Kind) {
     case SubobjectAdjustment::DerivedToBaseAdjustment:
       if (!HandleLValueBasePath(Info, Adjustments[I].DerivedToBase.BasePath,
                                 Type, Result))
         return false;
       Type = Adjustments[I].DerivedToBase.BasePath->getType();
       break;
 
     case SubobjectAdjustment::FieldAdjustment:
       if (!HandleLValueMember(Info, E, Result, Adjustments[I].Field))
         return false;
       Type = Adjustments[I].Field->getType();
       break;
 
     case SubobjectAdjustment::MemberPointerAdjustment:
       if (!HandleMemberPointerAccess(this->Info, Type, Result,
                                      Adjustments[I].Ptr.RHS))
         return false;
       Type = Adjustments[I].Ptr.MPT->getPointeeType();
       break;
     }
   }
 
   return true;
 }
 
 bool
 LValueExprEvaluator::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
   assert((!Info.getLangOpts().CPlusPlus || E->isFileScope()) &&
          "lvalue compound literal in c++?");
   // Defer visiting the literal until the lvalue-to-rvalue conversion. We can
   // only see this when folding in C, so there's no standard to follow here.
   return Success(E);
 }
 
 bool LValueExprEvaluator::VisitCXXTypeidExpr(const CXXTypeidExpr *E) {
   TypeInfoLValue TypeInfo;
 
   if (!E->isPotentiallyEvaluated()) {
     if (E->isTypeOperand())
       TypeInfo = TypeInfoLValue(E->getTypeOperand(Info.Ctx).getTypePtr());
     else
       TypeInfo = TypeInfoLValue(E->getExprOperand()->getType().getTypePtr());
   } else {
     if (!Info.Ctx.getLangOpts().CPlusPlus20) {
       Info.CCEDiag(E, diag::note_constexpr_typeid_polymorphic)
         << E->getExprOperand()->getType()
         << E->getExprOperand()->getSourceRange();
     }
 
     if (!Visit(E->getExprOperand()))
       return false;
 
     Optional<DynamicType> DynType =
         ComputeDynamicType(Info, E, Result, AK_TypeId);
     if (!DynType)
       return false;
 
     TypeInfo =
         TypeInfoLValue(Info.Ctx.getRecordType(DynType->Type).getTypePtr());
   }
 
   return Success(APValue::LValueBase::getTypeInfo(TypeInfo, E->getType()));
 }
 
 bool LValueExprEvaluator::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {
   return Success(E->getGuidDecl());
 }
 
 bool LValueExprEvaluator::VisitMemberExpr(const MemberExpr *E) {
   // Handle static data members.
   if (const VarDecl *VD = dyn_cast<VarDecl>(E->getMemberDecl())) {
     VisitIgnoredBaseExpression(E->getBase());
     return VisitVarDecl(E, VD);
   }
 
   // Handle static member functions.
   if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(E->getMemberDecl())) {
     if (MD->isStatic()) {
       VisitIgnoredBaseExpression(E->getBase());
       return Success(MD);
     }
   }
 
   // Handle non-static data members.
   return LValueExprEvaluatorBaseTy::VisitMemberExpr(E);
 }
 
 bool LValueExprEvaluator::VisitArraySubscriptExpr(const ArraySubscriptExpr *E) {
   // FIXME: Deal with vectors as array subscript bases.
   if (E->getBase()->getType()->isVectorType())
     return Error(E);
 
   bool Success = true;
   if (!evaluatePointer(E->getBase(), Result)) {
     if (!Info.noteFailure())
       return false;
     Success = false;
   }
 
   APSInt Index;
   if (!EvaluateInteger(E->getIdx(), Index, Info))
     return false;
 
   return Success &&
          HandleLValueArrayAdjustment(Info, E, Result, E->getType(), Index);
 }
 
 bool LValueExprEvaluator::VisitUnaryDeref(const UnaryOperator *E) {
   return evaluatePointer(E->getSubExpr(), Result);
 }
 
 bool LValueExprEvaluator::VisitUnaryReal(const UnaryOperator *E) {
   if (!Visit(E->getSubExpr()))
     return false;
   // __real is a no-op on scalar lvalues.
   if (E->getSubExpr()->getType()->isAnyComplexType())
     HandleLValueComplexElement(Info, E, Result, E->getType(), false);
   return true;
 }
 
 bool LValueExprEvaluator::VisitUnaryImag(const UnaryOperator *E) {
   assert(E->getSubExpr()->getType()->isAnyComplexType() &&
          "lvalue __imag__ on scalar?");
   if (!Visit(E->getSubExpr()))
     return false;
   HandleLValueComplexElement(Info, E, Result, E->getType(), true);
   return true;
 }
 
 bool LValueExprEvaluator::VisitUnaryPreIncDec(const UnaryOperator *UO) {
   if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
     return Error(UO);
 
   if (!this->Visit(UO->getSubExpr()))
     return false;
 
   return handleIncDec(
       this->Info, UO, Result, UO->getSubExpr()->getType(),
       UO->isIncrementOp(), nullptr);
 }
 
 bool LValueExprEvaluator::VisitCompoundAssignOperator(
     const CompoundAssignOperator *CAO) {
   if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
     return Error(CAO);
 
   APValue RHS;
 
   // The overall lvalue result is the result of evaluating the LHS.
   if (!this->Visit(CAO->getLHS())) {
     if (Info.noteFailure())
       Evaluate(RHS, this->Info, CAO->getRHS());
     return false;
   }
 
   if (!Evaluate(RHS, this->Info, CAO->getRHS()))
     return false;
 
   return handleCompoundAssignment(
       this->Info, CAO,
       Result, CAO->getLHS()->getType(), CAO->getComputationLHSType(),
       CAO->getOpForCompoundAssignment(CAO->getOpcode()), RHS);
 }
 
 bool LValueExprEvaluator::VisitBinAssign(const BinaryOperator *E) {
   if (!Info.getLangOpts().CPlusPlus14 && !Info.keepEvaluatingAfterFailure())
     return Error(E);
 
   APValue NewVal;
 
   if (!this->Visit(E->getLHS())) {
     if (Info.noteFailure())
       Evaluate(NewVal, this->Info, E->getRHS());
     return false;
   }
 
   if (!Evaluate(NewVal, this->Info, E->getRHS()))
     return false;
 
   if (Info.getLangOpts().CPlusPlus20 &&
       !HandleUnionActiveMemberChange(Info, E->getLHS(), Result))
     return false;
 
   return handleAssignment(this->Info, E, Result, E->getLHS()->getType(),
                           NewVal);
 }
 
 //===----------------------------------------------------------------------===//
 // Pointer Evaluation
 //===----------------------------------------------------------------------===//
 
 /// Attempts to compute the number of bytes available at the pointer
 /// returned by a function with the alloc_size attribute. Returns true if we
 /// were successful. Places an unsigned number into `Result`.
 ///
 /// This expects the given CallExpr to be a call to a function with an
 /// alloc_size attribute.
 static bool getBytesReturnedByAllocSizeCall(const ASTContext &Ctx,
                                             const CallExpr *Call,
                                             llvm::APInt &Result) {
   const AllocSizeAttr *AllocSize = getAllocSizeAttr(Call);
 
   assert(AllocSize && AllocSize->getElemSizeParam().isValid());
   unsigned SizeArgNo = AllocSize->getElemSizeParam().getASTIndex();
   unsigned BitsInSizeT = Ctx.getTypeSize(Ctx.getSizeType());
   if (Call->getNumArgs() <= SizeArgNo)
     return false;
 
   auto EvaluateAsSizeT = [&](const Expr *E, APSInt &Into) {
     Expr::EvalResult ExprResult;
     if (!E->EvaluateAsInt(ExprResult, Ctx, Expr::SE_AllowSideEffects))
       return false;
     Into = ExprResult.Val.getInt();
     if (Into.isNegative() || !Into.isIntN(BitsInSizeT))
       return false;
     Into = Into.zextOrSelf(BitsInSizeT);
     return true;
   };
 
   APSInt SizeOfElem;
   if (!EvaluateAsSizeT(Call->getArg(SizeArgNo), SizeOfElem))
     return false;
 
   if (!AllocSize->getNumElemsParam().isValid()) {
     Result = std::move(SizeOfElem);
     return true;
   }
 
   APSInt NumberOfElems;
   unsigned NumArgNo = AllocSize->getNumElemsParam().getASTIndex();
   if (!EvaluateAsSizeT(Call->getArg(NumArgNo), NumberOfElems))
     return false;
 
   bool Overflow;
   llvm::APInt BytesAvailable = SizeOfElem.umul_ov(NumberOfElems, Overflow);
   if (Overflow)
     return false;
 
   Result = std::move(BytesAvailable);
   return true;
 }
 
 /// Convenience function. LVal's base must be a call to an alloc_size
 /// function.
 static bool getBytesReturnedByAllocSizeCall(const ASTContext &Ctx,
                                             const LValue &LVal,
                                             llvm::APInt &Result) {
   assert(isBaseAnAllocSizeCall(LVal.getLValueBase()) &&
          "Can't get the size of a non alloc_size function");
   const auto *Base = LVal.getLValueBase().get<const Expr *>();
   const CallExpr *CE = tryUnwrapAllocSizeCall(Base);
   return getBytesReturnedByAllocSizeCall(Ctx, CE, Result);
 }
 
 /// Attempts to evaluate the given LValueBase as the result of a call to
 /// a function with the alloc_size attribute. If it was possible to do so, this
 /// function will return true, make Result's Base point to said function call,
 /// and mark Result's Base as invalid.
 static bool evaluateLValueAsAllocSize(EvalInfo &Info, APValue::LValueBase Base,
                                       LValue &Result) {
   if (Base.isNull())
     return false;
 
   // Because we do no form of static analysis, we only support const variables.
   //
   // Additionally, we can't support parameters, nor can we support static
   // variables (in the latter case, use-before-assign isn't UB; in the former,
   // we have no clue what they'll be assigned to).
   const auto *VD =
       dyn_cast_or_null<VarDecl>(Base.dyn_cast<const ValueDecl *>());
   if (!VD || !VD->isLocalVarDecl() || !VD->getType().isConstQualified())
     return false;
 
   const Expr *Init = VD->getAnyInitializer();
   if (!Init)
     return false;
 
   const Expr *E = Init->IgnoreParens();
   if (!tryUnwrapAllocSizeCall(E))
     return false;
 
   // Store E instead of E unwrapped so that the type of the LValue's base is
   // what the user wanted.
   Result.setInvalid(E);
 
   QualType Pointee = E->getType()->castAs<PointerType>()->getPointeeType();
   Result.addUnsizedArray(Info, E, Pointee);
   return true;
 }
 
 namespace {
 class PointerExprEvaluator
   : public ExprEvaluatorBase<PointerExprEvaluator> {
   LValue &Result;
   bool InvalidBaseOK;
 
   bool Success(const Expr *E) {
     Result.set(E);
     return true;
   }
 
   bool evaluateLValue(const Expr *E, LValue &Result) {
     return EvaluateLValue(E, Result, Info, InvalidBaseOK);
   }
 
   bool evaluatePointer(const Expr *E, LValue &Result) {
     return EvaluatePointer(E, Result, Info, InvalidBaseOK);
   }
 
   bool visitNonBuiltinCallExpr(const CallExpr *E);
 public:
 
   PointerExprEvaluator(EvalInfo &info, LValue &Result, bool InvalidBaseOK)
       : ExprEvaluatorBaseTy(info), Result(Result),
         InvalidBaseOK(InvalidBaseOK) {}
 
   bool Success(const APValue &V, const Expr *E) {
     Result.setFrom(Info.Ctx, V);
     return true;
   }
   bool ZeroInitialization(const Expr *E) {
     Result.setNull(Info.Ctx, E->getType());
     return true;
   }
 
   bool VisitBinaryOperator(const BinaryOperator *E);
   bool VisitCastExpr(const CastExpr* E);
   bool VisitUnaryAddrOf(const UnaryOperator *E);
   bool VisitObjCStringLiteral(const ObjCStringLiteral *E)
       { return Success(E); }
   bool VisitObjCBoxedExpr(const ObjCBoxedExpr *E) {
     if (E->isExpressibleAsConstantInitializer())
       return Success(E);
     if (Info.noteFailure())
       EvaluateIgnoredValue(Info, E->getSubExpr());
     return Error(E);
   }
   bool VisitAddrLabelExpr(const AddrLabelExpr *E)
       { return Success(E); }
   bool VisitCallExpr(const CallExpr *E);
   bool VisitBuiltinCallExpr(const CallExpr *E, unsigned BuiltinOp);
   bool VisitBlockExpr(const BlockExpr *E) {
     if (!E->getBlockDecl()->hasCaptures())
       return Success(E);
     return Error(E);
   }
   bool VisitCXXThisExpr(const CXXThisExpr *E) {
     // Can't look at 'this' when checking a potential constant expression.
     if (Info.checkingPotentialConstantExpression())
       return false;
     if (!Info.CurrentCall->This) {
       if (Info.getLangOpts().CPlusPlus11)
         Info.FFDiag(E, diag::note_constexpr_this) << E->isImplicit();
       else
         Info.FFDiag(E);
       return false;
     }
     Result = *Info.CurrentCall->This;
     // If we are inside a lambda's call operator, the 'this' expression refers
     // to the enclosing '*this' object (either by value or reference) which is
     // either copied into the closure object's field that represents the '*this'
     // or refers to '*this'.
     if (isLambdaCallOperator(Info.CurrentCall->Callee)) {
       // Ensure we actually have captured 'this'. (an error will have
       // been previously reported if not).
       if (!Info.CurrentCall->LambdaThisCaptureField)
         return false;
 
       // Update 'Result' to refer to the data member/field of the closure object
       // that represents the '*this' capture.
       if (!HandleLValueMember(Info, E, Result,
                              Info.CurrentCall->LambdaThisCaptureField))
         return false;
       // If we captured '*this' by reference, replace the field with its referent.
       if (Info.CurrentCall->LambdaThisCaptureField->getType()
               ->isPointerType()) {
         APValue RVal;
         if (!handleLValueToRValueConversion(Info, E, E->getType(), Result,
                                             RVal))
           return false;
 
         Result.setFrom(Info.Ctx, RVal);
       }
     }
     return true;
   }
 
   bool VisitCXXNewExpr(const CXXNewExpr *E);
 
   bool VisitSourceLocExpr(const SourceLocExpr *E) {
     assert(E->isStringType() && "SourceLocExpr isn't a pointer type?");
     APValue LValResult = E->EvaluateInContext(
         Info.Ctx, Info.CurrentCall->CurSourceLocExprScope.getDefaultExpr());
     Result.setFrom(Info.Ctx, LValResult);
     return true;
   }
 
   // FIXME: Missing: @protocol, @selector
 };
 } // end anonymous namespace
 
 static bool EvaluatePointer(const Expr* E, LValue& Result, EvalInfo &Info,
                             bool InvalidBaseOK) {
   assert(E->isRValue() && E->getType()->hasPointerRepresentation());
   return PointerExprEvaluator(Info, Result, InvalidBaseOK).Visit(E);
 }
 
 bool PointerExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
   if (E->getOpcode() != BO_Add &&
       E->getOpcode() != BO_Sub)
     return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
 
   const Expr *PExp = E->getLHS();
   const Expr *IExp = E->getRHS();
   if (IExp->getType()->isPointerType())
     std::swap(PExp, IExp);
 
   bool EvalPtrOK = evaluatePointer(PExp, Result);
   if (!EvalPtrOK && !Info.noteFailure())
     return false;
 
   llvm::APSInt Offset;
   if (!EvaluateInteger(IExp, Offset, Info) || !EvalPtrOK)
     return false;
 
   if (E->getOpcode() == BO_Sub)
     negateAsSigned(Offset);
 
   QualType Pointee = PExp->getType()->castAs<PointerType>()->getPointeeType();
   return HandleLValueArrayAdjustment(Info, E, Result, Pointee, Offset);
 }
 
 bool PointerExprEvaluator::VisitUnaryAddrOf(const UnaryOperator *E) {
   return evaluateLValue(E->getSubExpr(), Result);
 }
 
 bool PointerExprEvaluator::VisitCastExpr(const CastExpr *E) {
   const Expr *SubExpr = E->getSubExpr();
 
   switch (E->getCastKind()) {
   default:
     break;
   case CK_BitCast:
   case CK_CPointerToObjCPointerCast:
   case CK_BlockPointerToObjCPointerCast:
   case CK_AnyPointerToBlockPointerCast:
   case CK_AddressSpaceConversion:
     if (!Visit(SubExpr))
       return false;
     // Bitcasts to cv void* are static_casts, not reinterpret_casts, so are
     // permitted in constant expressions in C++11. Bitcasts from cv void* are
     // also static_casts, but we disallow them as a resolution to DR1312.
     if (!E->getType()->isVoidPointerType()) {
       if (!Result.InvalidBase && !Result.Designator.Invalid &&
           !Result.IsNullPtr &&
           Info.Ctx.hasSameUnqualifiedType(Result.Designator.getType(Info.Ctx),
                                           E->getType()->getPointeeType()) &&
           Info.getStdAllocatorCaller("allocate")) {
         // Inside a call to std::allocator::allocate and friends, we permit
         // casting from void* back to cv1 T* for a pointer that points to a
         // cv2 T.
       } else {
         Result.Designator.setInvalid();
         if (SubExpr->getType()->isVoidPointerType())
           CCEDiag(E, diag::note_constexpr_invalid_cast)
             << 3 << SubExpr->getType();
         else
           CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
       }
     }
     if (E->getCastKind() == CK_AddressSpaceConversion && Result.IsNullPtr)
       ZeroInitialization(E);
     return true;
 
   case CK_DerivedToBase:
   case CK_UncheckedDerivedToBase:
     if (!evaluatePointer(E->getSubExpr(), Result))
       return false;
     if (!Result.Base && Result.Offset.isZero())
       return true;
 
     // Now figure out the necessary offset to add to the base LV to get from
     // the derived class to the base class.
     return HandleLValueBasePath(Info, E, E->getSubExpr()->getType()->
                                   castAs<PointerType>()->getPointeeType(),
                                 Result);
 
   case CK_BaseToDerived:
     if (!Visit(E->getSubExpr()))
       return false;
     if (!Result.Base && Result.Offset.isZero())
       return true;
     return HandleBaseToDerivedCast(Info, E, Result);
 
   case CK_Dynamic:
     if (!Visit(E->getSubExpr()))
       return false;
     return HandleDynamicCast(Info, cast<ExplicitCastExpr>(E), Result);
 
   case CK_NullToPointer:
     VisitIgnoredValue(E->getSubExpr());
     return ZeroInitialization(E);
 
   case CK_IntegralToPointer: {
     CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
 
     APValue Value;
     if (!EvaluateIntegerOrLValue(SubExpr, Value, Info))
       break;
 
     if (Value.isInt()) {
       unsigned Size = Info.Ctx.getTypeSize(E->getType());
       uint64_t N = Value.getInt().extOrTrunc(Size).getZExtValue();
       Result.Base = (Expr*)nullptr;
       Result.InvalidBase = false;
       Result.Offset = CharUnits::fromQuantity(N);
       Result.Designator.setInvalid();
       Result.IsNullPtr = false;
       return true;
     } else {
       // Cast is of an lvalue, no need to change value.
       Result.setFrom(Info.Ctx, Value);
       return true;
     }
   }
 
   case CK_ArrayToPointerDecay: {
     if (SubExpr->isGLValue()) {
       if (!evaluateLValue(SubExpr, Result))
         return false;
     } else {
       APValue &Value = Info.CurrentCall->createTemporary(
           SubExpr, SubExpr->getType(), false, Result);
       if (!EvaluateInPlace(Value, Info, Result, SubExpr))
         return false;
     }
     // The result is a pointer to the first element of the array.
     auto *AT = Info.Ctx.getAsArrayType(SubExpr->getType());
     if (auto *CAT = dyn_cast<ConstantArrayType>(AT))
       Result.addArray(Info, E, CAT);
     else
       Result.addUnsizedArray(Info, E, AT->getElementType());
     return true;
   }
 
   case CK_FunctionToPointerDecay:
     return evaluateLValue(SubExpr, Result);
 
   case CK_LValueToRValue: {
     LValue LVal;
     if (!evaluateLValue(E->getSubExpr(), LVal))
       return false;
 
     APValue RVal;
     // Note, we use the subexpression's type in order to retain cv-qualifiers.
     if (!handleLValueToRValueConversion(Info, E, E->getSubExpr()->getType(),
                                         LVal, RVal))
       return InvalidBaseOK &&
              evaluateLValueAsAllocSize(Info, LVal.Base, Result);
     return Success(RVal, E);
   }
   }
 
   return ExprEvaluatorBaseTy::VisitCastExpr(E);
 }
 
 static CharUnits GetAlignOfType(EvalInfo &Info, QualType T,
                                 UnaryExprOrTypeTrait ExprKind) {
   // C++ [expr.alignof]p3:
   //     When alignof is applied to a reference type, the result is the
   //     alignment of the referenced type.
   if (const ReferenceType *Ref = T->getAs<ReferenceType>())
     T = Ref->getPointeeType();
 
   if (T.getQualifiers().hasUnaligned())
     return CharUnits::One();
 
   const bool AlignOfReturnsPreferred =
       Info.Ctx.getLangOpts().getClangABICompat() <= LangOptions::ClangABI::Ver7;
 
   // __alignof is defined to return the preferred alignment.
   // Before 8, clang returned the preferred alignment for alignof and _Alignof
   // as well.
   if (ExprKind == UETT_PreferredAlignOf || AlignOfReturnsPreferred)
     return Info.Ctx.toCharUnitsFromBits(
       Info.Ctx.getPreferredTypeAlign(T.getTypePtr()));
   // alignof and _Alignof are defined to return the ABI alignment.
   else if (ExprKind == UETT_AlignOf)
     return Info.Ctx.getTypeAlignInChars(T.getTypePtr());
   else
     llvm_unreachable("GetAlignOfType on a non-alignment ExprKind");
 }
 
 static CharUnits GetAlignOfExpr(EvalInfo &Info, const Expr *E,
                                 UnaryExprOrTypeTrait ExprKind) {
   E = E->IgnoreParens();
 
   // The kinds of expressions that we have special-case logic here for
   // should be kept up to date with the special checks for those
   // expressions in Sema.
 
   // alignof decl is always accepted, even if it doesn't make sense: we default
   // to 1 in those cases.
   if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
     return Info.Ctx.getDeclAlign(DRE->getDecl(),
                                  /*RefAsPointee*/true);
 
   if (const MemberExpr *ME = dyn_cast<MemberExpr>(E))
     return Info.Ctx.getDeclAlign(ME->getMemberDecl(),
                                  /*RefAsPointee*/true);
 
   return GetAlignOfType(Info, E->getType(), ExprKind);
 }
 
 static CharUnits getBaseAlignment(EvalInfo &Info, const LValue &Value) {
   if (const auto *VD = Value.Base.dyn_cast<const ValueDecl *>())
     return Info.Ctx.getDeclAlign(VD);
   if (const auto *E = Value.Base.dyn_cast<const Expr *>())
     return GetAlignOfExpr(Info, E, UETT_AlignOf);
   return GetAlignOfType(Info, Value.Base.getTypeInfoType(), UETT_AlignOf);
 }
 
 /// Evaluate the value of the alignment argument to __builtin_align_{up,down},
 /// __builtin_is_aligned and __builtin_assume_aligned.
 static bool getAlignmentArgument(const Expr *E, QualType ForType,
                                  EvalInfo &Info, APSInt &Alignment) {
   if (!EvaluateInteger(E, Alignment, Info))
     return false;
   if (Alignment < 0 || !Alignment.isPowerOf2()) {
     Info.FFDiag(E, diag::note_constexpr_invalid_alignment) << Alignment;
     return false;
   }
   unsigned SrcWidth = Info.Ctx.getIntWidth(ForType);
   APSInt MaxValue(APInt::getOneBitSet(SrcWidth, SrcWidth - 1));
   if (APSInt::compareValues(Alignment, MaxValue) > 0) {
     Info.FFDiag(E, diag::note_constexpr_alignment_too_big)
         << MaxValue << ForType << Alignment;
     return false;
   }
   // Ensure both alignment and source value have the same bit width so that we
   // don't assert when computing the resulting value.
   APSInt ExtAlignment =
       APSInt(Alignment.zextOrTrunc(SrcWidth), /*isUnsigned=*/true);
   assert(APSInt::compareValues(Alignment, ExtAlignment) == 0 &&
          "Alignment should not be changed by ext/trunc");
   Alignment = ExtAlignment;
   assert(Alignment.getBitWidth() == SrcWidth);
   return true;
 }
 
 // To be clear: this happily visits unsupported builtins. Better name welcomed.
 bool PointerExprEvaluator::visitNonBuiltinCallExpr(const CallExpr *E) {
   if (ExprEvaluatorBaseTy::VisitCallExpr(E))
     return true;
 
   if (!(InvalidBaseOK && getAllocSizeAttr(E)))
     return false;
 
   Result.setInvalid(E);
   QualType PointeeTy = E->getType()->castAs<PointerType>()->getPointeeType();
   Result.addUnsizedArray(Info, E, PointeeTy);
   return true;
 }
 
 bool PointerExprEvaluator::VisitCallExpr(const CallExpr *E) {
   if (IsStringLiteralCall(E))
     return Success(E);
 
   if (unsigned BuiltinOp = E->getBuiltinCallee())
     return VisitBuiltinCallExpr(E, BuiltinOp);
 
   return visitNonBuiltinCallExpr(E);
 }
 
 // Determine if T is a character type for which we guarantee that
 // sizeof(T) == 1.
 static bool isOneByteCharacterType(QualType T) {
   return T->isCharType() || T->isChar8Type();
 }
 
 bool PointerExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
                                                 unsigned BuiltinOp) {
   switch (BuiltinOp) {
   case Builtin::BI__builtin_addressof:
     return evaluateLValue(E->getArg(0), Result);
   case Builtin::BI__builtin_assume_aligned: {
     // We need to be very careful here because: if the pointer does not have the
     // asserted alignment, then the behavior is undefined, and undefined
     // behavior is non-constant.
     if (!evaluatePointer(E->getArg(0), Result))
       return false;
 
     LValue OffsetResult(Result);
     APSInt Alignment;
     if (!getAlignmentArgument(E->getArg(1), E->getArg(0)->getType(), Info,
                               Alignment))
       return false;
     CharUnits Align = CharUnits::fromQuantity(Alignment.getZExtValue());
 
     if (E->getNumArgs() > 2) {
       APSInt Offset;
       if (!EvaluateInteger(E->getArg(2), Offset, Info))
         return false;
 
       int64_t AdditionalOffset = -Offset.getZExtValue();
       OffsetResult.Offset += CharUnits::fromQuantity(AdditionalOffset);
     }
 
     // If there is a base object, then it must have the correct alignment.
     if (OffsetResult.Base) {
       CharUnits BaseAlignment = getBaseAlignment(Info, OffsetResult);
 
       if (BaseAlignment < Align) {
         Result.Designator.setInvalid();
         // FIXME: Add support to Diagnostic for long / long long.
         CCEDiag(E->getArg(0),
                 diag::note_constexpr_baa_insufficient_alignment) << 0
           << (unsigned)BaseAlignment.getQuantity()
           << (unsigned)Align.getQuantity();
         return false;
       }
     }
 
     // The offset must also have the correct alignment.
     if (OffsetResult.Offset.alignTo(Align) != OffsetResult.Offset) {
       Result.Designator.setInvalid();
 
       (OffsetResult.Base
            ? CCEDiag(E->getArg(0),
                      diag::note_constexpr_baa_insufficient_alignment) << 1
            : CCEDiag(E->getArg(0),
                      diag::note_constexpr_baa_value_insufficient_alignment))
         << (int)OffsetResult.Offset.getQuantity()
         << (unsigned)Align.getQuantity();
       return false;
     }
 
     return true;
   }
   case Builtin::BI__builtin_align_up:
   case Builtin::BI__builtin_align_down: {
     if (!evaluatePointer(E->getArg(0), Result))
       return false;
     APSInt Alignment;
     if (!getAlignmentArgument(E->getArg(1), E->getArg(0)->getType(), Info,
                               Alignment))
       return false;
     CharUnits BaseAlignment = getBaseAlignment(Info, Result);
     CharUnits PtrAlign = BaseAlignment.alignmentAtOffset(Result.Offset);
     // For align_up/align_down, we can return the same value if the alignment
     // is known to be greater or equal to the requested value.
     if (PtrAlign.getQuantity() >= Alignment)
       return true;
 
     // The alignment could be greater than the minimum at run-time, so we cannot
     // infer much about the resulting pointer value. One case is possible:
     // For `_Alignas(32) char buf[N]; __builtin_align_down(&buf[idx], 32)` we
     // can infer the correct index if the requested alignment is smaller than
     // the base alignment so we can perform the computation on the offset.
     if (BaseAlignment.getQuantity() >= Alignment) {
       assert(Alignment.getBitWidth() <= 64 &&
              "Cannot handle > 64-bit address-space");
       uint64_t Alignment64 = Alignment.getZExtValue();
       CharUnits NewOffset = CharUnits::fromQuantity(
           BuiltinOp == Builtin::BI__builtin_align_down
               ? llvm::alignDown(Result.Offset.getQuantity(), Alignment64)
               : llvm::alignTo(Result.Offset.getQuantity(), Alignment64));
       Result.adjustOffset(NewOffset - Result.Offset);
       // TODO: diagnose out-of-bounds values/only allow for arrays?
       return true;
     }
     // Otherwise, we cannot constant-evaluate the result.
     Info.FFDiag(E->getArg(0), diag::note_constexpr_alignment_adjust)
         << Alignment;
     return false;
   }
   case Builtin::BI__builtin_operator_new:
     return HandleOperatorNewCall(Info, E, Result);
   case Builtin::BI__builtin_launder:
     return evaluatePointer(E->getArg(0), Result);
   case Builtin::BIstrchr:
   case Builtin::BIwcschr:
   case Builtin::BImemchr:
   case Builtin::BIwmemchr:
     if (Info.getLangOpts().CPlusPlus11)
       Info.CCEDiag(E, diag::note_constexpr_invalid_function)
         << /*isConstexpr*/0 << /*isConstructor*/0
         << (std::string("'") + Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'");
     else
       Info.CCEDiag(E, diag::note_invalid_subexpr_in_const_expr);
     LLVM_FALLTHROUGH;
   case Builtin::BI__builtin_strchr:
   case Builtin::BI__builtin_wcschr:
   case Builtin::BI__builtin_memchr:
   case Builtin::BI__builtin_char_memchr:
   case Builtin::BI__builtin_wmemchr: {
     if (!Visit(E->getArg(0)))
       return false;
     APSInt Desired;
     if (!EvaluateInteger(E->getArg(1), Desired, Info))
       return false;
     uint64_t MaxLength = uint64_t(-1);
     if (BuiltinOp != Builtin::BIstrchr &&
         BuiltinOp != Builtin::BIwcschr &&
         BuiltinOp != Builtin::BI__builtin_strchr &&
         BuiltinOp != Builtin::BI__builtin_wcschr) {
       APSInt N;
       if (!EvaluateInteger(E->getArg(2), N, Info))
         return false;
       MaxLength = N.getExtValue();
     }
     // We cannot find the value if there are no candidates to match against.
     if (MaxLength == 0u)
       return ZeroInitialization(E);
     if (!Result.checkNullPointerForFoldAccess(Info, E, AK_Read) ||
         Result.Designator.Invalid)
       return false;
     QualType CharTy = Result.Designator.getType(Info.Ctx);
     bool IsRawByte = BuiltinOp == Builtin::BImemchr ||
                      BuiltinOp == Builtin::BI__builtin_memchr;
     assert(IsRawByte ||
            Info.Ctx.hasSameUnqualifiedType(
                CharTy, E->getArg(0)->getType()->getPointeeType()));
     // Pointers to const void may point to objects of incomplete type.
     if (IsRawByte && CharTy->isIncompleteType()) {
       Info.FFDiag(E, diag::note_constexpr_ltor_incomplete_type) << CharTy;
       return false;
     }
     // Give up on byte-oriented matching against multibyte elements.
     // FIXME: We can compare the bytes in the correct order.
     if (IsRawByte && !isOneByteCharacterType(CharTy)) {
       Info.FFDiag(E, diag::note_constexpr_memchr_unsupported)
           << (std::string("'") + Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'")
           << CharTy;
       return false;
     }
     // Figure out what value we're actually looking for (after converting to
     // the corresponding unsigned type if necessary).
     uint64_t DesiredVal;
     bool StopAtNull = false;
     switch (BuiltinOp) {
     case Builtin::BIstrchr:
     case Builtin::BI__builtin_strchr:
       // strchr compares directly to the passed integer, and therefore
       // always fails if given an int that is not a char.
       if (!APSInt::isSameValue(HandleIntToIntCast(Info, E, CharTy,
                                                   E->getArg(1)->getType(),
                                                   Desired),
                                Desired))
         return ZeroInitialization(E);
       StopAtNull = true;
       LLVM_FALLTHROUGH;
     case Builtin::BImemchr:
     case Builtin::BI__builtin_memchr:
     case Builtin::BI__builtin_char_memchr:
       // memchr compares by converting both sides to unsigned char. That's also
       // correct for strchr if we get this far (to cope with plain char being
       // unsigned in the strchr case).
       DesiredVal = Desired.trunc(Info.Ctx.getCharWidth()).getZExtValue();
       break;
 
     case Builtin::BIwcschr:
     case Builtin::BI__builtin_wcschr:
       StopAtNull = true;
       LLVM_FALLTHROUGH;
     case Builtin::BIwmemchr:
     case Builtin::BI__builtin_wmemchr:
       // wcschr and wmemchr are given a wchar_t to look for. Just use it.
       DesiredVal = Desired.getZExtValue();
       break;
     }
 
     for (; MaxLength; --MaxLength) {
       APValue Char;
       if (!handleLValueToRValueConversion(Info, E, CharTy, Result, Char) ||
           !Char.isInt())
         return false;
       if (Char.getInt().getZExtValue() == DesiredVal)
         return true;
       if (StopAtNull && !Char.getInt())
         break;
       if (!HandleLValueArrayAdjustment(Info, E, Result, CharTy, 1))
         return false;
     }
     // Not found: return nullptr.
     return ZeroInitialization(E);
   }
 
   case Builtin::BImemcpy:
   case Builtin::BImemmove:
   case Builtin::BIwmemcpy:
   case Builtin::BIwmemmove:
     if (Info.getLangOpts().CPlusPlus11)
       Info.CCEDiag(E, diag::note_constexpr_invalid_function)
         << /*isConstexpr*/0 << /*isConstructor*/0
         << (std::string("'") + Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'");
     else
       Info.CCEDiag(E, diag::note_invalid_subexpr_in_const_expr);
     LLVM_FALLTHROUGH;
   case Builtin::BI__builtin_memcpy:
   case Builtin::BI__builtin_memmove:
   case Builtin::BI__builtin_wmemcpy:
   case Builtin::BI__builtin_wmemmove: {
     bool WChar = BuiltinOp == Builtin::BIwmemcpy ||
                  BuiltinOp == Builtin::BIwmemmove ||
                  BuiltinOp == Builtin::BI__builtin_wmemcpy ||
                  BuiltinOp == Builtin::BI__builtin_wmemmove;
     bool Move = BuiltinOp == Builtin::BImemmove ||
                 BuiltinOp == Builtin::BIwmemmove ||
                 BuiltinOp == Builtin::BI__builtin_memmove ||
                 BuiltinOp == Builtin::BI__builtin_wmemmove;
 
     // The result of mem* is the first argument.
     if (!Visit(E->getArg(0)))
       return false;
     LValue Dest = Result;
 
     LValue Src;
     if (!EvaluatePointer(E->getArg(1), Src, Info))
       return false;
 
     APSInt N;
     if (!EvaluateInteger(E->getArg(2), N, Info))
       return false;
     assert(!N.isSigned() && "memcpy and friends take an unsigned size");
 
     // If the size is zero, we treat this as always being a valid no-op.
     // (Even if one of the src and dest pointers is null.)
     if (!N)
       return true;
 
     // Otherwise, if either of the operands is null, we can't proceed. Don't
     // try to determine the type of the copied objects, because there aren't
     // any.
     if (!Src.Base || !Dest.Base) {
       APValue Val;
       (!Src.Base ? Src : Dest).moveInto(Val);
       Info.FFDiag(E, diag::note_constexpr_memcpy_null)
           << Move << WChar << !!Src.Base
           << Val.getAsString(Info.Ctx, E->getArg(0)->getType());
       return false;
     }
     if (Src.Designator.Invalid || Dest.Designator.Invalid)
       return false;
 
     // We require that Src and Dest are both pointers to arrays of
     // trivially-copyable type. (For the wide version, the designator will be
     // invalid if the designated object is not a wchar_t.)
     QualType T = Dest.Designator.getType(Info.Ctx);
     QualType SrcT = Src.Designator.getType(Info.Ctx);
     if (!Info.Ctx.hasSameUnqualifiedType(T, SrcT)) {
       // FIXME: Consider using our bit_cast implementation to support this.
       Info.FFDiag(E, diag::note_constexpr_memcpy_type_pun) << Move << SrcT << T;
       return false;
     }
     if (T->isIncompleteType()) {
       Info.FFDiag(E, diag::note_constexpr_memcpy_incomplete_type) << Move << T;
       return false;
     }
     if (!T.isTriviallyCopyableType(Info.Ctx)) {
       Info.FFDiag(E, diag::note_constexpr_memcpy_nontrivial) << Move << T;
       return false;
     }
 
     // Figure out how many T's we're copying.
     uint64_t TSize = Info.Ctx.getTypeSizeInChars(T).getQuantity();
     if (!WChar) {
       uint64_t Remainder;
       llvm::APInt OrigN = N;
       llvm::APInt::udivrem(OrigN, TSize, N, Remainder);
       if (Remainder) {
         Info.FFDiag(E, diag::note_constexpr_memcpy_unsupported)
             << Move << WChar << 0 << T << OrigN.toString(10, /*Signed*/false)
             << (unsigned)TSize;
         return false;
       }
     }
 
     // Check that the copying will remain within the arrays, just so that we
     // can give a more meaningful diagnostic. This implicitly also checks that
     // N fits into 64 bits.
     uint64_t RemainingSrcSize = Src.Designator.validIndexAdjustments().second;
     uint64_t RemainingDestSize = Dest.Designator.validIndexAdjustments().second;
     if (N.ugt(RemainingSrcSize) || N.ugt(RemainingDestSize)) {
       Info.FFDiag(E, diag::note_constexpr_memcpy_unsupported)
           << Move << WChar << (N.ugt(RemainingSrcSize) ? 1 : 2) << T
           << N.toString(10, /*Signed*/false);
       return false;
     }
     uint64_t NElems = N.getZExtValue();
     uint64_t NBytes = NElems * TSize;
 
     // Check for overlap.
     int Direction = 1;
     if (HasSameBase(Src, Dest)) {
       uint64_t SrcOffset = Src.getLValueOffset().getQuantity();
       uint64_t DestOffset = Dest.getLValueOffset().getQuantity();
       if (DestOffset >= SrcOffset && DestOffset - SrcOffset < NBytes) {
         // Dest is inside the source region.
         if (!Move) {
           Info.FFDiag(E, diag::note_constexpr_memcpy_overlap) << WChar;
           return false;
         }
         // For memmove and friends, copy backwards.
         if (!HandleLValueArrayAdjustment(Info, E, Src, T, NElems - 1) ||
             !HandleLValueArrayAdjustment(Info, E, Dest, T, NElems - 1))
           return false;
         Direction = -1;
       } else if (!Move && SrcOffset >= DestOffset &&
                  SrcOffset - DestOffset < NBytes) {
         // Src is inside the destination region for memcpy: invalid.
         Info.FFDiag(E, diag::note_constexpr_memcpy_overlap) << WChar;
         return false;
       }
     }
 
     while (true) {
       APValue Val;
       // FIXME: Set WantObjectRepresentation to true if we're copying a
       // char-like type?
       if (!handleLValueToRValueConversion(Info, E, T, Src, Val) ||
           !handleAssignment(Info, E, Dest, T, Val))
         return false;
       // Do not iterate past the last element; if we're copying backwards, that
       // might take us off the start of the array.
       if (--NElems == 0)
         return true;
       if (!HandleLValueArrayAdjustment(Info, E, Src, T, Direction) ||
           !HandleLValueArrayAdjustment(Info, E, Dest, T, Direction))
         return false;
     }
   }
 
   default:
     break;
   }
 
   return visitNonBuiltinCallExpr(E);
 }
 
 static bool EvaluateArrayNewInitList(EvalInfo &Info, LValue &This,
                                      APValue &Result, const InitListExpr *ILE,
                                      QualType AllocType);
 static bool EvaluateArrayNewConstructExpr(EvalInfo &Info, LValue &This,
                                           APValue &Result,
                                           const CXXConstructExpr *CCE,
                                           QualType AllocType);
 
 bool PointerExprEvaluator::VisitCXXNewExpr(const CXXNewExpr *E) {
   if (!Info.getLangOpts().CPlusPlus20)
     Info.CCEDiag(E, diag::note_constexpr_new);
 
   // We cannot speculatively evaluate a delete expression.
   if (Info.SpeculativeEvaluationDepth)
     return false;
 
   FunctionDecl *OperatorNew = E->getOperatorNew();
 
   bool IsNothrow = false;
   bool IsPlacement = false;
   if (OperatorNew->isReservedGlobalPlacementOperator() &&
       Info.CurrentCall->isStdFunction() && !E->isArray()) {
     // FIXME Support array placement new.
     assert(E->getNumPlacementArgs() == 1);
     if (!EvaluatePointer(E->getPlacementArg(0), Result, Info))
       return false;
     if (Result.Designator.Invalid)
       return false;
     IsPlacement = true;
   } else if (!OperatorNew->isReplaceableGlobalAllocationFunction()) {
     Info.FFDiag(E, diag::note_constexpr_new_non_replaceable)
         << isa<CXXMethodDecl>(OperatorNew) << OperatorNew;
     return false;
   } else if (E->getNumPlacementArgs()) {
     // The only new-placement list we support is of the form (std::nothrow).
     //
     // FIXME: There is no restriction on this, but it's not clear that any
     // other form makes any sense. We get here for cases such as:
     //
     //   new (std::align_val_t{N}) X(int)
     //
     // (which should presumably be valid only if N is a multiple of
     // alignof(int), and in any case can't be deallocated unless N is
     // alignof(X) and X has new-extended alignment).
     if (E->getNumPlacementArgs() != 1 ||
         !E->getPlacementArg(0)->getType()->isNothrowT())
       return Error(E, diag::note_constexpr_new_placement);
 
     LValue Nothrow;
     if (!EvaluateLValue(E->getPlacementArg(0), Nothrow, Info))
       return false;
     IsNothrow = true;
   }
 
   const Expr *Init = E->getInitializer();
   const InitListExpr *ResizedArrayILE = nullptr;
   const CXXConstructExpr *ResizedArrayCCE = nullptr;
 
   QualType AllocType = E->getAllocatedType();
   if (Optional<const Expr*> ArraySize = E->getArraySize()) {
     const Expr *Stripped = *ArraySize;
     for (; auto *ICE = dyn_cast<ImplicitCastExpr>(Stripped);
          Stripped = ICE->getSubExpr())
       if (ICE->getCastKind() != CK_NoOp &&
           ICE->getCastKind() != CK_IntegralCast)
         break;
 
     llvm::APSInt ArrayBound;
     if (!EvaluateInteger(Stripped, ArrayBound, Info))
       return false;
 
     // C++ [expr.new]p9:
     //   The expression is erroneous if:
     //   -- [...] its value before converting to size_t [or] applying the
     //      second standard conversion sequence is less than zero
     if (ArrayBound.isSigned() && ArrayBound.isNegative()) {
       if (IsNothrow)
         return ZeroInitialization(E);
 
       Info.FFDiag(*ArraySize, diag::note_constexpr_new_negative)
           << ArrayBound << (*ArraySize)->getSourceRange();
       return false;
     }
 
     //   -- its value is such that the size of the allocated object would
     //      exceed the implementation-defined limit
     if (ConstantArrayType::getNumAddressingBits(Info.Ctx, AllocType,
                                                 ArrayBound) >
         ConstantArrayType::getMaxSizeBits(Info.Ctx)) {
       if (IsNothrow)
         return ZeroInitialization(E);
 
       Info.FFDiag(*ArraySize, diag::note_constexpr_new_too_large)
         << ArrayBound << (*ArraySize)->getSourceRange();
       return false;
     }
 
     //   -- the new-initializer is a braced-init-list and the number of
     //      array elements for which initializers are provided [...]
     //      exceeds the number of elements to initialize
     if (Init && !isa<CXXConstructExpr>(Init)) {
       auto *CAT = Info.Ctx.getAsConstantArrayType(Init->getType());
       assert(CAT && "unexpected type for array initializer");
 
       unsigned Bits =
           std::max(CAT->getSize().getBitWidth(), ArrayBound.getBitWidth());
       llvm::APInt InitBound = CAT->getSize().zextOrSelf(Bits);
       llvm::APInt AllocBound = ArrayBound.zextOrSelf(Bits);
       if (InitBound.ugt(AllocBound)) {
         if (IsNothrow)
           return ZeroInitialization(E);
 
         Info.FFDiag(*ArraySize, diag::note_constexpr_new_too_small)
             << AllocBound.toString(10, /*Signed=*/false)
             << InitBound.toString(10, /*Signed=*/false)
             << (*ArraySize)->getSourceRange();
         return false;
       }
 
       // If the sizes differ, we must have an initializer list, and we need
       // special handling for this case when we initialize.
       if (InitBound != AllocBound)
         ResizedArrayILE = cast<InitListExpr>(Init);
     } else if (Init) {
       ResizedArrayCCE = cast<CXXConstructExpr>(Init);
     }
 
     AllocType = Info.Ctx.getConstantArrayType(AllocType, ArrayBound, nullptr,
                                               ArrayType::Normal, 0);
   } else {
     assert(!AllocType->isArrayType() &&
            "array allocation with non-array new");
   }
 
   APValue *Val;
   if (IsPlacement) {
     AccessKinds AK = AK_Construct;
     struct FindObjectHandler {
       EvalInfo &Info;
       const Expr *E;
       QualType AllocType;
       const AccessKinds AccessKind;
       APValue *Value;
 
       typedef bool result_type;
       bool failed() { return false; }
       bool found(APValue &Subobj, QualType SubobjType) {
         // FIXME: Reject the cases where [basic.life]p8 would not permit the
         // old name of the object to be used to name the new object.
         if (!Info.Ctx.hasSameUnqualifiedType(SubobjType, AllocType)) {
           Info.FFDiag(E, diag::note_constexpr_placement_new_wrong_type) <<
             SubobjType << AllocType;
           return false;
         }
         Value = &Subobj;
         return true;
       }
       bool found(APSInt &Value, QualType SubobjType) {
         Info.FFDiag(E, diag::note_constexpr_construct_complex_elem);
         return false;
       }
       bool found(APFloat &Value, QualType SubobjType) {
         Info.FFDiag(E, diag::note_constexpr_construct_complex_elem);
         return false;
       }
     } Handler = {Info, E, AllocType, AK, nullptr};
 
     CompleteObject Obj = findCompleteObject(Info, E, AK, Result, AllocType);
     if (!Obj || !findSubobject(Info, E, Obj, Result.Designator, Handler))
       return false;
 
     Val = Handler.Value;
 
     // [basic.life]p1:
     //   The lifetime of an object o of type T ends when [...] the storage
     //   which the object occupies is [...] reused by an object that is not
     //   nested within o (6.6.2).
     *Val = APValue();
   } else {
     // Perform the allocation and obtain a pointer to the resulting object.
     Val = Info.createHeapAlloc(E, AllocType, Result);
     if (!Val)
       return false;
   }
 
   if (ResizedArrayILE) {
     if (!EvaluateArrayNewInitList(Info, Result, *Val, ResizedArrayILE,
                                   AllocType))
       return false;
   } else if (ResizedArrayCCE) {
     if (!EvaluateArrayNewConstructExpr(Info, Result, *Val, ResizedArrayCCE,
                                        AllocType))
       return false;
   } else if (Init) {
     if (!EvaluateInPlace(*Val, Info, Result, Init))
       return false;
   } else if (!getDefaultInitValue(AllocType, *Val)) {
     return false;
   }
 
   // Array new returns a pointer to the first element, not a pointer to the
   // array.
   if (auto *AT = AllocType->getAsArrayTypeUnsafe())
     Result.addArray(Info, E, cast<ConstantArrayType>(AT));
 
   return true;
 }
 //===----------------------------------------------------------------------===//
 // Member Pointer Evaluation
 //===----------------------------------------------------------------------===//
 
 namespace {
 class MemberPointerExprEvaluator
   : public ExprEvaluatorBase<MemberPointerExprEvaluator> {
   MemberPtr &Result;
 
   bool Success(const ValueDecl *D) {
     Result = MemberPtr(D);
     return true;
   }
 public:
 
   MemberPointerExprEvaluator(EvalInfo &Info, MemberPtr &Result)
     : ExprEvaluatorBaseTy(Info), Result(Result) {}
 
   bool Success(const APValue &V, const Expr *E) {
     Result.setFrom(V);
     return true;
   }
   bool ZeroInitialization(const Expr *E) {
     return Success((const ValueDecl*)nullptr);
   }
 
   bool VisitCastExpr(const CastExpr *E);
   bool VisitUnaryAddrOf(const UnaryOperator *E);
 };
 } // end anonymous namespace
 
 static bool EvaluateMemberPointer(const Expr *E, MemberPtr &Result,
                                   EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isMemberPointerType());
   return MemberPointerExprEvaluator(Info, Result).Visit(E);
 }
 
 bool MemberPointerExprEvaluator::VisitCastExpr(const CastExpr *E) {
   switch (E->getCastKind()) {
   default:
     return ExprEvaluatorBaseTy::VisitCastExpr(E);
 
   case CK_NullToMemberPointer:
     VisitIgnoredValue(E->getSubExpr());
     return ZeroInitialization(E);
 
   case CK_BaseToDerivedMemberPointer: {
     if (!Visit(E->getSubExpr()))
       return false;
     if (E->path_empty())
       return true;
     // Base-to-derived member pointer casts store the path in derived-to-base
     // order, so iterate backwards. The CXXBaseSpecifier also provides us with
     // the wrong end of the derived->base arc, so stagger the path by one class.
     typedef std::reverse_iterator<CastExpr::path_const_iterator> ReverseIter;
     for (ReverseIter PathI(E->path_end() - 1), PathE(E->path_begin());
          PathI != PathE; ++PathI) {
       assert(!(*PathI)->isVirtual() && "memptr cast through vbase");
       const CXXRecordDecl *Derived = (*PathI)->getType()->getAsCXXRecordDecl();
       if (!Result.castToDerived(Derived))
         return Error(E);
     }
     const Type *FinalTy = E->getType()->castAs<MemberPointerType>()->getClass();
     if (!Result.castToDerived(FinalTy->getAsCXXRecordDecl()))
       return Error(E);
     return true;
   }
 
   case CK_DerivedToBaseMemberPointer:
     if (!Visit(E->getSubExpr()))
       return false;
     for (CastExpr::path_const_iterator PathI = E->path_begin(),
          PathE = E->path_end(); PathI != PathE; ++PathI) {
       assert(!(*PathI)->isVirtual() && "memptr cast through vbase");
       const CXXRecordDecl *Base = (*PathI)->getType()->getAsCXXRecordDecl();
       if (!Result.castToBase(Base))
         return Error(E);
     }
     return true;
   }
 }
 
 bool MemberPointerExprEvaluator::VisitUnaryAddrOf(const UnaryOperator *E) {
   // C++11 [expr.unary.op]p3 has very strict rules on how the address of a
   // member can be formed.
   return Success(cast<DeclRefExpr>(E->getSubExpr())->getDecl());
 }
 
 //===----------------------------------------------------------------------===//
 // Record Evaluation
 //===----------------------------------------------------------------------===//
 
 namespace {
   class RecordExprEvaluator
   : public ExprEvaluatorBase<RecordExprEvaluator> {
     const LValue &This;
     APValue &Result;
   public:
 
     RecordExprEvaluator(EvalInfo &info, const LValue &This, APValue &Result)
       : ExprEvaluatorBaseTy(info), This(This), Result(Result) {}
 
     bool Success(const APValue &V, const Expr *E) {
       Result = V;
       return true;
     }
     bool ZeroInitialization(const Expr *E) {
       return ZeroInitialization(E, E->getType());
     }
     bool ZeroInitialization(const Expr *E, QualType T);
 
     bool VisitCallExpr(const CallExpr *E) {
       return handleCallExpr(E, Result, &This);
     }
     bool VisitCastExpr(const CastExpr *E);
     bool VisitInitListExpr(const InitListExpr *E);
     bool VisitCXXConstructExpr(const CXXConstructExpr *E) {
       return VisitCXXConstructExpr(E, E->getType());
     }
     bool VisitLambdaExpr(const LambdaExpr *E);
     bool VisitCXXInheritedCtorInitExpr(const CXXInheritedCtorInitExpr *E);
     bool VisitCXXConstructExpr(const CXXConstructExpr *E, QualType T);
     bool VisitCXXStdInitializerListExpr(const CXXStdInitializerListExpr *E);
     bool VisitBinCmp(const BinaryOperator *E);
   };
 }
 
 /// Perform zero-initialization on an object of non-union class type.
 /// C++11 [dcl.init]p5:
 ///  To zero-initialize an object or reference of type T means:
 ///    [...]
 ///    -- if T is a (possibly cv-qualified) non-union class type,
 ///       each non-static data member and each base-class subobject is
 ///       zero-initialized
 static bool HandleClassZeroInitialization(EvalInfo &Info, const Expr *E,
                                           const RecordDecl *RD,
                                           const LValue &This, APValue &Result) {
   assert(!RD->isUnion() && "Expected non-union class type");
   const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD);
   Result = APValue(APValue::UninitStruct(), CD ? CD->getNumBases() : 0,
                    std::distance(RD->field_begin(), RD->field_end()));
 
   if (RD->isInvalidDecl()) return false;
   const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
 
   if (CD) {
     unsigned Index = 0;
     for (CXXRecordDecl::base_class_const_iterator I = CD->bases_begin(),
            End = CD->bases_end(); I != End; ++I, ++Index) {
       const CXXRecordDecl *Base = I->getType()->getAsCXXRecordDecl();
       LValue Subobject = This;
       if (!HandleLValueDirectBase(Info, E, Subobject, CD, Base, &Layout))
         return false;
       if (!HandleClassZeroInitialization(Info, E, Base, Subobject,
                                          Result.getStructBase(Index)))
         return false;
     }
   }
 
   for (const auto *I : RD->fields()) {
     // -- if T is a reference type, no initialization is performed.
     if (I->getType()->isReferenceType())
       continue;
 
     LValue Subobject = This;
     if (!HandleLValueMember(Info, E, Subobject, I, &Layout))
       return false;
 
     ImplicitValueInitExpr VIE(I->getType());
     if (!EvaluateInPlace(
           Result.getStructField(I->getFieldIndex()), Info, Subobject, &VIE))
       return false;
   }
 
   return true;
 }
 
 bool RecordExprEvaluator::ZeroInitialization(const Expr *E, QualType T) {
   const RecordDecl *RD = T->castAs<RecordType>()->getDecl();
   if (RD->isInvalidDecl()) return false;
   if (RD->isUnion()) {
     // C++11 [dcl.init]p5: If T is a (possibly cv-qualified) union type, the
     // object's first non-static named data member is zero-initialized
     RecordDecl::field_iterator I = RD->field_begin();
     if (I == RD->field_end()) {
       Result = APValue((const FieldDecl*)nullptr);
       return true;
     }
 
     LValue Subobject = This;
     if (!HandleLValueMember(Info, E, Subobject, *I))
       return false;
     Result = APValue(*I);
     ImplicitValueInitExpr VIE(I->getType());
     return EvaluateInPlace(Result.getUnionValue(), Info, Subobject, &VIE);
   }
 
   if (isa<CXXRecordDecl>(RD) && cast<CXXRecordDecl>(RD)->getNumVBases()) {
     Info.FFDiag(E, diag::note_constexpr_virtual_base) << RD;
     return false;
   }
 
   return HandleClassZeroInitialization(Info, E, RD, This, Result);
 }
 
 bool RecordExprEvaluator::VisitCastExpr(const CastExpr *E) {
   switch (E->getCastKind()) {
   default:
     return ExprEvaluatorBaseTy::VisitCastExpr(E);
 
   case CK_ConstructorConversion:
     return Visit(E->getSubExpr());
 
   case CK_DerivedToBase:
   case CK_UncheckedDerivedToBase: {
     APValue DerivedObject;
     if (!Evaluate(DerivedObject, Info, E->getSubExpr()))
       return false;
     if (!DerivedObject.isStruct())
       return Error(E->getSubExpr());
 
     // Derived-to-base rvalue conversion: just slice off the derived part.
     APValue *Value = &DerivedObject;
     const CXXRecordDecl *RD = E->getSubExpr()->getType()->getAsCXXRecordDecl();
     for (CastExpr::path_const_iterator PathI = E->path_begin(),
          PathE = E->path_end(); PathI != PathE; ++PathI) {
       assert(!(*PathI)->isVirtual() && "record rvalue with virtual base");
       const CXXRecordDecl *Base = (*PathI)->getType()->getAsCXXRecordDecl();
       Value = &Value->getStructBase(getBaseIndex(RD, Base));
       RD = Base;
     }
     Result = *Value;
     return true;
   }
   }
 }
 
 bool RecordExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
   if (E->isTransparent())
     return Visit(E->getInit(0));
 
   const RecordDecl *RD = E->getType()->castAs<RecordType>()->getDecl();
   if (RD->isInvalidDecl()) return false;
   const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
   auto *CXXRD = dyn_cast<CXXRecordDecl>(RD);
 
   EvalInfo::EvaluatingConstructorRAII EvalObj(
       Info,
       ObjectUnderConstruction{This.getLValueBase(), This.Designator.Entries},
       CXXRD && CXXRD->getNumBases());
 
   if (RD->isUnion()) {
     const FieldDecl *Field = E->getInitializedFieldInUnion();
     Result = APValue(Field);
     if (!Field)
       return true;
 
     // If the initializer list for a union does not contain any elements, the
     // first element of the union is value-initialized.
     // FIXME: The element should be initialized from an initializer list.
     //        Is this difference ever observable for initializer lists which
     //        we don't build?
     ImplicitValueInitExpr VIE(Field->getType());
     const Expr *InitExpr = E->getNumInits() ? E->getInit(0) : &VIE;
 
     LValue Subobject = This;
     if (!HandleLValueMember(Info, InitExpr, Subobject, Field, &Layout))
       return false;
 
     // Temporarily override This, in case there's a CXXDefaultInitExpr in here.
     ThisOverrideRAII ThisOverride(*Info.CurrentCall, &This,
                                   isa<CXXDefaultInitExpr>(InitExpr));
 
     return EvaluateInPlace(Result.getUnionValue(), Info, Subobject, InitExpr);
   }
 
   if (!Result.hasValue())
     Result = APValue(APValue::UninitStruct(), CXXRD ? CXXRD->getNumBases() : 0,
                      std::distance(RD->field_begin(), RD->field_end()));
   unsigned ElementNo = 0;
   bool Success = true;
 
   // Initialize base classes.
   if (CXXRD && CXXRD->getNumBases()) {
     for (const auto &Base : CXXRD->bases()) {
       assert(ElementNo < E->getNumInits() && "missing init for base class");
       const Expr *Init = E->getInit(ElementNo);
 
       LValue Subobject = This;
       if (!HandleLValueBase(Info, Init, Subobject, CXXRD, &Base))
         return false;
 
       APValue &FieldVal = Result.getStructBase(ElementNo);
       if (!EvaluateInPlace(FieldVal, Info, Subobject, Init)) {
         if (!Info.noteFailure())
           return false;
         Success = false;
       }
       ++ElementNo;
     }
 
     EvalObj.finishedConstructingBases();
   }
 
   // Initialize members.
   for (const auto *Field : RD->fields()) {
     // Anonymous bit-fields are not considered members of the class for
     // purposes of aggregate initialization.
     if (Field->isUnnamedBitfield())
       continue;
 
     LValue Subobject = This;
 
     bool HaveInit = ElementNo < E->getNumInits();
 
     // FIXME: Diagnostics here should point to the end of the initializer
     // list, not the start.
     if (!HandleLValueMember(Info, HaveInit ? E->getInit(ElementNo) : E,
                             Subobject, Field, &Layout))
       return false;
 
     // Perform an implicit value-initialization for members beyond the end of
     // the initializer list.
     ImplicitValueInitExpr VIE(HaveInit ? Info.Ctx.IntTy : Field->getType());
     const Expr *Init = HaveInit ? E->getInit(ElementNo++) : &VIE;
 
     // Temporarily override This, in case there's a CXXDefaultInitExpr in here.
     ThisOverrideRAII ThisOverride(*Info.CurrentCall, &This,
                                   isa<CXXDefaultInitExpr>(Init));
 
     APValue &FieldVal = Result.getStructField(Field->getFieldIndex());
     if (!EvaluateInPlace(FieldVal, Info, Subobject, Init) ||
         (Field->isBitField() && !truncateBitfieldValue(Info, Init,
                                                        FieldVal, Field))) {
       if (!Info.noteFailure())
         return false;
       Success = false;
     }
   }
 
   EvalObj.finishedConstructingFields();
 
   return Success;
 }
 
 bool RecordExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E,
                                                 QualType T) {
   // Note that E's type is not necessarily the type of our class here; we might
   // be initializing an array element instead.
   const CXXConstructorDecl *FD = E->getConstructor();
   if (FD->isInvalidDecl() || FD->getParent()->isInvalidDecl()) return false;
 
   bool ZeroInit = E->requiresZeroInitialization();
   if (CheckTrivialDefaultConstructor(Info, E->getExprLoc(), FD, ZeroInit)) {
     // If we've already performed zero-initialization, we're already done.
     if (Result.hasValue())
       return true;
 
     if (ZeroInit)
       return ZeroInitialization(E, T);
 
     return getDefaultInitValue(T, Result);
   }
 
   const FunctionDecl *Definition = nullptr;
   auto Body = FD->getBody(Definition);
 
   if (!CheckConstexprFunction(Info, E->getExprLoc(), FD, Definition, Body))
     return false;
 
   // Avoid materializing a temporary for an elidable copy/move constructor.
   if (E->isElidable() && !ZeroInit)
     if (const MaterializeTemporaryExpr *ME
           = dyn_cast<MaterializeTemporaryExpr>(E->getArg(0)))
       return Visit(ME->getSubExpr());
 
   if (ZeroInit && !ZeroInitialization(E, T))
     return false;
 
   auto Args = llvm::makeArrayRef(E->getArgs(), E->getNumArgs());
   return HandleConstructorCall(E, This, Args,
                                cast<CXXConstructorDecl>(Definition), Info,
                                Result);
 }
 
 bool RecordExprEvaluator::VisitCXXInheritedCtorInitExpr(
     const CXXInheritedCtorInitExpr *E) {
   if (!Info.CurrentCall) {
     assert(Info.checkingPotentialConstantExpression());
     return false;
   }
 
   const CXXConstructorDecl *FD = E->getConstructor();
   if (FD->isInvalidDecl() || FD->getParent()->isInvalidDecl())
     return false;
 
   const FunctionDecl *Definition = nullptr;
   auto Body = FD->getBody(Definition);
 
   if (!CheckConstexprFunction(Info, E->getExprLoc(), FD, Definition, Body))
     return false;
 
   return HandleConstructorCall(E, This, Info.CurrentCall->Arguments,
                                cast<CXXConstructorDecl>(Definition), Info,
                                Result);
 }
 
 bool RecordExprEvaluator::VisitCXXStdInitializerListExpr(
     const CXXStdInitializerListExpr *E) {
   const ConstantArrayType *ArrayType =
       Info.Ctx.getAsConstantArrayType(E->getSubExpr()->getType());
 
   LValue Array;
   if (!EvaluateLValue(E->getSubExpr(), Array, Info))
     return false;
 
   // Get a pointer to the first element of the array.
   Array.addArray(Info, E, ArrayType);
 
   auto InvalidType = [&] {
     Info.FFDiag(E, diag::note_constexpr_unsupported_layout)
       << E->getType();
     return false;
   };
 
   // FIXME: Perform the checks on the field types in SemaInit.
   RecordDecl *Record = E->getType()->castAs<RecordType>()->getDecl();
   RecordDecl::field_iterator Field = Record->field_begin();
   if (Field == Record->field_end())
     return InvalidType();
 
   // Start pointer.
   if (!Field->getType()->isPointerType() ||
       !Info.Ctx.hasSameType(Field->getType()->getPointeeType(),
                             ArrayType->getElementType()))
     return InvalidType();
 
   // FIXME: What if the initializer_list type has base classes, etc?
   Result = APValue(APValue::UninitStruct(), 0, 2);
   Array.moveInto(Result.getStructField(0));
 
   if (++Field == Record->field_end())
     return InvalidType();
 
   if (Field->getType()->isPointerType() &&
       Info.Ctx.hasSameType(Field->getType()->getPointeeType(),
                            ArrayType->getElementType())) {
     // End pointer.
     if (!HandleLValueArrayAdjustment(Info, E, Array,
                                      ArrayType->getElementType(),
                                      ArrayType->getSize().getZExtValue()))
       return false;
     Array.moveInto(Result.getStructField(1));
   } else if (Info.Ctx.hasSameType(Field->getType(), Info.Ctx.getSizeType()))
     // Length.
     Result.getStructField(1) = APValue(APSInt(ArrayType->getSize()));
   else
     return InvalidType();
 
   if (++Field != Record->field_end())
     return InvalidType();
 
   return true;
 }
 
 bool RecordExprEvaluator::VisitLambdaExpr(const LambdaExpr *E) {
   const CXXRecordDecl *ClosureClass = E->getLambdaClass();
   if (ClosureClass->isInvalidDecl())
     return false;
 
   const size_t NumFields =
       std::distance(ClosureClass->field_begin(), ClosureClass->field_end());
 
   assert(NumFields == (size_t)std::distance(E->capture_init_begin(),
                                             E->capture_init_end()) &&
          "The number of lambda capture initializers should equal the number of "
          "fields within the closure type");
 
   Result = APValue(APValue::UninitStruct(), /*NumBases*/0, NumFields);
   // Iterate through all the lambda's closure object's fields and initialize
   // them.
   auto *CaptureInitIt = E->capture_init_begin();
   const LambdaCapture *CaptureIt = ClosureClass->captures_begin();
   bool Success = true;
   for (const auto *Field : ClosureClass->fields()) {
     assert(CaptureInitIt != E->capture_init_end());
     // Get the initializer for this field
     Expr *const CurFieldInit = *CaptureInitIt++;
 
     // If there is no initializer, either this is a VLA or an error has
     // occurred.
     if (!CurFieldInit)
       return Error(E);
 
     APValue &FieldVal = Result.getStructField(Field->getFieldIndex());
     if (!EvaluateInPlace(FieldVal, Info, This, CurFieldInit)) {
       if (!Info.keepEvaluatingAfterFailure())
         return false;
       Success = false;
     }
     ++CaptureIt;
   }
   return Success;
 }
 
 static bool EvaluateRecord(const Expr *E, const LValue &This,
                            APValue &Result, EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isRecordType() &&
          "can't evaluate expression as a record rvalue");
   return RecordExprEvaluator(Info, This, Result).Visit(E);
 }
 
 //===----------------------------------------------------------------------===//
 // Temporary Evaluation
 //
 // Temporaries are represented in the AST as rvalues, but generally behave like
 // lvalues. The full-object of which the temporary is a subobject is implicitly
 // materialized so that a reference can bind to it.
 //===----------------------------------------------------------------------===//
 namespace {
 class TemporaryExprEvaluator
   : public LValueExprEvaluatorBase<TemporaryExprEvaluator> {
 public:
   TemporaryExprEvaluator(EvalInfo &Info, LValue &Result) :
     LValueExprEvaluatorBaseTy(Info, Result, false) {}
 
   /// Visit an expression which constructs the value of this temporary.
   bool VisitConstructExpr(const Expr *E) {
     APValue &Value =
         Info.CurrentCall->createTemporary(E, E->getType(), false, Result);
     return EvaluateInPlace(Value, Info, Result, E);
   }
 
   bool VisitCastExpr(const CastExpr *E) {
     switch (E->getCastKind()) {
     default:
       return LValueExprEvaluatorBaseTy::VisitCastExpr(E);
 
     case CK_ConstructorConversion:
       return VisitConstructExpr(E->getSubExpr());
     }
   }
   bool VisitInitListExpr(const InitListExpr *E) {
     return VisitConstructExpr(E);
   }
   bool VisitCXXConstructExpr(const CXXConstructExpr *E) {
     return VisitConstructExpr(E);
   }
   bool VisitCallExpr(const CallExpr *E) {
     return VisitConstructExpr(E);
   }
   bool VisitCXXStdInitializerListExpr(const CXXStdInitializerListExpr *E) {
     return VisitConstructExpr(E);
   }
   bool VisitLambdaExpr(const LambdaExpr *E) {
     return VisitConstructExpr(E);
   }
 };
 } // end anonymous namespace
 
 /// Evaluate an expression of record type as a temporary.
 static bool EvaluateTemporary(const Expr *E, LValue &Result, EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isRecordType());
   return TemporaryExprEvaluator(Info, Result).Visit(E);
 }
 
 //===----------------------------------------------------------------------===//
 // Vector Evaluation
 //===----------------------------------------------------------------------===//
 
 namespace {
   class VectorExprEvaluator
   : public ExprEvaluatorBase<VectorExprEvaluator> {
     APValue &Result;
   public:
 
     VectorExprEvaluator(EvalInfo &info, APValue &Result)
       : ExprEvaluatorBaseTy(info), Result(Result) {}
 
     bool Success(ArrayRef<APValue> V, const Expr *E) {
       assert(V.size() == E->getType()->castAs<VectorType>()->getNumElements());
       // FIXME: remove this APValue copy.
       Result = APValue(V.data(), V.size());
       return true;
     }
     bool Success(const APValue &V, const Expr *E) {
       assert(V.isVector());
       Result = V;
       return true;
     }
     bool ZeroInitialization(const Expr *E);
 
     bool VisitUnaryReal(const UnaryOperator *E)
       { return Visit(E->getSubExpr()); }
     bool VisitCastExpr(const CastExpr* E);
     bool VisitInitListExpr(const InitListExpr *E);
     bool VisitUnaryImag(const UnaryOperator *E);
     bool VisitBinaryOperator(const BinaryOperator *E);
     // FIXME: Missing: unary -, unary ~, conditional operator (for GNU
     //                 conditional select), shufflevector, ExtVectorElementExpr
   };
 } // end anonymous namespace
 
 static bool EvaluateVector(const Expr* E, APValue& Result, EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isVectorType() &&"not a vector rvalue");
   return VectorExprEvaluator(Info, Result).Visit(E);
 }
 
 bool VectorExprEvaluator::VisitCastExpr(const CastExpr *E) {
   const VectorType *VTy = E->getType()->castAs<VectorType>();
   unsigned NElts = VTy->getNumElements();
 
   const Expr *SE = E->getSubExpr();
   QualType SETy = SE->getType();
 
   switch (E->getCastKind()) {
   case CK_VectorSplat: {
     APValue Val = APValue();
     if (SETy->isIntegerType()) {
       APSInt IntResult;
       if (!EvaluateInteger(SE, IntResult, Info))
         return false;
       Val = APValue(std::move(IntResult));
     } else if (SETy->isRealFloatingType()) {
       APFloat FloatResult(0.0);
       if (!EvaluateFloat(SE, FloatResult, Info))
         return false;
       Val = APValue(std::move(FloatResult));
     } else {
       return Error(E);
     }
 
     // Splat and create vector APValue.
     SmallVector<APValue, 4> Elts(NElts, Val);
     return Success(Elts, E);
   }
   case CK_BitCast: {
     // Evaluate the operand into an APInt we can extract from.
     llvm::APInt SValInt;
     if (!EvalAndBitcastToAPInt(Info, SE, SValInt))
       return false;
     // Extract the elements
     QualType EltTy = VTy->getElementType();
     unsigned EltSize = Info.Ctx.getTypeSize(EltTy);
     bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
     SmallVector<APValue, 4> Elts;
     if (EltTy->isRealFloatingType()) {
       const llvm::fltSemantics &Sem = Info.Ctx.getFloatTypeSemantics(EltTy);
       unsigned FloatEltSize = EltSize;
       if (&Sem == &APFloat::x87DoubleExtended())
         FloatEltSize = 80;
       for (unsigned i = 0; i < NElts; i++) {
         llvm::APInt Elt;
         if (BigEndian)
           Elt = SValInt.rotl(i*EltSize+FloatEltSize).trunc(FloatEltSize);
         else
           Elt = SValInt.rotr(i*EltSize).trunc(FloatEltSize);
         Elts.push_back(APValue(APFloat(Sem, Elt)));
       }
     } else if (EltTy->isIntegerType()) {
       for (unsigned i = 0; i < NElts; i++) {
         llvm::APInt Elt;
         if (BigEndian)
           Elt = SValInt.rotl(i*EltSize+EltSize).zextOrTrunc(EltSize);
         else
           Elt = SValInt.rotr(i*EltSize).zextOrTrunc(EltSize);
         Elts.push_back(APValue(APSInt(Elt, EltTy->isSignedIntegerType())));
       }
     } else {
       return Error(E);
     }
     return Success(Elts, E);
   }
   default:
     return ExprEvaluatorBaseTy::VisitCastExpr(E);
   }
 }
 
 bool
 VectorExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
   const VectorType *VT = E->getType()->castAs<VectorType>();
   unsigned NumInits = E->getNumInits();
   unsigned NumElements = VT->getNumElements();
 
   QualType EltTy = VT->getElementType();
   SmallVector<APValue, 4> Elements;
 
   // The number of initializers can be less than the number of
   // vector elements. For OpenCL, this can be due to nested vector
   // initialization. For GCC compatibility, missing trailing elements
   // should be initialized with zeroes.
   unsigned CountInits = 0, CountElts = 0;
   while (CountElts < NumElements) {
     // Handle nested vector initialization.
     if (CountInits < NumInits
         && E->getInit(CountInits)->getType()->isVectorType()) {
       APValue v;
       if (!EvaluateVector(E->getInit(CountInits), v, Info))
         return Error(E);
       unsigned vlen = v.getVectorLength();
       for (unsigned j = 0; j < vlen; j++)
         Elements.push_back(v.getVectorElt(j));
       CountElts += vlen;
     } else if (EltTy->isIntegerType()) {
       llvm::APSInt sInt(32);
       if (CountInits < NumInits) {
         if (!EvaluateInteger(E->getInit(CountInits), sInt, Info))
           return false;
       } else // trailing integer zero.
         sInt = Info.Ctx.MakeIntValue(0, EltTy);
       Elements.push_back(APValue(sInt));
       CountElts++;
     } else {
       llvm::APFloat f(0.0);
       if (CountInits < NumInits) {
         if (!EvaluateFloat(E->getInit(CountInits), f, Info))
           return false;
       } else // trailing float zero.
         f = APFloat::getZero(Info.Ctx.getFloatTypeSemantics(EltTy));
       Elements.push_back(APValue(f));
       CountElts++;
     }
     CountInits++;
   }
   return Success(Elements, E);
 }
 
 bool
 VectorExprEvaluator::ZeroInitialization(const Expr *E) {
   const auto *VT = E->getType()->castAs<VectorType>();
   QualType EltTy = VT->getElementType();
   APValue ZeroElement;
   if (EltTy->isIntegerType())
     ZeroElement = APValue(Info.Ctx.MakeIntValue(0, EltTy));
   else
     ZeroElement =
         APValue(APFloat::getZero(Info.Ctx.getFloatTypeSemantics(EltTy)));
 
   SmallVector<APValue, 4> Elements(VT->getNumElements(), ZeroElement);
   return Success(Elements, E);
 }
 
 bool VectorExprEvaluator::VisitUnaryImag(const UnaryOperator *E) {
   VisitIgnoredValue(E->getSubExpr());
   return ZeroInitialization(E);
 }
 
 bool VectorExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
   BinaryOperatorKind Op = E->getOpcode();
   assert(Op != BO_PtrMemD && Op != BO_PtrMemI && Op != BO_Cmp &&
          "Operation not supported on vector types");
 
   if (Op == BO_Comma)
     return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
 
   Expr *LHS = E->getLHS();
   Expr *RHS = E->getRHS();
 
   assert(LHS->getType()->isVectorType() && RHS->getType()->isVectorType() &&
          "Must both be vector types");
   // Checking JUST the types are the same would be fine, except shifts don't
   // need to have their types be the same (since you always shift by an int).
   assert(LHS->getType()->getAs<VectorType>()->getNumElements() ==
              E->getType()->getAs<VectorType>()->getNumElements() &&
          RHS->getType()->getAs<VectorType>()->getNumElements() ==
              E->getType()->getAs<VectorType>()->getNumElements() &&
          "All operands must be the same size.");
 
   APValue LHSValue;
   APValue RHSValue;
   bool LHSOK = Evaluate(LHSValue, Info, LHS);
   if (!LHSOK && !Info.noteFailure())
     return false;
   if (!Evaluate(RHSValue, Info, RHS) || !LHSOK)
     return false;
 
   if (!handleVectorVectorBinOp(Info, E, Op, LHSValue, RHSValue))
     return false;
 
   return Success(LHSValue, E);
 }
 
 //===----------------------------------------------------------------------===//
 // Array Evaluation
 //===----------------------------------------------------------------------===//
 
 namespace {
   class ArrayExprEvaluator
   : public ExprEvaluatorBase<ArrayExprEvaluator> {
     const LValue &This;
     APValue &Result;
   public:
 
     ArrayExprEvaluator(EvalInfo &Info, const LValue &This, APValue &Result)
       : ExprEvaluatorBaseTy(Info), This(This), Result(Result) {}
 
     bool Success(const APValue &V, const Expr *E) {
       assert(V.isArray() && "expected array");
       Result = V;
       return true;
     }
 
     bool ZeroInitialization(const Expr *E) {
       const ConstantArrayType *CAT =
           Info.Ctx.getAsConstantArrayType(E->getType());
       if (!CAT) {
         if (E->getType()->isIncompleteArrayType()) {
           // We can be asked to zero-initialize a flexible array member; this
           // is represented as an ImplicitValueInitExpr of incomplete array
           // type. In this case, the array has zero elements.
           Result = APValue(APValue::UninitArray(), 0, 0);
           return true;
         }
         // FIXME: We could handle VLAs here.
         return Error(E);
       }
 
       Result = APValue(APValue::UninitArray(), 0,
                        CAT->getSize().getZExtValue());
       if (!Result.hasArrayFiller()) return true;
 
       // Zero-initialize all elements.
       LValue Subobject = This;
       Subobject.addArray(Info, E, CAT);
       ImplicitValueInitExpr VIE(CAT->getElementType());
       return EvaluateInPlace(Result.getArrayFiller(), Info, Subobject, &VIE);
     }
 
     bool VisitCallExpr(const CallExpr *E) {
       return handleCallExpr(E, Result, &This);
     }
     bool VisitInitListExpr(const InitListExpr *E,
                            QualType AllocType = QualType());
     bool VisitArrayInitLoopExpr(const ArrayInitLoopExpr *E);
     bool VisitCXXConstructExpr(const CXXConstructExpr *E);
     bool VisitCXXConstructExpr(const CXXConstructExpr *E,
                                const LValue &Subobject,
                                APValue *Value, QualType Type);
     bool VisitStringLiteral(const StringLiteral *E,
                             QualType AllocType = QualType()) {
       expandStringLiteral(Info, E, Result, AllocType);
       return true;
     }
   };
 } // end anonymous namespace
 
 static bool EvaluateArray(const Expr *E, const LValue &This,
                           APValue &Result, EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isArrayType() && "not an array rvalue");
   return ArrayExprEvaluator(Info, This, Result).Visit(E);
 }
 
 static bool EvaluateArrayNewInitList(EvalInfo &Info, LValue &This,
                                      APValue &Result, const InitListExpr *ILE,
                                      QualType AllocType) {
   assert(ILE->isRValue() && ILE->getType()->isArrayType() &&
          "not an array rvalue");
   return ArrayExprEvaluator(Info, This, Result)
       .VisitInitListExpr(ILE, AllocType);
 }
 
 static bool EvaluateArrayNewConstructExpr(EvalInfo &Info, LValue &This,
                                           APValue &Result,
                                           const CXXConstructExpr *CCE,
                                           QualType AllocType) {
   assert(CCE->isRValue() && CCE->getType()->isArrayType() &&
          "not an array rvalue");
   return ArrayExprEvaluator(Info, This, Result)
       .VisitCXXConstructExpr(CCE, This, &Result, AllocType);
 }
 
 // Return true iff the given array filler may depend on the element index.
 static bool MaybeElementDependentArrayFiller(const Expr *FillerExpr) {
   // For now, just allow non-class value-initialization and initialization
   // lists comprised of them.
   if (isa<ImplicitValueInitExpr>(FillerExpr))
     return false;
   if (const InitListExpr *ILE = dyn_cast<InitListExpr>(FillerExpr)) {
     for (unsigned I = 0, E = ILE->getNumInits(); I != E; ++I) {
       if (MaybeElementDependentArrayFiller(ILE->getInit(I)))
         return true;
     }
     return false;
   }
   return true;
 }
 
 bool ArrayExprEvaluator::VisitInitListExpr(const InitListExpr *E,
                                            QualType AllocType) {
   const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(
       AllocType.isNull() ? E->getType() : AllocType);
   if (!CAT)
     return Error(E);
 
   // C++11 [dcl.init.string]p1: A char array [...] can be initialized by [...]
   // an appropriately-typed string literal enclosed in braces.
   if (E->isStringLiteralInit()) {
     auto *SL = dyn_cast<StringLiteral>(E->getInit(0)->IgnoreParens());
     // FIXME: Support ObjCEncodeExpr here once we support it in
     // ArrayExprEvaluator generally.
     if (!SL)
       return Error(E);
     return VisitStringLiteral(SL, AllocType);
   }
 
   bool Success = true;
 
   assert((!Result.isArray() || Result.getArrayInitializedElts() == 0) &&
          "zero-initialized array shouldn't have any initialized elts");
   APValue Filler;
   if (Result.isArray() && Result.hasArrayFiller())
     Filler = Result.getArrayFiller();
 
   unsigned NumEltsToInit = E->getNumInits();
   unsigned NumElts = CAT->getSize().getZExtValue();
   const Expr *FillerExpr = E->hasArrayFiller() ? E->getArrayFiller() : nullptr;
 
   // If the initializer might depend on the array index, run it for each
   // array element.
   if (NumEltsToInit != NumElts && MaybeElementDependentArrayFiller(FillerExpr))
     NumEltsToInit = NumElts;
 
   LLVM_DEBUG(llvm::dbgs() << "The number of elements to initialize: "
                           << NumEltsToInit << ".\n");
 
   Result = APValue(APValue::UninitArray(), NumEltsToInit, NumElts);
 
   // If the array was previously zero-initialized, preserve the
   // zero-initialized values.
   if (Filler.hasValue()) {
     for (unsigned I = 0, E = Result.getArrayInitializedElts(); I != E; ++I)
       Result.getArrayInitializedElt(I) = Filler;
     if (Result.hasArrayFiller())
       Result.getArrayFiller() = Filler;
   }
 
   LValue Subobject = This;
   Subobject.addArray(Info, E, CAT);
   for (unsigned Index = 0; Index != NumEltsToInit; ++Index) {
     const Expr *Init =
         Index < E->getNumInits() ? E->getInit(Index) : FillerExpr;
     if (!EvaluateInPlace(Result.getArrayInitializedElt(Index),
                          Info, Subobject, Init) ||
         !HandleLValueArrayAdjustment(Info, Init, Subobject,
                                      CAT->getElementType(), 1)) {
       if (!Info.noteFailure())
         return false;
       Success = false;
     }
   }
 
   if (!Result.hasArrayFiller())
     return Success;
 
   // If we get here, we have a trivial filler, which we can just evaluate
   // once and splat over the rest of the array elements.
   assert(FillerExpr && "no array filler for incomplete init list");
   return EvaluateInPlace(Result.getArrayFiller(), Info, Subobject,
                          FillerExpr) && Success;
 }
 
 bool ArrayExprEvaluator::VisitArrayInitLoopExpr(const ArrayInitLoopExpr *E) {
   LValue CommonLV;
   if (E->getCommonExpr() &&
       !Evaluate(Info.CurrentCall->createTemporary(
                     E->getCommonExpr(),
                     getStorageType(Info.Ctx, E->getCommonExpr()), false,
                     CommonLV),
                 Info, E->getCommonExpr()->getSourceExpr()))
     return false;
 
   auto *CAT = cast<ConstantArrayType>(E->getType()->castAsArrayTypeUnsafe());
 
   uint64_t Elements = CAT->getSize().getZExtValue();
   Result = APValue(APValue::UninitArray(), Elements, Elements);
 
   LValue Subobject = This;
   Subobject.addArray(Info, E, CAT);
 
   bool Success = true;
   for (EvalInfo::ArrayInitLoopIndex Index(Info); Index != Elements; ++Index) {
     if (!EvaluateInPlace(Result.getArrayInitializedElt(Index),
                          Info, Subobject, E->getSubExpr()) ||
         !HandleLValueArrayAdjustment(Info, E, Subobject,
                                      CAT->getElementType(), 1)) {
       if (!Info.noteFailure())
         return false;
       Success = false;
     }
   }
 
   return Success;
 }
 
 bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E) {
   return VisitCXXConstructExpr(E, This, &Result, E->getType());
 }
 
 bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E,
                                                const LValue &Subobject,
                                                APValue *Value,
                                                QualType Type) {
   bool HadZeroInit = Value->hasValue();
 
   if (const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(Type)) {
     unsigned N = CAT->getSize().getZExtValue();
 
     // Preserve the array filler if we had prior zero-initialization.
     APValue Filler =
       HadZeroInit && Value->hasArrayFiller() ? Value->getArrayFiller()
                                              : APValue();
 
     *Value = APValue(APValue::UninitArray(), N, N);
 
     if (HadZeroInit)
       for (unsigned I = 0; I != N; ++I)
         Value->getArrayInitializedElt(I) = Filler;
 
     // Initialize the elements.
     LValue ArrayElt = Subobject;
     ArrayElt.addArray(Info, E, CAT);
     for (unsigned I = 0; I != N; ++I)
       if (!VisitCXXConstructExpr(E, ArrayElt, &Value->getArrayInitializedElt(I),
                                  CAT->getElementType()) ||
           !HandleLValueArrayAdjustment(Info, E, ArrayElt,
                                        CAT->getElementType(), 1))
         return false;
 
     return true;
   }
 
   if (!Type->isRecordType())
     return Error(E);
 
   return RecordExprEvaluator(Info, Subobject, *Value)
              .VisitCXXConstructExpr(E, Type);
 }
 
 //===----------------------------------------------------------------------===//
 // Integer Evaluation
 //
 // As a GNU extension, we support casting pointers to sufficiently-wide integer
 // types and back in constant folding. Integer values are thus represented
 // either as an integer-valued APValue, or as an lvalue-valued APValue.
 //===----------------------------------------------------------------------===//
 
 namespace {
 class IntExprEvaluator
         : public ExprEvaluatorBase<IntExprEvaluator> {
   APValue &Result;
 public:
   IntExprEvaluator(EvalInfo &info, APValue &result)
       : ExprEvaluatorBaseTy(info), Result(result) {}
 
   bool Success(const llvm::APSInt &SI, const Expr *E, APValue &Result) {
     assert(E->getType()->isIntegralOrEnumerationType() &&
            "Invalid evaluation result.");
     assert(SI.isSigned() == E->getType()->isSignedIntegerOrEnumerationType() &&
            "Invalid evaluation result.");
     assert(SI.getBitWidth() == Info.Ctx.getIntWidth(E->getType()) &&
            "Invalid evaluation result.");
     Result = APValue(SI);
     return true;
   }
   bool Success(const llvm::APSInt &SI, const Expr *E) {
     return Success(SI, E, Result);
   }
 
   bool Success(const llvm::APInt &I, const Expr *E, APValue &Result) {
     assert(E->getType()->isIntegralOrEnumerationType() &&
            "Invalid evaluation result.");
     assert(I.getBitWidth() == Info.Ctx.getIntWidth(E->getType()) &&
            "Invalid evaluation result.");
     Result = APValue(APSInt(I));
     Result.getInt().setIsUnsigned(
                             E->getType()->isUnsignedIntegerOrEnumerationType());
     return true;
   }
   bool Success(const llvm::APInt &I, const Expr *E) {
     return Success(I, E, Result);
   }
 
   bool Success(uint64_t Value, const Expr *E, APValue &Result) {
     assert(E->getType()->isIntegralOrEnumerationType() &&
            "Invalid evaluation result.");
     Result = APValue(Info.Ctx.MakeIntValue(Value, E->getType()));
     return true;
   }
   bool Success(uint64_t Value, const Expr *E) {
     return Success(Value, E, Result);
   }
 
   bool Success(CharUnits Size, const Expr *E) {
     return Success(Size.getQuantity(), E);
   }
 
   bool Success(const APValue &V, const Expr *E) {
     if (V.isLValue() || V.isAddrLabelDiff() || V.isIndeterminate()) {
       Result = V;
       return true;
     }
     return Success(V.getInt(), E);
   }
 
   bool ZeroInitialization(const Expr *E) { return Success(0, E); }
 
   //===--------------------------------------------------------------------===//
   //                            Visitor Methods
   //===--------------------------------------------------------------------===//
 
   bool VisitIntegerLiteral(const IntegerLiteral *E) {
     return Success(E->getValue(), E);
   }
   bool VisitCharacterLiteral(const CharacterLiteral *E) {
     return Success(E->getValue(), E);
   }
 
   bool CheckReferencedDecl(const Expr *E, const Decl *D);
   bool VisitDeclRefExpr(const DeclRefExpr *E) {
     if (CheckReferencedDecl(E, E->getDecl()))
       return true;
 
     return ExprEvaluatorBaseTy::VisitDeclRefExpr(E);
   }
   bool VisitMemberExpr(const MemberExpr *E) {
     if (CheckReferencedDecl(E, E->getMemberDecl())) {
       VisitIgnoredBaseExpression(E->getBase());
       return true;
     }
 
     return ExprEvaluatorBaseTy::VisitMemberExpr(E);
   }
 
   bool VisitCallExpr(const CallExpr *E);
   bool VisitBuiltinCallExpr(const CallExpr *E, unsigned BuiltinOp);
   bool VisitBinaryOperator(const BinaryOperator *E);
   bool VisitOffsetOfExpr(const OffsetOfExpr *E);
   bool VisitUnaryOperator(const UnaryOperator *E);
 
   bool VisitCastExpr(const CastExpr* E);
   bool VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *E);
 
   bool VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E) {
     return Success(E->getValue(), E);
   }
 
   bool VisitObjCBoolLiteralExpr(const ObjCBoolLiteralExpr *E) {
     return Success(E->getValue(), E);
   }
 
   bool VisitArrayInitIndexExpr(const ArrayInitIndexExpr *E) {
     if (Info.ArrayInitIndex == uint64_t(-1)) {
       // We were asked to evaluate this subexpression independent of the
       // enclosing ArrayInitLoopExpr. We can't do that.
       Info.FFDiag(E);
       return false;
     }
     return Success(Info.ArrayInitIndex, E);
   }
 
   // Note, GNU defines __null as an integer, not a pointer.
   bool VisitGNUNullExpr(const GNUNullExpr *E) {
     return ZeroInitialization(E);
   }
 
   bool VisitTypeTraitExpr(const TypeTraitExpr *E) {
     return Success(E->getValue(), E);
   }
 
   bool VisitArrayTypeTraitExpr(const ArrayTypeTraitExpr *E) {
     return Success(E->getValue(), E);
   }
 
   bool VisitExpressionTraitExpr(const ExpressionTraitExpr *E) {
     return Success(E->getValue(), E);
   }
 
   bool VisitUnaryReal(const UnaryOperator *E);
   bool VisitUnaryImag(const UnaryOperator *E);
 
   bool VisitCXXNoexceptExpr(const CXXNoexceptExpr *E);
   bool VisitSizeOfPackExpr(const SizeOfPackExpr *E);
   bool VisitSourceLocExpr(const SourceLocExpr *E);
   bool VisitConceptSpecializationExpr(const ConceptSpecializationExpr *E);
   bool VisitRequiresExpr(const RequiresExpr *E);
   // FIXME: Missing: array subscript of vector, member of vector
 };
 
 class FixedPointExprEvaluator
     : public ExprEvaluatorBase<FixedPointExprEvaluator> {
   APValue &Result;
 
  public:
   FixedPointExprEvaluator(EvalInfo &info, APValue &result)
       : ExprEvaluatorBaseTy(info), Result(result) {}
 
   bool Success(const llvm::APInt &I, const Expr *E) {
     return Success(
         APFixedPoint(I, Info.Ctx.getFixedPointSemantics(E->getType())), E);
   }
 
   bool Success(uint64_t Value, const Expr *E) {
     return Success(
         APFixedPoint(Value, Info.Ctx.getFixedPointSemantics(E->getType())), E);
   }
 
   bool Success(const APValue &V, const Expr *E) {
     return Success(V.getFixedPoint(), E);
   }
 
   bool Success(const APFixedPoint &V, const Expr *E) {
     assert(E->getType()->isFixedPointType() && "Invalid evaluation result.");
     assert(V.getWidth() == Info.Ctx.getIntWidth(E->getType()) &&
            "Invalid evaluation result.");
     Result = APValue(V);
     return true;
   }
 
   //===--------------------------------------------------------------------===//
   //                            Visitor Methods
   //===--------------------------------------------------------------------===//
 
   bool VisitFixedPointLiteral(const FixedPointLiteral *E) {
     return Success(E->getValue(), E);
   }
 
   bool VisitCastExpr(const CastExpr *E);
   bool VisitUnaryOperator(const UnaryOperator *E);
   bool VisitBinaryOperator(const BinaryOperator *E);
 };
 } // end anonymous namespace
 
 /// EvaluateIntegerOrLValue - Evaluate an rvalue integral-typed expression, and
 /// produce either the integer value or a pointer.
 ///
 /// GCC has a heinous extension which folds casts between pointer types and
 /// pointer-sized integral types. We support this by allowing the evaluation of
 /// an integer rvalue to produce a pointer (represented as an lvalue) instead.
 /// Some simple arithmetic on such values is supported (they are treated much
 /// like char*).
 static bool EvaluateIntegerOrLValue(const Expr *E, APValue &Result,
                                     EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isIntegralOrEnumerationType());
   return IntExprEvaluator(Info, Result).Visit(E);
 }
 
 static bool EvaluateInteger(const Expr *E, APSInt &Result, EvalInfo &Info) {
   APValue Val;
   if (!EvaluateIntegerOrLValue(E, Val, Info))
     return false;
   if (!Val.isInt()) {
     // FIXME: It would be better to produce the diagnostic for casting
     //        a pointer to an integer.
     Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
     return false;
   }
   Result = Val.getInt();
   return true;
 }
 
 bool IntExprEvaluator::VisitSourceLocExpr(const SourceLocExpr *E) {
   APValue Evaluated = E->EvaluateInContext(
       Info.Ctx, Info.CurrentCall->CurSourceLocExprScope.getDefaultExpr());
   return Success(Evaluated, E);
 }
 
 static bool EvaluateFixedPoint(const Expr *E, APFixedPoint &Result,
                                EvalInfo &Info) {
   if (E->getType()->isFixedPointType()) {
     APValue Val;
     if (!FixedPointExprEvaluator(Info, Val).Visit(E))
       return false;
     if (!Val.isFixedPoint())
       return false;
 
     Result = Val.getFixedPoint();
     return true;
   }
   return false;
 }
 
 static bool EvaluateFixedPointOrInteger(const Expr *E, APFixedPoint &Result,
                                         EvalInfo &Info) {
   if (E->getType()->isIntegerType()) {
     auto FXSema = Info.Ctx.getFixedPointSemantics(E->getType());
     APSInt Val;
     if (!EvaluateInteger(E, Val, Info))
       return false;
     Result = APFixedPoint(Val, FXSema);
     return true;
   } else if (E->getType()->isFixedPointType()) {
     return EvaluateFixedPoint(E, Result, Info);
   }
   return false;
 }
 
 /// Check whether the given declaration can be directly converted to an integral
 /// rvalue. If not, no diagnostic is produced; there are other things we can
 /// try.
 bool IntExprEvaluator::CheckReferencedDecl(const Expr* E, const Decl* D) {
   // Enums are integer constant exprs.
   if (const EnumConstantDecl *ECD = dyn_cast<EnumConstantDecl>(D)) {
     // Check for signedness/width mismatches between E type and ECD value.
     bool SameSign = (ECD->getInitVal().isSigned()
                      == E->getType()->isSignedIntegerOrEnumerationType());
     bool SameWidth = (ECD->getInitVal().getBitWidth()
                       == Info.Ctx.getIntWidth(E->getType()));
     if (SameSign && SameWidth)
       return Success(ECD->getInitVal(), E);
     else {
       // Get rid of mismatch (otherwise Success assertions will fail)
       // by computing a new value matching the type of E.
       llvm::APSInt Val = ECD->getInitVal();
       if (!SameSign)
         Val.setIsSigned(!ECD->getInitVal().isSigned());
       if (!SameWidth)
         Val = Val.extOrTrunc(Info.Ctx.getIntWidth(E->getType()));
       return Success(Val, E);
     }
   }
   return false;
 }
 
 /// Values returned by __builtin_classify_type, chosen to match the values
 /// produced by GCC's builtin.
 enum class GCCTypeClass {
   None = -1,
   Void = 0,
   Integer = 1,
   // GCC reserves 2 for character types, but instead classifies them as
   // integers.
   Enum = 3,
   Bool = 4,
   Pointer = 5,
   // GCC reserves 6 for references, but appears to never use it (because
   // expressions never have reference type, presumably).
   PointerToDataMember = 7,
   RealFloat = 8,
   Complex = 9,
   // GCC reserves 10 for functions, but does not use it since GCC version 6 due
   // to decay to pointer. (Prior to version 6 it was only used in C++ mode).
   // GCC claims to reserve 11 for pointers to member functions, but *actually*
   // uses 12 for that purpose, same as for a class or struct. Maybe it
   // internally implements a pointer to member as a struct?  Who knows.
   PointerToMemberFunction = 12, // Not a bug, see above.
   ClassOrStruct = 12,
   Union = 13,
   // GCC reserves 14 for arrays, but does not use it since GCC version 6 due to
   // decay to pointer. (Prior to version 6 it was only used in C++ mode).
   // GCC reserves 15 for strings, but actually uses 5 (pointer) for string
   // literals.
 };
 
 /// EvaluateBuiltinClassifyType - Evaluate __builtin_classify_type the same way
 /// as GCC.
 static GCCTypeClass
 EvaluateBuiltinClassifyType(QualType T, const LangOptions &LangOpts) {
   assert(!T->isDependentType() && "unexpected dependent type");
 
   QualType CanTy = T.getCanonicalType();
   const BuiltinType *BT = dyn_cast<BuiltinType>(CanTy);
 
   switch (CanTy->getTypeClass()) {
 #define TYPE(ID, BASE)
 #define DEPENDENT_TYPE(ID, BASE) case Type::ID:
 #define NON_CANONICAL_TYPE(ID, BASE) case Type::ID:
 #define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(ID, BASE) case Type::ID:
 #include "clang/AST/TypeNodes.inc"
   case Type::Auto:
   case Type::DeducedTemplateSpecialization:
       llvm_unreachable("unexpected non-canonical or dependent type");
 
   case Type::Builtin:
     switch (BT->getKind()) {
 #define BUILTIN_TYPE(ID, SINGLETON_ID)
 #define SIGNED_TYPE(ID, SINGLETON_ID) \
     case BuiltinType::ID: return GCCTypeClass::Integer;
 #define FLOATING_TYPE(ID, SINGLETON_ID) \
     case BuiltinType::ID: return GCCTypeClass::RealFloat;
 #define PLACEHOLDER_TYPE(ID, SINGLETON_ID) \
     case BuiltinType::ID: break;
 #include "clang/AST/BuiltinTypes.def"
     case BuiltinType::Void:
       return GCCTypeClass::Void;
 
     case BuiltinType::Bool:
       return GCCTypeClass::Bool;
 
     case BuiltinType::Char_U:
     case BuiltinType::UChar:
     case BuiltinType::WChar_U:
     case BuiltinType::Char8:
     case BuiltinType::Char16:
     case BuiltinType::Char32:
     case BuiltinType::UShort:
     case BuiltinType::UInt:
     case BuiltinType::ULong:
     case BuiltinType::ULongLong:
     case BuiltinType::UInt128:
       return GCCTypeClass::Integer;
 
     case BuiltinType::UShortAccum:
     case BuiltinType::UAccum:
     case BuiltinType::ULongAccum:
     case BuiltinType::UShortFract:
     case BuiltinType::UFract:
     case BuiltinType::ULongFract:
     case BuiltinType::SatUShortAccum:
     case BuiltinType::SatUAccum:
     case BuiltinType::SatULongAccum:
     case BuiltinType::SatUShortFract:
     case BuiltinType::SatUFract:
     case BuiltinType::SatULongFract:
       return GCCTypeClass::None;
 
     case BuiltinType::NullPtr:
 
     case BuiltinType::ObjCId:
     case BuiltinType::ObjCClass:
     case BuiltinType::ObjCSel:
 #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
     case BuiltinType::Id:
 #include "clang/Basic/OpenCLImageTypes.def"
 #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
     case BuiltinType::Id:
 #include "clang/Basic/OpenCLExtensionTypes.def"
     case BuiltinType::OCLSampler:
     case BuiltinType::OCLEvent:
     case BuiltinType::OCLClkEvent:
     case BuiltinType::OCLQueue:
     case BuiltinType::OCLReserveID:
 #define SVE_TYPE(Name, Id, SingletonId) \
     case BuiltinType::Id:
 #include "clang/Basic/AArch64SVEACLETypes.def"
       return GCCTypeClass::None;
 
     case BuiltinType::Dependent:
       llvm_unreachable("unexpected dependent type");
     };
     llvm_unreachable("unexpected placeholder type");
 
   case Type::Enum:
     return LangOpts.CPlusPlus ? GCCTypeClass::Enum : GCCTypeClass::Integer;
 
   case Type::Pointer:
   case Type::ConstantArray:
   case Type::VariableArray:
   case Type::IncompleteArray:
   case Type::FunctionNoProto:
   case Type::FunctionProto:
     return GCCTypeClass::Pointer;
 
   case Type::MemberPointer:
     return CanTy->isMemberDataPointerType()
                ? GCCTypeClass::PointerToDataMember
                : GCCTypeClass::PointerToMemberFunction;
 
   case Type::Complex:
     return GCCTypeClass::Complex;
 
   case Type::Record:
     return CanTy->isUnionType() ? GCCTypeClass::Union
                                 : GCCTypeClass::ClassOrStruct;
 
   case Type::Atomic:
     // GCC classifies _Atomic T the same as T.
     return EvaluateBuiltinClassifyType(
         CanTy->castAs<AtomicType>()->getValueType(), LangOpts);
 
   case Type::BlockPointer:
   case Type::Vector:
   case Type::ExtVector:
   case Type::ConstantMatrix:
   case Type::ObjCObject:
   case Type::ObjCInterface:
   case Type::ObjCObjectPointer:
   case Type::Pipe:
   case Type::ExtInt:
     // GCC classifies vectors as None. We follow its lead and classify all
     // other types that don't fit into the regular classification the same way.
     return GCCTypeClass::None;
 
   case Type::LValueReference:
   case Type::RValueReference:
     llvm_unreachable("invalid type for expression");
   }
 
   llvm_unreachable("unexpected type class");
 }
 
 /// EvaluateBuiltinClassifyType - Evaluate __builtin_classify_type the same way
 /// as GCC.
 static GCCTypeClass
 EvaluateBuiltinClassifyType(const CallExpr *E, const LangOptions &LangOpts) {
   // If no argument was supplied, default to None. This isn't
   // ideal, however it is what gcc does.
   if (E->getNumArgs() == 0)
     return GCCTypeClass::None;
 
   // FIXME: Bizarrely, GCC treats a call with more than one argument as not
   // being an ICE, but still folds it to a constant using the type of the first
   // argument.
   return EvaluateBuiltinClassifyType(E->getArg(0)->getType(), LangOpts);
 }
 
 /// EvaluateBuiltinConstantPForLValue - Determine the result of
 /// __builtin_constant_p when applied to the given pointer.
 ///
 /// A pointer is only "constant" if it is null (or a pointer cast to integer)
 /// or it points to the first character of a string literal.
 static bool EvaluateBuiltinConstantPForLValue(const APValue &LV) {
   APValue::LValueBase Base = LV.getLValueBase();
   if (Base.isNull()) {
     // A null base is acceptable.
     return true;
   } else if (const Expr *E = Base.dyn_cast<const Expr *>()) {
     if (!isa<StringLiteral>(E))
       return false;
     return LV.getLValueOffset().isZero();
   } else if (Base.is<TypeInfoLValue>()) {
     // Surprisingly, GCC considers __builtin_constant_p(&typeid(int)) to
     // evaluate to true.
     return true;
   } else {
     // Any other base is not constant enough for GCC.
     return false;
   }
 }
 
 /// EvaluateBuiltinConstantP - Evaluate __builtin_constant_p as similarly to
 /// GCC as we can manage.
 static bool EvaluateBuiltinConstantP(EvalInfo &Info, const Expr *Arg) {
   // This evaluation is not permitted to have side-effects, so evaluate it in
   // a speculative evaluation context.
   SpeculativeEvaluationRAII SpeculativeEval(Info);
 
   // Constant-folding is always enabled for the operand of __builtin_constant_p
   // (even when the enclosing evaluation context otherwise requires a strict
   // language-specific constant expression).
   FoldConstant Fold(Info, true);
 
   QualType ArgType = Arg->getType();
 
   // __builtin_constant_p always has one operand. The rules which gcc follows
   // are not precisely documented, but are as follows:
   //
   //  - If the operand is of integral, floating, complex or enumeration type,
   //    and can be folded to a known value of that type, it returns 1.
   //  - If the operand can be folded to a pointer to the first character
   //    of a string literal (or such a pointer cast to an integral type)
   //    or to a null pointer or an integer cast to a pointer, it returns 1.
   //
   // Otherwise, it returns 0.
   //
   // FIXME: GCC also intends to return 1 for literals of aggregate types, but
   // its support for this did not work prior to GCC 9 and is not yet well
   // understood.
   if (ArgType->isIntegralOrEnumerationType() || ArgType->isFloatingType() ||
       ArgType->isAnyComplexType() || ArgType->isPointerType() ||
       ArgType->isNullPtrType()) {
     APValue V;
     if (!::EvaluateAsRValue(Info, Arg, V) || Info.EvalStatus.HasSideEffects) {
       Fold.keepDiagnostics();
       return false;
     }
 
     // For a pointer (possibly cast to integer), there are special rules.
     if (V.getKind() == APValue::LValue)
       return EvaluateBuiltinConstantPForLValue(V);
 
     // Otherwise, any constant value is good enough.
     return V.hasValue();
   }
 
   // Anything else isn't considered to be sufficiently constant.
   return false;
 }
 
 /// Retrieves the "underlying object type" of the given expression,
 /// as used by __builtin_object_size.
 static QualType getObjectType(APValue::LValueBase B) {
   if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
     if (const VarDecl *VD = dyn_cast<VarDecl>(D))
       return VD->getType();
   } else if (const Expr *E = B.dyn_cast<const Expr*>()) {
     if (isa<CompoundLiteralExpr>(E))
       return E->getType();
   } else if (B.is<TypeInfoLValue>()) {
     return B.getTypeInfoType();
   } else if (B.is<DynamicAllocLValue>()) {
     return B.getDynamicAllocType();
   }
 
   return QualType();
 }
 
 /// A more selective version of E->IgnoreParenCasts for
 /// tryEvaluateBuiltinObjectSize. This ignores some casts/parens that serve only
 /// to change the type of E.
 /// Ex. For E = `(short*)((char*)(&foo))`, returns `&foo`
 ///
 /// Always returns an RValue with a pointer representation.
 static const Expr *ignorePointerCastsAndParens(const Expr *E) {
   assert(E->isRValue() && E->getType()->hasPointerRepresentation());
 
   auto *NoParens = E->IgnoreParens();
   auto *Cast = dyn_cast<CastExpr>(NoParens);
   if (Cast == nullptr)
     return NoParens;
 
   // We only conservatively allow a few kinds of casts, because this code is
   // inherently a simple solution that seeks to support the common case.
   auto CastKind = Cast->getCastKind();
   if (CastKind != CK_NoOp && CastKind != CK_BitCast &&
       CastKind != CK_AddressSpaceConversion)
     return NoParens;
 
   auto *SubExpr = Cast->getSubExpr();
   if (!SubExpr->getType()->hasPointerRepresentation() || !SubExpr->isRValue())
     return NoParens;
   return ignorePointerCastsAndParens(SubExpr);
 }
 
 /// Checks to see if the given LValue's Designator is at the end of the LValue's
 /// record layout. e.g.
 ///   struct { struct { int a, b; } fst, snd; } obj;
 ///   obj.fst   // no
 ///   obj.snd   // yes
 ///   obj.fst.a // no
 ///   obj.fst.b // no
 ///   obj.snd.a // no
 ///   obj.snd.b // yes
 ///
 /// Please note: this function is specialized for how __builtin_object_size
 /// views "objects".
 ///
 /// If this encounters an invalid RecordDecl or otherwise cannot determine the
 /// correct result, it will always return true.
 static bool isDesignatorAtObjectEnd(const ASTContext &Ctx, const LValue &LVal) {
   assert(!LVal.Designator.Invalid);
 
   auto IsLastOrInvalidFieldDecl = [&Ctx](const FieldDecl *FD, bool &Invalid) {
     const RecordDecl *Parent = FD->getParent();
     Invalid = Parent->isInvalidDecl();
     if (Invalid || Parent->isUnion())
       return true;
     const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(Parent);
     return FD->getFieldIndex() + 1 == Layout.getFieldCount();
   };
 
   auto &Base = LVal.getLValueBase();
   if (auto *ME = dyn_cast_or_null<MemberExpr>(Base.dyn_cast<const Expr *>())) {
     if (auto *FD = dyn_cast<FieldDecl>(ME->getMemberDecl())) {
       bool Invalid;
       if (!IsLastOrInvalidFieldDecl(FD, Invalid))
         return Invalid;
     } else if (auto *IFD = dyn_cast<IndirectFieldDecl>(ME->getMemberDecl())) {
       for (auto *FD : IFD->chain()) {
         bool Invalid;
         if (!IsLastOrInvalidFieldDecl(cast<FieldDecl>(FD), Invalid))
           return Invalid;
       }
     }
   }
 
   unsigned I = 0;
   QualType BaseType = getType(Base);
   if (LVal.Designator.FirstEntryIsAnUnsizedArray) {
     // If we don't know the array bound, conservatively assume we're looking at
     // the final array element.
     ++I;
     if (BaseType->isIncompleteArrayType())
       BaseType = Ctx.getAsArrayType(BaseType)->getElementType();
     else
       BaseType = BaseType->castAs<PointerType>()->getPointeeType();
   }
 
   for (unsigned E = LVal.Designator.Entries.size(); I != E; ++I) {
     const auto &Entry = LVal.Designator.Entries[I];
     if (BaseType->isArrayType()) {
       // Because __builtin_object_size treats arrays as objects, we can ignore
       // the index iff this is the last array in the Designator.
       if (I + 1 == E)
         return true;
       const auto *CAT = cast<ConstantArrayType>(Ctx.getAsArrayType(BaseType));
       uint64_t Index = Entry.getAsArrayIndex();
       if (Index + 1 != CAT->getSize())
         return false;
       BaseType = CAT->getElementType();
     } else if (BaseType->isAnyComplexType()) {
       const auto *CT = BaseType->castAs<ComplexType>();
       uint64_t Index = Entry.getAsArrayIndex();
       if (Index != 1)
         return false;
       BaseType = CT->getElementType();
     } else if (auto *FD = getAsField(Entry)) {
       bool Invalid;
       if (!IsLastOrInvalidFieldDecl(FD, Invalid))
         return Invalid;
       BaseType = FD->getType();
     } else {
       assert(getAsBaseClass(Entry) && "Expecting cast to a base class");
       return false;
     }
   }
   return true;
 }
 
 /// Tests to see if the LValue has a user-specified designator (that isn't
 /// necessarily valid). Note that this always returns 'true' if the LValue has
 /// an unsized array as its first designator entry, because there's currently no
 /// way to tell if the user typed *foo or foo[0].
 static bool refersToCompleteObject(const LValue &LVal) {
   if (LVal.Designator.Invalid)
     return false;
 
   if (!LVal.Designator.Entries.empty())
     return LVal.Designator.isMostDerivedAnUnsizedArray();
 
   if (!LVal.InvalidBase)
     return true;
 
   // If `E` is a MemberExpr, then the first part of the designator is hiding in
   // the LValueBase.
   const auto *E = LVal.Base.dyn_cast<const Expr *>();
   return !E || !isa<MemberExpr>(E);
 }
 
 /// Attempts to detect a user writing into a piece of memory that's impossible
 /// to figure out the size of by just using types.
 static bool isUserWritingOffTheEnd(const ASTContext &Ctx, const LValue &LVal) {
   const SubobjectDesignator &Designator = LVal.Designator;
   // Notes:
   // - Users can only write off of the end when we have an invalid base. Invalid
   //   bases imply we don't know where the memory came from.
   // - We used to be a bit more aggressive here; we'd only be conservative if
   //   the array at the end was flexible, or if it had 0 or 1 elements. This
   //   broke some common standard library extensions (PR30346), but was
   //   otherwise seemingly fine. It may be useful to reintroduce this behavior
   //   with some sort of list. OTOH, it seems that GCC is always
   //   conservative with the last element in structs (if it's an array), so our
   //   current behavior is more compatible than an explicit list approach would
   //   be.
   return LVal.InvalidBase &&
          Designator.Entries.size() == Designator.MostDerivedPathLength &&
          Designator.MostDerivedIsArrayElement &&
          isDesignatorAtObjectEnd(Ctx, LVal);
 }
 
 /// Converts the given APInt to CharUnits, assuming the APInt is unsigned.
 /// Fails if the conversion would cause loss of precision.
 static bool convertUnsignedAPIntToCharUnits(const llvm::APInt &Int,
                                             CharUnits &Result) {
   auto CharUnitsMax = std::numeric_limits<CharUnits::QuantityType>::max();
   if (Int.ugt(CharUnitsMax))
     return false;
   Result = CharUnits::fromQuantity(Int.getZExtValue());
   return true;
 }
 
 /// Helper for tryEvaluateBuiltinObjectSize -- Given an LValue, this will
 /// determine how many bytes exist from the beginning of the object to either
 /// the end of the current subobject, or the end of the object itself, depending
 /// on what the LValue looks like + the value of Type.
 ///
 /// If this returns false, the value of Result is undefined.
 static bool determineEndOffset(EvalInfo &Info, SourceLocation ExprLoc,
                                unsigned Type, const LValue &LVal,
                                CharUnits &EndOffset) {
   bool DetermineForCompleteObject = refersToCompleteObject(LVal);
 
   auto CheckedHandleSizeof = [&](QualType Ty, CharUnits &Result) {
     if (Ty.isNull() || Ty->isIncompleteType() || Ty->isFunctionType())
       return false;
     return HandleSizeof(Info, ExprLoc, Ty, Result);
   };
 
   // We want to evaluate the size of the entire object. This is a valid fallback
   // for when Type=1 and the designator is invalid, because we're asked for an
   // upper-bound.
   if (!(Type & 1) || LVal.Designator.Invalid || DetermineForCompleteObject) {
     // Type=3 wants a lower bound, so we can't fall back to this.
     if (Type == 3 && !DetermineForCompleteObject)
       return false;
 
     llvm::APInt APEndOffset;
     if (isBaseAnAllocSizeCall(LVal.getLValueBase()) &&
         getBytesReturnedByAllocSizeCall(Info.Ctx, LVal, APEndOffset))
       return convertUnsignedAPIntToCharUnits(APEndOffset, EndOffset);
 
     if (LVal.InvalidBase)
       return false;
 
     QualType BaseTy = getObjectType(LVal.getLValueBase());
     return CheckedHandleSizeof(BaseTy, EndOffset);
   }
 
   // We want to evaluate the size of a subobject.
   const SubobjectDesignator &Designator = LVal.Designator;
 
   // The following is a moderately common idiom in C:
   //
   // struct Foo { int a; char c[1]; };
   // struct Foo *F = (struct Foo *)malloc(sizeof(struct Foo) + strlen(Bar));
   // strcpy(&F->c[0], Bar);
   //
   // In order to not break too much legacy code, we need to support it.
   if (isUserWritingOffTheEnd(Info.Ctx, LVal)) {
     // If we can resolve this to an alloc_size call, we can hand that back,
     // because we know for certain how many bytes there are to write to.
     llvm::APInt APEndOffset;
     if (isBaseAnAllocSizeCall(LVal.getLValueBase()) &&
         getBytesReturnedByAllocSizeCall(Info.Ctx, LVal, APEndOffset))
       return convertUnsignedAPIntToCharUnits(APEndOffset, EndOffset);
 
     // If we cannot determine the size of the initial allocation, then we can't
     // given an accurate upper-bound. However, we are still able to give
     // conservative lower-bounds for Type=3.
     if (Type == 1)
       return false;
   }
 
   CharUnits BytesPerElem;
   if (!CheckedHandleSizeof(Designator.MostDerivedType, BytesPerElem))
     return false;
 
   // According to the GCC documentation, we want the size of the subobject
   // denoted by the pointer. But that's not quite right -- what we actually
   // want is the size of the immediately-enclosing array, if there is one.
   int64_t ElemsRemaining;
   if (Designator.MostDerivedIsArrayElement &&
       Designator.Entries.size() == Designator.MostDerivedPathLength) {
     uint64_t ArraySize = Designator.getMostDerivedArraySize();
     uint64_t ArrayIndex = Designator.Entries.back().getAsArrayIndex();
     ElemsRemaining = ArraySize <= ArrayIndex ? 0 : ArraySize - ArrayIndex;
   } else {
     ElemsRemaining = Designator.isOnePastTheEnd() ? 0 : 1;
   }
 
   EndOffset = LVal.getLValueOffset() + BytesPerElem * ElemsRemaining;
   return true;
 }
 
 /// Tries to evaluate the __builtin_object_size for @p E. If successful,
 /// returns true and stores the result in @p Size.
 ///
 /// If @p WasError is non-null, this will report whether the failure to evaluate
 /// is to be treated as an Error in IntExprEvaluator.
 static bool tryEvaluateBuiltinObjectSize(const Expr *E, unsigned Type,
                                          EvalInfo &Info, uint64_t &Size) {
   // Determine the denoted object.
   LValue LVal;
   {
     // The operand of __builtin_object_size is never evaluated for side-effects.
     // If there are any, but we can determine the pointed-to object anyway, then
     // ignore the side-effects.
     SpeculativeEvaluationRAII SpeculativeEval(Info);
     IgnoreSideEffectsRAII Fold(Info);
 
     if (E->isGLValue()) {
       // It's possible for us to be given GLValues if we're called via
       // Expr::tryEvaluateObjectSize.
       APValue RVal;
       if (!EvaluateAsRValue(Info, E, RVal))
         return false;
       LVal.setFrom(Info.Ctx, RVal);
     } else if (!EvaluatePointer(ignorePointerCastsAndParens(E), LVal, Info,
                                 /*InvalidBaseOK=*/true))
       return false;
   }
 
   // If we point to before the start of the object, there are no accessible
   // bytes.
   if (LVal.getLValueOffset().isNegative()) {
     Size = 0;
     return true;
   }
 
   CharUnits EndOffset;
   if (!determineEndOffset(Info, E->getExprLoc(), Type, LVal, EndOffset))
     return false;
 
   // If we've fallen outside of the end offset, just pretend there's nothing to
   // write to/read from.
   if (EndOffset <= LVal.getLValueOffset())
     Size = 0;
   else
     Size = (EndOffset - LVal.getLValueOffset()).getQuantity();
   return true;
 }
 
 bool IntExprEvaluator::VisitCallExpr(const CallExpr *E) {
   if (unsigned BuiltinOp = E->getBuiltinCallee())
     return VisitBuiltinCallExpr(E, BuiltinOp);
 
   return ExprEvaluatorBaseTy::VisitCallExpr(E);
 }
 
 static bool getBuiltinAlignArguments(const CallExpr *E, EvalInfo &Info,
                                      APValue &Val, APSInt &Alignment) {
   QualType SrcTy = E->getArg(0)->getType();
   if (!getAlignmentArgument(E->getArg(1), SrcTy, Info, Alignment))
     return false;
   // Even though we are evaluating integer expressions we could get a pointer
   // argument for the __builtin_is_aligned() case.
   if (SrcTy->isPointerType()) {
     LValue Ptr;
     if (!EvaluatePointer(E->getArg(0), Ptr, Info))
       return false;
     Ptr.moveInto(Val);
   } else if (!SrcTy->isIntegralOrEnumerationType()) {
     Info.FFDiag(E->getArg(0));
     return false;
   } else {
     APSInt SrcInt;
     if (!EvaluateInteger(E->getArg(0), SrcInt, Info))
       return false;
     assert(SrcInt.getBitWidth() >= Alignment.getBitWidth() &&
            "Bit widths must be the same");
     Val = APValue(SrcInt);
   }
   assert(Val.hasValue());
   return true;
 }
 
 bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
                                             unsigned BuiltinOp) {
   switch (BuiltinOp) {
   default:
     return ExprEvaluatorBaseTy::VisitCallExpr(E);
 
   case Builtin::BI__builtin_dynamic_object_size:
   case Builtin::BI__builtin_object_size: {
     // The type was checked when we built the expression.
     unsigned Type =
         E->getArg(1)->EvaluateKnownConstInt(Info.Ctx).getZExtValue();
     assert(Type <= 3 && "unexpected type");
 
     uint64_t Size;
     if (tryEvaluateBuiltinObjectSize(E->getArg(0), Type, Info, Size))
       return Success(Size, E);
 
     if (E->getArg(0)->HasSideEffects(Info.Ctx))
       return Success((Type & 2) ? 0 : -1, E);
 
     // Expression had no side effects, but we couldn't statically determine the
     // size of the referenced object.
     switch (Info.EvalMode) {
     case EvalInfo::EM_ConstantExpression:
     case EvalInfo::EM_ConstantFold:
     case EvalInfo::EM_IgnoreSideEffects:
       // Leave it to IR generation.
       return Error(E);
     case EvalInfo::EM_ConstantExpressionUnevaluated:
       // Reduce it to a constant now.
       return Success((Type & 2) ? 0 : -1, E);
     }
 
     llvm_unreachable("unexpected EvalMode");
   }
 
   case Builtin::BI__builtin_os_log_format_buffer_size: {
     analyze_os_log::OSLogBufferLayout Layout;
     analyze_os_log::computeOSLogBufferLayout(Info.Ctx, E, Layout);
     return Success(Layout.size().getQuantity(), E);
   }
 
   case Builtin::BI__builtin_is_aligned: {
     APValue Src;
     APSInt Alignment;
     if (!getBuiltinAlignArguments(E, Info, Src, Alignment))
       return false;
     if (Src.isLValue()) {
       // If we evaluated a pointer, check the minimum known alignment.
       LValue Ptr;
       Ptr.setFrom(Info.Ctx, Src);
       CharUnits BaseAlignment = getBaseAlignment(Info, Ptr);
       CharUnits PtrAlign = BaseAlignment.alignmentAtOffset(Ptr.Offset);
       // We can return true if the known alignment at the computed offset is
       // greater than the requested alignment.
       assert(PtrAlign.isPowerOfTwo());
       assert(Alignment.isPowerOf2());
       if (PtrAlign.getQuantity() >= Alignment)
         return Success(1, E);
       // If the alignment is not known to be sufficient, some cases could still
       // be aligned at run time. However, if the requested alignment is less or
       // equal to the base alignment and the offset is not aligned, we know that
       // the run-time value can never be aligned.
       if (BaseAlignment.getQuantity() >= Alignment &&
           PtrAlign.getQuantity() < Alignment)
         return Success(0, E);
       // Otherwise we can't infer whether the value is sufficiently aligned.
       // TODO: __builtin_is_aligned(__builtin_align_{down,up{(expr, N), N)
       //  in cases where we can't fully evaluate the pointer.
       Info.FFDiag(E->getArg(0), diag::note_constexpr_alignment_compute)
           << Alignment;
       return false;
     }
     assert(Src.isInt());
     return Success((Src.getInt() & (Alignment - 1)) == 0 ? 1 : 0, E);
   }
   case Builtin::BI__builtin_align_up: {
     APValue Src;
     APSInt Alignment;
     if (!getBuiltinAlignArguments(E, Info, Src, Alignment))
       return false;
     if (!Src.isInt())
       return Error(E);
     APSInt AlignedVal =
         APSInt((Src.getInt() + (Alignment - 1)) & ~(Alignment - 1),
                Src.getInt().isUnsigned());
     assert(AlignedVal.getBitWidth() == Src.getInt().getBitWidth());
     return Success(AlignedVal, E);
   }
   case Builtin::BI__builtin_align_down: {
     APValue Src;
     APSInt Alignment;
     if (!getBuiltinAlignArguments(E, Info, Src, Alignment))
       return false;
     if (!Src.isInt())
       return Error(E);
     APSInt AlignedVal =
         APSInt(Src.getInt() & ~(Alignment - 1), Src.getInt().isUnsigned());
     assert(AlignedVal.getBitWidth() == Src.getInt().getBitWidth());
     return Success(AlignedVal, E);
   }
 
   case Builtin::BI__builtin_bswap16:
   case Builtin::BI__builtin_bswap32:
   case Builtin::BI__builtin_bswap64: {
     APSInt Val;
     if (!EvaluateInteger(E->getArg(0), Val, Info))
       return false;
 
     return Success(Val.byteSwap(), E);
   }
 
   case Builtin::BI__builtin_classify_type:
     return Success((int)EvaluateBuiltinClassifyType(E, Info.getLangOpts()), E);
 
   case Builtin::BI__builtin_clrsb:
   case Builtin::BI__builtin_clrsbl:
   case Builtin::BI__builtin_clrsbll: {
     APSInt Val;
     if (!EvaluateInteger(E->getArg(0), Val, Info))
       return false;
 
     return Success(Val.getBitWidth() - Val.getMinSignedBits(), E);
   }
 
   case Builtin::BI__builtin_clz:
   case Builtin::BI__builtin_clzl:
   case Builtin::BI__builtin_clzll:
   case Builtin::BI__builtin_clzs: {
     APSInt Val;
     if (!EvaluateInteger(E->getArg(0), Val, Info))
       return false;
     if (!Val)
       return Error(E);
 
     return Success(Val.countLeadingZeros(), E);
   }
 
   case Builtin::BI__builtin_constant_p: {
     const Expr *Arg = E->getArg(0);
     if (EvaluateBuiltinConstantP(Info, Arg))
       return Success(true, E);
     if (Info.InConstantContext || Arg->HasSideEffects(Info.Ctx)) {
       // Outside a constant context, eagerly evaluate to false in the presence
       // of side-effects in order to avoid -Wunsequenced false-positives in
       // a branch on __builtin_constant_p(expr).
       return Success(false, E);
     }
     Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
     return false;
   }
 
   case Builtin::BI__builtin_is_constant_evaluated: {
     const auto *Callee = Info.CurrentCall->getCallee();
     if (Info.InConstantContext && !Info.CheckingPotentialConstantExpression &&
         (Info.CallStackDepth == 1 ||
          (Info.CallStackDepth == 2 && Callee->isInStdNamespace() &&
           Callee->getIdentifier() &&
           Callee->getIdentifier()->isStr("is_constant_evaluated")))) {
       // FIXME: Find a better way to avoid duplicated diagnostics.
       if (Info.EvalStatus.Diag)
         Info.report((Info.CallStackDepth == 1) ? E->getExprLoc()
                                                : Info.CurrentCall->CallLoc,
                     diag::warn_is_constant_evaluated_always_true_constexpr)
             << (Info.CallStackDepth == 1 ? "__builtin_is_constant_evaluated"
                                          : "std::is_constant_evaluated");
     }
 
     return Success(Info.InConstantContext, E);
   }
 
   case Builtin::BI__builtin_ctz:
   case Builtin::BI__builtin_ctzl:
   case Builtin::BI__builtin_ctzll:
   case Builtin::BI__builtin_ctzs: {
     APSInt Val;
     if (!EvaluateInteger(E->getArg(0), Val, Info))
       return false;
     if (!Val)
       return Error(E);
 
     return Success(Val.countTrailingZeros(), E);
   }
 
   case Builtin::BI__builtin_eh_return_data_regno: {
     int Operand = E->getArg(0)->EvaluateKnownConstInt(Info.Ctx).getZExtValue();
     Operand = Info.Ctx.getTargetInfo().getEHDataRegisterNumber(Operand);
     return Success(Operand, E);
   }
 
   case Builtin::BI__builtin_expect:
   case Builtin::BI__builtin_expect_with_probability:
     return Visit(E->getArg(0));
 
   case Builtin::BI__builtin_ffs:
   case Builtin::BI__builtin_ffsl:
   case Builtin::BI__builtin_ffsll: {
     APSInt Val;
     if (!EvaluateInteger(E->getArg(0), Val, Info))
       return false;
 
     unsigned N = Val.countTrailingZeros();
     return Success(N == Val.getBitWidth() ? 0 : N + 1, E);
   }
 
   case Builtin::BI__builtin_fpclassify: {
     APFloat Val(0.0);
     if (!EvaluateFloat(E->getArg(5), Val, Info))
       return false;
     unsigned Arg;
     switch (Val.getCategory()) {
     case APFloat::fcNaN: Arg = 0; break;
     case APFloat::fcInfinity: Arg = 1; break;
     case APFloat::fcNormal: Arg = Val.isDenormal() ? 3 : 2; break;
     case APFloat::fcZero: Arg = 4; break;
     }
     return Visit(E->getArg(Arg));
   }
 
   case Builtin::BI__builtin_isinf_sign: {
     APFloat Val(0.0);
     return EvaluateFloat(E->getArg(0), Val, Info) &&
            Success(Val.isInfinity() ? (Val.isNegative() ? -1 : 1) : 0, E);
   }
 
   case Builtin::BI__builtin_isinf: {
     APFloat Val(0.0);
     return EvaluateFloat(E->getArg(0), Val, Info) &&
            Success(Val.isInfinity() ? 1 : 0, E);
   }
 
   case Builtin::BI__builtin_isfinite: {
     APFloat Val(0.0);
     return EvaluateFloat(E->getArg(0), Val, Info) &&
            Success(Val.isFinite() ? 1 : 0, E);
   }
 
   case Builtin::BI__builtin_isnan: {
     APFloat Val(0.0);
     return EvaluateFloat(E->getArg(0), Val, Info) &&
            Success(Val.isNaN() ? 1 : 0, E);
   }
 
   case Builtin::BI__builtin_isnormal: {
     APFloat Val(0.0);
     return EvaluateFloat(E->getArg(0), Val, Info) &&
            Success(Val.isNormal() ? 1 : 0, E);
   }
 
   case Builtin::BI__builtin_parity:
   case Builtin::BI__builtin_parityl:
   case Builtin::BI__builtin_parityll: {
     APSInt Val;
     if (!EvaluateInteger(E->getArg(0), Val, Info))
       return false;
 
     return Success(Val.countPopulation() % 2, E);
   }
 
   case Builtin::BI__builtin_popcount:
   case Builtin::BI__builtin_popcountl:
   case Builtin::BI__builtin_popcountll: {
     APSInt Val;
     if (!EvaluateInteger(E->getArg(0), Val, Info))
       return false;
 
     return Success(Val.countPopulation(), E);
   }
 
   case Builtin::BIstrlen:
   case Builtin::BIwcslen:
     // A call to strlen is not a constant expression.
     if (Info.getLangOpts().CPlusPlus11)
       Info.CCEDiag(E, diag::note_constexpr_invalid_function)
         << /*isConstexpr*/0 << /*isConstructor*/0
         << (std::string("'") + Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'");
     else
       Info.CCEDiag(E, diag::note_invalid_subexpr_in_const_expr);
     LLVM_FALLTHROUGH;
   case Builtin::BI__builtin_strlen:
   case Builtin::BI__builtin_wcslen: {
     // As an extension, we support __builtin_strlen() as a constant expression,
     // and support folding strlen() to a constant.
     LValue String;
     if (!EvaluatePointer(E->getArg(0), String, Info))
       return false;
 
     QualType CharTy = E->getArg(0)->getType()->getPointeeType();
 
     // Fast path: if it's a string literal, search the string value.
     if (const StringLiteral *S = dyn_cast_or_null<StringLiteral>(
             String.getLValueBase().dyn_cast<const Expr *>())) {
       // The string literal may have embedded null characters. Find the first
       // one and truncate there.
       StringRef Str = S->getBytes();
       int64_t Off = String.Offset.getQuantity();
       if (Off >= 0 && (uint64_t)Off <= (uint64_t)Str.size() &&
           S->getCharByteWidth() == 1 &&
           // FIXME: Add fast-path for wchar_t too.
           Info.Ctx.hasSameUnqualifiedType(CharTy, Info.Ctx.CharTy)) {
         Str = Str.substr(Off);
 
         StringRef::size_type Pos = Str.find(0);
         if (Pos != StringRef::npos)
           Str = Str.substr(0, Pos);
 
         return Success(Str.size(), E);
       }
 
       // Fall through to slow path to issue appropriate diagnostic.
     }
 
     // Slow path: scan the bytes of the string looking for the terminating 0.
     for (uint64_t Strlen = 0; /**/; ++Strlen) {
       APValue Char;
       if (!handleLValueToRValueConversion(Info, E, CharTy, String, Char) ||
           !Char.isInt())
         return false;
       if (!Char.getInt())
         return Success(Strlen, E);
       if (!HandleLValueArrayAdjustment(Info, E, String, CharTy, 1))
         return false;
     }
   }
 
   case Builtin::BIstrcmp:
   case Builtin::BIwcscmp:
   case Builtin::BIstrncmp:
   case Builtin::BIwcsncmp:
   case Builtin::BImemcmp:
   case Builtin::BIbcmp:
   case Builtin::BIwmemcmp:
     // A call to strlen is not a constant expression.
     if (Info.getLangOpts().CPlusPlus11)
       Info.CCEDiag(E, diag::note_constexpr_invalid_function)
         << /*isConstexpr*/0 << /*isConstructor*/0
         << (std::string("'") + Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'");
     else
       Info.CCEDiag(E, diag::note_invalid_subexpr_in_const_expr);
     LLVM_FALLTHROUGH;
   case Builtin::BI__builtin_strcmp:
   case Builtin::BI__builtin_wcscmp:
   case Builtin::BI__builtin_strncmp:
   case Builtin::BI__builtin_wcsncmp:
   case Builtin::BI__builtin_memcmp:
   case Builtin::BI__builtin_bcmp:
   case Builtin::BI__builtin_wmemcmp: {
     LValue String1, String2;
     if (!EvaluatePointer(E->getArg(0), String1, Info) ||
         !EvaluatePointer(E->getArg(1), String2, Info))
       return false;
 
     uint64_t MaxLength = uint64_t(-1);
     if (BuiltinOp != Builtin::BIstrcmp &&
         BuiltinOp != Builtin::BIwcscmp &&
         BuiltinOp != Builtin::BI__builtin_strcmp &&
         BuiltinOp != Builtin::BI__builtin_wcscmp) {
       APSInt N;
       if (!EvaluateInteger(E->getArg(2), N, Info))
         return false;
       MaxLength = N.getExtValue();
     }
 
     // Empty substrings compare equal by definition.
     if (MaxLength == 0u)
       return Success(0, E);
 
     if (!String1.checkNullPointerForFoldAccess(Info, E, AK_Read) ||
         !String2.checkNullPointerForFoldAccess(Info, E, AK_Read) ||
         String1.Designator.Invalid || String2.Designator.Invalid)
       return false;
 
     QualType CharTy1 = String1.Designator.getType(Info.Ctx);
     QualType CharTy2 = String2.Designator.getType(Info.Ctx);
 
     bool IsRawByte = BuiltinOp == Builtin::BImemcmp ||
                      BuiltinOp == Builtin::BIbcmp ||
                      BuiltinOp == Builtin::BI__builtin_memcmp ||
                      BuiltinOp == Builtin::BI__builtin_bcmp;
 
     assert(IsRawByte ||
            (Info.Ctx.hasSameUnqualifiedType(
                 CharTy1, E->getArg(0)->getType()->getPointeeType()) &&
             Info.Ctx.hasSameUnqualifiedType(CharTy1, CharTy2)));
 
     // For memcmp, allow comparing any arrays of '[[un]signed] char' or
     // 'char8_t', but no other types.
     if (IsRawByte &&
         !(isOneByteCharacterType(CharTy1) && isOneByteCharacterType(CharTy2))) {
       // FIXME: Consider using our bit_cast implementation to support this.
       Info.FFDiag(E, diag::note_constexpr_memcmp_unsupported)
           << (std::string("'") + Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'")
           << CharTy1 << CharTy2;
       return false;
     }
 
     const auto &ReadCurElems = [&](APValue &Char1, APValue &Char2) {
       return handleLValueToRValueConversion(Info, E, CharTy1, String1, Char1) &&
              handleLValueToRValueConversion(Info, E, CharTy2, String2, Char2) &&
              Char1.isInt() && Char2.isInt();
     };
     const auto &AdvanceElems = [&] {
       return HandleLValueArrayAdjustment(Info, E, String1, CharTy1, 1) &&
              HandleLValueArrayAdjustment(Info, E, String2, CharTy2, 1);
     };
 
     bool StopAtNull =
         (BuiltinOp != Builtin::BImemcmp && BuiltinOp != Builtin::BIbcmp &&
          BuiltinOp != Builtin::BIwmemcmp &&
          BuiltinOp != Builtin::BI__builtin_memcmp &&
          BuiltinOp != Builtin::BI__builtin_bcmp &&
          BuiltinOp != Builtin::BI__builtin_wmemcmp);
     bool IsWide = BuiltinOp == Builtin::BIwcscmp ||
                   BuiltinOp == Builtin::BIwcsncmp ||
                   BuiltinOp == Builtin::BIwmemcmp ||
                   BuiltinOp == Builtin::BI__builtin_wcscmp ||
                   BuiltinOp == Builtin::BI__builtin_wcsncmp ||
                   BuiltinOp == Builtin::BI__builtin_wmemcmp;
 
     for (; MaxLength; --MaxLength) {
       APValue Char1, Char2;
       if (!ReadCurElems(Char1, Char2))
         return false;
       if (Char1.getInt().ne(Char2.getInt())) {
         if (IsWide) // wmemcmp compares with wchar_t signedness.
           return Success(Char1.getInt() < Char2.getInt() ? -1 : 1, E);
         // memcmp always compares unsigned chars.
         return Success(Char1.getInt().ult(Char2.getInt()) ? -1 : 1, E);
       }
       if (StopAtNull && !Char1.getInt())
         return Success(0, E);
       assert(!(StopAtNull && !Char2.getInt()));
       if (!AdvanceElems())
         return false;
     }
     // We hit the strncmp / memcmp limit.
     return Success(0, E);
   }
 
   case Builtin::BI__atomic_always_lock_free:
   case Builtin::BI__atomic_is_lock_free:
   case Builtin::BI__c11_atomic_is_lock_free: {
     APSInt SizeVal;
     if (!EvaluateInteger(E->getArg(0), SizeVal, Info))
       return false;
 
     // For __atomic_is_lock_free(sizeof(_Atomic(T))), if the size is a power
     // of two less than the maximum inline atomic width, we know it is
     // lock-free.  If the size isn't a power of two, or greater than the
     // maximum alignment where we promote atomics, we know it is not lock-free
     // (at least not in the sense of atomic_is_lock_free).  Otherwise,
     // the answer can only be determined at runtime; for example, 16-byte
     // atomics have lock-free implementations on some, but not all,
     // x86-64 processors.
 
     // Check power-of-two.
     CharUnits Size = CharUnits::fromQuantity(SizeVal.getZExtValue());
     if (Size.isPowerOfTwo()) {
       // Check against inlining width.
       unsigned InlineWidthBits =
           Info.Ctx.getTargetInfo().getMaxAtomicInlineWidth();
       if (Size <= Info.Ctx.toCharUnitsFromBits(InlineWidthBits)) {
         if (BuiltinOp == Builtin::BI__c11_atomic_is_lock_free ||
             Size == CharUnits::One() ||
             E->getArg(1)->isNullPointerConstant(Info.Ctx,
                                                 Expr::NPC_NeverValueDependent))
           // OK, we will inline appropriately-aligned operations of this size,
           // and _Atomic(T) is appropriately-aligned.
           return Success(1, E);
 
         QualType PointeeType = E->getArg(1)->IgnoreImpCasts()->getType()->
           castAs<PointerType>()->getPointeeType();
         if (!PointeeType->isIncompleteType() &&
             Info.Ctx.getTypeAlignInChars(PointeeType) >= Size) {
           // OK, we will inline operations on this object.
           return Success(1, E);
         }
       }
     }
 
+    // Avoid emiting call for runtime decision on PowerPC 32-bit
+    // The lock free possibilities on this platform are covered by the lines 
+    // above and we know in advance other cases require lock
+    if (Info.Ctx.getTargetInfo().getTriple().getArch() == llvm::Triple::ppc) {
+        return Success(0, E);
+    }
+
     return BuiltinOp == Builtin::BI__atomic_always_lock_free ?
         Success(0, E) : Error(E);
   }
   case Builtin::BIomp_is_initial_device:
     // We can decide statically which value the runtime would return if called.
     return Success(Info.getLangOpts().OpenMPIsDevice ? 0 : 1, E);
   case Builtin::BI__builtin_add_overflow:
   case Builtin::BI__builtin_sub_overflow:
   case Builtin::BI__builtin_mul_overflow:
   case Builtin::BI__builtin_sadd_overflow:
   case Builtin::BI__builtin_uadd_overflow:
   case Builtin::BI__builtin_uaddl_overflow:
   case Builtin::BI__builtin_uaddll_overflow:
   case Builtin::BI__builtin_usub_overflow:
   case Builtin::BI__builtin_usubl_overflow:
   case Builtin::BI__builtin_usubll_overflow:
   case Builtin::BI__builtin_umul_overflow:
   case Builtin::BI__builtin_umull_overflow:
   case Builtin::BI__builtin_umulll_overflow:
   case Builtin::BI__builtin_saddl_overflow:
   case Builtin::BI__builtin_saddll_overflow:
   case Builtin::BI__builtin_ssub_overflow:
   case Builtin::BI__builtin_ssubl_overflow:
   case Builtin::BI__builtin_ssubll_overflow:
   case Builtin::BI__builtin_smul_overflow:
   case Builtin::BI__builtin_smull_overflow:
   case Builtin::BI__builtin_smulll_overflow: {
     LValue ResultLValue;
     APSInt LHS, RHS;
 
     QualType ResultType = E->getArg(2)->getType()->getPointeeType();
     if (!EvaluateInteger(E->getArg(0), LHS, Info) ||
         !EvaluateInteger(E->getArg(1), RHS, Info) ||
         !EvaluatePointer(E->getArg(2), ResultLValue, Info))
       return false;
 
     APSInt Result;
     bool DidOverflow = false;
 
     // If the types don't have to match, enlarge all 3 to the largest of them.
     if (BuiltinOp == Builtin::BI__builtin_add_overflow ||
         BuiltinOp == Builtin::BI__builtin_sub_overflow ||
         BuiltinOp == Builtin::BI__builtin_mul_overflow) {
       bool IsSigned = LHS.isSigned() || RHS.isSigned() ||
                       ResultType->isSignedIntegerOrEnumerationType();
       bool AllSigned = LHS.isSigned() && RHS.isSigned() &&
                       ResultType->isSignedIntegerOrEnumerationType();
       uint64_t LHSSize = LHS.getBitWidth();
       uint64_t RHSSize = RHS.getBitWidth();
       uint64_t ResultSize = Info.Ctx.getTypeSize(ResultType);
       uint64_t MaxBits = std::max(std::max(LHSSize, RHSSize), ResultSize);
 
       // Add an additional bit if the signedness isn't uniformly agreed to. We
       // could do this ONLY if there is a signed and an unsigned that both have
       // MaxBits, but the code to check that is pretty nasty.  The issue will be
       // caught in the shrink-to-result later anyway.
       if (IsSigned && !AllSigned)
         ++MaxBits;
 
       LHS = APSInt(LHS.extOrTrunc(MaxBits), !IsSigned);
       RHS = APSInt(RHS.extOrTrunc(MaxBits), !IsSigned);
       Result = APSInt(MaxBits, !IsSigned);
     }
 
     // Find largest int.
     switch (BuiltinOp) {
     default:
       llvm_unreachable("Invalid value for BuiltinOp");
     case Builtin::BI__builtin_add_overflow:
     case Builtin::BI__builtin_sadd_overflow:
     case Builtin::BI__builtin_saddl_overflow:
     case Builtin::BI__builtin_saddll_overflow:
     case Builtin::BI__builtin_uadd_overflow:
     case Builtin::BI__builtin_uaddl_overflow:
     case Builtin::BI__builtin_uaddll_overflow:
       Result = LHS.isSigned() ? LHS.sadd_ov(RHS, DidOverflow)
                               : LHS.uadd_ov(RHS, DidOverflow);
       break;
     case Builtin::BI__builtin_sub_overflow:
     case Builtin::BI__builtin_ssub_overflow:
     case Builtin::BI__builtin_ssubl_overflow:
     case Builtin::BI__builtin_ssubll_overflow:
     case Builtin::BI__builtin_usub_overflow:
     case Builtin::BI__builtin_usubl_overflow:
     case Builtin::BI__builtin_usubll_overflow:
       Result = LHS.isSigned() ? LHS.ssub_ov(RHS, DidOverflow)
                               : LHS.usub_ov(RHS, DidOverflow);
       break;
     case Builtin::BI__builtin_mul_overflow:
     case Builtin::BI__builtin_smul_overflow:
     case Builtin::BI__builtin_smull_overflow:
     case Builtin::BI__builtin_smulll_overflow:
     case Builtin::BI__builtin_umul_overflow:
     case Builtin::BI__builtin_umull_overflow:
     case Builtin::BI__builtin_umulll_overflow:
       Result = LHS.isSigned() ? LHS.smul_ov(RHS, DidOverflow)
                               : LHS.umul_ov(RHS, DidOverflow);
       break;
     }
 
     // In the case where multiple sizes are allowed, truncate and see if
     // the values are the same.
     if (BuiltinOp == Builtin::BI__builtin_add_overflow ||
         BuiltinOp == Builtin::BI__builtin_sub_overflow ||
         BuiltinOp == Builtin::BI__builtin_mul_overflow) {
       // APSInt doesn't have a TruncOrSelf, so we use extOrTrunc instead,
       // since it will give us the behavior of a TruncOrSelf in the case where
       // its parameter <= its size.  We previously set Result to be at least the
       // type-size of the result, so getTypeSize(ResultType) <= Result.BitWidth
       // will work exactly like TruncOrSelf.
       APSInt Temp = Result.extOrTrunc(Info.Ctx.getTypeSize(ResultType));
       Temp.setIsSigned(ResultType->isSignedIntegerOrEnumerationType());
 
       if (!APSInt::isSameValue(Temp, Result))
         DidOverflow = true;
       Result = Temp;
     }
 
     APValue APV{Result};
     if (!handleAssignment(Info, E, ResultLValue, ResultType, APV))
       return false;
     return Success(DidOverflow, E);
   }
   }
 }
 
 /// Determine whether this is a pointer past the end of the complete
 /// object referred to by the lvalue.
 static bool isOnePastTheEndOfCompleteObject(const ASTContext &Ctx,
                                             const LValue &LV) {
   // A null pointer can be viewed as being "past the end" but we don't
   // choose to look at it that way here.
   if (!LV.getLValueBase())
     return false;
 
   // If the designator is valid and refers to a subobject, we're not pointing
   // past the end.
   if (!LV.getLValueDesignator().Invalid &&
       !LV.getLValueDesignator().isOnePastTheEnd())
     return false;
 
   // A pointer to an incomplete type might be past-the-end if the type's size is
   // zero.  We cannot tell because the type is incomplete.
   QualType Ty = getType(LV.getLValueBase());
   if (Ty->isIncompleteType())
     return true;
 
   // We're a past-the-end pointer if we point to the byte after the object,
   // no matter what our type or path is.
   auto Size = Ctx.getTypeSizeInChars(Ty);
   return LV.getLValueOffset() == Size;
 }
 
 namespace {
 
 /// Data recursive integer evaluator of certain binary operators.
 ///
 /// We use a data recursive algorithm for binary operators so that we are able
 /// to handle extreme cases of chained binary operators without causing stack
 /// overflow.
 class DataRecursiveIntBinOpEvaluator {
   struct EvalResult {
     APValue Val;
     bool Failed;
 
     EvalResult() : Failed(false) { }
 
     void swap(EvalResult &RHS) {
       Val.swap(RHS.Val);
       Failed = RHS.Failed;
       RHS.Failed = false;
     }
   };
 
   struct Job {
     const Expr *E;
     EvalResult LHSResult; // meaningful only for binary operator expression.
     enum { AnyExprKind, BinOpKind, BinOpVisitedLHSKind } Kind;
 
     Job() = default;
     Job(Job &&) = default;
 
     void startSpeculativeEval(EvalInfo &Info) {
       SpecEvalRAII = SpeculativeEvaluationRAII(Info);
     }
 
   private:
     SpeculativeEvaluationRAII SpecEvalRAII;
   };
 
   SmallVector<Job, 16> Queue;
 
   IntExprEvaluator &IntEval;
   EvalInfo &Info;
   APValue &FinalResult;
 
 public:
   DataRecursiveIntBinOpEvaluator(IntExprEvaluator &IntEval, APValue &Result)
     : IntEval(IntEval), Info(IntEval.getEvalInfo()), FinalResult(Result) { }
 
   /// True if \param E is a binary operator that we are going to handle
   /// data recursively.
   /// We handle binary operators that are comma, logical, or that have operands
   /// with integral or enumeration type.
   static bool shouldEnqueue(const BinaryOperator *E) {
     return E->getOpcode() == BO_Comma || E->isLogicalOp() ||
            (E->isRValue() && E->getType()->isIntegralOrEnumerationType() &&
             E->getLHS()->getType()->isIntegralOrEnumerationType() &&
             E->getRHS()->getType()->isIntegralOrEnumerationType());
   }
 
   bool Traverse(const BinaryOperator *E) {
     enqueue(E);
     EvalResult PrevResult;
     while (!Queue.empty())
       process(PrevResult);
 
     if (PrevResult.Failed) return false;
 
     FinalResult.swap(PrevResult.Val);
     return true;
   }
 
 private:
   bool Success(uint64_t Value, const Expr *E, APValue &Result) {
     return IntEval.Success(Value, E, Result);
   }
   bool Success(const APSInt &Value, const Expr *E, APValue &Result) {
     return IntEval.Success(Value, E, Result);
   }
   bool Error(const Expr *E) {
     return IntEval.Error(E);
   }
   bool Error(const Expr *E, diag::kind D) {
     return IntEval.Error(E, D);
   }
 
   OptionalDiagnostic CCEDiag(const Expr *E, diag::kind D) {
     return Info.CCEDiag(E, D);
   }
 
   // Returns true if visiting the RHS is necessary, false otherwise.
   bool VisitBinOpLHSOnly(EvalResult &LHSResult, const BinaryOperator *E,
                          bool &SuppressRHSDiags);
 
   bool VisitBinOp(const EvalResult &LHSResult, const EvalResult &RHSResult,
                   const BinaryOperator *E, APValue &Result);
 
   void EvaluateExpr(const Expr *E, EvalResult &Result) {
     Result.Failed = !Evaluate(Result.Val, Info, E);
     if (Result.Failed)
       Result.Val = APValue();
   }
 
   void process(EvalResult &Result);
 
   void enqueue(const Expr *E) {
     E = E->IgnoreParens();
     Queue.resize(Queue.size()+1);
     Queue.back().E = E;
     Queue.back().Kind = Job::AnyExprKind;
   }
 };
 
 }
 
 bool DataRecursiveIntBinOpEvaluator::
        VisitBinOpLHSOnly(EvalResult &LHSResult, const BinaryOperator *E,
                          bool &SuppressRHSDiags) {
   if (E->getOpcode() == BO_Comma) {
     // Ignore LHS but note if we could not evaluate it.
     if (LHSResult.Failed)
       return Info.noteSideEffect();
     return true;
   }
 
   if (E->isLogicalOp()) {
     bool LHSAsBool;
     if (!LHSResult.Failed && HandleConversionToBool(LHSResult.Val, LHSAsBool)) {
       // We were able to evaluate the LHS, see if we can get away with not
       // evaluating the RHS: 0 && X -> 0, 1 || X -> 1
       if (LHSAsBool == (E->getOpcode() == BO_LOr)) {
         Success(LHSAsBool, E, LHSResult.Val);
         return false; // Ignore RHS
       }
     } else {
       LHSResult.Failed = true;
 
       // Since we weren't able to evaluate the left hand side, it
       // might have had side effects.
       if (!Info.noteSideEffect())
         return false;
 
       // We can't evaluate the LHS; however, sometimes the result
       // is determined by the RHS: X && 0 -> 0, X || 1 -> 1.
       // Don't ignore RHS and suppress diagnostics from this arm.
       SuppressRHSDiags = true;
     }
 
     return true;
   }
 
   assert(E->getLHS()->getType()->isIntegralOrEnumerationType() &&
          E->getRHS()->getType()->isIntegralOrEnumerationType());
 
   if (LHSResult.Failed && !Info.noteFailure())
     return false; // Ignore RHS;
 
   return true;
 }
 
 static void addOrSubLValueAsInteger(APValue &LVal, const APSInt &Index,
                                     bool IsSub) {
   // Compute the new offset in the appropriate width, wrapping at 64 bits.
   // FIXME: When compiling for a 32-bit target, we should use 32-bit
   // offsets.
   assert(!LVal.hasLValuePath() && "have designator for integer lvalue");
   CharUnits &Offset = LVal.getLValueOffset();
   uint64_t Offset64 = Offset.getQuantity();
   uint64_t Index64 = Index.extOrTrunc(64).getZExtValue();
   Offset = CharUnits::fromQuantity(IsSub ? Offset64 - Index64
                                          : Offset64 + Index64);
 }
 
 bool DataRecursiveIntBinOpEvaluator::
        VisitBinOp(const EvalResult &LHSResult, const EvalResult &RHSResult,
                   const BinaryOperator *E, APValue &Result) {
   if (E->getOpcode() == BO_Comma) {
     if (RHSResult.Failed)
       return false;
     Result = RHSResult.Val;
     return true;
   }
 
   if (E->isLogicalOp()) {
     bool lhsResult, rhsResult;
     bool LHSIsOK = HandleConversionToBool(LHSResult.Val, lhsResult);
     bool RHSIsOK = HandleConversionToBool(RHSResult.Val, rhsResult);
 
     if (LHSIsOK) {
       if (RHSIsOK) {
         if (E->getOpcode() == BO_LOr)
           return Success(lhsResult || rhsResult, E, Result);
         else
           return Success(lhsResult && rhsResult, E, Result);
       }
     } else {
       if (RHSIsOK) {
         // We can't evaluate the LHS; however, sometimes the result
         // is determined by the RHS: X && 0 -> 0, X || 1 -> 1.
         if (rhsResult == (E->getOpcode() == BO_LOr))
           return Success(rhsResult, E, Result);
       }
     }
 
     return false;
   }
 
   assert(E->getLHS()->getType()->isIntegralOrEnumerationType() &&
          E->getRHS()->getType()->isIntegralOrEnumerationType());
 
   if (LHSResult.Failed || RHSResult.Failed)
     return false;
 
   const APValue &LHSVal = LHSResult.Val;
   const APValue &RHSVal = RHSResult.Val;
 
   // Handle cases like (unsigned long)&a + 4.
   if (E->isAdditiveOp() && LHSVal.isLValue() && RHSVal.isInt()) {
     Result = LHSVal;
     addOrSubLValueAsInteger(Result, RHSVal.getInt(), E->getOpcode() == BO_Sub);
     return true;
   }
 
   // Handle cases like 4 + (unsigned long)&a
   if (E->getOpcode() == BO_Add &&
       RHSVal.isLValue() && LHSVal.isInt()) {
     Result = RHSVal;
     addOrSubLValueAsInteger(Result, LHSVal.getInt(), /*IsSub*/false);
     return true;
   }
 
   if (E->getOpcode() == BO_Sub && LHSVal.isLValue() && RHSVal.isLValue()) {
     // Handle (intptr_t)&&A - (intptr_t)&&B.
     if (!LHSVal.getLValueOffset().isZero() ||
         !RHSVal.getLValueOffset().isZero())
       return false;
     const Expr *LHSExpr = LHSVal.getLValueBase().dyn_cast<const Expr*>();
     const Expr *RHSExpr = RHSVal.getLValueBase().dyn_cast<const Expr*>();
     if (!LHSExpr || !RHSExpr)
       return false;
     const AddrLabelExpr *LHSAddrExpr = dyn_cast<AddrLabelExpr>(LHSExpr);
     const AddrLabelExpr *RHSAddrExpr = dyn_cast<AddrLabelExpr>(RHSExpr);
     if (!LHSAddrExpr || !RHSAddrExpr)
       return false;
     // Make sure both labels come from the same function.
     if (LHSAddrExpr->getLabel()->getDeclContext() !=
         RHSAddrExpr->getLabel()->getDeclContext())
       return false;
     Result = APValue(LHSAddrExpr, RHSAddrExpr);
     return true;
   }
 
   // All the remaining cases expect both operands to be an integer
   if (!LHSVal.isInt() || !RHSVal.isInt())
     return Error(E);
 
   // Set up the width and signedness manually, in case it can't be deduced
   // from the operation we're performing.
   // FIXME: Don't do this in the cases where we can deduce it.
   APSInt Value(Info.Ctx.getIntWidth(E->getType()),
                E->getType()->isUnsignedIntegerOrEnumerationType());
   if (!handleIntIntBinOp(Info, E, LHSVal.getInt(), E->getOpcode(),
                          RHSVal.getInt(), Value))
     return false;
   return Success(Value, E, Result);
 }
 
 void DataRecursiveIntBinOpEvaluator::process(EvalResult &Result) {
   Job &job = Queue.back();
 
   switch (job.Kind) {
     case Job::AnyExprKind: {
       if (const BinaryOperator *Bop = dyn_cast<BinaryOperator>(job.E)) {
         if (shouldEnqueue(Bop)) {
           job.Kind = Job::BinOpKind;
           enqueue(Bop->getLHS());
           return;
         }
       }
 
       EvaluateExpr(job.E, Result);
       Queue.pop_back();
       return;
     }
 
     case Job::BinOpKind: {
       const BinaryOperator *Bop = cast<BinaryOperator>(job.E);
       bool SuppressRHSDiags = false;
       if (!VisitBinOpLHSOnly(Result, Bop, SuppressRHSDiags)) {
         Queue.pop_back();
         return;
       }
       if (SuppressRHSDiags)
         job.startSpeculativeEval(Info);
       job.LHSResult.swap(Result);
       job.Kind = Job::BinOpVisitedLHSKind;
       enqueue(Bop->getRHS());
       return;
     }
 
     case Job::BinOpVisitedLHSKind: {
       const BinaryOperator *Bop = cast<BinaryOperator>(job.E);
       EvalResult RHS;
       RHS.swap(Result);
       Result.Failed = !VisitBinOp(job.LHSResult, RHS, Bop, Result.Val);
       Queue.pop_back();
       return;
     }
   }
 
   llvm_unreachable("Invalid Job::Kind!");
 }
 
 namespace {
 /// Used when we determine that we should fail, but can keep evaluating prior to
 /// noting that we had a failure.
 class DelayedNoteFailureRAII {
   EvalInfo &Info;
   bool NoteFailure;
 
 public:
   DelayedNoteFailureRAII(EvalInfo &Info, bool NoteFailure = true)
       : Info(Info), NoteFailure(NoteFailure) {}
   ~DelayedNoteFailureRAII() {
     if (NoteFailure) {
       bool ContinueAfterFailure = Info.noteFailure();
       (void)ContinueAfterFailure;
       assert(ContinueAfterFailure &&
              "Shouldn't have kept evaluating on failure.");
     }
   }
 };
 
 enum class CmpResult {
   Unequal,
   Less,
   Equal,
   Greater,
   Unordered,
 };
 }
 
 template <class SuccessCB, class AfterCB>
 static bool
 EvaluateComparisonBinaryOperator(EvalInfo &Info, const BinaryOperator *E,
                                  SuccessCB &&Success, AfterCB &&DoAfter) {
   assert(E->isComparisonOp() && "expected comparison operator");
   assert((E->getOpcode() == BO_Cmp ||
           E->getType()->isIntegralOrEnumerationType()) &&
          "unsupported binary expression evaluation");
   auto Error = [&](const Expr *E) {
     Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
     return false;
   };
 
   bool IsRelational = E->isRelationalOp() || E->getOpcode() == BO_Cmp;
   bool IsEquality = E->isEqualityOp();
 
   QualType LHSTy = E->getLHS()->getType();
   QualType RHSTy = E->getRHS()->getType();
 
   if (LHSTy->isIntegralOrEnumerationType() &&
       RHSTy->isIntegralOrEnumerationType()) {
     APSInt LHS, RHS;
     bool LHSOK = EvaluateInteger(E->getLHS(), LHS, Info);
     if (!LHSOK && !Info.noteFailure())
       return false;
     if (!EvaluateInteger(E->getRHS(), RHS, Info) || !LHSOK)
       return false;
     if (LHS < RHS)
       return Success(CmpResult::Less, E);
     if (LHS > RHS)
       return Success(CmpResult::Greater, E);
     return Success(CmpResult::Equal, E);
   }
 
   if (LHSTy->isFixedPointType() || RHSTy->isFixedPointType()) {
     APFixedPoint LHSFX(Info.Ctx.getFixedPointSemantics(LHSTy));
     APFixedPoint RHSFX(Info.Ctx.getFixedPointSemantics(RHSTy));
 
     bool LHSOK = EvaluateFixedPointOrInteger(E->getLHS(), LHSFX, Info);
     if (!LHSOK && !Info.noteFailure())
       return false;
     if (!EvaluateFixedPointOrInteger(E->getRHS(), RHSFX, Info) || !LHSOK)
       return false;
     if (LHSFX < RHSFX)
       return Success(CmpResult::Less, E);
     if (LHSFX > RHSFX)
       return Success(CmpResult::Greater, E);
     return Success(CmpResult::Equal, E);
   }
 
   if (LHSTy->isAnyComplexType() || RHSTy->isAnyComplexType()) {
     ComplexValue LHS, RHS;
     bool LHSOK;
     if (E->isAssignmentOp()) {
       LValue LV;
       EvaluateLValue(E->getLHS(), LV, Info);
       LHSOK = false;
     } else if (LHSTy->isRealFloatingType()) {
       LHSOK = EvaluateFloat(E->getLHS(), LHS.FloatReal, Info);
       if (LHSOK) {
         LHS.makeComplexFloat();
         LHS.FloatImag = APFloat(LHS.FloatReal.getSemantics());
       }
     } else {
       LHSOK = EvaluateComplex(E->getLHS(), LHS, Info);
     }
     if (!LHSOK && !Info.noteFailure())
       return false;
 
     if (E->getRHS()->getType()->isRealFloatingType()) {
       if (!EvaluateFloat(E->getRHS(), RHS.FloatReal, Info) || !LHSOK)
         return false;
       RHS.makeComplexFloat();
       RHS.FloatImag = APFloat(RHS.FloatReal.getSemantics());
     } else if (!EvaluateComplex(E->getRHS(), RHS, Info) || !LHSOK)
       return false;
 
     if (LHS.isComplexFloat()) {
       APFloat::cmpResult CR_r =
         LHS.getComplexFloatReal().compare(RHS.getComplexFloatReal());
       APFloat::cmpResult CR_i =
         LHS.getComplexFloatImag().compare(RHS.getComplexFloatImag());
       bool IsEqual = CR_r == APFloat::cmpEqual && CR_i == APFloat::cmpEqual;
       return Success(IsEqual ? CmpResult::Equal : CmpResult::Unequal, E);
     } else {
       assert(IsEquality && "invalid complex comparison");
       bool IsEqual = LHS.getComplexIntReal() == RHS.getComplexIntReal() &&
                      LHS.getComplexIntImag() == RHS.getComplexIntImag();
       return Success(IsEqual ? CmpResult::Equal : CmpResult::Unequal, E);
     }
   }
 
   if (LHSTy->isRealFloatingType() &&
       RHSTy->isRealFloatingType()) {
     APFloat RHS(0.0), LHS(0.0);
 
     bool LHSOK = EvaluateFloat(E->getRHS(), RHS, Info);
     if (!LHSOK && !Info.noteFailure())
       return false;
 
     if (!EvaluateFloat(E->getLHS(), LHS, Info) || !LHSOK)
       return false;
 
     assert(E->isComparisonOp() && "Invalid binary operator!");
     auto GetCmpRes = [&]() {
       switch (LHS.compare(RHS)) {
       case APFloat::cmpEqual:
         return CmpResult::Equal;
       case APFloat::cmpLessThan:
         return CmpResult::Less;
       case APFloat::cmpGreaterThan:
         return CmpResult::Greater;
       case APFloat::cmpUnordered:
         return CmpResult::Unordered;
       }
       llvm_unreachable("Unrecognised APFloat::cmpResult enum");
     };
     return Success(GetCmpRes(), E);
   }
 
   if (LHSTy->isPointerType() && RHSTy->isPointerType()) {
     LValue LHSValue, RHSValue;
 
     bool LHSOK = EvaluatePointer(E->getLHS(), LHSValue, Info);
     if (!LHSOK && !Info.noteFailure())
       return false;
 
     if (!EvaluatePointer(E->getRHS(), RHSValue, Info) || !LHSOK)
       return false;
 
     // Reject differing bases from the normal codepath; we special-case
     // comparisons to null.
     if (!HasSameBase(LHSValue, RHSValue)) {
       // Inequalities and subtractions between unrelated pointers have
       // unspecified or undefined behavior.
       if (!IsEquality) {
         Info.FFDiag(E, diag::note_constexpr_pointer_comparison_unspecified);
         return false;
       }
       // A constant address may compare equal to the address of a symbol.
       // The one exception is that address of an object cannot compare equal
       // to a null pointer constant.
       if ((!LHSValue.Base && !LHSValue.Offset.isZero()) ||
           (!RHSValue.Base && !RHSValue.Offset.isZero()))
         return Error(E);
       // It's implementation-defined whether distinct literals will have
       // distinct addresses. In clang, the result of such a comparison is
       // unspecified, so it is not a constant expression. However, we do know
       // that the address of a literal will be non-null.
       if ((IsLiteralLValue(LHSValue) || IsLiteralLValue(RHSValue)) &&
           LHSValue.Base && RHSValue.Base)
         return Error(E);
       // We can't tell whether weak symbols will end up pointing to the same
       // object.
       if (IsWeakLValue(LHSValue) || IsWeakLValue(RHSValue))
         return Error(E);
       // We can't compare the address of the start of one object with the
       // past-the-end address of another object, per C++ DR1652.
       if ((LHSValue.Base && LHSValue.Offset.isZero() &&
            isOnePastTheEndOfCompleteObject(Info.Ctx, RHSValue)) ||
           (RHSValue.Base && RHSValue.Offset.isZero() &&
            isOnePastTheEndOfCompleteObject(Info.Ctx, LHSValue)))
         return Error(E);
       // We can't tell whether an object is at the same address as another
       // zero sized object.
       if ((RHSValue.Base && isZeroSized(LHSValue)) ||
           (LHSValue.Base && isZeroSized(RHSValue)))
         return Error(E);
       return Success(CmpResult::Unequal, E);
     }
 
     const CharUnits &LHSOffset = LHSValue.getLValueOffset();
     const CharUnits &RHSOffset = RHSValue.getLValueOffset();
 
     SubobjectDesignator &LHSDesignator = LHSValue.getLValueDesignator();
     SubobjectDesignator &RHSDesignator = RHSValue.getLValueDesignator();
 
     // C++11 [expr.rel]p3:
     //   Pointers to void (after pointer conversions) can be compared, with a
     //   result defined as follows: If both pointers represent the same
     //   address or are both the null pointer value, the result is true if the
     //   operator is <= or >= and false otherwise; otherwise the result is
     //   unspecified.
     // We interpret this as applying to pointers to *cv* void.
     if (LHSTy->isVoidPointerType() && LHSOffset != RHSOffset && IsRelational)
       Info.CCEDiag(E, diag::note_constexpr_void_comparison);
 
     // C++11 [expr.rel]p2:
     // - If two pointers point to non-static data members of the same object,
     //   or to subobjects or array elements fo such members, recursively, the
     //   pointer to the later declared member compares greater provided the
     //   two members have the same access control and provided their class is
     //   not a union.
     //   [...]
     // - Otherwise pointer comparisons are unspecified.
     if (!LHSDesignator.Invalid && !RHSDesignator.Invalid && IsRelational) {
       bool WasArrayIndex;
       unsigned Mismatch = FindDesignatorMismatch(
           getType(LHSValue.Base), LHSDesignator, RHSDesignator, WasArrayIndex);
       // At the point where the designators diverge, the comparison has a
       // specified value if:
       //  - we are comparing array indices
       //  - we are comparing fields of a union, or fields with the same access
       // Otherwise, the result is unspecified and thus the comparison is not a
       // constant expression.
       if (!WasArrayIndex && Mismatch < LHSDesignator.Entries.size() &&
           Mismatch < RHSDesignator.Entries.size()) {
         const FieldDecl *LF = getAsField(LHSDesignator.Entries[Mismatch]);
         const FieldDecl *RF = getAsField(RHSDesignator.Entries[Mismatch]);
         if (!LF && !RF)
           Info.CCEDiag(E, diag::note_constexpr_pointer_comparison_base_classes);
         else if (!LF)
           Info.CCEDiag(E, diag::note_constexpr_pointer_comparison_base_field)
               << getAsBaseClass(LHSDesignator.Entries[Mismatch])
               << RF->getParent() << RF;
         else if (!RF)
           Info.CCEDiag(E, diag::note_constexpr_pointer_comparison_base_field)
               << getAsBaseClass(RHSDesignator.Entries[Mismatch])
               << LF->getParent() << LF;
         else if (!LF->getParent()->isUnion() &&
                  LF->getAccess() != RF->getAccess())
           Info.CCEDiag(E,
                        diag::note_constexpr_pointer_comparison_differing_access)
               << LF << LF->getAccess() << RF << RF->getAccess()
               << LF->getParent();
       }
     }
 
     // The comparison here must be unsigned, and performed with the same
     // width as the pointer.
     unsigned PtrSize = Info.Ctx.getTypeSize(LHSTy);
     uint64_t CompareLHS = LHSOffset.getQuantity();
     uint64_t CompareRHS = RHSOffset.getQuantity();
     assert(PtrSize <= 64 && "Unexpected pointer width");
     uint64_t Mask = ~0ULL >> (64 - PtrSize);
     CompareLHS &= Mask;
     CompareRHS &= Mask;
 
     // If there is a base and this is a relational operator, we can only
     // compare pointers within the object in question; otherwise, the result
     // depends on where the object is located in memory.
     if (!LHSValue.Base.isNull() && IsRelational) {
       QualType BaseTy = getType(LHSValue.Base);
       if (BaseTy->isIncompleteType())
         return Error(E);
       CharUnits Size = Info.Ctx.getTypeSizeInChars(BaseTy);
       uint64_t OffsetLimit = Size.getQuantity();
       if (CompareLHS > OffsetLimit || CompareRHS > OffsetLimit)
         return Error(E);
     }
 
     if (CompareLHS < CompareRHS)
       return Success(CmpResult::Less, E);
     if (CompareLHS > CompareRHS)
       return Success(CmpResult::Greater, E);
     return Success(CmpResult::Equal, E);
   }
 
   if (LHSTy->isMemberPointerType()) {
     assert(IsEquality && "unexpected member pointer operation");
     assert(RHSTy->isMemberPointerType() && "invalid comparison");
 
     MemberPtr LHSValue, RHSValue;
 
     bool LHSOK = EvaluateMemberPointer(E->getLHS(), LHSValue, Info);
     if (!LHSOK && !Info.noteFailure())
       return false;
 
     if (!EvaluateMemberPointer(E->getRHS(), RHSValue, Info) || !LHSOK)
       return false;
 
     // C++11 [expr.eq]p2:
     //   If both operands are null, they compare equal. Otherwise if only one is
     //   null, they compare unequal.
     if (!LHSValue.getDecl() || !RHSValue.getDecl()) {
       bool Equal = !LHSValue.getDecl() && !RHSValue.getDecl();
       return Success(Equal ? CmpResult::Equal : CmpResult::Unequal, E);
     }
 
     //   Otherwise if either is a pointer to a virtual member function, the
     //   result is unspecified.
     if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(LHSValue.getDecl()))
       if (MD->isVirtual())
         Info.CCEDiag(E, diag::note_constexpr_compare_virtual_mem_ptr) << MD;
     if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(RHSValue.getDecl()))
       if (MD->isVirtual())
         Info.CCEDiag(E, diag::note_constexpr_compare_virtual_mem_ptr) << MD;
 
     //   Otherwise they compare equal if and only if they would refer to the
     //   same member of the same most derived object or the same subobject if
     //   they were dereferenced with a hypothetical object of the associated
     //   class type.
     bool Equal = LHSValue == RHSValue;
     return Success(Equal ? CmpResult::Equal : CmpResult::Unequal, E);
   }
 
   if (LHSTy->isNullPtrType()) {
     assert(E->isComparisonOp() && "unexpected nullptr operation");
     assert(RHSTy->isNullPtrType() && "missing pointer conversion");
     // C++11 [expr.rel]p4, [expr.eq]p3: If two operands of type std::nullptr_t
     // are compared, the result is true of the operator is <=, >= or ==, and
     // false otherwise.
     return Success(CmpResult::Equal, E);
   }
 
   return DoAfter();
 }
 
 bool RecordExprEvaluator::VisitBinCmp(const BinaryOperator *E) {
   if (!CheckLiteralType(Info, E))
     return false;
 
   auto OnSuccess = [&](CmpResult CR, const BinaryOperator *E) {
     ComparisonCategoryResult CCR;
     switch (CR) {
     case CmpResult::Unequal:
       llvm_unreachable("should never produce Unequal for three-way comparison");
     case CmpResult::Less:
       CCR = ComparisonCategoryResult::Less;
       break;
     case CmpResult::Equal:
       CCR = ComparisonCategoryResult::Equal;
       break;
     case CmpResult::Greater:
       CCR = ComparisonCategoryResult::Greater;
       break;
     case CmpResult::Unordered:
       CCR = ComparisonCategoryResult::Unordered;
       break;
     }
     // Evaluation succeeded. Lookup the information for the comparison category
     // type and fetch the VarDecl for the result.
     const ComparisonCategoryInfo &CmpInfo =
         Info.Ctx.CompCategories.getInfoForType(E->getType());
     const VarDecl *VD = CmpInfo.getValueInfo(CmpInfo.makeWeakResult(CCR))->VD;
     // Check and evaluate the result as a constant expression.
     LValue LV;
     LV.set(VD);
     if (!handleLValueToRValueConversion(Info, E, E->getType(), LV, Result))
       return false;
     return CheckConstantExpression(Info, E->getExprLoc(), E->getType(), Result);
   };
   return EvaluateComparisonBinaryOperator(Info, E, OnSuccess, [&]() {
     return ExprEvaluatorBaseTy::VisitBinCmp(E);
   });
 }
 
 bool IntExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
   // We don't call noteFailure immediately because the assignment happens after
   // we evaluate LHS and RHS.
   if (!Info.keepEvaluatingAfterFailure() && E->isAssignmentOp())
     return Error(E);
 
   DelayedNoteFailureRAII MaybeNoteFailureLater(Info, E->isAssignmentOp());
   if (DataRecursiveIntBinOpEvaluator::shouldEnqueue(E))
     return DataRecursiveIntBinOpEvaluator(*this, Result).Traverse(E);
 
   assert((!E->getLHS()->getType()->isIntegralOrEnumerationType() ||
           !E->getRHS()->getType()->isIntegralOrEnumerationType()) &&
          "DataRecursiveIntBinOpEvaluator should have handled integral types");
 
   if (E->isComparisonOp()) {
     // Evaluate builtin binary comparisons by evaluating them as three-way
     // comparisons and then translating the result.
     auto OnSuccess = [&](CmpResult CR, const BinaryOperator *E) {
       assert((CR != CmpResult::Unequal || E->isEqualityOp()) &&
              "should only produce Unequal for equality comparisons");
       bool IsEqual   = CR == CmpResult::Equal,
            IsLess    = CR == CmpResult::Less,
            IsGreater = CR == CmpResult::Greater;
       auto Op = E->getOpcode();
       switch (Op) {
       default:
         llvm_unreachable("unsupported binary operator");
       case BO_EQ:
       case BO_NE:
         return Success(IsEqual == (Op == BO_EQ), E);
       case BO_LT:
         return Success(IsLess, E);
       case BO_GT:
         return Success(IsGreater, E);
       case BO_LE:
         return Success(IsEqual || IsLess, E);
       case BO_GE:
         return Success(IsEqual || IsGreater, E);
       }
     };
     return EvaluateComparisonBinaryOperator(Info, E, OnSuccess, [&]() {
       return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
     });
   }
 
   QualType LHSTy = E->getLHS()->getType();
   QualType RHSTy = E->getRHS()->getType();
 
   if (LHSTy->isPointerType() && RHSTy->isPointerType() &&
       E->getOpcode() == BO_Sub) {
     LValue LHSValue, RHSValue;
 
     bool LHSOK = EvaluatePointer(E->getLHS(), LHSValue, Info);
     if (!LHSOK && !Info.noteFailure())
       return false;
 
     if (!EvaluatePointer(E->getRHS(), RHSValue, Info) || !LHSOK)
       return false;
 
     // Reject differing bases from the normal codepath; we special-case
     // comparisons to null.
     if (!HasSameBase(LHSValue, RHSValue)) {
       // Handle &&A - &&B.
       if (!LHSValue.Offset.isZero() || !RHSValue.Offset.isZero())
         return Error(E);
       const Expr *LHSExpr = LHSValue.Base.dyn_cast<const Expr *>();
       const Expr *RHSExpr = RHSValue.Base.dyn_cast<const Expr *>();
       if (!LHSExpr || !RHSExpr)
         return Error(E);
       const AddrLabelExpr *LHSAddrExpr = dyn_cast<AddrLabelExpr>(LHSExpr);
       const AddrLabelExpr *RHSAddrExpr = dyn_cast<AddrLabelExpr>(RHSExpr);
       if (!LHSAddrExpr || !RHSAddrExpr)
         return Error(E);
       // Make sure both labels come from the same function.
       if (LHSAddrExpr->getLabel()->getDeclContext() !=
           RHSAddrExpr->getLabel()->getDeclContext())
         return Error(E);
       return Success(APValue(LHSAddrExpr, RHSAddrExpr), E);
     }
     const CharUnits &LHSOffset = LHSValue.getLValueOffset();
     const CharUnits &RHSOffset = RHSValue.getLValueOffset();
 
     SubobjectDesignator &LHSDesignator = LHSValue.getLValueDesignator();
     SubobjectDesignator &RHSDesignator = RHSValue.getLValueDesignator();
 
     // C++11 [expr.add]p6:
     //   Unless both pointers point to elements of the same array object, or
     //   one past the last element of the array object, the behavior is
     //   undefined.
     if (!LHSDesignator.Invalid && !RHSDesignator.Invalid &&
         !AreElementsOfSameArray(getType(LHSValue.Base), LHSDesignator,
                                 RHSDesignator))
       Info.CCEDiag(E, diag::note_constexpr_pointer_subtraction_not_same_array);
 
     QualType Type = E->getLHS()->getType();
     QualType ElementType = Type->castAs<PointerType>()->getPointeeType();
 
     CharUnits ElementSize;
     if (!HandleSizeof(Info, E->getExprLoc(), ElementType, ElementSize))
       return false;
 
     // As an extension, a type may have zero size (empty struct or union in
     // C, array of zero length). Pointer subtraction in such cases has
     // undefined behavior, so is not constant.
     if (ElementSize.isZero()) {
       Info.FFDiag(E, diag::note_constexpr_pointer_subtraction_zero_size)
           << ElementType;
       return false;
     }
 
     // FIXME: LLVM and GCC both compute LHSOffset - RHSOffset at runtime,
     // and produce incorrect results when it overflows. Such behavior
     // appears to be non-conforming, but is common, so perhaps we should
     // assume the standard intended for such cases to be undefined behavior
     // and check for them.
 
     // Compute (LHSOffset - RHSOffset) / Size carefully, checking for
     // overflow in the final conversion to ptrdiff_t.
     APSInt LHS(llvm::APInt(65, (int64_t)LHSOffset.getQuantity(), true), false);
     APSInt RHS(llvm::APInt(65, (int64_t)RHSOffset.getQuantity(), true), false);
     APSInt ElemSize(llvm::APInt(65, (int64_t)ElementSize.getQuantity(), true),
                     false);
     APSInt TrueResult = (LHS - RHS) / ElemSize;
     APSInt Result = TrueResult.trunc(Info.Ctx.getIntWidth(E->getType()));
 
     if (Result.extend(65) != TrueResult &&
         !HandleOverflow(Info, E, TrueResult, E->getType()))
       return false;
     return Success(Result, E);
   }
 
   return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
 }
 
 /// VisitUnaryExprOrTypeTraitExpr - Evaluate a sizeof, alignof or vec_step with
 /// a result as the expression's type.
 bool IntExprEvaluator::VisitUnaryExprOrTypeTraitExpr(
                                     const UnaryExprOrTypeTraitExpr *E) {
   switch(E->getKind()) {
   case UETT_PreferredAlignOf:
   case UETT_AlignOf: {
     if (E->isArgumentType())
       return Success(GetAlignOfType(Info, E->getArgumentType(), E->getKind()),
                      E);
     else
       return Success(GetAlignOfExpr(Info, E->getArgumentExpr(), E->getKind()),
                      E);
   }
 
   case UETT_VecStep: {
     QualType Ty = E->getTypeOfArgument();
 
     if (Ty->isVectorType()) {
       unsigned n = Ty->castAs<VectorType>()->getNumElements();
 
       // The vec_step built-in functions that take a 3-component
       // vector return 4. (OpenCL 1.1 spec 6.11.12)
       if (n == 3)
         n = 4;
 
       return Success(n, E);
     } else
       return Success(1, E);
   }
 
   case UETT_SizeOf: {
     QualType SrcTy = E->getTypeOfArgument();
     // C++ [expr.sizeof]p2: "When applied to a reference or a reference type,
     //   the result is the size of the referenced type."
     if (const ReferenceType *Ref = SrcTy->getAs<ReferenceType>())
       SrcTy = Ref->getPointeeType();
 
     CharUnits Sizeof;
     if (!HandleSizeof(Info, E->getExprLoc(), SrcTy, Sizeof))
       return false;
     return Success(Sizeof, E);
   }
   case UETT_OpenMPRequiredSimdAlign:
     assert(E->isArgumentType());
     return Success(
         Info.Ctx.toCharUnitsFromBits(
                     Info.Ctx.getOpenMPDefaultSimdAlign(E->getArgumentType()))
             .getQuantity(),
         E);
   }
 
   llvm_unreachable("unknown expr/type trait");
 }
 
 bool IntExprEvaluator::VisitOffsetOfExpr(const OffsetOfExpr *OOE) {
   CharUnits Result;
   unsigned n = OOE->getNumComponents();
   if (n == 0)
     return Error(OOE);
   QualType CurrentType = OOE->getTypeSourceInfo()->getType();
   for (unsigned i = 0; i != n; ++i) {
     OffsetOfNode ON = OOE->getComponent(i);
     switch (ON.getKind()) {
     case OffsetOfNode::Array: {
       const Expr *Idx = OOE->getIndexExpr(ON.getArrayExprIndex());
       APSInt IdxResult;
       if (!EvaluateInteger(Idx, IdxResult, Info))
         return false;
       const ArrayType *AT = Info.Ctx.getAsArrayType(CurrentType);
       if (!AT)
         return Error(OOE);
       CurrentType = AT->getElementType();
       CharUnits ElementSize = Info.Ctx.getTypeSizeInChars(CurrentType);
       Result += IdxResult.getSExtValue() * ElementSize;
       break;
     }
 
     case OffsetOfNode::Field: {
       FieldDecl *MemberDecl = ON.getField();
       const RecordType *RT = CurrentType->getAs<RecordType>();
       if (!RT)
         return Error(OOE);
       RecordDecl *RD = RT->getDecl();
       if (RD->isInvalidDecl()) return false;
       const ASTRecordLayout &RL = Info.Ctx.getASTRecordLayout(RD);
       unsigned i = MemberDecl->getFieldIndex();
       assert(i < RL.getFieldCount() && "offsetof field in wrong type");
       Result += Info.Ctx.toCharUnitsFromBits(RL.getFieldOffset(i));
       CurrentType = MemberDecl->getType().getNonReferenceType();
       break;
     }
 
     case OffsetOfNode::Identifier:
       llvm_unreachable("dependent __builtin_offsetof");
 
     case OffsetOfNode::Base: {
       CXXBaseSpecifier *BaseSpec = ON.getBase();
       if (BaseSpec->isVirtual())
         return Error(OOE);
 
       // Find the layout of the class whose base we are looking into.
       const RecordType *RT = CurrentType->getAs<RecordType>();
       if (!RT)
         return Error(OOE);
       RecordDecl *RD = RT->getDecl();
       if (RD->isInvalidDecl()) return false;
       const ASTRecordLayout &RL = Info.Ctx.getASTRecordLayout(RD);
 
       // Find the base class itself.
       CurrentType = BaseSpec->getType();
       const RecordType *BaseRT = CurrentType->getAs<RecordType>();
       if (!BaseRT)
         return Error(OOE);
 
       // Add the offset to the base.
       Result += RL.getBaseClassOffset(cast<CXXRecordDecl>(BaseRT->getDecl()));
       break;
     }
     }
   }
   return Success(Result, OOE);
 }
 
 bool IntExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
   switch (E->getOpcode()) {
   default:
     // Address, indirect, pre/post inc/dec, etc are not valid constant exprs.
     // See C99 6.6p3.
     return Error(E);
   case UO_Extension:
     // FIXME: Should extension allow i-c-e extension expressions in its scope?
     // If so, we could clear the diagnostic ID.
     return Visit(E->getSubExpr());
   case UO_Plus:
     // The result is just the value.
     return Visit(E->getSubExpr());
   case UO_Minus: {
     if (!Visit(E->getSubExpr()))
       return false;
     if (!Result.isInt()) return Error(E);
     const APSInt &Value = Result.getInt();
     if (Value.isSigned() && Value.isMinSignedValue() && E->canOverflow() &&
         !HandleOverflow(Info, E, -Value.extend(Value.getBitWidth() + 1),
                         E->getType()))
       return false;
     return Success(-Value, E);
   }
   case UO_Not: {
     if (!Visit(E->getSubExpr()))
       return false;
     if (!Result.isInt()) return Error(E);
     return Success(~Result.getInt(), E);
   }
   case UO_LNot: {
     bool bres;
     if (!EvaluateAsBooleanCondition(E->getSubExpr(), bres, Info))
       return false;
     return Success(!bres, E);
   }
   }
 }
 
 /// HandleCast - This is used to evaluate implicit or explicit casts where the
 /// result type is integer.
 bool IntExprEvaluator::VisitCastExpr(const CastExpr *E) {
   const Expr *SubExpr = E->getSubExpr();
   QualType DestType = E->getType();
   QualType SrcType = SubExpr->getType();
 
   switch (E->getCastKind()) {
   case CK_BaseToDerived:
   case CK_DerivedToBase:
   case CK_UncheckedDerivedToBase:
   case CK_Dynamic:
   case CK_ToUnion:
   case CK_ArrayToPointerDecay:
   case CK_FunctionToPointerDecay:
   case CK_NullToPointer:
   case CK_NullToMemberPointer:
   case CK_BaseToDerivedMemberPointer:
   case CK_DerivedToBaseMemberPointer:
   case CK_ReinterpretMemberPointer:
   case CK_ConstructorConversion:
   case CK_IntegralToPointer:
   case CK_ToVoid:
   case CK_VectorSplat:
   case CK_IntegralToFloating:
   case CK_FloatingCast:
   case CK_CPointerToObjCPointerCast:
   case CK_BlockPointerToObjCPointerCast:
   case CK_AnyPointerToBlockPointerCast:
   case CK_ObjCObjectLValueCast:
   case CK_FloatingRealToComplex:
   case CK_FloatingComplexToReal:
   case CK_FloatingComplexCast:
   case CK_FloatingComplexToIntegralComplex:
   case CK_IntegralRealToComplex:
   case CK_IntegralComplexCast:
   case CK_IntegralComplexToFloatingComplex:
   case CK_BuiltinFnToFnPtr:
   case CK_ZeroToOCLOpaqueType:
   case CK_NonAtomicToAtomic:
   case CK_AddressSpaceConversion:
   case CK_IntToOCLSampler:
   case CK_FixedPointCast:
   case CK_IntegralToFixedPoint:
     llvm_unreachable("invalid cast kind for integral value");
 
   case CK_BitCast:
   case CK_Dependent:
   case CK_LValueBitCast:
   case CK_ARCProduceObject:
   case CK_ARCConsumeObject:
   case CK_ARCReclaimReturnedObject:
   case CK_ARCExtendBlockObject:
   case CK_CopyAndAutoreleaseBlockObject:
     return Error(E);
 
   case CK_UserDefinedConversion:
   case CK_LValueToRValue:
   case CK_AtomicToNonAtomic:
   case CK_NoOp:
   case CK_LValueToRValueBitCast:
     return ExprEvaluatorBaseTy::VisitCastExpr(E);
 
   case CK_MemberPointerToBoolean:
   case CK_PointerToBoolean:
   case CK_IntegralToBoolean:
   case CK_FloatingToBoolean:
   case CK_BooleanToSignedIntegral:
   case CK_FloatingComplexToBoolean:
   case CK_IntegralComplexToBoolean: {
     bool BoolResult;
     if (!EvaluateAsBooleanCondition(SubExpr, BoolResult, Info))
       return false;
     uint64_t IntResult = BoolResult;
     if (BoolResult && E->getCastKind() == CK_BooleanToSignedIntegral)
       IntResult = (uint64_t)-1;
     return Success(IntResult, E);
   }
 
   case CK_FixedPointToIntegral: {
     APFixedPoint Src(Info.Ctx.getFixedPointSemantics(SrcType));
     if (!EvaluateFixedPoint(SubExpr, Src, Info))
       return false;
     bool Overflowed;
     llvm::APSInt Result = Src.convertToInt(
         Info.Ctx.getIntWidth(DestType),
         DestType->isSignedIntegerOrEnumerationType(), &Overflowed);
     if (Overflowed && !HandleOverflow(Info, E, Result, DestType))
       return false;
     return Success(Result, E);
   }
 
   case CK_FixedPointToBoolean: {
     // Unsigned padding does not affect this.
     APValue Val;
     if (!Evaluate(Val, Info, SubExpr))
       return false;
     return Success(Val.getFixedPoint().getBoolValue(), E);
   }
 
   case CK_IntegralCast: {
     if (!Visit(SubExpr))
       return false;
 
     if (!Result.isInt()) {
       // Allow casts of address-of-label differences if they are no-ops
       // or narrowing.  (The narrowing case isn't actually guaranteed to
       // be constant-evaluatable except in some narrow cases which are hard
       // to detect here.  We let it through on the assumption the user knows
       // what they are doing.)
       if (Result.isAddrLabelDiff())
         return Info.Ctx.getTypeSize(DestType) <= Info.Ctx.getTypeSize(SrcType);
       // Only allow casts of lvalues if they are lossless.
       return Info.Ctx.getTypeSize(DestType) == Info.Ctx.getTypeSize(SrcType);
     }
 
     return Success(HandleIntToIntCast(Info, E, DestType, SrcType,
                                       Result.getInt()), E);
   }
 
   case CK_PointerToIntegral: {
     CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
 
     LValue LV;
     if (!EvaluatePointer(SubExpr, LV, Info))
       return false;
 
     if (LV.getLValueBase()) {
       // Only allow based lvalue casts if they are lossless.
       // FIXME: Allow a larger integer size than the pointer size, and allow
       // narrowing back down to pointer width in subsequent integral casts.
       // FIXME: Check integer type's active bits, not its type size.
       if (Info.Ctx.getTypeSize(DestType) != Info.Ctx.getTypeSize(SrcType))
         return Error(E);
 
       LV.Designator.setInvalid();
       LV.moveInto(Result);
       return true;
     }
 
     APSInt AsInt;
     APValue V;
     LV.moveInto(V);
     if (!V.toIntegralConstant(AsInt, SrcType, Info.Ctx))
       llvm_unreachable("Can't cast this!");
 
     return Success(HandleIntToIntCast(Info, E, DestType, SrcType, AsInt), E);
   }
 
   case CK_IntegralComplexToReal: {
     ComplexValue C;
     if (!EvaluateComplex(SubExpr, C, Info))
       return false;
     return Success(C.getComplexIntReal(), E);
   }
 
   case CK_FloatingToIntegral: {
     APFloat F(0.0);
     if (!EvaluateFloat(SubExpr, F, Info))
       return false;
 
     APSInt Value;
     if (!HandleFloatToIntCast(Info, E, SrcType, F, DestType, Value))
       return false;
     return Success(Value, E);
   }
   }
 
   llvm_unreachable("unknown cast resulting in integral value");
 }
 
 bool IntExprEvaluator::VisitUnaryReal(const UnaryOperator *E) {
   if (E->getSubExpr()->getType()->isAnyComplexType()) {
     ComplexValue LV;
     if (!EvaluateComplex(E->getSubExpr(), LV, Info))
       return false;
     if (!LV.isComplexInt())
       return Error(E);
     return Success(LV.getComplexIntReal(), E);
   }
 
   return Visit(E->getSubExpr());
 }
 
 bool IntExprEvaluator::VisitUnaryImag(const UnaryOperator *E) {
   if (E->getSubExpr()->getType()->isComplexIntegerType()) {
     ComplexValue LV;
     if (!EvaluateComplex(E->getSubExpr(), LV, Info))
       return false;
     if (!LV.isComplexInt())
       return Error(E);
     return Success(LV.getComplexIntImag(), E);
   }
 
   VisitIgnoredValue(E->getSubExpr());
   return Success(0, E);
 }
 
 bool IntExprEvaluator::VisitSizeOfPackExpr(const SizeOfPackExpr *E) {
   return Success(E->getPackLength(), E);
 }
 
 bool IntExprEvaluator::VisitCXXNoexceptExpr(const CXXNoexceptExpr *E) {
   return Success(E->getValue(), E);
 }
 
 bool IntExprEvaluator::VisitConceptSpecializationExpr(
        const ConceptSpecializationExpr *E) {
   return Success(E->isSatisfied(), E);
 }
 
 bool IntExprEvaluator::VisitRequiresExpr(const RequiresExpr *E) {
   return Success(E->isSatisfied(), E);
 }
 
 bool FixedPointExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
   switch (E->getOpcode()) {
     default:
       // Invalid unary operators
       return Error(E);
     case UO_Plus:
       // The result is just the value.
       return Visit(E->getSubExpr());
     case UO_Minus: {
       if (!Visit(E->getSubExpr())) return false;
       if (!Result.isFixedPoint())
         return Error(E);
       bool Overflowed;
       APFixedPoint Negated = Result.getFixedPoint().negate(&Overflowed);
       if (Overflowed && !HandleOverflow(Info, E, Negated, E->getType()))
         return false;
       return Success(Negated, E);
     }
     case UO_LNot: {
       bool bres;
       if (!EvaluateAsBooleanCondition(E->getSubExpr(), bres, Info))
         return false;
       return Success(!bres, E);
     }
   }
 }
 
 bool FixedPointExprEvaluator::VisitCastExpr(const CastExpr *E) {
   const Expr *SubExpr = E->getSubExpr();
   QualType DestType = E->getType();
   assert(DestType->isFixedPointType() &&
          "Expected destination type to be a fixed point type");
   auto DestFXSema = Info.Ctx.getFixedPointSemantics(DestType);
 
   switch (E->getCastKind()) {
   case CK_FixedPointCast: {
     APFixedPoint Src(Info.Ctx.getFixedPointSemantics(SubExpr->getType()));
     if (!EvaluateFixedPoint(SubExpr, Src, Info))
       return false;
     bool Overflowed;
     APFixedPoint Result = Src.convert(DestFXSema, &Overflowed);
     if (Overflowed) {
       if (Info.checkingForUndefinedBehavior())
         Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
                                          diag::warn_fixedpoint_constant_overflow)
           << Result.toString() << E->getType();
       else if (!HandleOverflow(Info, E, Result, E->getType()))
         return false;
     }
     return Success(Result, E);
   }
   case CK_IntegralToFixedPoint: {
     APSInt Src;
     if (!EvaluateInteger(SubExpr, Src, Info))
       return false;
 
     bool Overflowed;
     APFixedPoint IntResult = APFixedPoint::getFromIntValue(
         Src, Info.Ctx.getFixedPointSemantics(DestType), &Overflowed);
 
     if (Overflowed) {
       if (Info.checkingForUndefinedBehavior())
         Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
                                          diag::warn_fixedpoint_constant_overflow)
           << IntResult.toString() << E->getType();
       else if (!HandleOverflow(Info, E, IntResult, E->getType()))
         return false;
     }
 
     return Success(IntResult, E);
   }
   case CK_NoOp:
   case CK_LValueToRValue:
     return ExprEvaluatorBaseTy::VisitCastExpr(E);
   default:
     return Error(E);
   }
 }
 
 bool FixedPointExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
   if (E->isPtrMemOp() || E->isAssignmentOp() || E->getOpcode() == BO_Comma)
     return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
 
   const Expr *LHS = E->getLHS();
   const Expr *RHS = E->getRHS();
   FixedPointSemantics ResultFXSema =
       Info.Ctx.getFixedPointSemantics(E->getType());
 
   APFixedPoint LHSFX(Info.Ctx.getFixedPointSemantics(LHS->getType()));
   if (!EvaluateFixedPointOrInteger(LHS, LHSFX, Info))
     return false;
   APFixedPoint RHSFX(Info.Ctx.getFixedPointSemantics(RHS->getType()));
   if (!EvaluateFixedPointOrInteger(RHS, RHSFX, Info))
     return false;
 
   bool OpOverflow = false, ConversionOverflow = false;
   APFixedPoint Result(LHSFX.getSemantics());
   switch (E->getOpcode()) {
   case BO_Add: {
     Result = LHSFX.add(RHSFX, &OpOverflow)
                   .convert(ResultFXSema, &ConversionOverflow);
     break;
   }
   case BO_Sub: {
     Result = LHSFX.sub(RHSFX, &OpOverflow)
                   .convert(ResultFXSema, &ConversionOverflow);
     break;
   }
   case BO_Mul: {
     Result = LHSFX.mul(RHSFX, &OpOverflow)
                   .convert(ResultFXSema, &ConversionOverflow);
     break;
   }
   case BO_Div: {
     if (RHSFX.getValue() == 0) {
       Info.FFDiag(E, diag::note_expr_divide_by_zero);
       return false;
     }
     Result = LHSFX.div(RHSFX, &OpOverflow)
                   .convert(ResultFXSema, &ConversionOverflow);
     break;
   }
   default:
     return false;
   }
   if (OpOverflow || ConversionOverflow) {
     if (Info.checkingForUndefinedBehavior())
       Info.Ctx.getDiagnostics().Report(E->getExprLoc(),
                                        diag::warn_fixedpoint_constant_overflow)
         << Result.toString() << E->getType();
     else if (!HandleOverflow(Info, E, Result, E->getType()))
       return false;
   }
   return Success(Result, E);
 }
 
 //===----------------------------------------------------------------------===//
 // Float Evaluation
 //===----------------------------------------------------------------------===//
 
 namespace {
 class FloatExprEvaluator
   : public ExprEvaluatorBase<FloatExprEvaluator> {
   APFloat &Result;
 public:
   FloatExprEvaluator(EvalInfo &info, APFloat &result)
     : ExprEvaluatorBaseTy(info), Result(result) {}
 
   bool Success(const APValue &V, const Expr *e) {
     Result = V.getFloat();
     return true;
   }
 
   bool ZeroInitialization(const Expr *E) {
     Result = APFloat::getZero(Info.Ctx.getFloatTypeSemantics(E->getType()));
     return true;
   }
 
   bool VisitCallExpr(const CallExpr *E);
 
   bool VisitUnaryOperator(const UnaryOperator *E);
   bool VisitBinaryOperator(const BinaryOperator *E);
   bool VisitFloatingLiteral(const FloatingLiteral *E);
   bool VisitCastExpr(const CastExpr *E);
 
   bool VisitUnaryReal(const UnaryOperator *E);
   bool VisitUnaryImag(const UnaryOperator *E);
 
   // FIXME: Missing: array subscript of vector, member of vector
 };
 } // end anonymous namespace
 
 static bool EvaluateFloat(const Expr* E, APFloat& Result, EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isRealFloatingType());
   return FloatExprEvaluator(Info, Result).Visit(E);
 }
 
 static bool TryEvaluateBuiltinNaN(const ASTContext &Context,
                                   QualType ResultTy,
                                   const Expr *Arg,
                                   bool SNaN,
                                   llvm::APFloat &Result) {
   const StringLiteral *S = dyn_cast<StringLiteral>(Arg->IgnoreParenCasts());
   if (!S) return false;
 
   const llvm::fltSemantics &Sem = Context.getFloatTypeSemantics(ResultTy);
 
   llvm::APInt fill;
 
   // Treat empty strings as if they were zero.
   if (S->getString().empty())
     fill = llvm::APInt(32, 0);
   else if (S->getString().getAsInteger(0, fill))
     return false;
 
   if (Context.getTargetInfo().isNan2008()) {
     if (SNaN)
       Result = llvm::APFloat::getSNaN(Sem, false, &fill);
     else
       Result = llvm::APFloat::getQNaN(Sem, false, &fill);
   } else {
     // Prior to IEEE 754-2008, architectures were allowed to choose whether
     // the first bit of their significand was set for qNaN or sNaN. MIPS chose
     // a different encoding to what became a standard in 2008, and for pre-
     // 2008 revisions, MIPS interpreted sNaN-2008 as qNan and qNaN-2008 as
     // sNaN. This is now known as "legacy NaN" encoding.
     if (SNaN)
       Result = llvm::APFloat::getQNaN(Sem, false, &fill);
     else
       Result = llvm::APFloat::getSNaN(Sem, false, &fill);
   }
 
   return true;
 }
 
 bool FloatExprEvaluator::VisitCallExpr(const CallExpr *E) {
   switch (E->getBuiltinCallee()) {
   default:
     return ExprEvaluatorBaseTy::VisitCallExpr(E);
 
   case Builtin::BI__builtin_huge_val:
   case Builtin::BI__builtin_huge_valf:
   case Builtin::BI__builtin_huge_vall:
   case Builtin::BI__builtin_huge_valf128:
   case Builtin::BI__builtin_inf:
   case Builtin::BI__builtin_inff:
   case Builtin::BI__builtin_infl:
   case Builtin::BI__builtin_inff128: {
     const llvm::fltSemantics &Sem =
       Info.Ctx.getFloatTypeSemantics(E->getType());
     Result = llvm::APFloat::getInf(Sem);
     return true;
   }
 
   case Builtin::BI__builtin_nans:
   case Builtin::BI__builtin_nansf:
   case Builtin::BI__builtin_nansl:
   case Builtin::BI__builtin_nansf128:
     if (!TryEvaluateBuiltinNaN(Info.Ctx, E->getType(), E->getArg(0),
                                true, Result))
       return Error(E);
     return true;
 
   case Builtin::BI__builtin_nan:
   case Builtin::BI__builtin_nanf:
   case Builtin::BI__builtin_nanl:
   case Builtin::BI__builtin_nanf128:
     // If this is __builtin_nan() turn this into a nan, otherwise we
     // can't constant fold it.
     if (!TryEvaluateBuiltinNaN(Info.Ctx, E->getType(), E->getArg(0),
                                false, Result))
       return Error(E);
     return true;
 
   case Builtin::BI__builtin_fabs:
   case Builtin::BI__builtin_fabsf:
   case Builtin::BI__builtin_fabsl:
   case Builtin::BI__builtin_fabsf128:
     if (!EvaluateFloat(E->getArg(0), Result, Info))
       return false;
 
     if (Result.isNegative())
       Result.changeSign();
     return true;
 
   // FIXME: Builtin::BI__builtin_powi
   // FIXME: Builtin::BI__builtin_powif
   // FIXME: Builtin::BI__builtin_powil
 
   case Builtin::BI__builtin_copysign:
   case Builtin::BI__builtin_copysignf:
   case Builtin::BI__builtin_copysignl:
   case Builtin::BI__builtin_copysignf128: {
     APFloat RHS(0.);
     if (!EvaluateFloat(E->getArg(0), Result, Info) ||
         !EvaluateFloat(E->getArg(1), RHS, Info))
       return false;
     Result.copySign(RHS);
     return true;
   }
   }
 }
 
 bool FloatExprEvaluator::VisitUnaryReal(const UnaryOperator *E) {
   if (E->getSubExpr()->getType()->isAnyComplexType()) {
     ComplexValue CV;
     if (!EvaluateComplex(E->getSubExpr(), CV, Info))
       return false;
     Result = CV.FloatReal;
     return true;
   }
 
   return Visit(E->getSubExpr());
 }
 
 bool FloatExprEvaluator::VisitUnaryImag(const UnaryOperator *E) {
   if (E->getSubExpr()->getType()->isAnyComplexType()) {
     ComplexValue CV;
     if (!EvaluateComplex(E->getSubExpr(), CV, Info))
       return false;
     Result = CV.FloatImag;
     return true;
   }
 
   VisitIgnoredValue(E->getSubExpr());
   const llvm::fltSemantics &Sem = Info.Ctx.getFloatTypeSemantics(E->getType());
   Result = llvm::APFloat::getZero(Sem);
   return true;
 }
 
 bool FloatExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
   switch (E->getOpcode()) {
   default: return Error(E);
   case UO_Plus:
     return EvaluateFloat(E->getSubExpr(), Result, Info);
   case UO_Minus:
     if (!EvaluateFloat(E->getSubExpr(), Result, Info))
       return false;
     Result.changeSign();
     return true;
   }
 }
 
 bool FloatExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
   if (E->isPtrMemOp() || E->isAssignmentOp() || E->getOpcode() == BO_Comma)
     return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
 
   APFloat RHS(0.0);
   bool LHSOK = EvaluateFloat(E->getLHS(), Result, Info);
   if (!LHSOK && !Info.noteFailure())
     return false;
   return EvaluateFloat(E->getRHS(), RHS, Info) && LHSOK &&
          handleFloatFloatBinOp(Info, E, Result, E->getOpcode(), RHS);
 }
 
 bool FloatExprEvaluator::VisitFloatingLiteral(const FloatingLiteral *E) {
   Result = E->getValue();
   return true;
 }
 
 bool FloatExprEvaluator::VisitCastExpr(const CastExpr *E) {
   const Expr* SubExpr = E->getSubExpr();
 
   switch (E->getCastKind()) {
   default:
     return ExprEvaluatorBaseTy::VisitCastExpr(E);
 
   case CK_IntegralToFloating: {
     APSInt IntResult;
     return EvaluateInteger(SubExpr, IntResult, Info) &&
            HandleIntToFloatCast(Info, E, SubExpr->getType(), IntResult,
                                 E->getType(), Result);
   }
 
   case CK_FloatingCast: {
     if (!Visit(SubExpr))
       return false;
     return HandleFloatToFloatCast(Info, E, SubExpr->getType(), E->getType(),
                                   Result);
   }
 
   case CK_FloatingComplexToReal: {
     ComplexValue V;
     if (!EvaluateComplex(SubExpr, V, Info))
       return false;
     Result = V.getComplexFloatReal();
     return true;
   }
   }
 }
 
 //===----------------------------------------------------------------------===//
 // Complex Evaluation (for float and integer)
 //===----------------------------------------------------------------------===//
 
 namespace {
 class ComplexExprEvaluator
   : public ExprEvaluatorBase<ComplexExprEvaluator> {
   ComplexValue &Result;
 
 public:
   ComplexExprEvaluator(EvalInfo &info, ComplexValue &Result)
     : ExprEvaluatorBaseTy(info), Result(Result) {}
 
   bool Success(const APValue &V, const Expr *e) {
     Result.setFrom(V);
     return true;
   }
 
   bool ZeroInitialization(const Expr *E);
 
   //===--------------------------------------------------------------------===//
   //                            Visitor Methods
   //===--------------------------------------------------------------------===//
 
   bool VisitImaginaryLiteral(const ImaginaryLiteral *E);
   bool VisitCastExpr(const CastExpr *E);
   bool VisitBinaryOperator(const BinaryOperator *E);
   bool VisitUnaryOperator(const UnaryOperator *E);
   bool VisitInitListExpr(const InitListExpr *E);
 };
 } // end anonymous namespace
 
 static bool EvaluateComplex(const Expr *E, ComplexValue &Result,
                             EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isAnyComplexType());
   return ComplexExprEvaluator(Info, Result).Visit(E);
 }
 
 bool ComplexExprEvaluator::ZeroInitialization(const Expr *E) {
   QualType ElemTy = E->getType()->castAs<ComplexType>()->getElementType();
   if (ElemTy->isRealFloatingType()) {
     Result.makeComplexFloat();
     APFloat Zero = APFloat::getZero(Info.Ctx.getFloatTypeSemantics(ElemTy));
     Result.FloatReal = Zero;
     Result.FloatImag = Zero;
   } else {
     Result.makeComplexInt();
     APSInt Zero = Info.Ctx.MakeIntValue(0, ElemTy);
     Result.IntReal = Zero;
     Result.IntImag = Zero;
   }
   return true;
 }
 
 bool ComplexExprEvaluator::VisitImaginaryLiteral(const ImaginaryLiteral *E) {
   const Expr* SubExpr = E->getSubExpr();
 
   if (SubExpr->getType()->isRealFloatingType()) {
     Result.makeComplexFloat();
     APFloat &Imag = Result.FloatImag;
     if (!EvaluateFloat(SubExpr, Imag, Info))
       return false;
 
     Result.FloatReal = APFloat(Imag.getSemantics());
     return true;
   } else {
     assert(SubExpr->getType()->isIntegerType() &&
            "Unexpected imaginary literal.");
 
     Result.makeComplexInt();
     APSInt &Imag = Result.IntImag;
     if (!EvaluateInteger(SubExpr, Imag, Info))
       return false;
 
     Result.IntReal = APSInt(Imag.getBitWidth(), !Imag.isSigned());
     return true;
   }
 }
 
 bool ComplexExprEvaluator::VisitCastExpr(const CastExpr *E) {
 
   switch (E->getCastKind()) {
   case CK_BitCast:
   case CK_BaseToDerived:
   case CK_DerivedToBase:
   case CK_UncheckedDerivedToBase:
   case CK_Dynamic:
   case CK_ToUnion:
   case CK_ArrayToPointerDecay:
   case CK_FunctionToPointerDecay:
   case CK_NullToPointer:
   case CK_NullToMemberPointer:
   case CK_BaseToDerivedMemberPointer:
   case CK_DerivedToBaseMemberPointer:
   case CK_MemberPointerToBoolean:
   case CK_ReinterpretMemberPointer:
   case CK_ConstructorConversion:
   case CK_IntegralToPointer:
   case CK_PointerToIntegral:
   case CK_PointerToBoolean:
   case CK_ToVoid:
   case CK_VectorSplat:
   case CK_IntegralCast:
   case CK_BooleanToSignedIntegral:
   case CK_IntegralToBoolean:
   case CK_IntegralToFloating:
   case CK_FloatingToIntegral:
   case CK_FloatingToBoolean:
   case CK_FloatingCast:
   case CK_CPointerToObjCPointerCast:
   case CK_BlockPointerToObjCPointerCast:
   case CK_AnyPointerToBlockPointerCast:
   case CK_ObjCObjectLValueCast:
   case CK_FloatingComplexToReal:
   case CK_FloatingComplexToBoolean:
   case CK_IntegralComplexToReal:
   case CK_IntegralComplexToBoolean:
   case CK_ARCProduceObject:
   case CK_ARCConsumeObject:
   case CK_ARCReclaimReturnedObject:
   case CK_ARCExtendBlockObject:
   case CK_CopyAndAutoreleaseBlockObject:
   case CK_BuiltinFnToFnPtr:
   case CK_ZeroToOCLOpaqueType:
   case CK_NonAtomicToAtomic:
   case CK_AddressSpaceConversion:
   case CK_IntToOCLSampler:
   case CK_FixedPointCast:
   case CK_FixedPointToBoolean:
   case CK_FixedPointToIntegral:
   case CK_IntegralToFixedPoint:
     llvm_unreachable("invalid cast kind for complex value");
 
   case CK_LValueToRValue:
   case CK_AtomicToNonAtomic:
   case CK_NoOp:
   case CK_LValueToRValueBitCast:
     return ExprEvaluatorBaseTy::VisitCastExpr(E);
 
   case CK_Dependent:
   case CK_LValueBitCast:
   case CK_UserDefinedConversion:
     return Error(E);
 
   case CK_FloatingRealToComplex: {
     APFloat &Real = Result.FloatReal;
     if (!EvaluateFloat(E->getSubExpr(), Real, Info))
       return false;
 
     Result.makeComplexFloat();
     Result.FloatImag = APFloat(Real.getSemantics());
     return true;
   }
 
   case CK_FloatingComplexCast: {
     if (!Visit(E->getSubExpr()))
       return false;
 
     QualType To = E->getType()->castAs<ComplexType>()->getElementType();
     QualType From
       = E->getSubExpr()->getType()->castAs<ComplexType>()->getElementType();
 
     return HandleFloatToFloatCast(Info, E, From, To, Result.FloatReal) &&
            HandleFloatToFloatCast(Info, E, From, To, Result.FloatImag);
   }
 
   case CK_FloatingComplexToIntegralComplex: {
     if (!Visit(E->getSubExpr()))
       return false;
 
     QualType To = E->getType()->castAs<ComplexType>()->getElementType();
     QualType From
       = E->getSubExpr()->getType()->castAs<ComplexType>()->getElementType();
     Result.makeComplexInt();
     return HandleFloatToIntCast(Info, E, From, Result.FloatReal,
                                 To, Result.IntReal) &&
            HandleFloatToIntCast(Info, E, From, Result.FloatImag,
                                 To, Result.IntImag);
   }
 
   case CK_IntegralRealToComplex: {
     APSInt &Real = Result.IntReal;
     if (!EvaluateInteger(E->getSubExpr(), Real, Info))
       return false;
 
     Result.makeComplexInt();
     Result.IntImag = APSInt(Real.getBitWidth(), !Real.isSigned());
     return true;
   }
 
   case CK_IntegralComplexCast: {
     if (!Visit(E->getSubExpr()))
       return false;
 
     QualType To = E->getType()->castAs<ComplexType>()->getElementType();
     QualType From
       = E->getSubExpr()->getType()->castAs<ComplexType>()->getElementType();
 
     Result.IntReal = HandleIntToIntCast(Info, E, To, From, Result.IntReal);
     Result.IntImag = HandleIntToIntCast(Info, E, To, From, Result.IntImag);
     return true;
   }
 
   case CK_IntegralComplexToFloatingComplex: {
     if (!Visit(E->getSubExpr()))
       return false;
 
     QualType To = E->getType()->castAs<ComplexType>()->getElementType();
     QualType From
       = E->getSubExpr()->getType()->castAs<ComplexType>()->getElementType();
     Result.makeComplexFloat();
     return HandleIntToFloatCast(Info, E, From, Result.IntReal,
                                 To, Result.FloatReal) &&
            HandleIntToFloatCast(Info, E, From, Result.IntImag,
                                 To, Result.FloatImag);
   }
   }
 
   llvm_unreachable("unknown cast resulting in complex value");
 }
 
 bool ComplexExprEvaluator::VisitBinaryOperator(const BinaryOperator *E) {
   if (E->isPtrMemOp() || E->isAssignmentOp() || E->getOpcode() == BO_Comma)
     return ExprEvaluatorBaseTy::VisitBinaryOperator(E);
 
   // Track whether the LHS or RHS is real at the type system level. When this is
   // the case we can simplify our evaluation strategy.
   bool LHSReal = false, RHSReal = false;
 
   bool LHSOK;
   if (E->getLHS()->getType()->isRealFloatingType()) {
     LHSReal = true;
     APFloat &Real = Result.FloatReal;
     LHSOK = EvaluateFloat(E->getLHS(), Real, Info);
     if (LHSOK) {
       Result.makeComplexFloat();
       Result.FloatImag = APFloat(Real.getSemantics());
     }
   } else {
     LHSOK = Visit(E->getLHS());
   }
   if (!LHSOK && !Info.noteFailure())
     return false;
 
   ComplexValue RHS;
   if (E->getRHS()->getType()->isRealFloatingType()) {
     RHSReal = true;
     APFloat &Real = RHS.FloatReal;
     if (!EvaluateFloat(E->getRHS(), Real, Info) || !LHSOK)
       return false;
     RHS.makeComplexFloat();
     RHS.FloatImag = APFloat(Real.getSemantics());
   } else if (!EvaluateComplex(E->getRHS(), RHS, Info) || !LHSOK)
     return false;
 
   assert(!(LHSReal && RHSReal) &&
          "Cannot have both operands of a complex operation be real.");
   switch (E->getOpcode()) {
   default: return Error(E);
   case BO_Add:
     if (Result.isComplexFloat()) {
       Result.getComplexFloatReal().add(RHS.getComplexFloatReal(),
                                        APFloat::rmNearestTiesToEven);
       if (LHSReal)
         Result.getComplexFloatImag() = RHS.getComplexFloatImag();
       else if (!RHSReal)
         Result.getComplexFloatImag().add(RHS.getComplexFloatImag(),
                                          APFloat::rmNearestTiesToEven);
     } else {
       Result.getComplexIntReal() += RHS.getComplexIntReal();
       Result.getComplexIntImag() += RHS.getComplexIntImag();
     }
     break;
   case BO_Sub:
     if (Result.isComplexFloat()) {
       Result.getComplexFloatReal().subtract(RHS.getComplexFloatReal(),
                                             APFloat::rmNearestTiesToEven);
       if (LHSReal) {
         Result.getComplexFloatImag() = RHS.getComplexFloatImag();
         Result.getComplexFloatImag().changeSign();
       } else if (!RHSReal) {
         Result.getComplexFloatImag().subtract(RHS.getComplexFloatImag(),
                                               APFloat::rmNearestTiesToEven);
       }
     } else {
       Result.getComplexIntReal() -= RHS.getComplexIntReal();
       Result.getComplexIntImag() -= RHS.getComplexIntImag();
     }
     break;
   case BO_Mul:
     if (Result.isComplexFloat()) {
       // This is an implementation of complex multiplication according to the
       // constraints laid out in C11 Annex G. The implementation uses the
       // following naming scheme:
       //   (a + ib) * (c + id)
       ComplexValue LHS = Result;
       APFloat &A = LHS.getComplexFloatReal();
       APFloat &B = LHS.getComplexFloatImag();
       APFloat &C = RHS.getComplexFloatReal();
       APFloat &D = RHS.getComplexFloatImag();
       APFloat &ResR = Result.getComplexFloatReal();
       APFloat &ResI = Result.getComplexFloatImag();
       if (LHSReal) {
         assert(!RHSReal && "Cannot have two real operands for a complex op!");
         ResR = A * C;
         ResI = A * D;
       } else if (RHSReal) {
         ResR = C * A;
         ResI = C * B;
       } else {
         // In the fully general case, we need to handle NaNs and infinities
         // robustly.
         APFloat AC = A * C;
         APFloat BD = B * D;
         APFloat AD = A * D;
         APFloat BC = B * C;
         ResR = AC - BD;
         ResI = AD + BC;
         if (ResR.isNaN() && ResI.isNaN()) {
           bool Recalc = false;
           if (A.isInfinity() || B.isInfinity()) {
             A = APFloat::copySign(
                 APFloat(A.getSemantics(), A.isInfinity() ? 1 : 0), A);
             B = APFloat::copySign(
                 APFloat(B.getSemantics(), B.isInfinity() ? 1 : 0), B);
             if (C.isNaN())
               C = APFloat::copySign(APFloat(C.getSemantics()), C);
             if (D.isNaN())
               D = APFloat::copySign(APFloat(D.getSemantics()), D);
             Recalc = true;
           }
           if (C.isInfinity() || D.isInfinity()) {
             C = APFloat::copySign(
                 APFloat(C.getSemantics(), C.isInfinity() ? 1 : 0), C);
             D = APFloat::copySign(
                 APFloat(D.getSemantics(), D.isInfinity() ? 1 : 0), D);
             if (A.isNaN())
               A = APFloat::copySign(APFloat(A.getSemantics()), A);
             if (B.isNaN())
               B = APFloat::copySign(APFloat(B.getSemantics()), B);
             Recalc = true;
           }
           if (!Recalc && (AC.isInfinity() || BD.isInfinity() ||
                           AD.isInfinity() || BC.isInfinity())) {
             if (A.isNaN())
               A = APFloat::copySign(APFloat(A.getSemantics()), A);
             if (B.isNaN())
               B = APFloat::copySign(APFloat(B.getSemantics()), B);
             if (C.isNaN())
               C = APFloat::copySign(APFloat(C.getSemantics()), C);
             if (D.isNaN())
               D = APFloat::copySign(APFloat(D.getSemantics()), D);
             Recalc = true;
           }
           if (Recalc) {
             ResR = APFloat::getInf(A.getSemantics()) * (A * C - B * D);
             ResI = APFloat::getInf(A.getSemantics()) * (A * D + B * C);
           }
         }
       }
     } else {
       ComplexValue LHS = Result;
       Result.getComplexIntReal() =
         (LHS.getComplexIntReal() * RHS.getComplexIntReal() -
          LHS.getComplexIntImag() * RHS.getComplexIntImag());
       Result.getComplexIntImag() =
         (LHS.getComplexIntReal() * RHS.getComplexIntImag() +
          LHS.getComplexIntImag() * RHS.getComplexIntReal());
     }
     break;
   case BO_Div:
     if (Result.isComplexFloat()) {
       // This is an implementation of complex division according to the
       // constraints laid out in C11 Annex G. The implementation uses the
       // following naming scheme:
       //   (a + ib) / (c + id)
       ComplexValue LHS = Result;
       APFloat &A = LHS.getComplexFloatReal();
       APFloat &B = LHS.getComplexFloatImag();
       APFloat &C = RHS.getComplexFloatReal();
       APFloat &D = RHS.getComplexFloatImag();
       APFloat &ResR = Result.getComplexFloatReal();
       APFloat &ResI = Result.getComplexFloatImag();
       if (RHSReal) {
         ResR = A / C;
         ResI = B / C;
       } else {
         if (LHSReal) {
           // No real optimizations we can do here, stub out with zero.
           B = APFloat::getZero(A.getSemantics());
         }
         int DenomLogB = 0;
         APFloat MaxCD = maxnum(abs(C), abs(D));
         if (MaxCD.isFinite()) {
           DenomLogB = ilogb(MaxCD);
           C = scalbn(C, -DenomLogB, APFloat::rmNearestTiesToEven);
           D = scalbn(D, -DenomLogB, APFloat::rmNearestTiesToEven);
         }
         APFloat Denom = C * C + D * D;
         ResR = scalbn((A * C + B * D) / Denom, -DenomLogB,
                       APFloat::rmNearestTiesToEven);
         ResI = scalbn((B * C - A * D) / Denom, -DenomLogB,
                       APFloat::rmNearestTiesToEven);
         if (ResR.isNaN() && ResI.isNaN()) {
           if (Denom.isPosZero() && (!A.isNaN() || !B.isNaN())) {
             ResR = APFloat::getInf(ResR.getSemantics(), C.isNegative()) * A;
             ResI = APFloat::getInf(ResR.getSemantics(), C.isNegative()) * B;
           } else if ((A.isInfinity() || B.isInfinity()) && C.isFinite() &&
                      D.isFinite()) {
             A = APFloat::copySign(
                 APFloat(A.getSemantics(), A.isInfinity() ? 1 : 0), A);
             B = APFloat::copySign(
                 APFloat(B.getSemantics(), B.isInfinity() ? 1 : 0), B);
             ResR = APFloat::getInf(ResR.getSemantics()) * (A * C + B * D);
             ResI = APFloat::getInf(ResI.getSemantics()) * (B * C - A * D);
           } else if (MaxCD.isInfinity() && A.isFinite() && B.isFinite()) {
             C = APFloat::copySign(
                 APFloat(C.getSemantics(), C.isInfinity() ? 1 : 0), C);
             D = APFloat::copySign(
                 APFloat(D.getSemantics(), D.isInfinity() ? 1 : 0), D);
             ResR = APFloat::getZero(ResR.getSemantics()) * (A * C + B * D);
             ResI = APFloat::getZero(ResI.getSemantics()) * (B * C - A * D);
           }
         }
       }
     } else {
       if (RHS.getComplexIntReal() == 0 && RHS.getComplexIntImag() == 0)
         return Error(E, diag::note_expr_divide_by_zero);
 
       ComplexValue LHS = Result;
       APSInt Den = RHS.getComplexIntReal() * RHS.getComplexIntReal() +
         RHS.getComplexIntImag() * RHS.getComplexIntImag();
       Result.getComplexIntReal() =
         (LHS.getComplexIntReal() * RHS.getComplexIntReal() +
          LHS.getComplexIntImag() * RHS.getComplexIntImag()) / Den;
       Result.getComplexIntImag() =
         (LHS.getComplexIntImag() * RHS.getComplexIntReal() -
          LHS.getComplexIntReal() * RHS.getComplexIntImag()) / Den;
     }
     break;
   }
 
   return true;
 }
 
 bool ComplexExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
   // Get the operand value into 'Result'.
   if (!Visit(E->getSubExpr()))
     return false;
 
   switch (E->getOpcode()) {
   default:
     return Error(E);
   case UO_Extension:
     return true;
   case UO_Plus:
     // The result is always just the subexpr.
     return true;
   case UO_Minus:
     if (Result.isComplexFloat()) {
       Result.getComplexFloatReal().changeSign();
       Result.getComplexFloatImag().changeSign();
     }
     else {
       Result.getComplexIntReal() = -Result.getComplexIntReal();
       Result.getComplexIntImag() = -Result.getComplexIntImag();
     }
     return true;
   case UO_Not:
     if (Result.isComplexFloat())
       Result.getComplexFloatImag().changeSign();
     else
       Result.getComplexIntImag() = -Result.getComplexIntImag();
     return true;
   }
 }
 
 bool ComplexExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
   if (E->getNumInits() == 2) {
     if (E->getType()->isComplexType()) {
       Result.makeComplexFloat();
       if (!EvaluateFloat(E->getInit(0), Result.FloatReal, Info))
         return false;
       if (!EvaluateFloat(E->getInit(1), Result.FloatImag, Info))
         return false;
     } else {
       Result.makeComplexInt();
       if (!EvaluateInteger(E->getInit(0), Result.IntReal, Info))
         return false;
       if (!EvaluateInteger(E->getInit(1), Result.IntImag, Info))
         return false;
     }
     return true;
   }
   return ExprEvaluatorBaseTy::VisitInitListExpr(E);
 }
 
 //===----------------------------------------------------------------------===//
 // Atomic expression evaluation, essentially just handling the NonAtomicToAtomic
 // implicit conversion.
 //===----------------------------------------------------------------------===//
 
 namespace {
 class AtomicExprEvaluator :
     public ExprEvaluatorBase<AtomicExprEvaluator> {
   const LValue *This;
   APValue &Result;
 public:
   AtomicExprEvaluator(EvalInfo &Info, const LValue *This, APValue &Result)
       : ExprEvaluatorBaseTy(Info), This(This), Result(Result) {}
 
   bool Success(const APValue &V, const Expr *E) {
     Result = V;
     return true;
   }
 
   bool ZeroInitialization(const Expr *E) {
     ImplicitValueInitExpr VIE(
         E->getType()->castAs<AtomicType>()->getValueType());
     // For atomic-qualified class (and array) types in C++, initialize the
     // _Atomic-wrapped subobject directly, in-place.
     return This ? EvaluateInPlace(Result, Info, *This, &VIE)
                 : Evaluate(Result, Info, &VIE);
   }
 
   bool VisitCastExpr(const CastExpr *E) {
     switch (E->getCastKind()) {
     default:
       return ExprEvaluatorBaseTy::VisitCastExpr(E);
     case CK_NonAtomicToAtomic:
       return This ? EvaluateInPlace(Result, Info, *This, E->getSubExpr())
                   : Evaluate(Result, Info, E->getSubExpr());
     }
   }
 };
 } // end anonymous namespace
 
 static bool EvaluateAtomic(const Expr *E, const LValue *This, APValue &Result,
                            EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isAtomicType());
   return AtomicExprEvaluator(Info, This, Result).Visit(E);
 }
 
 //===----------------------------------------------------------------------===//
 // Void expression evaluation, primarily for a cast to void on the LHS of a
 // comma operator
 //===----------------------------------------------------------------------===//
 
 namespace {
 class VoidExprEvaluator
   : public ExprEvaluatorBase<VoidExprEvaluator> {
 public:
   VoidExprEvaluator(EvalInfo &Info) : ExprEvaluatorBaseTy(Info) {}
 
   bool Success(const APValue &V, const Expr *e) { return true; }
 
   bool ZeroInitialization(const Expr *E) { return true; }
 
   bool VisitCastExpr(const CastExpr *E) {
     switch (E->getCastKind()) {
     default:
       return ExprEvaluatorBaseTy::VisitCastExpr(E);
     case CK_ToVoid:
       VisitIgnoredValue(E->getSubExpr());
       return true;
     }
   }
 
   bool VisitCallExpr(const CallExpr *E) {
     switch (E->getBuiltinCallee()) {
     case Builtin::BI__assume:
     case Builtin::BI__builtin_assume:
       // The argument is not evaluated!
       return true;
 
     case Builtin::BI__builtin_operator_delete:
       return HandleOperatorDeleteCall(Info, E);
 
     default:
       break;
     }
 
     return ExprEvaluatorBaseTy::VisitCallExpr(E);
   }
 
   bool VisitCXXDeleteExpr(const CXXDeleteExpr *E);
 };
 } // end anonymous namespace
 
 bool VoidExprEvaluator::VisitCXXDeleteExpr(const CXXDeleteExpr *E) {
   // We cannot speculatively evaluate a delete expression.
   if (Info.SpeculativeEvaluationDepth)
     return false;
 
   FunctionDecl *OperatorDelete = E->getOperatorDelete();
   if (!OperatorDelete->isReplaceableGlobalAllocationFunction()) {
     Info.FFDiag(E, diag::note_constexpr_new_non_replaceable)
         << isa<CXXMethodDecl>(OperatorDelete) << OperatorDelete;
     return false;
   }
 
   const Expr *Arg = E->getArgument();
 
   LValue Pointer;
   if (!EvaluatePointer(Arg, Pointer, Info))
     return false;
   if (Pointer.Designator.Invalid)
     return false;
 
   // Deleting a null pointer has no effect.
   if (Pointer.isNullPointer()) {
     // This is the only case where we need to produce an extension warning:
     // the only other way we can succeed is if we find a dynamic allocation,
     // and we will have warned when we allocated it in that case.
     if (!Info.getLangOpts().CPlusPlus20)
       Info.CCEDiag(E, diag::note_constexpr_new);
     return true;
   }
 
   Optional<DynAlloc *> Alloc = CheckDeleteKind(
       Info, E, Pointer, E->isArrayForm() ? DynAlloc::ArrayNew : DynAlloc::New);
   if (!Alloc)
     return false;
   QualType AllocType = Pointer.Base.getDynamicAllocType();
 
   // For the non-array case, the designator must be empty if the static type
   // does not have a virtual destructor.
   if (!E->isArrayForm() && Pointer.Designator.Entries.size() != 0 &&
       !hasVirtualDestructor(Arg->getType()->getPointeeType())) {
     Info.FFDiag(E, diag::note_constexpr_delete_base_nonvirt_dtor)
         << Arg->getType()->getPointeeType() << AllocType;
     return false;
   }
 
   // For a class type with a virtual destructor, the selected operator delete
   // is the one looked up when building the destructor.
   if (!E->isArrayForm() && !E->isGlobalDelete()) {
     const FunctionDecl *VirtualDelete = getVirtualOperatorDelete(AllocType);
     if (VirtualDelete &&
         !VirtualDelete->isReplaceableGlobalAllocationFunction()) {
       Info.FFDiag(E, diag::note_constexpr_new_non_replaceable)
           << isa<CXXMethodDecl>(VirtualDelete) << VirtualDelete;
       return false;
     }
   }
 
   if (!HandleDestruction(Info, E->getExprLoc(), Pointer.getLValueBase(),
                          (*Alloc)->Value, AllocType))
     return false;
 
   if (!Info.HeapAllocs.erase(Pointer.Base.dyn_cast<DynamicAllocLValue>())) {
     // The element was already erased. This means the destructor call also
     // deleted the object.
     // FIXME: This probably results in undefined behavior before we get this
     // far, and should be diagnosed elsewhere first.
     Info.FFDiag(E, diag::note_constexpr_double_delete);
     return false;
   }
 
   return true;
 }
 
 static bool EvaluateVoid(const Expr *E, EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isVoidType());
   return VoidExprEvaluator(Info).Visit(E);
 }
 
 //===----------------------------------------------------------------------===//
 // Top level Expr::EvaluateAsRValue method.
 //===----------------------------------------------------------------------===//
 
 static bool Evaluate(APValue &Result, EvalInfo &Info, const Expr *E) {
   // In C, function designators are not lvalues, but we evaluate them as if they
   // are.
   QualType T = E->getType();
   if (E->isGLValue() || T->isFunctionType()) {
     LValue LV;
     if (!EvaluateLValue(E, LV, Info))
       return false;
     LV.moveInto(Result);
   } else if (T->isVectorType()) {
     if (!EvaluateVector(E, Result, Info))
       return false;
   } else if (T->isIntegralOrEnumerationType()) {
     if (!IntExprEvaluator(Info, Result).Visit(E))
       return false;
   } else if (T->hasPointerRepresentation()) {
     LValue LV;
     if (!EvaluatePointer(E, LV, Info))
       return false;
     LV.moveInto(Result);
   } else if (T->isRealFloatingType()) {
     llvm::APFloat F(0.0);
     if (!EvaluateFloat(E, F, Info))
       return false;
     Result = APValue(F);
   } else if (T->isAnyComplexType()) {
     ComplexValue C;
     if (!EvaluateComplex(E, C, Info))
       return false;
     C.moveInto(Result);
   } else if (T->isFixedPointType()) {
     if (!FixedPointExprEvaluator(Info, Result).Visit(E)) return false;
   } else if (T->isMemberPointerType()) {
     MemberPtr P;
     if (!EvaluateMemberPointer(E, P, Info))
       return false;
     P.moveInto(Result);
     return true;
   } else if (T->isArrayType()) {
     LValue LV;
     APValue &Value =
         Info.CurrentCall->createTemporary(E, T, false, LV);
     if (!EvaluateArray(E, LV, Value, Info))
       return false;
     Result = Value;
   } else if (T->isRecordType()) {
     LValue LV;
     APValue &Value = Info.CurrentCall->createTemporary(E, T, false, LV);
     if (!EvaluateRecord(E, LV, Value, Info))
       return false;
     Result = Value;
   } else if (T->isVoidType()) {
     if (!Info.getLangOpts().CPlusPlus11)
       Info.CCEDiag(E, diag::note_constexpr_nonliteral)
         << E->getType();
     if (!EvaluateVoid(E, Info))
       return false;
   } else if (T->isAtomicType()) {
     QualType Unqual = T.getAtomicUnqualifiedType();
     if (Unqual->isArrayType() || Unqual->isRecordType()) {
       LValue LV;
       APValue &Value = Info.CurrentCall->createTemporary(E, Unqual, false, LV);
       if (!EvaluateAtomic(E, &LV, Value, Info))
         return false;
     } else {
       if (!EvaluateAtomic(E, nullptr, Result, Info))
         return false;
     }
   } else if (Info.getLangOpts().CPlusPlus11) {
     Info.FFDiag(E, diag::note_constexpr_nonliteral) << E->getType();
     return false;
   } else {
     Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
     return false;
   }
 
   return true;
 }
 
 /// EvaluateInPlace - Evaluate an expression in-place in an APValue. In some
 /// cases, the in-place evaluation is essential, since later initializers for
 /// an object can indirectly refer to subobjects which were initialized earlier.
 static bool EvaluateInPlace(APValue &Result, EvalInfo &Info, const LValue &This,
                             const Expr *E, bool AllowNonLiteralTypes) {
   assert(!E->isValueDependent());
 
   if (!AllowNonLiteralTypes && !CheckLiteralType(Info, E, &This))
     return false;
 
   if (E->isRValue()) {
     // Evaluate arrays and record types in-place, so that later initializers can
     // refer to earlier-initialized members of the object.
     QualType T = E->getType();
     if (T->isArrayType())
       return EvaluateArray(E, This, Result, Info);
     else if (T->isRecordType())
       return EvaluateRecord(E, This, Result, Info);
     else if (T->isAtomicType()) {
       QualType Unqual = T.getAtomicUnqualifiedType();
       if (Unqual->isArrayType() || Unqual->isRecordType())
         return EvaluateAtomic(E, &This, Result, Info);
     }
   }
 
   // For any other type, in-place evaluation is unimportant.
   return Evaluate(Result, Info, E);
 }
 
 /// EvaluateAsRValue - Try to evaluate this expression, performing an implicit
 /// lvalue-to-rvalue cast if it is an lvalue.
 static bool EvaluateAsRValue(EvalInfo &Info, const Expr *E, APValue &Result) {
   if (Info.EnableNewConstInterp) {
     if (!Info.Ctx.getInterpContext().evaluateAsRValue(Info, E, Result))
       return false;
   } else {
     if (E->getType().isNull())
       return false;
 
     if (!CheckLiteralType(Info, E))
       return false;
 
     if (!::Evaluate(Result, Info, E))
       return false;
 
     if (E->isGLValue()) {
       LValue LV;
       LV.setFrom(Info.Ctx, Result);
       if (!handleLValueToRValueConversion(Info, E, E->getType(), LV, Result))
         return false;
     }
   }
 
   // Check this core constant expression is a constant expression.
   return CheckConstantExpression(Info, E->getExprLoc(), E->getType(), Result) &&
          CheckMemoryLeaks(Info);
 }
 
 static bool FastEvaluateAsRValue(const Expr *Exp, Expr::EvalResult &Result,
                                  const ASTContext &Ctx, bool &IsConst) {
   // Fast-path evaluations of integer literals, since we sometimes see files
   // containing vast quantities of these.
   if (const IntegerLiteral *L = dyn_cast<IntegerLiteral>(Exp)) {
     Result.Val = APValue(APSInt(L->getValue(),
                                 L->getType()->isUnsignedIntegerType()));
     IsConst = true;
     return true;
   }
 
   // This case should be rare, but we need to check it before we check on
   // the type below.
   if (Exp->getType().isNull()) {
     IsConst = false;
     return true;
   }
 
   // FIXME: Evaluating values of large array and record types can cause
   // performance problems. Only do so in C++11 for now.
   if (Exp->isRValue() && (Exp->getType()->isArrayType() ||
                           Exp->getType()->isRecordType()) &&
       !Ctx.getLangOpts().CPlusPlus11) {
     IsConst = false;
     return true;
   }
   return false;
 }
 
 static bool hasUnacceptableSideEffect(Expr::EvalStatus &Result,
                                       Expr::SideEffectsKind SEK) {
   return (SEK < Expr::SE_AllowSideEffects && Result.HasSideEffects) ||
          (SEK < Expr::SE_AllowUndefinedBehavior && Result.HasUndefinedBehavior);
 }
 
 static bool EvaluateAsRValue(const Expr *E, Expr::EvalResult &Result,
                              const ASTContext &Ctx, EvalInfo &Info) {
   bool IsConst;
   if (FastEvaluateAsRValue(E, Result, Ctx, IsConst))
     return IsConst;
 
   return EvaluateAsRValue(Info, E, Result.Val);
 }
 
 static bool EvaluateAsInt(const Expr *E, Expr::EvalResult &ExprResult,
                           const ASTContext &Ctx,
                           Expr::SideEffectsKind AllowSideEffects,
                           EvalInfo &Info) {
   if (!E->getType()->isIntegralOrEnumerationType())
     return false;
 
   if (!::EvaluateAsRValue(E, ExprResult, Ctx, Info) ||
       !ExprResult.Val.isInt() ||
       hasUnacceptableSideEffect(ExprResult, AllowSideEffects))
     return false;
 
   return true;
 }
 
 static bool EvaluateAsFixedPoint(const Expr *E, Expr::EvalResult &ExprResult,
                                  const ASTContext &Ctx,
                                  Expr::SideEffectsKind AllowSideEffects,
                                  EvalInfo &Info) {
   if (!E->getType()->isFixedPointType())
     return false;
 
   if (!::EvaluateAsRValue(E, ExprResult, Ctx, Info))
     return false;
 
   if (!ExprResult.Val.isFixedPoint() ||
       hasUnacceptableSideEffect(ExprResult, AllowSideEffects))
     return false;
 
   return true;
 }
 
 /// EvaluateAsRValue - Return true if this is a constant which we can fold using
 /// any crazy technique (that has nothing to do with language standards) that
 /// we want to.  If this function returns true, it returns the folded constant
 /// in Result. If this expression is a glvalue, an lvalue-to-rvalue conversion
 /// will be applied to the result.
 bool Expr::EvaluateAsRValue(EvalResult &Result, const ASTContext &Ctx,
                             bool InConstantContext) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
   EvalInfo Info(Ctx, Result, EvalInfo::EM_IgnoreSideEffects);
   Info.InConstantContext = InConstantContext;
   return ::EvaluateAsRValue(this, Result, Ctx, Info);
 }
 
 bool Expr::EvaluateAsBooleanCondition(bool &Result, const ASTContext &Ctx,
                                       bool InConstantContext) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
   EvalResult Scratch;
   return EvaluateAsRValue(Scratch, Ctx, InConstantContext) &&
          HandleConversionToBool(Scratch.Val, Result);
 }
 
 bool Expr::EvaluateAsInt(EvalResult &Result, const ASTContext &Ctx,
                          SideEffectsKind AllowSideEffects,
                          bool InConstantContext) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
   EvalInfo Info(Ctx, Result, EvalInfo::EM_IgnoreSideEffects);
   Info.InConstantContext = InConstantContext;
   return ::EvaluateAsInt(this, Result, Ctx, AllowSideEffects, Info);
 }
 
 bool Expr::EvaluateAsFixedPoint(EvalResult &Result, const ASTContext &Ctx,
                                 SideEffectsKind AllowSideEffects,
                                 bool InConstantContext) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
   EvalInfo Info(Ctx, Result, EvalInfo::EM_IgnoreSideEffects);
   Info.InConstantContext = InConstantContext;
   return ::EvaluateAsFixedPoint(this, Result, Ctx, AllowSideEffects, Info);
 }
 
 bool Expr::EvaluateAsFloat(APFloat &Result, const ASTContext &Ctx,
                            SideEffectsKind AllowSideEffects,
                            bool InConstantContext) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   if (!getType()->isRealFloatingType())
     return false;
 
   EvalResult ExprResult;
   if (!EvaluateAsRValue(ExprResult, Ctx, InConstantContext) ||
       !ExprResult.Val.isFloat() ||
       hasUnacceptableSideEffect(ExprResult, AllowSideEffects))
     return false;
 
   Result = ExprResult.Val.getFloat();
   return true;
 }
 
 bool Expr::EvaluateAsLValue(EvalResult &Result, const ASTContext &Ctx,
                             bool InConstantContext) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   EvalInfo Info(Ctx, Result, EvalInfo::EM_ConstantFold);
   Info.InConstantContext = InConstantContext;
   LValue LV;
   CheckedTemporaries CheckedTemps;
   if (!EvaluateLValue(this, LV, Info) || !Info.discardCleanups() ||
       Result.HasSideEffects ||
       !CheckLValueConstantExpression(Info, getExprLoc(),
                                      Ctx.getLValueReferenceType(getType()), LV,
                                      Expr::EvaluateForCodeGen, CheckedTemps))
     return false;
 
   LV.moveInto(Result.Val);
   return true;
 }
 
 bool Expr::EvaluateAsConstantExpr(EvalResult &Result, ConstExprUsage Usage,
                                   const ASTContext &Ctx, bool InPlace) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   EvalInfo::EvaluationMode EM = EvalInfo::EM_ConstantExpression;
   EvalInfo Info(Ctx, Result, EM);
   Info.InConstantContext = true;
 
   if (InPlace) {
     Info.setEvaluatingDecl(this, Result.Val);
     LValue LVal;
     LVal.set(this);
     if (!::EvaluateInPlace(Result.Val, Info, LVal, this) ||
         Result.HasSideEffects)
       return false;
   } else if (!::Evaluate(Result.Val, Info, this) || Result.HasSideEffects)
     return false;
 
   if (!Info.discardCleanups())
     llvm_unreachable("Unhandled cleanup; missing full expression marker?");
 
   return CheckConstantExpression(Info, getExprLoc(), getStorageType(Ctx, this),
                                  Result.Val, Usage) &&
          CheckMemoryLeaks(Info);
 }
 
 bool Expr::EvaluateAsInitializer(APValue &Value, const ASTContext &Ctx,
                                  const VarDecl *VD,
                             SmallVectorImpl<PartialDiagnosticAt> &Notes) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   // FIXME: Evaluating initializers for large array and record types can cause
   // performance problems. Only do so in C++11 for now.
   if (isRValue() && (getType()->isArrayType() || getType()->isRecordType()) &&
       !Ctx.getLangOpts().CPlusPlus11)
     return false;
 
   Expr::EvalStatus EStatus;
   EStatus.Diag = &Notes;
 
   EvalInfo Info(Ctx, EStatus, VD->isConstexpr()
                                       ? EvalInfo::EM_ConstantExpression
                                       : EvalInfo::EM_ConstantFold);
   Info.setEvaluatingDecl(VD, Value);
   Info.InConstantContext = true;
 
   SourceLocation DeclLoc = VD->getLocation();
   QualType DeclTy = VD->getType();
 
   if (Info.EnableNewConstInterp) {
     auto &InterpCtx = const_cast<ASTContext &>(Ctx).getInterpContext();
     if (!InterpCtx.evaluateAsInitializer(Info, VD, Value))
       return false;
   } else {
     LValue LVal;
     LVal.set(VD);
 
     if (!EvaluateInPlace(Value, Info, LVal, this,
                          /*AllowNonLiteralTypes=*/true) ||
         EStatus.HasSideEffects)
       return false;
 
     // At this point, any lifetime-extended temporaries are completely
     // initialized.
     Info.performLifetimeExtension();
 
     if (!Info.discardCleanups())
       llvm_unreachable("Unhandled cleanup; missing full expression marker?");
   }
   return CheckConstantExpression(Info, DeclLoc, DeclTy, Value) &&
          CheckMemoryLeaks(Info);
 }
 
 bool VarDecl::evaluateDestruction(
     SmallVectorImpl<PartialDiagnosticAt> &Notes) const {
   Expr::EvalStatus EStatus;
   EStatus.Diag = &Notes;
 
   // Make a copy of the value for the destructor to mutate, if we know it.
   // Otherwise, treat the value as default-initialized; if the destructor works
   // anyway, then the destruction is constant (and must be essentially empty).
   APValue DestroyedValue;
   if (getEvaluatedValue() && !getEvaluatedValue()->isAbsent())
     DestroyedValue = *getEvaluatedValue();
   else if (!getDefaultInitValue(getType(), DestroyedValue))
     return false;
 
   EvalInfo Info(getASTContext(), EStatus, EvalInfo::EM_ConstantExpression);
   Info.setEvaluatingDecl(this, DestroyedValue,
                          EvalInfo::EvaluatingDeclKind::Dtor);
   Info.InConstantContext = true;
 
   SourceLocation DeclLoc = getLocation();
   QualType DeclTy = getType();
 
   LValue LVal;
   LVal.set(this);
 
   if (!HandleDestruction(Info, DeclLoc, LVal.Base, DestroyedValue, DeclTy) ||
       EStatus.HasSideEffects)
     return false;
 
   if (!Info.discardCleanups())
     llvm_unreachable("Unhandled cleanup; missing full expression marker?");
 
   ensureEvaluatedStmt()->HasConstantDestruction = true;
   return true;
 }
 
 /// isEvaluatable - Call EvaluateAsRValue to see if this expression can be
 /// constant folded, but discard the result.
 bool Expr::isEvaluatable(const ASTContext &Ctx, SideEffectsKind SEK) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   EvalResult Result;
   return EvaluateAsRValue(Result, Ctx, /* in constant context */ true) &&
          !hasUnacceptableSideEffect(Result, SEK);
 }
 
 APSInt Expr::EvaluateKnownConstInt(const ASTContext &Ctx,
                     SmallVectorImpl<PartialDiagnosticAt> *Diag) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   EvalResult EVResult;
   EVResult.Diag = Diag;
   EvalInfo Info(Ctx, EVResult, EvalInfo::EM_IgnoreSideEffects);
   Info.InConstantContext = true;
 
   bool Result = ::EvaluateAsRValue(this, EVResult, Ctx, Info);
   (void)Result;
   assert(Result && "Could not evaluate expression");
   assert(EVResult.Val.isInt() && "Expression did not evaluate to integer");
 
   return EVResult.Val.getInt();
 }
 
 APSInt Expr::EvaluateKnownConstIntCheckOverflow(
     const ASTContext &Ctx, SmallVectorImpl<PartialDiagnosticAt> *Diag) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   EvalResult EVResult;
   EVResult.Diag = Diag;
   EvalInfo Info(Ctx, EVResult, EvalInfo::EM_IgnoreSideEffects);
   Info.InConstantContext = true;
   Info.CheckingForUndefinedBehavior = true;
 
   bool Result = ::EvaluateAsRValue(Info, this, EVResult.Val);
   (void)Result;
   assert(Result && "Could not evaluate expression");
   assert(EVResult.Val.isInt() && "Expression did not evaluate to integer");
 
   return EVResult.Val.getInt();
 }
 
 void Expr::EvaluateForOverflow(const ASTContext &Ctx) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   bool IsConst;
   EvalResult EVResult;
   if (!FastEvaluateAsRValue(this, EVResult, Ctx, IsConst)) {
     EvalInfo Info(Ctx, EVResult, EvalInfo::EM_IgnoreSideEffects);
     Info.CheckingForUndefinedBehavior = true;
     (void)::EvaluateAsRValue(Info, this, EVResult.Val);
   }
 }
 
 bool Expr::EvalResult::isGlobalLValue() const {
   assert(Val.isLValue());
   return IsGlobalLValue(Val.getLValueBase());
 }
 
 
 /// isIntegerConstantExpr - this recursive routine will test if an expression is
 /// an integer constant expression.
 
 /// FIXME: Pass up a reason why! Invalid operation in i-c-e, division by zero,
 /// comma, etc
 
 // CheckICE - This function does the fundamental ICE checking: the returned
 // ICEDiag contains an ICEKind indicating whether the expression is an ICE,
 // and a (possibly null) SourceLocation indicating the location of the problem.
 //
 // Note that to reduce code duplication, this helper does no evaluation
 // itself; the caller checks whether the expression is evaluatable, and
 // in the rare cases where CheckICE actually cares about the evaluated
 // value, it calls into Evaluate.
 
 namespace {
 
 enum ICEKind {
   /// This expression is an ICE.
   IK_ICE,
   /// This expression is not an ICE, but if it isn't evaluated, it's
   /// a legal subexpression for an ICE. This return value is used to handle
   /// the comma operator in C99 mode, and non-constant subexpressions.
   IK_ICEIfUnevaluated,
   /// This expression is not an ICE, and is not a legal subexpression for one.
   IK_NotICE
 };
 
 struct ICEDiag {
   ICEKind Kind;
   SourceLocation Loc;
 
   ICEDiag(ICEKind IK, SourceLocation l) : Kind(IK), Loc(l) {}
 };
 
 }
 
 static ICEDiag NoDiag() { return ICEDiag(IK_ICE, SourceLocation()); }
 
 static ICEDiag Worst(ICEDiag A, ICEDiag B) { return A.Kind >= B.Kind ? A : B; }
 
 static ICEDiag CheckEvalInICE(const Expr* E, const ASTContext &Ctx) {
   Expr::EvalResult EVResult;
   Expr::EvalStatus Status;
   EvalInfo Info(Ctx, Status, EvalInfo::EM_ConstantExpression);
 
   Info.InConstantContext = true;
   if (!::EvaluateAsRValue(E, EVResult, Ctx, Info) || EVResult.HasSideEffects ||
       !EVResult.Val.isInt())
     return ICEDiag(IK_NotICE, E->getBeginLoc());
 
   return NoDiag();
 }
 
 static ICEDiag CheckICE(const Expr* E, const ASTContext &Ctx) {
   assert(!E->isValueDependent() && "Should not see value dependent exprs!");
   if (!E->getType()->isIntegralOrEnumerationType())
     return ICEDiag(IK_NotICE, E->getBeginLoc());
 
   switch (E->getStmtClass()) {
 #define ABSTRACT_STMT(Node)
 #define STMT(Node, Base) case Expr::Node##Class:
 #define EXPR(Node, Base)
 #include "clang/AST/StmtNodes.inc"
   case Expr::PredefinedExprClass:
   case Expr::FloatingLiteralClass:
   case Expr::ImaginaryLiteralClass:
   case Expr::StringLiteralClass:
   case Expr::ArraySubscriptExprClass:
   case Expr::MatrixSubscriptExprClass:
   case Expr::OMPArraySectionExprClass:
   case Expr::OMPArrayShapingExprClass:
   case Expr::OMPIteratorExprClass:
   case Expr::MemberExprClass:
   case Expr::CompoundAssignOperatorClass:
   case Expr::CompoundLiteralExprClass:
   case Expr::ExtVectorElementExprClass:
   case Expr::DesignatedInitExprClass:
   case Expr::ArrayInitLoopExprClass:
   case Expr::ArrayInitIndexExprClass:
   case Expr::NoInitExprClass:
   case Expr::DesignatedInitUpdateExprClass:
   case Expr::ImplicitValueInitExprClass:
   case Expr::ParenListExprClass:
   case Expr::VAArgExprClass:
   case Expr::AddrLabelExprClass:
   case Expr::StmtExprClass:
   case Expr::CXXMemberCallExprClass:
   case Expr::CUDAKernelCallExprClass:
   case Expr::CXXAddrspaceCastExprClass:
   case Expr::CXXDynamicCastExprClass:
   case Expr::CXXTypeidExprClass:
   case Expr::CXXUuidofExprClass:
   case Expr::MSPropertyRefExprClass:
   case Expr::MSPropertySubscriptExprClass:
   case Expr::CXXNullPtrLiteralExprClass:
   case Expr::UserDefinedLiteralClass:
   case Expr::CXXThisExprClass:
   case Expr::CXXThrowExprClass:
   case Expr::CXXNewExprClass:
   case Expr::CXXDeleteExprClass:
   case Expr::CXXPseudoDestructorExprClass:
   case Expr::UnresolvedLookupExprClass:
   case Expr::TypoExprClass:
   case Expr::RecoveryExprClass:
   case Expr::DependentScopeDeclRefExprClass:
   case Expr::CXXConstructExprClass:
   case Expr::CXXInheritedCtorInitExprClass:
   case Expr::CXXStdInitializerListExprClass:
   case Expr::CXXBindTemporaryExprClass:
   case Expr::ExprWithCleanupsClass:
   case Expr::CXXTemporaryObjectExprClass:
   case Expr::CXXUnresolvedConstructExprClass:
   case Expr::CXXDependentScopeMemberExprClass:
   case Expr::UnresolvedMemberExprClass:
   case Expr::ObjCStringLiteralClass:
   case Expr::ObjCBoxedExprClass:
   case Expr::ObjCArrayLiteralClass:
   case Expr::ObjCDictionaryLiteralClass:
   case Expr::ObjCEncodeExprClass:
   case Expr::ObjCMessageExprClass:
   case Expr::ObjCSelectorExprClass:
   case Expr::ObjCProtocolExprClass:
   case Expr::ObjCIvarRefExprClass:
   case Expr::ObjCPropertyRefExprClass:
   case Expr::ObjCSubscriptRefExprClass:
   case Expr::ObjCIsaExprClass:
   case Expr::ObjCAvailabilityCheckExprClass:
   case Expr::ShuffleVectorExprClass:
   case Expr::ConvertVectorExprClass:
   case Expr::BlockExprClass:
   case Expr::NoStmtClass:
   case Expr::OpaqueValueExprClass:
   case Expr::PackExpansionExprClass:
   case Expr::SubstNonTypeTemplateParmPackExprClass:
   case Expr::FunctionParmPackExprClass:
   case Expr::AsTypeExprClass:
   case Expr::ObjCIndirectCopyRestoreExprClass:
   case Expr::MaterializeTemporaryExprClass:
   case Expr::PseudoObjectExprClass:
   case Expr::AtomicExprClass:
   case Expr::LambdaExprClass:
   case Expr::CXXFoldExprClass:
   case Expr::CoawaitExprClass:
   case Expr::DependentCoawaitExprClass:
   case Expr::CoyieldExprClass:
     return ICEDiag(IK_NotICE, E->getBeginLoc());
 
   case Expr::InitListExprClass: {
     // C++03 [dcl.init]p13: If T is a scalar type, then a declaration of the
     // form "T x = { a };" is equivalent to "T x = a;".
     // Unless we're initializing a reference, T is a scalar as it is known to be
     // of integral or enumeration type.
     if (E->isRValue())
       if (cast<InitListExpr>(E)->getNumInits() == 1)
         return CheckICE(cast<InitListExpr>(E)->getInit(0), Ctx);
     return ICEDiag(IK_NotICE, E->getBeginLoc());
   }
 
   case Expr::SizeOfPackExprClass:
   case Expr::GNUNullExprClass:
   case Expr::SourceLocExprClass:
     return NoDiag();
 
   case Expr::SubstNonTypeTemplateParmExprClass:
     return
       CheckICE(cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement(), Ctx);
 
   case Expr::ConstantExprClass:
     return CheckICE(cast<ConstantExpr>(E)->getSubExpr(), Ctx);
 
   case Expr::ParenExprClass:
     return CheckICE(cast<ParenExpr>(E)->getSubExpr(), Ctx);
   case Expr::GenericSelectionExprClass:
     return CheckICE(cast<GenericSelectionExpr>(E)->getResultExpr(), Ctx);
   case Expr::IntegerLiteralClass:
   case Expr::FixedPointLiteralClass:
   case Expr::CharacterLiteralClass:
   case Expr::ObjCBoolLiteralExprClass:
   case Expr::CXXBoolLiteralExprClass:
   case Expr::CXXScalarValueInitExprClass:
   case Expr::TypeTraitExprClass:
   case Expr::ConceptSpecializationExprClass:
   case Expr::RequiresExprClass:
   case Expr::ArrayTypeTraitExprClass:
   case Expr::ExpressionTraitExprClass:
   case Expr::CXXNoexceptExprClass:
     return NoDiag();
   case Expr::CallExprClass:
   case Expr::CXXOperatorCallExprClass: {
     // C99 6.6/3 allows function calls within unevaluated subexpressions of
     // constant expressions, but they can never be ICEs because an ICE cannot
     // contain an operand of (pointer to) function type.
     const CallExpr *CE = cast<CallExpr>(E);
     if (CE->getBuiltinCallee())
       return CheckEvalInICE(E, Ctx);
     return ICEDiag(IK_NotICE, E->getBeginLoc());
   }
   case Expr::CXXRewrittenBinaryOperatorClass:
     return CheckICE(cast<CXXRewrittenBinaryOperator>(E)->getSemanticForm(),
                     Ctx);
   case Expr::DeclRefExprClass: {
     if (isa<EnumConstantDecl>(cast<DeclRefExpr>(E)->getDecl()))
       return NoDiag();
     const ValueDecl *D = cast<DeclRefExpr>(E)->getDecl();
     if (Ctx.getLangOpts().CPlusPlus &&
         D && IsConstNonVolatile(D->getType())) {
       // Parameter variables are never constants.  Without this check,
       // getAnyInitializer() can find a default argument, which leads
       // to chaos.
       if (isa<ParmVarDecl>(D))
         return ICEDiag(IK_NotICE, cast<DeclRefExpr>(E)->getLocation());
 
       // C++ 7.1.5.1p2
       //   A variable of non-volatile const-qualified integral or enumeration
       //   type initialized by an ICE can be used in ICEs.
       if (const VarDecl *Dcl = dyn_cast<VarDecl>(D)) {
         if (!Dcl->getType()->isIntegralOrEnumerationType())
           return ICEDiag(IK_NotICE, cast<DeclRefExpr>(E)->getLocation());
 
         const VarDecl *VD;
         // Look for a declaration of this variable that has an initializer, and
         // check whether it is an ICE.
         if (Dcl->getAnyInitializer(VD) && VD->checkInitIsICE())
           return NoDiag();
         else
           return ICEDiag(IK_NotICE, cast<DeclRefExpr>(E)->getLocation());
       }
     }
     return ICEDiag(IK_NotICE, E->getBeginLoc());
   }
   case Expr::UnaryOperatorClass: {
     const UnaryOperator *Exp = cast<UnaryOperator>(E);
     switch (Exp->getOpcode()) {
     case UO_PostInc:
     case UO_PostDec:
     case UO_PreInc:
     case UO_PreDec:
     case UO_AddrOf:
     case UO_Deref:
     case UO_Coawait:
       // C99 6.6/3 allows increment and decrement within unevaluated
       // subexpressions of constant expressions, but they can never be ICEs
       // because an ICE cannot contain an lvalue operand.
       return ICEDiag(IK_NotICE, E->getBeginLoc());
     case UO_Extension:
     case UO_LNot:
     case UO_Plus:
     case UO_Minus:
     case UO_Not:
     case UO_Real:
     case UO_Imag:
       return CheckICE(Exp->getSubExpr(), Ctx);
     }
     llvm_unreachable("invalid unary operator class");
   }
   case Expr::OffsetOfExprClass: {
     // Note that per C99, offsetof must be an ICE. And AFAIK, using
     // EvaluateAsRValue matches the proposed gcc behavior for cases like
     // "offsetof(struct s{int x[4];}, x[1.0])".  This doesn't affect
     // compliance: we should warn earlier for offsetof expressions with
     // array subscripts that aren't ICEs, and if the array subscripts
     // are ICEs, the value of the offsetof must be an integer constant.
     return CheckEvalInICE(E, Ctx);
   }
   case Expr::UnaryExprOrTypeTraitExprClass: {
     const UnaryExprOrTypeTraitExpr *Exp = cast<UnaryExprOrTypeTraitExpr>(E);
     if ((Exp->getKind() ==  UETT_SizeOf) &&
         Exp->getTypeOfArgument()->isVariableArrayType())
       return ICEDiag(IK_NotICE, E->getBeginLoc());
     return NoDiag();
   }
   case Expr::BinaryOperatorClass: {
     const BinaryOperator *Exp = cast<BinaryOperator>(E);
     switch (Exp->getOpcode()) {
     case BO_PtrMemD:
     case BO_PtrMemI:
     case BO_Assign:
     case BO_MulAssign:
     case BO_DivAssign:
     case BO_RemAssign:
     case BO_AddAssign:
     case BO_SubAssign:
     case BO_ShlAssign:
     case BO_ShrAssign:
     case BO_AndAssign:
     case BO_XorAssign:
     case BO_OrAssign:
       // C99 6.6/3 allows assignments within unevaluated subexpressions of
       // constant expressions, but they can never be ICEs because an ICE cannot
       // contain an lvalue operand.
       return ICEDiag(IK_NotICE, E->getBeginLoc());
 
     case BO_Mul:
     case BO_Div:
     case BO_Rem:
     case BO_Add:
     case BO_Sub:
     case BO_Shl:
     case BO_Shr:
     case BO_LT:
     case BO_GT:
     case BO_LE:
     case BO_GE:
     case BO_EQ:
     case BO_NE:
     case BO_And:
     case BO_Xor:
     case BO_Or:
     case BO_Comma:
     case BO_Cmp: {
       ICEDiag LHSResult = CheckICE(Exp->getLHS(), Ctx);
       ICEDiag RHSResult = CheckICE(Exp->getRHS(), Ctx);
       if (Exp->getOpcode() == BO_Div ||
           Exp->getOpcode() == BO_Rem) {
         // EvaluateAsRValue gives an error for undefined Div/Rem, so make sure
         // we don't evaluate one.
         if (LHSResult.Kind == IK_ICE && RHSResult.Kind == IK_ICE) {
           llvm::APSInt REval = Exp->getRHS()->EvaluateKnownConstInt(Ctx);
           if (REval == 0)
             return ICEDiag(IK_ICEIfUnevaluated, E->getBeginLoc());
           if (REval.isSigned() && REval.isAllOnesValue()) {
             llvm::APSInt LEval = Exp->getLHS()->EvaluateKnownConstInt(Ctx);
             if (LEval.isMinSignedValue())
               return ICEDiag(IK_ICEIfUnevaluated, E->getBeginLoc());
           }
         }
       }
       if (Exp->getOpcode() == BO_Comma) {
         if (Ctx.getLangOpts().C99) {
           // C99 6.6p3 introduces a strange edge case: comma can be in an ICE
           // if it isn't evaluated.
           if (LHSResult.Kind == IK_ICE && RHSResult.Kind == IK_ICE)
             return ICEDiag(IK_ICEIfUnevaluated, E->getBeginLoc());
         } else {
           // In both C89 and C++, commas in ICEs are illegal.
           return ICEDiag(IK_NotICE, E->getBeginLoc());
         }
       }
       return Worst(LHSResult, RHSResult);
     }
     case BO_LAnd:
     case BO_LOr: {
       ICEDiag LHSResult = CheckICE(Exp->getLHS(), Ctx);
       ICEDiag RHSResult = CheckICE(Exp->getRHS(), Ctx);
       if (LHSResult.Kind == IK_ICE && RHSResult.Kind == IK_ICEIfUnevaluated) {
         // Rare case where the RHS has a comma "side-effect"; we need
         // to actually check the condition to see whether the side
         // with the comma is evaluated.
         if ((Exp->getOpcode() == BO_LAnd) !=
             (Exp->getLHS()->EvaluateKnownConstInt(Ctx) == 0))
           return RHSResult;
         return NoDiag();
       }
 
       return Worst(LHSResult, RHSResult);
     }
     }
     llvm_unreachable("invalid binary operator kind");
   }
   case Expr::ImplicitCastExprClass:
   case Expr::CStyleCastExprClass:
   case Expr::CXXFunctionalCastExprClass:
   case Expr::CXXStaticCastExprClass:
   case Expr::CXXReinterpretCastExprClass:
   case Expr::CXXConstCastExprClass:
   case Expr::ObjCBridgedCastExprClass: {
     const Expr *SubExpr = cast<CastExpr>(E)->getSubExpr();
     if (isa<ExplicitCastExpr>(E)) {
       if (const FloatingLiteral *FL
             = dyn_cast<FloatingLiteral>(SubExpr->IgnoreParenImpCasts())) {
         unsigned DestWidth = Ctx.getIntWidth(E->getType());
         bool DestSigned = E->getType()->isSignedIntegerOrEnumerationType();
         APSInt IgnoredVal(DestWidth, !DestSigned);
         bool Ignored;
         // If the value does not fit in the destination type, the behavior is
         // undefined, so we are not required to treat it as a constant
         // expression.
         if (FL->getValue().convertToInteger(IgnoredVal,
                                             llvm::APFloat::rmTowardZero,
                                             &Ignored) & APFloat::opInvalidOp)
           return ICEDiag(IK_NotICE, E->getBeginLoc());
         return NoDiag();
       }
     }
     switch (cast<CastExpr>(E)->getCastKind()) {
     case CK_LValueToRValue:
     case CK_AtomicToNonAtomic:
     case CK_NonAtomicToAtomic:
     case CK_NoOp:
     case CK_IntegralToBoolean:
     case CK_IntegralCast:
       return CheckICE(SubExpr, Ctx);
     default:
       return ICEDiag(IK_NotICE, E->getBeginLoc());
     }
   }
   case Expr::BinaryConditionalOperatorClass: {
     const BinaryConditionalOperator *Exp = cast<BinaryConditionalOperator>(E);
     ICEDiag CommonResult = CheckICE(Exp->getCommon(), Ctx);
     if (CommonResult.Kind == IK_NotICE) return CommonResult;
     ICEDiag FalseResult = CheckICE(Exp->getFalseExpr(), Ctx);
     if (FalseResult.Kind == IK_NotICE) return FalseResult;
     if (CommonResult.Kind == IK_ICEIfUnevaluated) return CommonResult;
     if (FalseResult.Kind == IK_ICEIfUnevaluated &&
         Exp->getCommon()->EvaluateKnownConstInt(Ctx) != 0) return NoDiag();
     return FalseResult;
   }
   case Expr::ConditionalOperatorClass: {
     const ConditionalOperator *Exp = cast<ConditionalOperator>(E);
     // If the condition (ignoring parens) is a __builtin_constant_p call,
     // then only the true side is actually considered in an integer constant
     // expression, and it is fully evaluated.  This is an important GNU
     // extension.  See GCC PR38377 for discussion.
     if (const CallExpr *CallCE
         = dyn_cast<CallExpr>(Exp->getCond()->IgnoreParenCasts()))
       if (CallCE->getBuiltinCallee() == Builtin::BI__builtin_constant_p)
         return CheckEvalInICE(E, Ctx);
     ICEDiag CondResult = CheckICE(Exp->getCond(), Ctx);
     if (CondResult.Kind == IK_NotICE)
       return CondResult;
 
     ICEDiag TrueResult = CheckICE(Exp->getTrueExpr(), Ctx);
     ICEDiag FalseResult = CheckICE(Exp->getFalseExpr(), Ctx);
 
     if (TrueResult.Kind == IK_NotICE)
       return TrueResult;
     if (FalseResult.Kind == IK_NotICE)
       return FalseResult;
     if (CondResult.Kind == IK_ICEIfUnevaluated)
       return CondResult;
     if (TrueResult.Kind == IK_ICE && FalseResult.Kind == IK_ICE)
       return NoDiag();
     // Rare case where the diagnostics depend on which side is evaluated
     // Note that if we get here, CondResult is 0, and at least one of
     // TrueResult and FalseResult is non-zero.
     if (Exp->getCond()->EvaluateKnownConstInt(Ctx) == 0)
       return FalseResult;
     return TrueResult;
   }
   case Expr::CXXDefaultArgExprClass:
     return CheckICE(cast<CXXDefaultArgExpr>(E)->getExpr(), Ctx);
   case Expr::CXXDefaultInitExprClass:
     return CheckICE(cast<CXXDefaultInitExpr>(E)->getExpr(), Ctx);
   case Expr::ChooseExprClass: {
     return CheckICE(cast<ChooseExpr>(E)->getChosenSubExpr(), Ctx);
   }
   case Expr::BuiltinBitCastExprClass: {
     if (!checkBitCastConstexprEligibility(nullptr, Ctx, cast<CastExpr>(E)))
       return ICEDiag(IK_NotICE, E->getBeginLoc());
     return CheckICE(cast<CastExpr>(E)->getSubExpr(), Ctx);
   }
   }
 
   llvm_unreachable("Invalid StmtClass!");
 }
 
 /// Evaluate an expression as a C++11 integral constant expression.
 static bool EvaluateCPlusPlus11IntegralConstantExpr(const ASTContext &Ctx,
                                                     const Expr *E,
                                                     llvm::APSInt *Value,
                                                     SourceLocation *Loc) {
   if (!E->getType()->isIntegralOrUnscopedEnumerationType()) {
     if (Loc) *Loc = E->getExprLoc();
     return false;
   }
 
   APValue Result;
   if (!E->isCXX11ConstantExpr(Ctx, &Result, Loc))
     return false;
 
   if (!Result.isInt()) {
     if (Loc) *Loc = E->getExprLoc();
     return false;
   }
 
   if (Value) *Value = Result.getInt();
   return true;
 }
 
 bool Expr::isIntegerConstantExpr(const ASTContext &Ctx,
                                  SourceLocation *Loc) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   if (Ctx.getLangOpts().CPlusPlus11)
     return EvaluateCPlusPlus11IntegralConstantExpr(Ctx, this, nullptr, Loc);
 
   ICEDiag D = CheckICE(this, Ctx);
   if (D.Kind != IK_ICE) {
     if (Loc) *Loc = D.Loc;
     return false;
   }
   return true;
 }
 
 bool Expr::isIntegerConstantExpr(llvm::APSInt &Value, const ASTContext &Ctx,
                                  SourceLocation *Loc, bool isEvaluated) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   if (Ctx.getLangOpts().CPlusPlus11)
     return EvaluateCPlusPlus11IntegralConstantExpr(Ctx, this, &Value, Loc);
 
   if (!isIntegerConstantExpr(Ctx, Loc))
     return false;
 
   // The only possible side-effects here are due to UB discovered in the
   // evaluation (for instance, INT_MAX + 1). In such a case, we are still
   // required to treat the expression as an ICE, so we produce the folded
   // value.
   EvalResult ExprResult;
   Expr::EvalStatus Status;
   EvalInfo Info(Ctx, Status, EvalInfo::EM_IgnoreSideEffects);
   Info.InConstantContext = true;
 
   if (!::EvaluateAsInt(this, ExprResult, Ctx, SE_AllowSideEffects, Info))
     llvm_unreachable("ICE cannot be evaluated!");
 
   Value = ExprResult.Val.getInt();
   return true;
 }
 
 bool Expr::isCXX98IntegralConstantExpr(const ASTContext &Ctx) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   return CheckICE(this, Ctx).Kind == IK_ICE;
 }
 
 bool Expr::isCXX11ConstantExpr(const ASTContext &Ctx, APValue *Result,
                                SourceLocation *Loc) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   // We support this checking in C++98 mode in order to diagnose compatibility
   // issues.
   assert(Ctx.getLangOpts().CPlusPlus);
 
   // Build evaluation settings.
   Expr::EvalStatus Status;
   SmallVector<PartialDiagnosticAt, 8> Diags;
   Status.Diag = &Diags;
   EvalInfo Info(Ctx, Status, EvalInfo::EM_ConstantExpression);
 
   APValue Scratch;
   bool IsConstExpr =
       ::EvaluateAsRValue(Info, this, Result ? *Result : Scratch) &&
       // FIXME: We don't produce a diagnostic for this, but the callers that
       // call us on arbitrary full-expressions should generally not care.
       Info.discardCleanups() && !Status.HasSideEffects;
 
   if (!Diags.empty()) {
     IsConstExpr = false;
     if (Loc) *Loc = Diags[0].first;
   } else if (!IsConstExpr) {
     // FIXME: This shouldn't happen.
     if (Loc) *Loc = getExprLoc();
   }
 
   return IsConstExpr;
 }
 
 bool Expr::EvaluateWithSubstitution(APValue &Value, ASTContext &Ctx,
                                     const FunctionDecl *Callee,
                                     ArrayRef<const Expr*> Args,
                                     const Expr *This) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   Expr::EvalStatus Status;
   EvalInfo Info(Ctx, Status, EvalInfo::EM_ConstantExpressionUnevaluated);
   Info.InConstantContext = true;
 
   LValue ThisVal;
   const LValue *ThisPtr = nullptr;
   if (This) {
 #ifndef NDEBUG
     auto *MD = dyn_cast<CXXMethodDecl>(Callee);
     assert(MD && "Don't provide `this` for non-methods.");
     assert(!MD->isStatic() && "Don't provide `this` for static methods.");
 #endif
     if (!This->isValueDependent() &&
         EvaluateObjectArgument(Info, This, ThisVal) &&
         !Info.EvalStatus.HasSideEffects)
       ThisPtr = &ThisVal;
 
     // Ignore any side-effects from a failed evaluation. This is safe because
     // they can't interfere with any other argument evaluation.
     Info.EvalStatus.HasSideEffects = false;
   }
 
   ArgVector ArgValues(Args.size());
   for (ArrayRef<const Expr*>::iterator I = Args.begin(), E = Args.end();
        I != E; ++I) {
     if ((*I)->isValueDependent() ||
         !Evaluate(ArgValues[I - Args.begin()], Info, *I) ||
         Info.EvalStatus.HasSideEffects)
       // If evaluation fails, throw away the argument entirely.
       ArgValues[I - Args.begin()] = APValue();
 
     // Ignore any side-effects from a failed evaluation. This is safe because
     // they can't interfere with any other argument evaluation.
     Info.EvalStatus.HasSideEffects = false;
   }
 
   // Parameter cleanups happen in the caller and are not part of this
   // evaluation.
   Info.discardCleanups();
   Info.EvalStatus.HasSideEffects = false;
 
   // Build fake call to Callee.
   CallStackFrame Frame(Info, Callee->getLocation(), Callee, ThisPtr,
                        ArgValues.data());
   // FIXME: Missing ExprWithCleanups in enable_if conditions?
   FullExpressionRAII Scope(Info);
   return Evaluate(Value, Info, this) && Scope.destroy() &&
          !Info.EvalStatus.HasSideEffects;
 }
 
 bool Expr::isPotentialConstantExpr(const FunctionDecl *FD,
                                    SmallVectorImpl<
                                      PartialDiagnosticAt> &Diags) {
   // FIXME: It would be useful to check constexpr function templates, but at the
   // moment the constant expression evaluator cannot cope with the non-rigorous
   // ASTs which we build for dependent expressions.
   if (FD->isDependentContext())
     return true;
 
   // Bail out if a constexpr constructor has an initializer that contains an
   // error. We deliberately don't produce a diagnostic, as we have produced a
   // relevant diagnostic when parsing the error initializer.
   if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(FD)) {
     for (const auto *InitExpr : Ctor->inits()) {
       if (InitExpr->getInit() && InitExpr->getInit()->containsErrors())
         return false;
     }
   }
   Expr::EvalStatus Status;
   Status.Diag = &Diags;
 
   EvalInfo Info(FD->getASTContext(), Status, EvalInfo::EM_ConstantExpression);
   Info.InConstantContext = true;
   Info.CheckingPotentialConstantExpression = true;
 
   // The constexpr VM attempts to compile all methods to bytecode here.
   if (Info.EnableNewConstInterp) {
     Info.Ctx.getInterpContext().isPotentialConstantExpr(Info, FD);
     return Diags.empty();
   }
 
   const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
   const CXXRecordDecl *RD = MD ? MD->getParent()->getCanonicalDecl() : nullptr;
 
   // Fabricate an arbitrary expression on the stack and pretend that it
   // is a temporary being used as the 'this' pointer.
   LValue This;
   ImplicitValueInitExpr VIE(RD ? Info.Ctx.getRecordType(RD) : Info.Ctx.IntTy);
   This.set({&VIE, Info.CurrentCall->Index});
 
   ArrayRef<const Expr*> Args;
 
   APValue Scratch;
   if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FD)) {
     // Evaluate the call as a constant initializer, to allow the construction
     // of objects of non-literal types.
     Info.setEvaluatingDecl(This.getLValueBase(), Scratch);
     HandleConstructorCall(&VIE, This, Args, CD, Info, Scratch);
   } else {
     SourceLocation Loc = FD->getLocation();
     HandleFunctionCall(Loc, FD, (MD && MD->isInstance()) ? &This : nullptr,
                        Args, FD->getBody(), Info, Scratch, nullptr);
   }
 
   return Diags.empty();
 }
 
 bool Expr::isPotentialConstantExprUnevaluated(Expr *E,
                                               const FunctionDecl *FD,
                                               SmallVectorImpl<
                                                 PartialDiagnosticAt> &Diags) {
   assert(!E->isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
   Expr::EvalStatus Status;
   Status.Diag = &Diags;
 
   EvalInfo Info(FD->getASTContext(), Status,
                 EvalInfo::EM_ConstantExpressionUnevaluated);
   Info.InConstantContext = true;
   Info.CheckingPotentialConstantExpression = true;
 
   // Fabricate a call stack frame to give the arguments a plausible cover story.
   ArrayRef<const Expr*> Args;
   ArgVector ArgValues(0);
   bool Success = EvaluateArgs(Args, ArgValues, Info, FD);
   (void)Success;
   assert(Success &&
          "Failed to set up arguments for potential constant evaluation");
   CallStackFrame Frame(Info, SourceLocation(), FD, nullptr, ArgValues.data());
 
   APValue ResultScratch;
   Evaluate(ResultScratch, Info, E);
   return Diags.empty();
 }
 
 bool Expr::tryEvaluateObjectSize(uint64_t &Result, ASTContext &Ctx,
                                  unsigned Type) const {
   if (!getType()->isPointerType())
     return false;
 
   Expr::EvalStatus Status;
   EvalInfo Info(Ctx, Status, EvalInfo::EM_ConstantFold);
   return tryEvaluateBuiltinObjectSize(this, Type, Info, Result);
 }
Index: projects/clang1100-import/contrib/llvm-project/compiler-rt/lib/builtins/atomic.c
===================================================================
--- projects/clang1100-import/contrib/llvm-project/compiler-rt/lib/builtins/atomic.c	(revision 363976)
+++ projects/clang1100-import/contrib/llvm-project/compiler-rt/lib/builtins/atomic.c	(revision 363977)
@@ -1,345 +1,352 @@
 //===-- atomic.c - Implement support functions for atomic operations.------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 //  atomic.c defines a set of functions for performing atomic accesses on
 //  arbitrary-sized memory locations.  This design uses locks that should
 //  be fast in the uncontended case, for two reasons:
 //
 //  1) This code must work with C programs that do not link to anything
 //     (including pthreads) and so it should not depend on any pthread
 //     functions.
 //  2) Atomic operations, rather than explicit mutexes, are most commonly used
 //     on code where contended operations are rate.
 //
 //  To avoid needing a per-object lock, this code allocates an array of
 //  locks and hashes the object pointers to find the one that it should use.
 //  For operations that must be atomic on two locations, the lower lock is
 //  always acquired first, to avoid deadlock.
 //
 //===----------------------------------------------------------------------===//
 
 #include <stdbool.h>
 #include <stdint.h>
 #include <string.h>
 
 #include "assembly.h"
 
 // Clang objects if you redefine a builtin.  This little hack allows us to
 // define a function with the same name as an intrinsic.
 #pragma redefine_extname __atomic_load_c SYMBOL_NAME(__atomic_load)
 #pragma redefine_extname __atomic_store_c SYMBOL_NAME(__atomic_store)
 #pragma redefine_extname __atomic_exchange_c SYMBOL_NAME(__atomic_exchange)
 #pragma redefine_extname __atomic_compare_exchange_c SYMBOL_NAME(              \
     __atomic_compare_exchange)
 
 /// Number of locks.  This allocates one page on 32-bit platforms, two on
 /// 64-bit.  This can be specified externally if a different trade between
 /// memory usage and contention probability is required for a given platform.
 #ifndef SPINLOCK_COUNT
 #define SPINLOCK_COUNT (1 << 10)
 #endif
 static const long SPINLOCK_MASK = SPINLOCK_COUNT - 1;
 
 ////////////////////////////////////////////////////////////////////////////////
 // Platform-specific lock implementation.  Falls back to spinlocks if none is
 // defined.  Each platform should define the Lock type, and corresponding
 // lock() and unlock() functions.
 ////////////////////////////////////////////////////////////////////////////////
 #ifdef __FreeBSD__
 #include <errno.h>
 // clang-format off
 #include <sys/types.h>
 #include <machine/atomic.h>
 #include <sys/umtx.h>
 // clang-format on
 typedef struct _usem Lock;
 __inline static void unlock(Lock *l) {
   __c11_atomic_store((_Atomic(uint32_t) *)&l->_count, 1, __ATOMIC_RELEASE);
   __c11_atomic_thread_fence(__ATOMIC_SEQ_CST);
   if (l->_has_waiters)
     _umtx_op(l, UMTX_OP_SEM_WAKE, 1, 0, 0);
 }
 __inline static void lock(Lock *l) {
   uint32_t old = 1;
   while (!__c11_atomic_compare_exchange_weak((_Atomic(uint32_t) *)&l->_count,
                                              &old, 0, __ATOMIC_ACQUIRE,
                                              __ATOMIC_RELAXED)) {
     _umtx_op(l, UMTX_OP_SEM_WAIT, 0, 0, 0);
     old = 1;
   }
 }
 /// locks for atomic operations
 static Lock locks[SPINLOCK_COUNT] = {[0 ... SPINLOCK_COUNT - 1] = {0, 1, 0}};
 
 #elif defined(__APPLE__)
 #include <libkern/OSAtomic.h>
 typedef OSSpinLock Lock;
 __inline static void unlock(Lock *l) { OSSpinLockUnlock(l); }
 /// Locks a lock.  In the current implementation, this is potentially
 /// unbounded in the contended case.
 __inline static void lock(Lock *l) { OSSpinLockLock(l); }
 static Lock locks[SPINLOCK_COUNT]; // initialized to OS_SPINLOCK_INIT which is 0
 
 #else
 typedef _Atomic(uintptr_t) Lock;
 /// Unlock a lock.  This is a release operation.
 __inline static void unlock(Lock *l) {
   __c11_atomic_store(l, 0, __ATOMIC_RELEASE);
 }
 /// Locks a lock.  In the current implementation, this is potentially
 /// unbounded in the contended case.
 __inline static void lock(Lock *l) {
   uintptr_t old = 0;
   while (!__c11_atomic_compare_exchange_weak(l, &old, 1, __ATOMIC_ACQUIRE,
                                              __ATOMIC_RELAXED))
     old = 0;
 }
 /// locks for atomic operations
 static Lock locks[SPINLOCK_COUNT];
 #endif
 
 /// Returns a lock to use for a given pointer.
 static __inline Lock *lock_for_pointer(void *ptr) {
   intptr_t hash = (intptr_t)ptr;
   // Disregard the lowest 4 bits.  We want all values that may be part of the
   // same memory operation to hash to the same value and therefore use the same
   // lock.
   hash >>= 4;
   // Use the next bits as the basis for the hash
   intptr_t low = hash & SPINLOCK_MASK;
   // Now use the high(er) set of bits to perturb the hash, so that we don't
   // get collisions from atomic fields in a single object
   hash >>= 16;
   hash ^= low;
   // Return a pointer to the word to use
   return locks + (hash & SPINLOCK_MASK);
 }
 
-/// Macros for determining whether a size is lock free.  Clang can not yet
-/// codegen __atomic_is_lock_free(16), so for now we assume 16-byte values are
-/// not lock free.
+/// Macros for determining whether a size is lock free.
 #define IS_LOCK_FREE_1 __c11_atomic_is_lock_free(1)
 #define IS_LOCK_FREE_2 __c11_atomic_is_lock_free(2)
 #define IS_LOCK_FREE_4 __c11_atomic_is_lock_free(4)
+
+/// 32 bit PowerPC doesn't support 8-byte lock_free atomics
+#if !defined(__powerpc64__) && defined(__powerpc__)
+#define IS_LOCK_FREE_8 0
+#else
 #define IS_LOCK_FREE_8 __c11_atomic_is_lock_free(8)
+#endif
+
+/// Clang can not yet codegen __atomic_is_lock_free(16), so for now we assume
+/// 16-byte values are not lock free.
 #define IS_LOCK_FREE_16 0
 
 /// Macro that calls the compiler-generated lock-free versions of functions
 /// when they exist.
 #define LOCK_FREE_CASES()                                                      \
   do {                                                                         \
     switch (size) {                                                            \
     case 1:                                                                    \
       if (IS_LOCK_FREE_1) {                                                    \
         LOCK_FREE_ACTION(uint8_t);                                             \
       }                                                                        \
       break;                                                                   \
     case 2:                                                                    \
       if (IS_LOCK_FREE_2) {                                                    \
         LOCK_FREE_ACTION(uint16_t);                                            \
       }                                                                        \
       break;                                                                   \
     case 4:                                                                    \
       if (IS_LOCK_FREE_4) {                                                    \
         LOCK_FREE_ACTION(uint32_t);                                            \
       }                                                                        \
       break;                                                                   \
     case 8:                                                                    \
       if (IS_LOCK_FREE_8) {                                                    \
         LOCK_FREE_ACTION(uint64_t);                                            \
       }                                                                        \
       break;                                                                   \
     case 16:                                                                   \
       if (IS_LOCK_FREE_16) {                                                   \
         /* FIXME: __uint128_t isn't available on 32 bit platforms.             \
         LOCK_FREE_ACTION(__uint128_t);*/                                       \
       }                                                                        \
       break;                                                                   \
     }                                                                          \
   } while (0)
 
 /// An atomic load operation.  This is atomic with respect to the source
 /// pointer only.
 void __atomic_load_c(int size, void *src, void *dest, int model) {
 #define LOCK_FREE_ACTION(type)                                                 \
   *((type *)dest) = __c11_atomic_load((_Atomic(type) *)src, model);            \
   return;
   LOCK_FREE_CASES();
 #undef LOCK_FREE_ACTION
   Lock *l = lock_for_pointer(src);
   lock(l);
   memcpy(dest, src, size);
   unlock(l);
 }
 
 /// An atomic store operation.  This is atomic with respect to the destination
 /// pointer only.
 void __atomic_store_c(int size, void *dest, void *src, int model) {
 #define LOCK_FREE_ACTION(type)                                                 \
   __c11_atomic_store((_Atomic(type) *)dest, *(type *)src, model);              \
   return;
   LOCK_FREE_CASES();
 #undef LOCK_FREE_ACTION
   Lock *l = lock_for_pointer(dest);
   lock(l);
   memcpy(dest, src, size);
   unlock(l);
 }
 
 /// Atomic compare and exchange operation.  If the value at *ptr is identical
 /// to the value at *expected, then this copies value at *desired to *ptr.  If
 /// they  are not, then this stores the current value from *ptr in *expected.
 ///
 /// This function returns 1 if the exchange takes place or 0 if it fails.
 int __atomic_compare_exchange_c(int size, void *ptr, void *expected,
                                 void *desired, int success, int failure) {
 #define LOCK_FREE_ACTION(type)                                                 \
   return __c11_atomic_compare_exchange_strong(                                 \
       (_Atomic(type) *)ptr, (type *)expected, *(type *)desired, success,       \
       failure)
   LOCK_FREE_CASES();
 #undef LOCK_FREE_ACTION
   Lock *l = lock_for_pointer(ptr);
   lock(l);
   if (memcmp(ptr, expected, size) == 0) {
     memcpy(ptr, desired, size);
     unlock(l);
     return 1;
   }
   memcpy(expected, ptr, size);
   unlock(l);
   return 0;
 }
 
 /// Performs an atomic exchange operation between two pointers.  This is atomic
 /// with respect to the target address.
 void __atomic_exchange_c(int size, void *ptr, void *val, void *old, int model) {
 #define LOCK_FREE_ACTION(type)                                                 \
   *(type *)old =                                                               \
       __c11_atomic_exchange((_Atomic(type) *)ptr, *(type *)val, model);        \
   return;
   LOCK_FREE_CASES();
 #undef LOCK_FREE_ACTION
   Lock *l = lock_for_pointer(ptr);
   lock(l);
   memcpy(old, ptr, size);
   memcpy(ptr, val, size);
   unlock(l);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // Where the size is known at compile time, the compiler may emit calls to
 // specialised versions of the above functions.
 ////////////////////////////////////////////////////////////////////////////////
 #ifdef __SIZEOF_INT128__
 #define OPTIMISED_CASES                                                        \
   OPTIMISED_CASE(1, IS_LOCK_FREE_1, uint8_t)                                   \
   OPTIMISED_CASE(2, IS_LOCK_FREE_2, uint16_t)                                  \
   OPTIMISED_CASE(4, IS_LOCK_FREE_4, uint32_t)                                  \
   OPTIMISED_CASE(8, IS_LOCK_FREE_8, uint64_t)                                  \
   OPTIMISED_CASE(16, IS_LOCK_FREE_16, __uint128_t)
 #else
 #define OPTIMISED_CASES                                                        \
   OPTIMISED_CASE(1, IS_LOCK_FREE_1, uint8_t)                                   \
   OPTIMISED_CASE(2, IS_LOCK_FREE_2, uint16_t)                                  \
   OPTIMISED_CASE(4, IS_LOCK_FREE_4, uint32_t)                                  \
   OPTIMISED_CASE(8, IS_LOCK_FREE_8, uint64_t)
 #endif
 
 #define OPTIMISED_CASE(n, lockfree, type)                                      \
   type __atomic_load_##n(type *src, int model) {                               \
     if (lockfree)                                                              \
       return __c11_atomic_load((_Atomic(type) *)src, model);                   \
     Lock *l = lock_for_pointer(src);                                           \
     lock(l);                                                                   \
     type val = *src;                                                           \
     unlock(l);                                                                 \
     return val;                                                                \
   }
 OPTIMISED_CASES
 #undef OPTIMISED_CASE
 
 #define OPTIMISED_CASE(n, lockfree, type)                                      \
   void __atomic_store_##n(type *dest, type val, int model) {                   \
     if (lockfree) {                                                            \
       __c11_atomic_store((_Atomic(type) *)dest, val, model);                   \
       return;                                                                  \
     }                                                                          \
     Lock *l = lock_for_pointer(dest);                                          \
     lock(l);                                                                   \
     *dest = val;                                                               \
     unlock(l);                                                                 \
     return;                                                                    \
   }
 OPTIMISED_CASES
 #undef OPTIMISED_CASE
 
 #define OPTIMISED_CASE(n, lockfree, type)                                      \
   type __atomic_exchange_##n(type *dest, type val, int model) {                \
     if (lockfree)                                                              \
       return __c11_atomic_exchange((_Atomic(type) *)dest, val, model);         \
     Lock *l = lock_for_pointer(dest);                                          \
     lock(l);                                                                   \
     type tmp = *dest;                                                          \
     *dest = val;                                                               \
     unlock(l);                                                                 \
     return tmp;                                                                \
   }
 OPTIMISED_CASES
 #undef OPTIMISED_CASE
 
 #define OPTIMISED_CASE(n, lockfree, type)                                      \
   bool __atomic_compare_exchange_##n(type *ptr, type *expected, type desired,  \
                                      int success, int failure) {               \
     if (lockfree)                                                              \
       return __c11_atomic_compare_exchange_strong(                             \
           (_Atomic(type) *)ptr, expected, desired, success, failure);          \
     Lock *l = lock_for_pointer(ptr);                                           \
     lock(l);                                                                   \
     if (*ptr == *expected) {                                                   \
       *ptr = desired;                                                          \
       unlock(l);                                                               \
       return true;                                                             \
     }                                                                          \
     *expected = *ptr;                                                          \
     unlock(l);                                                                 \
     return false;                                                              \
   }
 OPTIMISED_CASES
 #undef OPTIMISED_CASE
 
 ////////////////////////////////////////////////////////////////////////////////
 // Atomic read-modify-write operations for integers of various sizes.
 ////////////////////////////////////////////////////////////////////////////////
 #define ATOMIC_RMW(n, lockfree, type, opname, op)                              \
   type __atomic_fetch_##opname##_##n(type *ptr, type val, int model) {         \
     if (lockfree)                                                              \
       return __c11_atomic_fetch_##opname((_Atomic(type) *)ptr, val, model);    \
     Lock *l = lock_for_pointer(ptr);                                           \
     lock(l);                                                                   \
     type tmp = *ptr;                                                           \
     *ptr = tmp op val;                                                         \
     unlock(l);                                                                 \
     return tmp;                                                                \
   }
 
 #define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, add, +)
 OPTIMISED_CASES
 #undef OPTIMISED_CASE
 #define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, sub, -)
 OPTIMISED_CASES
 #undef OPTIMISED_CASE
 #define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, and, &)
 OPTIMISED_CASES
 #undef OPTIMISED_CASE
 #define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, or, |)
 OPTIMISED_CASES
 #undef OPTIMISED_CASE
 #define OPTIMISED_CASE(n, lockfree, type) ATOMIC_RMW(n, lockfree, type, xor, ^)
 OPTIMISED_CASES
 #undef OPTIMISED_CASE