diff --git a/contrib/llvm-project/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/contrib/llvm-project/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index e323aaaeefaf..49047719fdaa 100644
--- a/contrib/llvm-project/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/contrib/llvm-project/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -1,1580 +1,1585 @@
 //===- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function ---===//
 //
 // 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 pass is responsible for finalizing the functions frame layout, saving
 // callee saved registers, and for emitting prolog & epilog code for the
 // function.
 //
 // This pass must be run after register allocation.  After this pass is
 // executed, it is illegal to construct MO_FrameIndex operands.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/RegisterScavenging.h"
 #include "llvm/CodeGen/TargetFrameLowering.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
 #include "llvm/CodeGen/TargetOpcodes.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/CodeGen/WinEHFuncInfo.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
 #include <functional>
 #include <limits>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "prologepilog"
 
 using MBBVector = SmallVector<MachineBasicBlock *, 4>;
 
 STATISTIC(NumLeafFuncWithSpills, "Number of leaf functions with CSRs");
 STATISTIC(NumFuncSeen, "Number of functions seen in PEI");
 
 
 namespace {
 
 class PEI : public MachineFunctionPass {
 public:
   static char ID;
 
   PEI() : MachineFunctionPass(ID) {
     initializePEIPass(*PassRegistry::getPassRegistry());
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
   /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
   /// frame indexes with appropriate references.
   bool runOnMachineFunction(MachineFunction &MF) override;
 
 private:
   RegScavenger *RS = nullptr;
 
   // MinCSFrameIndex, MaxCSFrameIndex - Keeps the range of callee saved
   // stack frame indexes.
   unsigned MinCSFrameIndex = std::numeric_limits<unsigned>::max();
   unsigned MaxCSFrameIndex = 0;
 
   // Save and Restore blocks of the current function. Typically there is a
   // single save block, unless Windows EH funclets are involved.
   MBBVector SaveBlocks;
   MBBVector RestoreBlocks;
 
   // Flag to control whether to use the register scavenger to resolve
   // frame index materialization registers. Set according to
   // TRI->requiresFrameIndexScavenging() for the current function.
   bool FrameIndexVirtualScavenging = false;
 
   // Flag to control whether the scavenger should be passed even though
   // FrameIndexVirtualScavenging is used.
   bool FrameIndexEliminationScavenging = false;
 
   // Emit remarks.
   MachineOptimizationRemarkEmitter *ORE = nullptr;
 
   void calculateCallFrameInfo(MachineFunction &MF);
   void calculateSaveRestoreBlocks(MachineFunction &MF);
   void spillCalleeSavedRegs(MachineFunction &MF);
 
   void calculateFrameObjectOffsets(MachineFunction &MF);
   void replaceFrameIndices(MachineFunction &MF);
   void replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &MF,
                            int &SPAdj);
   // Frame indices in debug values are encoded in a target independent
   // way with simply the frame index and offset rather than any
   // target-specific addressing mode.
   bool replaceFrameIndexDebugInstr(MachineFunction &MF, MachineInstr &MI,
                                    unsigned OpIdx, int SPAdj = 0);
   // Does same as replaceFrameIndices but using the backward MIR walk and
   // backward register scavenger walk. Does not yet support call sequence
   // processing.
   void replaceFrameIndicesBackward(MachineBasicBlock *BB, MachineFunction &MF,
                                    int &SPAdj);
 
   void insertPrologEpilogCode(MachineFunction &MF);
   void insertZeroCallUsedRegs(MachineFunction &MF);
 };
 
 } // end anonymous namespace
 
 char PEI::ID = 0;
 
 char &llvm::PrologEpilogCodeInserterID = PEI::ID;
 
 INITIALIZE_PASS_BEGIN(PEI, DEBUG_TYPE, "Prologue/Epilogue Insertion", false,
                       false)
 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
 INITIALIZE_PASS_DEPENDENCY(MachineOptimizationRemarkEmitterPass)
 INITIALIZE_PASS_END(PEI, DEBUG_TYPE,
                     "Prologue/Epilogue Insertion & Frame Finalization", false,
                     false)
 
 MachineFunctionPass *llvm::createPrologEpilogInserterPass() {
   return new PEI();
 }
 
 STATISTIC(NumBytesStackSpace,
           "Number of bytes used for stack in all functions");
 
 void PEI::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesCFG();
   AU.addPreserved<MachineLoopInfo>();
   AU.addPreserved<MachineDominatorTree>();
   AU.addRequired<MachineOptimizationRemarkEmitterPass>();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
 
 /// StackObjSet - A set of stack object indexes
 using StackObjSet = SmallSetVector<int, 8>;
 
 using SavedDbgValuesMap =
     SmallDenseMap<MachineBasicBlock *, SmallVector<MachineInstr *, 4>, 4>;
 
 /// Stash DBG_VALUEs that describe parameters and which are placed at the start
 /// of the block. Later on, after the prologue code has been emitted, the
 /// stashed DBG_VALUEs will be reinserted at the start of the block.
 static void stashEntryDbgValues(MachineBasicBlock &MBB,
                                 SavedDbgValuesMap &EntryDbgValues) {
   SmallVector<const MachineInstr *, 4> FrameIndexValues;
 
   for (auto &MI : MBB) {
     if (!MI.isDebugInstr())
       break;
     if (!MI.isDebugValue() || !MI.getDebugVariable()->isParameter())
       continue;
     if (any_of(MI.debug_operands(),
                [](const MachineOperand &MO) { return MO.isFI(); })) {
       // We can only emit valid locations for frame indices after the frame
       // setup, so do not stash away them.
       FrameIndexValues.push_back(&MI);
       continue;
     }
     const DILocalVariable *Var = MI.getDebugVariable();
     const DIExpression *Expr = MI.getDebugExpression();
     auto Overlaps = [Var, Expr](const MachineInstr *DV) {
       return Var == DV->getDebugVariable() &&
              Expr->fragmentsOverlap(DV->getDebugExpression());
     };
     // See if the debug value overlaps with any preceding debug value that will
     // not be stashed. If that is the case, then we can't stash this value, as
     // we would then reorder the values at reinsertion.
     if (llvm::none_of(FrameIndexValues, Overlaps))
       EntryDbgValues[&MBB].push_back(&MI);
   }
 
   // Remove stashed debug values from the block.
   if (EntryDbgValues.count(&MBB))
     for (auto *MI : EntryDbgValues[&MBB])
       MI->removeFromParent();
 }
 
 /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
 /// frame indexes with appropriate references.
 bool PEI::runOnMachineFunction(MachineFunction &MF) {
   NumFuncSeen++;
   const Function &F = MF.getFunction();
   const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
   const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
 
   RS = TRI->requiresRegisterScavenging(MF) ? new RegScavenger() : nullptr;
   FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(MF);
   ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE();
 
   // Calculate the MaxCallFrameSize and AdjustsStack variables for the
   // function's frame information. Also eliminates call frame pseudo
   // instructions.
   calculateCallFrameInfo(MF);
 
   // Determine placement of CSR spill/restore code and prolog/epilog code:
   // place all spills in the entry block, all restores in return blocks.
   calculateSaveRestoreBlocks(MF);
 
   // Stash away DBG_VALUEs that should not be moved by insertion of prolog code.
   SavedDbgValuesMap EntryDbgValues;
   for (MachineBasicBlock *SaveBlock : SaveBlocks)
     stashEntryDbgValues(*SaveBlock, EntryDbgValues);
 
   // Handle CSR spilling and restoring, for targets that need it.
   if (MF.getTarget().usesPhysRegsForValues())
     spillCalleeSavedRegs(MF);
 
   // Allow the target machine to make final modifications to the function
   // before the frame layout is finalized.
   TFI->processFunctionBeforeFrameFinalized(MF, RS);
 
   // Calculate actual frame offsets for all abstract stack objects...
   calculateFrameObjectOffsets(MF);
 
   // Add prolog and epilog code to the function.  This function is required
   // to align the stack frame as necessary for any stack variables or
   // called functions.  Because of this, calculateCalleeSavedRegisters()
   // must be called before this function in order to set the AdjustsStack
   // and MaxCallFrameSize variables.
   if (!F.hasFnAttribute(Attribute::Naked))
     insertPrologEpilogCode(MF);
 
   // Reinsert stashed debug values at the start of the entry blocks.
   for (auto &I : EntryDbgValues)
     I.first->insert(I.first->begin(), I.second.begin(), I.second.end());
 
   // Allow the target machine to make final modifications to the function
   // before the frame layout is finalized.
   TFI->processFunctionBeforeFrameIndicesReplaced(MF, RS);
 
   // Replace all MO_FrameIndex operands with physical register references
   // and actual offsets.
   //
   replaceFrameIndices(MF);
 
   // If register scavenging is needed, as we've enabled doing it as a
   // post-pass, scavenge the virtual registers that frame index elimination
   // inserted.
   if (TRI->requiresRegisterScavenging(MF) && FrameIndexVirtualScavenging)
     scavengeFrameVirtualRegs(MF, *RS);
 
   // Warn on stack size when we exceeds the given limit.
   MachineFrameInfo &MFI = MF.getFrameInfo();
   uint64_t StackSize = MFI.getStackSize();
 
   unsigned Threshold = UINT_MAX;
   if (MF.getFunction().hasFnAttribute("warn-stack-size")) {
     bool Failed = MF.getFunction()
                       .getFnAttribute("warn-stack-size")
                       .getValueAsString()
                       .getAsInteger(10, Threshold);
     // Verifier should have caught this.
     assert(!Failed && "Invalid warn-stack-size fn attr value");
     (void)Failed;
   }
   uint64_t UnsafeStackSize = MFI.getUnsafeStackSize();
   if (MF.getFunction().hasFnAttribute(Attribute::SafeStack))
     StackSize += UnsafeStackSize;
 
   if (StackSize > Threshold) {
     DiagnosticInfoStackSize DiagStackSize(F, StackSize, Threshold, DS_Warning);
     F.getContext().diagnose(DiagStackSize);
     int64_t SpillSize = 0;
     for (int Idx = MFI.getObjectIndexBegin(), End = MFI.getObjectIndexEnd();
          Idx != End; ++Idx) {
       if (MFI.isSpillSlotObjectIndex(Idx))
         SpillSize += MFI.getObjectSize(Idx);
     }
 
     [[maybe_unused]] float SpillPct =
         static_cast<float>(SpillSize) / static_cast<float>(StackSize);
     LLVM_DEBUG(
         dbgs() << formatv("{0}/{1} ({3:P}) spills, {2}/{1} ({4:P}) variables",
                           SpillSize, StackSize, StackSize - SpillSize, SpillPct,
                           1.0f - SpillPct));
     if (UnsafeStackSize != 0) {
       LLVM_DEBUG(dbgs() << formatv(", {0}/{2} ({1:P}) unsafe stack",
                                    UnsafeStackSize,
                                    static_cast<float>(UnsafeStackSize) /
                                        static_cast<float>(StackSize),
                                    StackSize));
     }
     LLVM_DEBUG(dbgs() << "\n");
   }
 
   ORE->emit([&]() {
     return MachineOptimizationRemarkAnalysis(DEBUG_TYPE, "StackSize",
                                              MF.getFunction().getSubprogram(),
                                              &MF.front())
            << ore::NV("NumStackBytes", StackSize) << " stack bytes in function";
   });
 
   delete RS;
   SaveBlocks.clear();
   RestoreBlocks.clear();
   MFI.setSavePoint(nullptr);
   MFI.setRestorePoint(nullptr);
   return true;
 }
 
 /// Calculate the MaxCallFrameSize and AdjustsStack
 /// variables for the function's frame information and eliminate call frame
 /// pseudo instructions.
 void PEI::calculateCallFrameInfo(MachineFunction &MF) {
   const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
   const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
   MachineFrameInfo &MFI = MF.getFrameInfo();
 
   unsigned MaxCallFrameSize = 0;
   bool AdjustsStack = MFI.adjustsStack();
 
   // Get the function call frame set-up and tear-down instruction opcode
   unsigned FrameSetupOpcode = TII.getCallFrameSetupOpcode();
   unsigned FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
 
   // Early exit for targets which have no call frame setup/destroy pseudo
   // instructions.
   if (FrameSetupOpcode == ~0u && FrameDestroyOpcode == ~0u)
     return;
 
   std::vector<MachineBasicBlock::iterator> FrameSDOps;
   for (MachineBasicBlock &BB : MF)
     for (MachineBasicBlock::iterator I = BB.begin(); I != BB.end(); ++I)
       if (TII.isFrameInstr(*I)) {
         unsigned Size = TII.getFrameSize(*I);
         if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
         AdjustsStack = true;
         FrameSDOps.push_back(I);
       } else if (I->isInlineAsm()) {
         // Some inline asm's need a stack frame, as indicated by operand 1.
         unsigned ExtraInfo = I->getOperand(InlineAsm::MIOp_ExtraInfo).getImm();
         if (ExtraInfo & InlineAsm::Extra_IsAlignStack)
           AdjustsStack = true;
       }
 
   assert(!MFI.isMaxCallFrameSizeComputed() ||
          (MFI.getMaxCallFrameSize() >= MaxCallFrameSize &&
           !(AdjustsStack && !MFI.adjustsStack())));
   MFI.setAdjustsStack(AdjustsStack);
   MFI.setMaxCallFrameSize(MaxCallFrameSize);
 
   for (MachineBasicBlock::iterator I : FrameSDOps) {
     // If call frames are not being included as part of the stack frame, and
     // the target doesn't indicate otherwise, remove the call frame pseudos
     // here. The sub/add sp instruction pairs are still inserted, but we don't
     // need to track the SP adjustment for frame index elimination.
     if (TFI->canSimplifyCallFramePseudos(MF))
       TFI->eliminateCallFramePseudoInstr(MF, *I->getParent(), I);
   }
 }
 
 /// Compute the sets of entry and return blocks for saving and restoring
 /// callee-saved registers, and placing prolog and epilog code.
 void PEI::calculateSaveRestoreBlocks(MachineFunction &MF) {
   const MachineFrameInfo &MFI = MF.getFrameInfo();
 
   // Even when we do not change any CSR, we still want to insert the
   // prologue and epilogue of the function.
   // So set the save points for those.
 
   // Use the points found by shrink-wrapping, if any.
   if (MFI.getSavePoint()) {
     SaveBlocks.push_back(MFI.getSavePoint());
     assert(MFI.getRestorePoint() && "Both restore and save must be set");
     MachineBasicBlock *RestoreBlock = MFI.getRestorePoint();
     // If RestoreBlock does not have any successor and is not a return block
     // then the end point is unreachable and we do not need to insert any
     // epilogue.
     if (!RestoreBlock->succ_empty() || RestoreBlock->isReturnBlock())
       RestoreBlocks.push_back(RestoreBlock);
     return;
   }
 
   // Save refs to entry and return blocks.
   SaveBlocks.push_back(&MF.front());
   for (MachineBasicBlock &MBB : MF) {
     if (MBB.isEHFuncletEntry())
       SaveBlocks.push_back(&MBB);
     if (MBB.isReturnBlock())
       RestoreBlocks.push_back(&MBB);
   }
 }
 
 static void assignCalleeSavedSpillSlots(MachineFunction &F,
                                         const BitVector &SavedRegs,
                                         unsigned &MinCSFrameIndex,
                                         unsigned &MaxCSFrameIndex) {
   if (SavedRegs.empty())
     return;
 
   const TargetRegisterInfo *RegInfo = F.getSubtarget().getRegisterInfo();
   const MCPhysReg *CSRegs = F.getRegInfo().getCalleeSavedRegs();
   BitVector CSMask(SavedRegs.size());
 
   for (unsigned i = 0; CSRegs[i]; ++i)
     CSMask.set(CSRegs[i]);
 
   std::vector<CalleeSavedInfo> CSI;
   for (unsigned i = 0; CSRegs[i]; ++i) {
     unsigned Reg = CSRegs[i];
     if (SavedRegs.test(Reg)) {
       bool SavedSuper = false;
       for (const MCPhysReg &SuperReg : RegInfo->superregs(Reg)) {
         // Some backends set all aliases for some registers as saved, such as
         // Mips's $fp, so they appear in SavedRegs but not CSRegs.
         if (SavedRegs.test(SuperReg) && CSMask.test(SuperReg)) {
           SavedSuper = true;
           break;
         }
       }
 
       if (!SavedSuper)
         CSI.push_back(CalleeSavedInfo(Reg));
     }
   }
 
   const TargetFrameLowering *TFI = F.getSubtarget().getFrameLowering();
   MachineFrameInfo &MFI = F.getFrameInfo();
   if (!TFI->assignCalleeSavedSpillSlots(F, RegInfo, CSI, MinCSFrameIndex,
                                         MaxCSFrameIndex)) {
     // If target doesn't implement this, use generic code.
 
     if (CSI.empty())
       return; // Early exit if no callee saved registers are modified!
 
     unsigned NumFixedSpillSlots;
     const TargetFrameLowering::SpillSlot *FixedSpillSlots =
         TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
 
     // Now that we know which registers need to be saved and restored, allocate
     // stack slots for them.
     for (auto &CS : CSI) {
       // If the target has spilled this register to another register, we don't
       // need to allocate a stack slot.
       if (CS.isSpilledToReg())
         continue;
 
       unsigned Reg = CS.getReg();
       const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
 
       int FrameIdx;
       if (RegInfo->hasReservedSpillSlot(F, Reg, FrameIdx)) {
         CS.setFrameIdx(FrameIdx);
         continue;
       }
 
       // Check to see if this physreg must be spilled to a particular stack slot
       // on this target.
       const TargetFrameLowering::SpillSlot *FixedSlot = FixedSpillSlots;
       while (FixedSlot != FixedSpillSlots + NumFixedSpillSlots &&
              FixedSlot->Reg != Reg)
         ++FixedSlot;
 
       unsigned Size = RegInfo->getSpillSize(*RC);
       if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
         // Nope, just spill it anywhere convenient.
         Align Alignment = RegInfo->getSpillAlign(*RC);
         // We may not be able to satisfy the desired alignment specification of
         // the TargetRegisterClass if the stack alignment is smaller. Use the
         // min.
         Alignment = std::min(Alignment, TFI->getStackAlign());
         FrameIdx = MFI.CreateStackObject(Size, Alignment, true);
         if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
         if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
       } else {
         // Spill it to the stack where we must.
         FrameIdx = MFI.CreateFixedSpillStackObject(Size, FixedSlot->Offset);
       }
 
       CS.setFrameIdx(FrameIdx);
     }
   }
 
   MFI.setCalleeSavedInfo(CSI);
 }
 
 /// Helper function to update the liveness information for the callee-saved
 /// registers.
 static void updateLiveness(MachineFunction &MF) {
   MachineFrameInfo &MFI = MF.getFrameInfo();
   // Visited will contain all the basic blocks that are in the region
   // where the callee saved registers are alive:
   // - Anything that is not Save or Restore -> LiveThrough.
   // - Save -> LiveIn.
   // - Restore -> LiveOut.
   // The live-out is not attached to the block, so no need to keep
   // Restore in this set.
   SmallPtrSet<MachineBasicBlock *, 8> Visited;
   SmallVector<MachineBasicBlock *, 8> WorkList;
   MachineBasicBlock *Entry = &MF.front();
   MachineBasicBlock *Save = MFI.getSavePoint();
 
   if (!Save)
     Save = Entry;
 
   if (Entry != Save) {
     WorkList.push_back(Entry);
     Visited.insert(Entry);
   }
   Visited.insert(Save);
 
   MachineBasicBlock *Restore = MFI.getRestorePoint();
   if (Restore)
     // By construction Restore cannot be visited, otherwise it
     // means there exists a path to Restore that does not go
     // through Save.
     WorkList.push_back(Restore);
 
   while (!WorkList.empty()) {
     const MachineBasicBlock *CurBB = WorkList.pop_back_val();
     // By construction, the region that is after the save point is
     // dominated by the Save and post-dominated by the Restore.
     if (CurBB == Save && Save != Restore)
       continue;
     // Enqueue all the successors not already visited.
     // Those are by construction either before Save or after Restore.
     for (MachineBasicBlock *SuccBB : CurBB->successors())
       if (Visited.insert(SuccBB).second)
         WorkList.push_back(SuccBB);
   }
 
   const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
 
   MachineRegisterInfo &MRI = MF.getRegInfo();
   for (const CalleeSavedInfo &I : CSI) {
     for (MachineBasicBlock *MBB : Visited) {
       MCPhysReg Reg = I.getReg();
       // Add the callee-saved register as live-in.
       // It's killed at the spill.
       if (!MRI.isReserved(Reg) && !MBB->isLiveIn(Reg))
         MBB->addLiveIn(Reg);
     }
     // If callee-saved register is spilled to another register rather than
     // spilling to stack, the destination register has to be marked as live for
     // each MBB between the prologue and epilogue so that it is not clobbered
     // before it is reloaded in the epilogue. The Visited set contains all
     // blocks outside of the region delimited by prologue/epilogue.
     if (I.isSpilledToReg()) {
       for (MachineBasicBlock &MBB : MF) {
         if (Visited.count(&MBB))
           continue;
         MCPhysReg DstReg = I.getDstReg();
         if (!MBB.isLiveIn(DstReg))
           MBB.addLiveIn(DstReg);
       }
     }
   }
 }
 
 /// Insert spill code for the callee-saved registers used in the function.
 static void insertCSRSaves(MachineBasicBlock &SaveBlock,
                            ArrayRef<CalleeSavedInfo> CSI) {
   MachineFunction &MF = *SaveBlock.getParent();
   const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
   const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
   const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
 
   MachineBasicBlock::iterator I = SaveBlock.begin();
   if (!TFI->spillCalleeSavedRegisters(SaveBlock, I, CSI, TRI)) {
     for (const CalleeSavedInfo &CS : CSI) {
       // Insert the spill to the stack frame.
       unsigned Reg = CS.getReg();
 
       if (CS.isSpilledToReg()) {
         BuildMI(SaveBlock, I, DebugLoc(),
                 TII.get(TargetOpcode::COPY), CS.getDstReg())
           .addReg(Reg, getKillRegState(true));
       } else {
         const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
         TII.storeRegToStackSlot(SaveBlock, I, Reg, true, CS.getFrameIdx(), RC,
                                 TRI, Register());
       }
     }
   }
 }
 
 /// Insert restore code for the callee-saved registers used in the function.
 static void insertCSRRestores(MachineBasicBlock &RestoreBlock,
                               std::vector<CalleeSavedInfo> &CSI) {
   MachineFunction &MF = *RestoreBlock.getParent();
   const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
   const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
   const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
 
   // Restore all registers immediately before the return and any
   // terminators that precede it.
   MachineBasicBlock::iterator I = RestoreBlock.getFirstTerminator();
 
   if (!TFI->restoreCalleeSavedRegisters(RestoreBlock, I, CSI, TRI)) {
     for (const CalleeSavedInfo &CI : reverse(CSI)) {
       unsigned Reg = CI.getReg();
       if (CI.isSpilledToReg()) {
         BuildMI(RestoreBlock, I, DebugLoc(), TII.get(TargetOpcode::COPY), Reg)
           .addReg(CI.getDstReg(), getKillRegState(true));
       } else {
         const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
         TII.loadRegFromStackSlot(RestoreBlock, I, Reg, CI.getFrameIdx(), RC,
                                  TRI, Register());
         assert(I != RestoreBlock.begin() &&
                "loadRegFromStackSlot didn't insert any code!");
         // Insert in reverse order.  loadRegFromStackSlot can insert
         // multiple instructions.
       }
     }
   }
 }
 
 void PEI::spillCalleeSavedRegs(MachineFunction &MF) {
   // We can't list this requirement in getRequiredProperties because some
   // targets (WebAssembly) use virtual registers past this point, and the pass
   // pipeline is set up without giving the passes a chance to look at the
   // TargetMachine.
   // FIXME: Find a way to express this in getRequiredProperties.
   assert(MF.getProperties().hasProperty(
       MachineFunctionProperties::Property::NoVRegs));
 
   const Function &F = MF.getFunction();
   const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
   MachineFrameInfo &MFI = MF.getFrameInfo();
   MinCSFrameIndex = std::numeric_limits<unsigned>::max();
   MaxCSFrameIndex = 0;
 
   // Determine which of the registers in the callee save list should be saved.
   BitVector SavedRegs;
   TFI->determineCalleeSaves(MF, SavedRegs, RS);
 
   // Assign stack slots for any callee-saved registers that must be spilled.
   assignCalleeSavedSpillSlots(MF, SavedRegs, MinCSFrameIndex, MaxCSFrameIndex);
 
   // Add the code to save and restore the callee saved registers.
   if (!F.hasFnAttribute(Attribute::Naked)) {
     MFI.setCalleeSavedInfoValid(true);
 
     std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
     if (!CSI.empty()) {
       if (!MFI.hasCalls())
         NumLeafFuncWithSpills++;
 
       for (MachineBasicBlock *SaveBlock : SaveBlocks)
         insertCSRSaves(*SaveBlock, CSI);
 
       // Update the live-in information of all the blocks up to the save point.
       updateLiveness(MF);
 
       for (MachineBasicBlock *RestoreBlock : RestoreBlocks)
         insertCSRRestores(*RestoreBlock, CSI);
     }
   }
 }
 
 /// AdjustStackOffset - Helper function used to adjust the stack frame offset.
 static inline void AdjustStackOffset(MachineFrameInfo &MFI, int FrameIdx,
                                      bool StackGrowsDown, int64_t &Offset,
                                      Align &MaxAlign) {
   // If the stack grows down, add the object size to find the lowest address.
   if (StackGrowsDown)
     Offset += MFI.getObjectSize(FrameIdx);
 
   Align Alignment = MFI.getObjectAlign(FrameIdx);
 
   // If the alignment of this object is greater than that of the stack, then
   // increase the stack alignment to match.
   MaxAlign = std::max(MaxAlign, Alignment);
 
   // Adjust to alignment boundary.
   Offset = alignTo(Offset, Alignment);
 
   if (StackGrowsDown) {
     LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset
                       << "]\n");
     MFI.setObjectOffset(FrameIdx, -Offset); // Set the computed offset
   } else {
     LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset
                       << "]\n");
     MFI.setObjectOffset(FrameIdx, Offset);
     Offset += MFI.getObjectSize(FrameIdx);
   }
 }
 
 /// Compute which bytes of fixed and callee-save stack area are unused and keep
 /// track of them in StackBytesFree.
 static inline void
 computeFreeStackSlots(MachineFrameInfo &MFI, bool StackGrowsDown,
                       unsigned MinCSFrameIndex, unsigned MaxCSFrameIndex,
                       int64_t FixedCSEnd, BitVector &StackBytesFree) {
   // Avoid undefined int64_t -> int conversion below in extreme case.
   if (FixedCSEnd > std::numeric_limits<int>::max())
     return;
 
   StackBytesFree.resize(FixedCSEnd, true);
 
   SmallVector<int, 16> AllocatedFrameSlots;
   // Add fixed objects.
   for (int i = MFI.getObjectIndexBegin(); i != 0; ++i)
     // StackSlot scavenging is only implemented for the default stack.
     if (MFI.getStackID(i) == TargetStackID::Default)
       AllocatedFrameSlots.push_back(i);
   // Add callee-save objects if there are any.
   if (MinCSFrameIndex <= MaxCSFrameIndex) {
     for (int i = MinCSFrameIndex; i <= (int)MaxCSFrameIndex; ++i)
       if (MFI.getStackID(i) == TargetStackID::Default)
         AllocatedFrameSlots.push_back(i);
   }
 
   for (int i : AllocatedFrameSlots) {
     // These are converted from int64_t, but they should always fit in int
     // because of the FixedCSEnd check above.
     int ObjOffset = MFI.getObjectOffset(i);
     int ObjSize = MFI.getObjectSize(i);
     int ObjStart, ObjEnd;
     if (StackGrowsDown) {
       // ObjOffset is negative when StackGrowsDown is true.
       ObjStart = -ObjOffset - ObjSize;
       ObjEnd = -ObjOffset;
     } else {
       ObjStart = ObjOffset;
       ObjEnd = ObjOffset + ObjSize;
     }
     // Ignore fixed holes that are in the previous stack frame.
     if (ObjEnd > 0)
       StackBytesFree.reset(ObjStart, ObjEnd);
   }
 }
 
 /// Assign frame object to an unused portion of the stack in the fixed stack
 /// object range.  Return true if the allocation was successful.
 static inline bool scavengeStackSlot(MachineFrameInfo &MFI, int FrameIdx,
                                      bool StackGrowsDown, Align MaxAlign,
                                      BitVector &StackBytesFree) {
   if (MFI.isVariableSizedObjectIndex(FrameIdx))
     return false;
 
   if (StackBytesFree.none()) {
     // clear it to speed up later scavengeStackSlot calls to
     // StackBytesFree.none()
     StackBytesFree.clear();
     return false;
   }
 
   Align ObjAlign = MFI.getObjectAlign(FrameIdx);
   if (ObjAlign > MaxAlign)
     return false;
 
   int64_t ObjSize = MFI.getObjectSize(FrameIdx);
   int FreeStart;
   for (FreeStart = StackBytesFree.find_first(); FreeStart != -1;
        FreeStart = StackBytesFree.find_next(FreeStart)) {
 
     // Check that free space has suitable alignment.
     unsigned ObjStart = StackGrowsDown ? FreeStart + ObjSize : FreeStart;
     if (alignTo(ObjStart, ObjAlign) != ObjStart)
       continue;
 
     if (FreeStart + ObjSize > StackBytesFree.size())
       return false;
 
     bool AllBytesFree = true;
     for (unsigned Byte = 0; Byte < ObjSize; ++Byte)
       if (!StackBytesFree.test(FreeStart + Byte)) {
         AllBytesFree = false;
         break;
       }
     if (AllBytesFree)
       break;
   }
 
   if (FreeStart == -1)
     return false;
 
   if (StackGrowsDown) {
     int ObjStart = -(FreeStart + ObjSize);
     LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") scavenged at SP["
                       << ObjStart << "]\n");
     MFI.setObjectOffset(FrameIdx, ObjStart);
   } else {
     LLVM_DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") scavenged at SP["
                       << FreeStart << "]\n");
     MFI.setObjectOffset(FrameIdx, FreeStart);
   }
 
   StackBytesFree.reset(FreeStart, FreeStart + ObjSize);
   return true;
 }
 
 /// AssignProtectedObjSet - Helper function to assign large stack objects (i.e.,
 /// those required to be close to the Stack Protector) to stack offsets.
 static void AssignProtectedObjSet(const StackObjSet &UnassignedObjs,
                                   SmallSet<int, 16> &ProtectedObjs,
                                   MachineFrameInfo &MFI, bool StackGrowsDown,
                                   int64_t &Offset, Align &MaxAlign) {
 
   for (int i : UnassignedObjs) {
     AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
     ProtectedObjs.insert(i);
   }
 }
 
 /// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
 /// abstract stack objects.
 void PEI::calculateFrameObjectOffsets(MachineFunction &MF) {
   const TargetFrameLowering &TFI = *MF.getSubtarget().getFrameLowering();
 
   bool StackGrowsDown =
     TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
 
   // Loop over all of the stack objects, assigning sequential addresses...
   MachineFrameInfo &MFI = MF.getFrameInfo();
 
   // Start at the beginning of the local area.
   // The Offset is the distance from the stack top in the direction
   // of stack growth -- so it's always nonnegative.
   int LocalAreaOffset = TFI.getOffsetOfLocalArea();
   if (StackGrowsDown)
     LocalAreaOffset = -LocalAreaOffset;
   assert(LocalAreaOffset >= 0
          && "Local area offset should be in direction of stack growth");
   int64_t Offset = LocalAreaOffset;
 
 #ifdef EXPENSIVE_CHECKS
   for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i)
     if (!MFI.isDeadObjectIndex(i) &&
         MFI.getStackID(i) == TargetStackID::Default)
       assert(MFI.getObjectAlign(i) <= MFI.getMaxAlign() &&
              "MaxAlignment is invalid");
 #endif
 
   // If there are fixed sized objects that are preallocated in the local area,
   // non-fixed objects can't be allocated right at the start of local area.
   // Adjust 'Offset' to point to the end of last fixed sized preallocated
   // object.
   for (int i = MFI.getObjectIndexBegin(); i != 0; ++i) {
     // Only allocate objects on the default stack.
     if (MFI.getStackID(i) != TargetStackID::Default)
       continue;
 
     int64_t FixedOff;
     if (StackGrowsDown) {
       // The maximum distance from the stack pointer is at lower address of
       // the object -- which is given by offset. For down growing stack
       // the offset is negative, so we negate the offset to get the distance.
       FixedOff = -MFI.getObjectOffset(i);
     } else {
       // The maximum distance from the start pointer is at the upper
       // address of the object.
       FixedOff = MFI.getObjectOffset(i) + MFI.getObjectSize(i);
     }
     if (FixedOff > Offset) Offset = FixedOff;
   }
 
   Align MaxAlign = MFI.getMaxAlign();
   // First assign frame offsets to stack objects that are used to spill
   // callee saved registers.
   if (MaxCSFrameIndex >= MinCSFrameIndex) {
     for (unsigned i = 0; i <= MaxCSFrameIndex - MinCSFrameIndex; ++i) {
       unsigned FrameIndex =
           StackGrowsDown ? MinCSFrameIndex + i : MaxCSFrameIndex - i;
 
       // Only allocate objects on the default stack.
       if (MFI.getStackID(FrameIndex) != TargetStackID::Default)
         continue;
 
       // TODO: should this just be if (MFI.isDeadObjectIndex(FrameIndex))
       if (!StackGrowsDown && MFI.isDeadObjectIndex(FrameIndex))
         continue;
 
       AdjustStackOffset(MFI, FrameIndex, StackGrowsDown, Offset, MaxAlign);
     }
   }
 
   assert(MaxAlign == MFI.getMaxAlign() &&
          "MFI.getMaxAlign should already account for all callee-saved "
          "registers without a fixed stack slot");
 
   // FixedCSEnd is the stack offset to the end of the fixed and callee-save
   // stack area.
   int64_t FixedCSEnd = Offset;
 
   // Make sure the special register scavenging spill slot is closest to the
   // incoming stack pointer if a frame pointer is required and is closer
   // to the incoming rather than the final stack pointer.
   const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
   bool EarlyScavengingSlots = TFI.allocateScavengingFrameIndexesNearIncomingSP(MF);
   if (RS && EarlyScavengingSlots) {
     SmallVector<int, 2> SFIs;
     RS->getScavengingFrameIndices(SFIs);
     for (int SFI : SFIs)
       AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
   }
 
   // FIXME: Once this is working, then enable flag will change to a target
   // check for whether the frame is large enough to want to use virtual
   // frame index registers. Functions which don't want/need this optimization
   // will continue to use the existing code path.
   if (MFI.getUseLocalStackAllocationBlock()) {
     Align Alignment = MFI.getLocalFrameMaxAlign();
 
     // Adjust to alignment boundary.
     Offset = alignTo(Offset, Alignment);
 
     LLVM_DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
 
     // Resolve offsets for objects in the local block.
     for (unsigned i = 0, e = MFI.getLocalFrameObjectCount(); i != e; ++i) {
       std::pair<int, int64_t> Entry = MFI.getLocalFrameObjectMap(i);
       int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
       LLVM_DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" << FIOffset
                         << "]\n");
       MFI.setObjectOffset(Entry.first, FIOffset);
     }
     // Allocate the local block
     Offset += MFI.getLocalFrameSize();
 
     MaxAlign = std::max(Alignment, MaxAlign);
   }
 
   // Retrieve the Exception Handler registration node.
   int EHRegNodeFrameIndex = std::numeric_limits<int>::max();
   if (const WinEHFuncInfo *FuncInfo = MF.getWinEHFuncInfo())
     EHRegNodeFrameIndex = FuncInfo->EHRegNodeFrameIndex;
 
   // Make sure that the stack protector comes before the local variables on the
   // stack.
   SmallSet<int, 16> ProtectedObjs;
   if (MFI.hasStackProtectorIndex()) {
     int StackProtectorFI = MFI.getStackProtectorIndex();
     StackObjSet LargeArrayObjs;
     StackObjSet SmallArrayObjs;
     StackObjSet AddrOfObjs;
 
     // If we need a stack protector, we need to make sure that
     // LocalStackSlotPass didn't already allocate a slot for it.
     // If we are told to use the LocalStackAllocationBlock, the stack protector
     // is expected to be already pre-allocated.
     if (MFI.getStackID(StackProtectorFI) != TargetStackID::Default) {
       // If the stack protector isn't on the default stack then it's up to the
       // target to set the stack offset.
       assert(MFI.getObjectOffset(StackProtectorFI) != 0 &&
              "Offset of stack protector on non-default stack expected to be "
              "already set.");
       assert(!MFI.isObjectPreAllocated(MFI.getStackProtectorIndex()) &&
              "Stack protector on non-default stack expected to not be "
              "pre-allocated by LocalStackSlotPass.");
     } else if (!MFI.getUseLocalStackAllocationBlock()) {
       AdjustStackOffset(MFI, StackProtectorFI, StackGrowsDown, Offset,
                         MaxAlign);
     } else if (!MFI.isObjectPreAllocated(MFI.getStackProtectorIndex())) {
       llvm_unreachable(
           "Stack protector not pre-allocated by LocalStackSlotPass.");
     }
 
     // Assign large stack objects first.
     for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) {
       if (MFI.isObjectPreAllocated(i) && MFI.getUseLocalStackAllocationBlock())
         continue;
       if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
         continue;
       if (RS && RS->isScavengingFrameIndex((int)i))
         continue;
       if (MFI.isDeadObjectIndex(i))
         continue;
       if (StackProtectorFI == (int)i || EHRegNodeFrameIndex == (int)i)
         continue;
       // Only allocate objects on the default stack.
       if (MFI.getStackID(i) != TargetStackID::Default)
         continue;
 
       switch (MFI.getObjectSSPLayout(i)) {
       case MachineFrameInfo::SSPLK_None:
         continue;
       case MachineFrameInfo::SSPLK_SmallArray:
         SmallArrayObjs.insert(i);
         continue;
       case MachineFrameInfo::SSPLK_AddrOf:
         AddrOfObjs.insert(i);
         continue;
       case MachineFrameInfo::SSPLK_LargeArray:
         LargeArrayObjs.insert(i);
         continue;
       }
       llvm_unreachable("Unexpected SSPLayoutKind.");
     }
 
     // We expect **all** the protected stack objects to be pre-allocated by
     // LocalStackSlotPass. If it turns out that PEI still has to allocate some
     // of them, we may end up messing up the expected order of the objects.
     if (MFI.getUseLocalStackAllocationBlock() &&
         !(LargeArrayObjs.empty() && SmallArrayObjs.empty() &&
           AddrOfObjs.empty()))
       llvm_unreachable("Found protected stack objects not pre-allocated by "
                        "LocalStackSlotPass.");
 
     AssignProtectedObjSet(LargeArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
                           Offset, MaxAlign);
     AssignProtectedObjSet(SmallArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
                           Offset, MaxAlign);
     AssignProtectedObjSet(AddrOfObjs, ProtectedObjs, MFI, StackGrowsDown,
                           Offset, MaxAlign);
   }
 
   SmallVector<int, 8> ObjectsToAllocate;
 
   // Then prepare to assign frame offsets to stack objects that are not used to
   // spill callee saved registers.
   for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) {
     if (MFI.isObjectPreAllocated(i) && MFI.getUseLocalStackAllocationBlock())
       continue;
     if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
       continue;
     if (RS && RS->isScavengingFrameIndex((int)i))
       continue;
     if (MFI.isDeadObjectIndex(i))
       continue;
     if (MFI.getStackProtectorIndex() == (int)i || EHRegNodeFrameIndex == (int)i)
       continue;
     if (ProtectedObjs.count(i))
       continue;
     // Only allocate objects on the default stack.
     if (MFI.getStackID(i) != TargetStackID::Default)
       continue;
 
     // Add the objects that we need to allocate to our working set.
     ObjectsToAllocate.push_back(i);
   }
 
   // Allocate the EH registration node first if one is present.
   if (EHRegNodeFrameIndex != std::numeric_limits<int>::max())
     AdjustStackOffset(MFI, EHRegNodeFrameIndex, StackGrowsDown, Offset,
                       MaxAlign);
 
   // Give the targets a chance to order the objects the way they like it.
   if (MF.getTarget().getOptLevel() != CodeGenOpt::None &&
       MF.getTarget().Options.StackSymbolOrdering)
     TFI.orderFrameObjects(MF, ObjectsToAllocate);
 
   // Keep track of which bytes in the fixed and callee-save range are used so we
   // can use the holes when allocating later stack objects.  Only do this if
   // stack protector isn't being used and the target requests it and we're
   // optimizing.
   BitVector StackBytesFree;
   if (!ObjectsToAllocate.empty() &&
       MF.getTarget().getOptLevel() != CodeGenOpt::None &&
       MFI.getStackProtectorIndex() < 0 && TFI.enableStackSlotScavenging(MF))
     computeFreeStackSlots(MFI, StackGrowsDown, MinCSFrameIndex, MaxCSFrameIndex,
                           FixedCSEnd, StackBytesFree);
 
   // Now walk the objects and actually assign base offsets to them.
   for (auto &Object : ObjectsToAllocate)
     if (!scavengeStackSlot(MFI, Object, StackGrowsDown, MaxAlign,
                            StackBytesFree))
       AdjustStackOffset(MFI, Object, StackGrowsDown, Offset, MaxAlign);
 
   // Make sure the special register scavenging spill slot is closest to the
   // stack pointer.
   if (RS && !EarlyScavengingSlots) {
     SmallVector<int, 2> SFIs;
     RS->getScavengingFrameIndices(SFIs);
     for (int SFI : SFIs)
       AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
   }
 
   if (!TFI.targetHandlesStackFrameRounding()) {
     // If we have reserved argument space for call sites in the function
     // immediately on entry to the current function, count it as part of the
     // overall stack size.
     if (MFI.adjustsStack() && TFI.hasReservedCallFrame(MF))
       Offset += MFI.getMaxCallFrameSize();
 
     // Round up the size to a multiple of the alignment.  If the function has
     // any calls or alloca's, align to the target's StackAlignment value to
     // ensure that the callee's frame or the alloca data is suitably aligned;
     // otherwise, for leaf functions, align to the TransientStackAlignment
     // value.
     Align StackAlign;
     if (MFI.adjustsStack() || MFI.hasVarSizedObjects() ||
         (RegInfo->hasStackRealignment(MF) && MFI.getObjectIndexEnd() != 0))
       StackAlign = TFI.getStackAlign();
     else
       StackAlign = TFI.getTransientStackAlign();
 
     // If the frame pointer is eliminated, all frame offsets will be relative to
     // SP not FP. Align to MaxAlign so this works.
     StackAlign = std::max(StackAlign, MaxAlign);
     int64_t OffsetBeforeAlignment = Offset;
     Offset = alignTo(Offset, StackAlign);
 
     // If we have increased the offset to fulfill the alignment constrants,
     // then the scavenging spill slots may become harder to reach from the
     // stack pointer, float them so they stay close.
     if (StackGrowsDown && OffsetBeforeAlignment != Offset && RS &&
         !EarlyScavengingSlots) {
       SmallVector<int, 2> SFIs;
       RS->getScavengingFrameIndices(SFIs);
       LLVM_DEBUG(if (!SFIs.empty()) llvm::dbgs()
                      << "Adjusting emergency spill slots!\n";);
       int64_t Delta = Offset - OffsetBeforeAlignment;
       for (int SFI : SFIs) {
         LLVM_DEBUG(llvm::dbgs()
                        << "Adjusting offset of emergency spill slot #" << SFI
                        << " from " << MFI.getObjectOffset(SFI););
         MFI.setObjectOffset(SFI, MFI.getObjectOffset(SFI) - Delta);
         LLVM_DEBUG(llvm::dbgs() << " to " << MFI.getObjectOffset(SFI) << "\n";);
       }
     }
   }
 
   // Update frame info to pretend that this is part of the stack...
   int64_t StackSize = Offset - LocalAreaOffset;
   MFI.setStackSize(StackSize);
   NumBytesStackSpace += StackSize;
 }
 
 /// insertPrologEpilogCode - Scan the function for modified callee saved
 /// registers, insert spill code for these callee saved registers, then add
 /// prolog and epilog code to the function.
 void PEI::insertPrologEpilogCode(MachineFunction &MF) {
   const TargetFrameLowering &TFI = *MF.getSubtarget().getFrameLowering();
 
   // Add prologue to the function...
   for (MachineBasicBlock *SaveBlock : SaveBlocks)
     TFI.emitPrologue(MF, *SaveBlock);
 
   // Add epilogue to restore the callee-save registers in each exiting block.
   for (MachineBasicBlock *RestoreBlock : RestoreBlocks)
     TFI.emitEpilogue(MF, *RestoreBlock);
 
   // Zero call used registers before restoring callee-saved registers.
   insertZeroCallUsedRegs(MF);
 
   for (MachineBasicBlock *SaveBlock : SaveBlocks)
     TFI.inlineStackProbe(MF, *SaveBlock);
 
   // Emit additional code that is required to support segmented stacks, if
   // we've been asked for it.  This, when linked with a runtime with support
   // for segmented stacks (libgcc is one), will result in allocating stack
   // space in small chunks instead of one large contiguous block.
   if (MF.shouldSplitStack()) {
     for (MachineBasicBlock *SaveBlock : SaveBlocks)
       TFI.adjustForSegmentedStacks(MF, *SaveBlock);
   }
 
   // Emit additional code that is required to explicitly handle the stack in
   // HiPE native code (if needed) when loaded in the Erlang/OTP runtime. The
   // approach is rather similar to that of Segmented Stacks, but it uses a
   // different conditional check and another BIF for allocating more stack
   // space.
   if (MF.getFunction().getCallingConv() == CallingConv::HiPE)
     for (MachineBasicBlock *SaveBlock : SaveBlocks)
       TFI.adjustForHiPEPrologue(MF, *SaveBlock);
 }
 
 /// insertZeroCallUsedRegs - Zero out call used registers.
 void PEI::insertZeroCallUsedRegs(MachineFunction &MF) {
   const Function &F = MF.getFunction();
 
   if (!F.hasFnAttribute("zero-call-used-regs"))
     return;
 
   using namespace ZeroCallUsedRegs;
 
   ZeroCallUsedRegsKind ZeroRegsKind =
       StringSwitch<ZeroCallUsedRegsKind>(
           F.getFnAttribute("zero-call-used-regs").getValueAsString())
           .Case("skip", ZeroCallUsedRegsKind::Skip)
           .Case("used-gpr-arg", ZeroCallUsedRegsKind::UsedGPRArg)
           .Case("used-gpr", ZeroCallUsedRegsKind::UsedGPR)
           .Case("used-arg", ZeroCallUsedRegsKind::UsedArg)
           .Case("used", ZeroCallUsedRegsKind::Used)
           .Case("all-gpr-arg", ZeroCallUsedRegsKind::AllGPRArg)
           .Case("all-gpr", ZeroCallUsedRegsKind::AllGPR)
           .Case("all-arg", ZeroCallUsedRegsKind::AllArg)
           .Case("all", ZeroCallUsedRegsKind::All);
 
   if (ZeroRegsKind == ZeroCallUsedRegsKind::Skip)
     return;
 
   const bool OnlyGPR = static_cast<unsigned>(ZeroRegsKind) & ONLY_GPR;
   const bool OnlyUsed = static_cast<unsigned>(ZeroRegsKind) & ONLY_USED;
   const bool OnlyArg = static_cast<unsigned>(ZeroRegsKind) & ONLY_ARG;
 
   const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
   const BitVector AllocatableSet(TRI.getAllocatableSet(MF));
 
   // Mark all used registers.
   BitVector UsedRegs(TRI.getNumRegs());
   if (OnlyUsed)
     for (const MachineBasicBlock &MBB : MF)
       for (const MachineInstr &MI : MBB) {
         // skip debug instructions
         if (MI.isDebugInstr())
           continue;
 
         for (const MachineOperand &MO : MI.operands()) {
           if (!MO.isReg())
             continue;
 
           MCRegister Reg = MO.getReg();
           if (AllocatableSet[Reg] && !MO.isImplicit() &&
               (MO.isDef() || MO.isUse()))
             UsedRegs.set(Reg);
         }
       }
 
   // Get a list of registers that are used.
   BitVector LiveIns(TRI.getNumRegs());
   for (const MachineBasicBlock::RegisterMaskPair &LI : MF.front().liveins())
     LiveIns.set(LI.PhysReg);
 
   BitVector RegsToZero(TRI.getNumRegs());
   for (MCRegister Reg : AllocatableSet.set_bits()) {
     // Skip over fixed registers.
     if (TRI.isFixedRegister(MF, Reg))
       continue;
 
     // Want only general purpose registers.
     if (OnlyGPR && !TRI.isGeneralPurposeRegister(MF, Reg))
       continue;
 
     // Want only used registers.
     if (OnlyUsed && !UsedRegs[Reg])
       continue;
 
     // Want only registers used for arguments.
     if (OnlyArg) {
       if (OnlyUsed) {
         if (!LiveIns[Reg])
           continue;
       } else if (!TRI.isArgumentRegister(MF, Reg)) {
         continue;
       }
     }
 
     RegsToZero.set(Reg);
   }
 
   // Don't clear registers that are live when leaving the function.
   for (const MachineBasicBlock &MBB : MF)
     for (const MachineInstr &MI : MBB.terminators()) {
       if (!MI.isReturn())
         continue;
 
       for (const auto &MO : MI.operands()) {
         if (!MO.isReg())
           continue;
 
         MCRegister Reg = MO.getReg();
+        if (!Reg)
+          continue;
 
         // This picks up sibling registers (e.q. %al -> %ah).
         for (MCRegUnit Unit : TRI.regunits(Reg))
           RegsToZero.reset(Unit);
 
         for (MCPhysReg SReg : TRI.sub_and_superregs_inclusive(Reg))
           RegsToZero.reset(SReg);
       }
     }
 
   // Don't need to clear registers that are used/clobbered by terminating
   // instructions.
   for (const MachineBasicBlock &MBB : MF) {
     if (!MBB.isReturnBlock())
       continue;
 
     MachineBasicBlock::const_iterator MBBI = MBB.getFirstTerminator();
     for (MachineBasicBlock::const_iterator I = MBBI, E = MBB.end(); I != E;
          ++I) {
       for (const MachineOperand &MO : I->operands()) {
         if (!MO.isReg())
           continue;
 
-        for (const MCPhysReg &Reg :
-             TRI.sub_and_superregs_inclusive(MO.getReg()))
+        MCRegister Reg = MO.getReg();
+        if (!Reg)
+          continue;
+
+        for (const MCPhysReg Reg : TRI.sub_and_superregs_inclusive(Reg))
           RegsToZero.reset(Reg);
       }
     }
   }
 
   // Don't clear registers that must be preserved.
   for (const MCPhysReg *CSRegs = TRI.getCalleeSavedRegs(&MF);
        MCPhysReg CSReg = *CSRegs; ++CSRegs)
     for (MCRegister Reg : TRI.sub_and_superregs_inclusive(CSReg))
       RegsToZero.reset(Reg);
 
   const TargetFrameLowering &TFI = *MF.getSubtarget().getFrameLowering();
   for (MachineBasicBlock &MBB : MF)
     if (MBB.isReturnBlock())
       TFI.emitZeroCallUsedRegs(RegsToZero, MBB);
 }
 
 /// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
 /// register references and actual offsets.
 void PEI::replaceFrameIndices(MachineFunction &MF) {
   const auto &ST = MF.getSubtarget();
   const TargetFrameLowering &TFI = *ST.getFrameLowering();
   if (!TFI.needsFrameIndexResolution(MF))
     return;
 
   const TargetRegisterInfo *TRI = ST.getRegisterInfo();
 
   // Allow the target to determine this after knowing the frame size.
   FrameIndexEliminationScavenging = (RS && !FrameIndexVirtualScavenging) ||
     TRI->requiresFrameIndexReplacementScavenging(MF);
 
   // Store SPAdj at exit of a basic block.
   SmallVector<int, 8> SPState;
   SPState.resize(MF.getNumBlockIDs());
   df_iterator_default_set<MachineBasicBlock*> Reachable;
 
   // Iterate over the reachable blocks in DFS order.
   for (auto DFI = df_ext_begin(&MF, Reachable), DFE = df_ext_end(&MF, Reachable);
        DFI != DFE; ++DFI) {
     int SPAdj = 0;
     // Check the exit state of the DFS stack predecessor.
     if (DFI.getPathLength() >= 2) {
       MachineBasicBlock *StackPred = DFI.getPath(DFI.getPathLength() - 2);
       assert(Reachable.count(StackPred) &&
              "DFS stack predecessor is already visited.\n");
       SPAdj = SPState[StackPred->getNumber()];
     }
     MachineBasicBlock *BB = *DFI;
     replaceFrameIndices(BB, MF, SPAdj);
     SPState[BB->getNumber()] = SPAdj;
   }
 
   // Handle the unreachable blocks.
   for (auto &BB : MF) {
     if (Reachable.count(&BB))
       // Already handled in DFS traversal.
       continue;
     int SPAdj = 0;
     replaceFrameIndices(&BB, MF, SPAdj);
   }
 }
 
 bool PEI::replaceFrameIndexDebugInstr(MachineFunction &MF, MachineInstr &MI,
                                       unsigned OpIdx, int SPAdj) {
   const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
   const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
   if (MI.isDebugValue()) {
 
     MachineOperand &Op = MI.getOperand(OpIdx);
     assert(MI.isDebugOperand(&Op) &&
            "Frame indices can only appear as a debug operand in a DBG_VALUE*"
            " machine instruction");
     Register Reg;
     unsigned FrameIdx = Op.getIndex();
     unsigned Size = MF.getFrameInfo().getObjectSize(FrameIdx);
 
     StackOffset Offset = TFI->getFrameIndexReference(MF, FrameIdx, Reg);
     Op.ChangeToRegister(Reg, false /*isDef*/);
 
     const DIExpression *DIExpr = MI.getDebugExpression();
 
     // If we have a direct DBG_VALUE, and its location expression isn't
     // currently complex, then adding an offset will morph it into a
     // complex location that is interpreted as being a memory address.
     // This changes a pointer-valued variable to dereference that pointer,
     // which is incorrect. Fix by adding DW_OP_stack_value.
 
     if (MI.isNonListDebugValue()) {
       unsigned PrependFlags = DIExpression::ApplyOffset;
       if (!MI.isIndirectDebugValue() && !DIExpr->isComplex())
         PrependFlags |= DIExpression::StackValue;
 
       // If we have DBG_VALUE that is indirect and has a Implicit location
       // expression need to insert a deref before prepending a Memory
       // location expression. Also after doing this we change the DBG_VALUE
       // to be direct.
       if (MI.isIndirectDebugValue() && DIExpr->isImplicit()) {
         SmallVector<uint64_t, 2> Ops = {dwarf::DW_OP_deref_size, Size};
         bool WithStackValue = true;
         DIExpr = DIExpression::prependOpcodes(DIExpr, Ops, WithStackValue);
         // Make the DBG_VALUE direct.
         MI.getDebugOffset().ChangeToRegister(0, false);
       }
       DIExpr = TRI.prependOffsetExpression(DIExpr, PrependFlags, Offset);
     } else {
       // The debug operand at DebugOpIndex was a frame index at offset
       // `Offset`; now the operand has been replaced with the frame
       // register, we must add Offset with `register x, plus Offset`.
       unsigned DebugOpIndex = MI.getDebugOperandIndex(&Op);
       SmallVector<uint64_t, 3> Ops;
       TRI.getOffsetOpcodes(Offset, Ops);
       DIExpr = DIExpression::appendOpsToArg(DIExpr, Ops, DebugOpIndex);
     }
     MI.getDebugExpressionOp().setMetadata(DIExpr);
     return true;
   }
 
   if (MI.isDebugPHI()) {
     // Allow stack ref to continue onwards.
     return true;
   }
 
   // TODO: This code should be commoned with the code for
   // PATCHPOINT. There's no good reason for the difference in
   // implementation other than historical accident.  The only
   // remaining difference is the unconditional use of the stack
   // pointer as the base register.
   if (MI.getOpcode() == TargetOpcode::STATEPOINT) {
     assert((!MI.isDebugValue() || OpIdx == 0) &&
            "Frame indicies can only appear as the first operand of a "
            "DBG_VALUE machine instruction");
     Register Reg;
     MachineOperand &Offset = MI.getOperand(OpIdx + 1);
     StackOffset refOffset = TFI->getFrameIndexReferencePreferSP(
         MF, MI.getOperand(OpIdx).getIndex(), Reg, /*IgnoreSPUpdates*/ false);
     assert(!refOffset.getScalable() &&
            "Frame offsets with a scalable component are not supported");
     Offset.setImm(Offset.getImm() + refOffset.getFixed() + SPAdj);
     MI.getOperand(OpIdx).ChangeToRegister(Reg, false /*isDef*/);
     return true;
   }
   return false;
 }
 
 void PEI::replaceFrameIndicesBackward(MachineBasicBlock *BB,
                                       MachineFunction &MF, int &SPAdj) {
   assert(MF.getSubtarget().getRegisterInfo() &&
          "getRegisterInfo() must be implemented!");
 
   const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
   const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
   const TargetFrameLowering &TFI = *MF.getSubtarget().getFrameLowering();
 
   RegScavenger *LocalRS = FrameIndexEliminationScavenging ? RS : nullptr;
   if (LocalRS)
     LocalRS->enterBasicBlockEnd(*BB);
 
   for (MachineInstr &MI : make_early_inc_range(reverse(*BB))) {
     if (TII.isFrameInstr(MI)) {
       TFI.eliminateCallFramePseudoInstr(MF, *BB, &MI);
       continue;
     }
 
     // Step backwards to get the liveness state at (immedately after) MI.
     if (LocalRS)
       LocalRS->backward(MI);
 
     for (unsigned i = 0; i != MI.getNumOperands(); ++i) {
       if (!MI.getOperand(i).isFI())
         continue;
 
       if (replaceFrameIndexDebugInstr(MF, MI, i, SPAdj))
         continue;
 
       // Eliminate this FrameIndex operand.
       //
       // Save and restore the scavenger's position around the call to
       // eliminateFrameIndex in case it erases MI and invalidates the iterator.
       MachineBasicBlock::iterator Save;
       if (LocalRS)
 	Save = std::next(LocalRS->getCurrentPosition());
       bool Removed = TRI.eliminateFrameIndex(MI, SPAdj, i, RS);
       if (LocalRS)
 	LocalRS->skipTo(std::prev(Save));
 
       if (Removed)
         break;
     }
   }
 }
 
 void PEI::replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &MF,
                               int &SPAdj) {
   assert(MF.getSubtarget().getRegisterInfo() &&
          "getRegisterInfo() must be implemented!");
   const TargetInstrInfo &TII = *MF.getSubtarget().getInstrInfo();
   const TargetRegisterInfo &TRI = *MF.getSubtarget().getRegisterInfo();
   const TargetFrameLowering *TFI = MF.getSubtarget().getFrameLowering();
 
   if (TRI.supportsBackwardScavenger())
     return replaceFrameIndicesBackward(BB, MF, SPAdj);
 
   if (RS && FrameIndexEliminationScavenging)
     RS->enterBasicBlock(*BB);
 
   bool InsideCallSequence = false;
 
   for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
     if (TII.isFrameInstr(*I)) {
       InsideCallSequence = TII.isFrameSetup(*I);
       SPAdj += TII.getSPAdjust(*I);
       I = TFI->eliminateCallFramePseudoInstr(MF, *BB, I);
       continue;
     }
 
     MachineInstr &MI = *I;
     bool DoIncr = true;
     bool DidFinishLoop = true;
     for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
       if (!MI.getOperand(i).isFI())
         continue;
 
       if (replaceFrameIndexDebugInstr(MF, MI, i, SPAdj))
         continue;
 
       // Some instructions (e.g. inline asm instructions) can have
       // multiple frame indices and/or cause eliminateFrameIndex
       // to insert more than one instruction. We need the register
       // scavenger to go through all of these instructions so that
       // it can update its register information. We keep the
       // iterator at the point before insertion so that we can
       // revisit them in full.
       bool AtBeginning = (I == BB->begin());
       if (!AtBeginning) --I;
 
       // If this instruction has a FrameIndex operand, we need to
       // use that target machine register info object to eliminate
       // it.
       TRI.eliminateFrameIndex(MI, SPAdj, i,
                               FrameIndexEliminationScavenging ?  RS : nullptr);
 
       // Reset the iterator if we were at the beginning of the BB.
       if (AtBeginning) {
         I = BB->begin();
         DoIncr = false;
       }
 
       DidFinishLoop = false;
       break;
     }
 
     // If we are looking at a call sequence, we need to keep track of
     // the SP adjustment made by each instruction in the sequence.
     // This includes both the frame setup/destroy pseudos (handled above),
     // as well as other instructions that have side effects w.r.t the SP.
     // Note that this must come after eliminateFrameIndex, because
     // if I itself referred to a frame index, we shouldn't count its own
     // adjustment.
     if (DidFinishLoop && InsideCallSequence)
       SPAdj += TII.getSPAdjust(MI);
 
     if (DoIncr && I != BB->end()) ++I;
 
     // Update register states.
     if (RS && FrameIndexEliminationScavenging && DidFinishLoop)
       RS->forward(MI);
   }
 }