Index: stable/11/contrib/llvm/lib/MC/ELFObjectWriter.cpp
===================================================================
--- stable/11/contrib/llvm/lib/MC/ELFObjectWriter.cpp	(revision 344216)
+++ stable/11/contrib/llvm/lib/MC/ELFObjectWriter.cpp	(revision 344217)
@@ -1,1520 +1,1526 @@
 //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements ELF object file writer information.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCFixupKindInfo.h"
 #include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCSymbolELF.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/SMLoc.h"
 #include "llvm/Support/StringSaver.h"
 #include "llvm/Support/SwapByteOrder.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <map>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
 
 #undef  DEBUG_TYPE
 #define DEBUG_TYPE "reloc-info"
 
 namespace {
 
 using SectionIndexMapTy = DenseMap<const MCSectionELF *, uint32_t>;
 
 class ELFObjectWriter;
 struct ELFWriter;
 
 bool isDwoSection(const MCSectionELF &Sec) {
   return Sec.getSectionName().endswith(".dwo");
 }
 
 class SymbolTableWriter {
   ELFWriter &EWriter;
   bool Is64Bit;
 
   // indexes we are going to write to .symtab_shndx.
   std::vector<uint32_t> ShndxIndexes;
 
   // The numbel of symbols written so far.
   unsigned NumWritten;
 
   void createSymtabShndx();
 
   template <typename T> void write(T Value);
 
 public:
   SymbolTableWriter(ELFWriter &EWriter, bool Is64Bit);
 
   void writeSymbol(uint32_t name, uint8_t info, uint64_t value, uint64_t size,
                    uint8_t other, uint32_t shndx, bool Reserved);
 
   ArrayRef<uint32_t> getShndxIndexes() const { return ShndxIndexes; }
 };
 
 struct ELFWriter {
   ELFObjectWriter &OWriter;
   support::endian::Writer W;
 
   enum DwoMode {
     AllSections,
     NonDwoOnly,
     DwoOnly,
   } Mode;
 
   static uint64_t SymbolValue(const MCSymbol &Sym, const MCAsmLayout &Layout);
   static bool isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
                          bool Used, bool Renamed);
 
   /// Helper struct for containing some precomputed information on symbols.
   struct ELFSymbolData {
     const MCSymbolELF *Symbol;
     uint32_t SectionIndex;
     StringRef Name;
 
     // Support lexicographic sorting.
     bool operator<(const ELFSymbolData &RHS) const {
       unsigned LHSType = Symbol->getType();
       unsigned RHSType = RHS.Symbol->getType();
       if (LHSType == ELF::STT_SECTION && RHSType != ELF::STT_SECTION)
         return false;
       if (LHSType != ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
         return true;
       if (LHSType == ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
         return SectionIndex < RHS.SectionIndex;
       return Name < RHS.Name;
     }
   };
 
   /// @}
   /// @name Symbol Table Data
   /// @{
 
   StringTableBuilder StrTabBuilder{StringTableBuilder::ELF};
 
   /// @}
 
   // This holds the symbol table index of the last local symbol.
   unsigned LastLocalSymbolIndex;
   // This holds the .strtab section index.
   unsigned StringTableIndex;
   // This holds the .symtab section index.
   unsigned SymbolTableIndex;
 
   // Sections in the order they are to be output in the section table.
   std::vector<const MCSectionELF *> SectionTable;
   unsigned addToSectionTable(const MCSectionELF *Sec);
 
   // TargetObjectWriter wrappers.
   bool is64Bit() const;
   bool hasRelocationAddend() const;
 
   void align(unsigned Alignment);
 
   bool maybeWriteCompression(uint64_t Size,
                              SmallVectorImpl<char> &CompressedContents,
                              bool ZLibStyle, unsigned Alignment);
 
 public:
   ELFWriter(ELFObjectWriter &OWriter, raw_pwrite_stream &OS,
             bool IsLittleEndian, DwoMode Mode)
       : OWriter(OWriter),
         W(OS, IsLittleEndian ? support::little : support::big), Mode(Mode) {}
 
   void WriteWord(uint64_t Word) {
     if (is64Bit())
       W.write<uint64_t>(Word);
     else
       W.write<uint32_t>(Word);
   }
 
   template <typename T> void write(T Val) {
     W.write(Val);
   }
 
   void writeHeader(const MCAssembler &Asm);
 
   void writeSymbol(SymbolTableWriter &Writer, uint32_t StringIndex,
                    ELFSymbolData &MSD, const MCAsmLayout &Layout);
 
   // Start and end offset of each section
   using SectionOffsetsTy =
       std::map<const MCSectionELF *, std::pair<uint64_t, uint64_t>>;
 
   // Map from a signature symbol to the group section index
   using RevGroupMapTy = DenseMap<const MCSymbol *, unsigned>;
 
   /// Compute the symbol table data
   ///
   /// \param Asm - The assembler.
   /// \param SectionIndexMap - Maps a section to its index.
   /// \param RevGroupMap - Maps a signature symbol to the group section.
   void computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
                           const SectionIndexMapTy &SectionIndexMap,
                           const RevGroupMapTy &RevGroupMap,
                           SectionOffsetsTy &SectionOffsets);
 
   void writeAddrsigSection();
 
   MCSectionELF *createRelocationSection(MCContext &Ctx,
                                         const MCSectionELF &Sec);
 
   const MCSectionELF *createStringTable(MCContext &Ctx);
 
   void writeSectionHeader(const MCAsmLayout &Layout,
                           const SectionIndexMapTy &SectionIndexMap,
                           const SectionOffsetsTy &SectionOffsets);
 
   void writeSectionData(const MCAssembler &Asm, MCSection &Sec,
                         const MCAsmLayout &Layout);
 
   void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
                         uint64_t Address, uint64_t Offset, uint64_t Size,
                         uint32_t Link, uint32_t Info, uint64_t Alignment,
                         uint64_t EntrySize);
 
   void writeRelocations(const MCAssembler &Asm, const MCSectionELF &Sec);
 
   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout);
   void writeSection(const SectionIndexMapTy &SectionIndexMap,
                     uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size,
                     const MCSectionELF &Section);
 };
 
 class ELFObjectWriter : public MCObjectWriter {
   /// The target specific ELF writer instance.
   std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
 
   DenseMap<const MCSectionELF *, std::vector<ELFRelocationEntry>> Relocations;
 
   DenseMap<const MCSymbolELF *, const MCSymbolELF *> Renames;
 
   bool EmitAddrsigSection = false;
   std::vector<const MCSymbol *> AddrsigSyms;
 
   bool hasRelocationAddend() const;
 
   bool shouldRelocateWithSymbol(const MCAssembler &Asm,
                                 const MCSymbolRefExpr *RefA,
                                 const MCSymbolELF *Sym, uint64_t C,
                                 unsigned Type) const;
 
 public:
   ELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW)
       : TargetObjectWriter(std::move(MOTW)) {}
 
   void reset() override {
     Relocations.clear();
     Renames.clear();
     MCObjectWriter::reset();
   }
 
   bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
                                               const MCSymbol &SymA,
                                               const MCFragment &FB, bool InSet,
                                               bool IsPCRel) const override;
 
   virtual bool checkRelocation(MCContext &Ctx, SMLoc Loc,
                                const MCSectionELF *From,
                                const MCSectionELF *To) {
     return true;
   }
 
   void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
                         const MCFragment *Fragment, const MCFixup &Fixup,
                         MCValue Target, uint64_t &FixedValue) override;
 
   void executePostLayoutBinding(MCAssembler &Asm,
                                 const MCAsmLayout &Layout) override;
 
   void emitAddrsigSection() override { EmitAddrsigSection = true; }
   void addAddrsigSymbol(const MCSymbol *Sym) override {
     AddrsigSyms.push_back(Sym);
   }
 
   friend struct ELFWriter;
 };
 
 class ELFSingleObjectWriter : public ELFObjectWriter {
   raw_pwrite_stream &OS;
   bool IsLittleEndian;
 
 public:
   ELFSingleObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
                         raw_pwrite_stream &OS, bool IsLittleEndian)
       : ELFObjectWriter(std::move(MOTW)), OS(OS),
         IsLittleEndian(IsLittleEndian) {}
 
   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override {
     return ELFWriter(*this, OS, IsLittleEndian, ELFWriter::AllSections)
         .writeObject(Asm, Layout);
   }
 
   friend struct ELFWriter;
 };
 
 class ELFDwoObjectWriter : public ELFObjectWriter {
   raw_pwrite_stream &OS, &DwoOS;
   bool IsLittleEndian;
 
 public:
   ELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
                      raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS,
                      bool IsLittleEndian)
       : ELFObjectWriter(std::move(MOTW)), OS(OS), DwoOS(DwoOS),
         IsLittleEndian(IsLittleEndian) {}
 
   virtual bool checkRelocation(MCContext &Ctx, SMLoc Loc,
                                const MCSectionELF *From,
                                const MCSectionELF *To) override {
     if (isDwoSection(*From)) {
       Ctx.reportError(Loc, "A dwo section may not contain relocations");
       return false;
     }
     if (To && isDwoSection(*To)) {
       Ctx.reportError(Loc, "A relocation may not refer to a dwo section");
       return false;
     }
     return true;
   }
 
   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override {
     uint64_t Size = ELFWriter(*this, OS, IsLittleEndian, ELFWriter::NonDwoOnly)
                         .writeObject(Asm, Layout);
     Size += ELFWriter(*this, DwoOS, IsLittleEndian, ELFWriter::DwoOnly)
                 .writeObject(Asm, Layout);
     return Size;
   }
 };
 
 } // end anonymous namespace
 
 void ELFWriter::align(unsigned Alignment) {
   uint64_t Padding = OffsetToAlignment(W.OS.tell(), Alignment);
   W.OS.write_zeros(Padding);
 }
 
 unsigned ELFWriter::addToSectionTable(const MCSectionELF *Sec) {
   SectionTable.push_back(Sec);
   StrTabBuilder.add(Sec->getSectionName());
   return SectionTable.size();
 }
 
 void SymbolTableWriter::createSymtabShndx() {
   if (!ShndxIndexes.empty())
     return;
 
   ShndxIndexes.resize(NumWritten);
 }
 
 template <typename T> void SymbolTableWriter::write(T Value) {
   EWriter.write(Value);
 }
 
 SymbolTableWriter::SymbolTableWriter(ELFWriter &EWriter, bool Is64Bit)
     : EWriter(EWriter), Is64Bit(Is64Bit), NumWritten(0) {}
 
 void SymbolTableWriter::writeSymbol(uint32_t name, uint8_t info, uint64_t value,
                                     uint64_t size, uint8_t other,
                                     uint32_t shndx, bool Reserved) {
   bool LargeIndex = shndx >= ELF::SHN_LORESERVE && !Reserved;
 
   if (LargeIndex)
     createSymtabShndx();
 
   if (!ShndxIndexes.empty()) {
     if (LargeIndex)
       ShndxIndexes.push_back(shndx);
     else
       ShndxIndexes.push_back(0);
   }
 
   uint16_t Index = LargeIndex ? uint16_t(ELF::SHN_XINDEX) : shndx;
 
   if (Is64Bit) {
     write(name);  // st_name
     write(info);  // st_info
     write(other); // st_other
     write(Index); // st_shndx
     write(value); // st_value
     write(size);  // st_size
   } else {
     write(name);            // st_name
     write(uint32_t(value)); // st_value
     write(uint32_t(size));  // st_size
     write(info);            // st_info
     write(other);           // st_other
     write(Index);           // st_shndx
   }
 
   ++NumWritten;
 }
 
 bool ELFWriter::is64Bit() const {
   return OWriter.TargetObjectWriter->is64Bit();
 }
 
 bool ELFWriter::hasRelocationAddend() const {
   return OWriter.hasRelocationAddend();
 }
 
 // Emit the ELF header.
 void ELFWriter::writeHeader(const MCAssembler &Asm) {
   // ELF Header
   // ----------
   //
   // Note
   // ----
   // emitWord method behaves differently for ELF32 and ELF64, writing
   // 4 bytes in the former and 8 in the latter.
 
   W.OS << ELF::ElfMagic; // e_ident[EI_MAG0] to e_ident[EI_MAG3]
 
   W.OS << char(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
 
   // e_ident[EI_DATA]
   W.OS << char(W.Endian == support::little ? ELF::ELFDATA2LSB
                                            : ELF::ELFDATA2MSB);
 
   W.OS << char(ELF::EV_CURRENT);        // e_ident[EI_VERSION]
   // e_ident[EI_OSABI]
   W.OS << char(OWriter.TargetObjectWriter->getOSABI());
   W.OS << char(0);                  // e_ident[EI_ABIVERSION]
 
   W.OS.write_zeros(ELF::EI_NIDENT - ELF::EI_PAD);
 
   W.write<uint16_t>(ELF::ET_REL);             // e_type
 
   W.write<uint16_t>(OWriter.TargetObjectWriter->getEMachine()); // e_machine = target
 
   W.write<uint32_t>(ELF::EV_CURRENT);         // e_version
   WriteWord(0);                    // e_entry, no entry point in .o file
   WriteWord(0);                    // e_phoff, no program header for .o
   WriteWord(0);                     // e_shoff = sec hdr table off in bytes
 
   // e_flags = whatever the target wants
   W.write<uint32_t>(Asm.getELFHeaderEFlags());
 
   // e_ehsize = ELF header size
   W.write<uint16_t>(is64Bit() ? sizeof(ELF::Elf64_Ehdr)
                               : sizeof(ELF::Elf32_Ehdr));
 
   W.write<uint16_t>(0);                  // e_phentsize = prog header entry size
   W.write<uint16_t>(0);                  // e_phnum = # prog header entries = 0
 
   // e_shentsize = Section header entry size
   W.write<uint16_t>(is64Bit() ? sizeof(ELF::Elf64_Shdr)
                               : sizeof(ELF::Elf32_Shdr));
 
   // e_shnum     = # of section header ents
   W.write<uint16_t>(0);
 
   // e_shstrndx  = Section # of '.shstrtab'
   assert(StringTableIndex < ELF::SHN_LORESERVE);
   W.write<uint16_t>(StringTableIndex);
 }
 
 uint64_t ELFWriter::SymbolValue(const MCSymbol &Sym,
                                 const MCAsmLayout &Layout) {
   if (Sym.isCommon() && Sym.isExternal())
     return Sym.getCommonAlignment();
 
   uint64_t Res;
   if (!Layout.getSymbolOffset(Sym, Res))
     return 0;
 
   if (Layout.getAssembler().isThumbFunc(&Sym))
     Res |= 1;
 
   return Res;
 }
 
 static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
   uint8_t Type = newType;
 
   // Propagation rules:
   // IFUNC > FUNC > OBJECT > NOTYPE
   // TLS_OBJECT > OBJECT > NOTYPE
   //
   // dont let the new type degrade the old type
   switch (origType) {
   default:
     break;
   case ELF::STT_GNU_IFUNC:
     if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
         Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
       Type = ELF::STT_GNU_IFUNC;
     break;
   case ELF::STT_FUNC:
     if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
         Type == ELF::STT_TLS)
       Type = ELF::STT_FUNC;
     break;
   case ELF::STT_OBJECT:
     if (Type == ELF::STT_NOTYPE)
       Type = ELF::STT_OBJECT;
     break;
   case ELF::STT_TLS:
     if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
         Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
       Type = ELF::STT_TLS;
     break;
   }
 
   return Type;
 }
 
 void ELFWriter::writeSymbol(SymbolTableWriter &Writer, uint32_t StringIndex,
                             ELFSymbolData &MSD, const MCAsmLayout &Layout) {
   const auto &Symbol = cast<MCSymbolELF>(*MSD.Symbol);
   const MCSymbolELF *Base =
       cast_or_null<MCSymbolELF>(Layout.getBaseSymbol(Symbol));
 
   // This has to be in sync with when computeSymbolTable uses SHN_ABS or
   // SHN_COMMON.
   bool IsReserved = !Base || Symbol.isCommon();
 
   // Binding and Type share the same byte as upper and lower nibbles
   uint8_t Binding = Symbol.getBinding();
   uint8_t Type = Symbol.getType();
   if (Base) {
     Type = mergeTypeForSet(Type, Base->getType());
   }
   uint8_t Info = (Binding << 4) | Type;
 
   // Other and Visibility share the same byte with Visibility using the lower
   // 2 bits
   uint8_t Visibility = Symbol.getVisibility();
   uint8_t Other = Symbol.getOther() | Visibility;
 
   uint64_t Value = SymbolValue(*MSD.Symbol, Layout);
   uint64_t Size = 0;
 
   const MCExpr *ESize = MSD.Symbol->getSize();
   if (!ESize && Base)
     ESize = Base->getSize();
 
   if (ESize) {
     int64_t Res;
     if (!ESize->evaluateKnownAbsolute(Res, Layout))
       report_fatal_error("Size expression must be absolute.");
     Size = Res;
   }
 
   // Write out the symbol table entry
   Writer.writeSymbol(StringIndex, Info, Value, Size, Other, MSD.SectionIndex,
                      IsReserved);
 }
 
 // True if the assembler knows nothing about the final value of the symbol.
 // This doesn't cover the comdat issues, since in those cases the assembler
 // can at least know that all symbols in the section will move together.
 static bool isWeak(const MCSymbolELF &Sym) {
   if (Sym.getType() == ELF::STT_GNU_IFUNC)
     return true;
 
   switch (Sym.getBinding()) {
   default:
     llvm_unreachable("Unknown binding");
   case ELF::STB_LOCAL:
     return false;
   case ELF::STB_GLOBAL:
     return false;
   case ELF::STB_WEAK:
   case ELF::STB_GNU_UNIQUE:
     return true;
   }
 }
 
 bool ELFWriter::isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
                            bool Used, bool Renamed) {
   if (Symbol.isVariable()) {
     const MCExpr *Expr = Symbol.getVariableValue();
     if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) {
       if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF)
         return false;
     }
   }
 
   if (Used)
     return true;
 
   if (Renamed)
     return false;
 
   if (Symbol.isVariable() && Symbol.isUndefined()) {
     // FIXME: this is here just to diagnose the case of a var = commmon_sym.
     Layout.getBaseSymbol(Symbol);
     return false;
   }
 
   if (Symbol.isUndefined() && !Symbol.isBindingSet())
     return false;
 
   if (Symbol.isTemporary())
     return false;
 
   if (Symbol.getType() == ELF::STT_SECTION)
     return false;
 
   return true;
 }
 
 void ELFWriter::computeSymbolTable(
     MCAssembler &Asm, const MCAsmLayout &Layout,
     const SectionIndexMapTy &SectionIndexMap, const RevGroupMapTy &RevGroupMap,
     SectionOffsetsTy &SectionOffsets) {
   MCContext &Ctx = Asm.getContext();
   SymbolTableWriter Writer(*this, is64Bit());
 
   // Symbol table
   unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
   MCSectionELF *SymtabSection =
       Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, EntrySize, "");
   SymtabSection->setAlignment(is64Bit() ? 8 : 4);
   SymbolTableIndex = addToSectionTable(SymtabSection);
 
   align(SymtabSection->getAlignment());
   uint64_t SecStart = W.OS.tell();
 
   // The first entry is the undefined symbol entry.
   Writer.writeSymbol(0, 0, 0, 0, 0, 0, false);
 
   std::vector<ELFSymbolData> LocalSymbolData;
   std::vector<ELFSymbolData> ExternalSymbolData;
 
   // Add the data for the symbols.
   bool HasLargeSectionIndex = false;
   for (const MCSymbol &S : Asm.symbols()) {
     const auto &Symbol = cast<MCSymbolELF>(S);
     bool Used = Symbol.isUsedInReloc();
     bool WeakrefUsed = Symbol.isWeakrefUsedInReloc();
     bool isSignature = Symbol.isSignature();
 
     if (!isInSymtab(Layout, Symbol, Used || WeakrefUsed || isSignature,
                     OWriter.Renames.count(&Symbol)))
       continue;
 
     if (Symbol.isTemporary() && Symbol.isUndefined()) {
       Ctx.reportError(SMLoc(), "Undefined temporary symbol");
       continue;
     }
 
     ELFSymbolData MSD;
     MSD.Symbol = cast<MCSymbolELF>(&Symbol);
 
     bool Local = Symbol.getBinding() == ELF::STB_LOCAL;
     assert(Local || !Symbol.isTemporary());
 
     if (Symbol.isAbsolute()) {
       MSD.SectionIndex = ELF::SHN_ABS;
     } else if (Symbol.isCommon()) {
       assert(!Local);
       MSD.SectionIndex = ELF::SHN_COMMON;
     } else if (Symbol.isUndefined()) {
       if (isSignature && !Used) {
         MSD.SectionIndex = RevGroupMap.lookup(&Symbol);
         if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
           HasLargeSectionIndex = true;
       } else {
         MSD.SectionIndex = ELF::SHN_UNDEF;
       }
     } else {
       const MCSectionELF &Section =
           static_cast<const MCSectionELF &>(Symbol.getSection());
       if (Mode == NonDwoOnly && isDwoSection(Section))
         continue;
       MSD.SectionIndex = SectionIndexMap.lookup(&Section);
       assert(MSD.SectionIndex && "Invalid section index!");
       if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
         HasLargeSectionIndex = true;
     }
 
     StringRef Name = Symbol.getName();
 
     // Sections have their own string table
     if (Symbol.getType() != ELF::STT_SECTION) {
       MSD.Name = Name;
       StrTabBuilder.add(Name);
     }
 
     if (Local)
       LocalSymbolData.push_back(MSD);
     else
       ExternalSymbolData.push_back(MSD);
   }
 
   // This holds the .symtab_shndx section index.
   unsigned SymtabShndxSectionIndex = 0;
 
   if (HasLargeSectionIndex) {
     MCSectionELF *SymtabShndxSection =
         Ctx.getELFSection(".symtab_shndxr", ELF::SHT_SYMTAB_SHNDX, 0, 4, "");
     SymtabShndxSectionIndex = addToSectionTable(SymtabShndxSection);
     SymtabShndxSection->setAlignment(4);
   }
 
   ArrayRef<std::string> FileNames = Asm.getFileNames();
   for (const std::string &Name : FileNames)
     StrTabBuilder.add(Name);
 
   StrTabBuilder.finalize();
 
   // File symbols are emitted first and handled separately from normal symbols,
   // i.e. a non-STT_FILE symbol with the same name may appear.
   for (const std::string &Name : FileNames)
     Writer.writeSymbol(StrTabBuilder.getOffset(Name),
                        ELF::STT_FILE | ELF::STB_LOCAL, 0, 0, ELF::STV_DEFAULT,
                        ELF::SHN_ABS, true);
 
   // Symbols are required to be in lexicographic order.
   array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
   array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
 
   // Set the symbol indices. Local symbols must come before all other
   // symbols with non-local bindings.
   unsigned Index = FileNames.size() + 1;
 
   for (ELFSymbolData &MSD : LocalSymbolData) {
     unsigned StringIndex = MSD.Symbol->getType() == ELF::STT_SECTION
                                ? 0
                                : StrTabBuilder.getOffset(MSD.Name);
     MSD.Symbol->setIndex(Index++);
     writeSymbol(Writer, StringIndex, MSD, Layout);
   }
 
   // Write the symbol table entries.
   LastLocalSymbolIndex = Index;
 
   for (ELFSymbolData &MSD : ExternalSymbolData) {
     unsigned StringIndex = StrTabBuilder.getOffset(MSD.Name);
     MSD.Symbol->setIndex(Index++);
     writeSymbol(Writer, StringIndex, MSD, Layout);
     assert(MSD.Symbol->getBinding() != ELF::STB_LOCAL);
   }
 
   uint64_t SecEnd = W.OS.tell();
   SectionOffsets[SymtabSection] = std::make_pair(SecStart, SecEnd);
 
   ArrayRef<uint32_t> ShndxIndexes = Writer.getShndxIndexes();
   if (ShndxIndexes.empty()) {
     assert(SymtabShndxSectionIndex == 0);
     return;
   }
   assert(SymtabShndxSectionIndex != 0);
 
   SecStart = W.OS.tell();
   const MCSectionELF *SymtabShndxSection =
       SectionTable[SymtabShndxSectionIndex - 1];
   for (uint32_t Index : ShndxIndexes)
     write(Index);
   SecEnd = W.OS.tell();
   SectionOffsets[SymtabShndxSection] = std::make_pair(SecStart, SecEnd);
 }
 
 void ELFWriter::writeAddrsigSection() {
   for (const MCSymbol *Sym : OWriter.AddrsigSyms)
     encodeULEB128(Sym->getIndex(), W.OS);
 }
 
 MCSectionELF *ELFWriter::createRelocationSection(MCContext &Ctx,
                                                  const MCSectionELF &Sec) {
   if (OWriter.Relocations[&Sec].empty())
     return nullptr;
 
   const StringRef SectionName = Sec.getSectionName();
   std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
   RelaSectionName += SectionName;
 
   unsigned EntrySize;
   if (hasRelocationAddend())
     EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
   else
     EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
 
   unsigned Flags = 0;
   if (Sec.getFlags() & ELF::SHF_GROUP)
     Flags = ELF::SHF_GROUP;
 
   MCSectionELF *RelaSection = Ctx.createELFRelSection(
       RelaSectionName, hasRelocationAddend() ? ELF::SHT_RELA : ELF::SHT_REL,
       Flags, EntrySize, Sec.getGroup(), &Sec);
   RelaSection->setAlignment(is64Bit() ? 8 : 4);
   return RelaSection;
 }
 
 // Include the debug info compression header.
 bool ELFWriter::maybeWriteCompression(
     uint64_t Size, SmallVectorImpl<char> &CompressedContents, bool ZLibStyle,
     unsigned Alignment) {
   if (ZLibStyle) {
     uint64_t HdrSize =
         is64Bit() ? sizeof(ELF::Elf32_Chdr) : sizeof(ELF::Elf64_Chdr);
     if (Size <= HdrSize + CompressedContents.size())
       return false;
     // Platform specific header is followed by compressed data.
     if (is64Bit()) {
       // Write Elf64_Chdr header.
       write(static_cast<ELF::Elf64_Word>(ELF::ELFCOMPRESS_ZLIB));
       write(static_cast<ELF::Elf64_Word>(0)); // ch_reserved field.
       write(static_cast<ELF::Elf64_Xword>(Size));
       write(static_cast<ELF::Elf64_Xword>(Alignment));
     } else {
       // Write Elf32_Chdr header otherwise.
       write(static_cast<ELF::Elf32_Word>(ELF::ELFCOMPRESS_ZLIB));
       write(static_cast<ELF::Elf32_Word>(Size));
       write(static_cast<ELF::Elf32_Word>(Alignment));
     }
     return true;
   }
 
   // "ZLIB" followed by 8 bytes representing the uncompressed size of the section,
   // useful for consumers to preallocate a buffer to decompress into.
   const StringRef Magic = "ZLIB";
   if (Size <= Magic.size() + sizeof(Size) + CompressedContents.size())
     return false;
   W.OS << Magic;
   support::endian::write(W.OS, Size, support::big);
   return true;
 }
 
 void ELFWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
                                  const MCAsmLayout &Layout) {
   MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
   StringRef SectionName = Section.getSectionName();
 
   auto &MC = Asm.getContext();
   const auto &MAI = MC.getAsmInfo();
 
   // Compressing debug_frame requires handling alignment fragments which is
   // more work (possibly generalizing MCAssembler.cpp:writeFragment to allow
   // for writing to arbitrary buffers) for little benefit.
   bool CompressionEnabled =
       MAI->compressDebugSections() != DebugCompressionType::None;
   if (!CompressionEnabled || !SectionName.startswith(".debug_") ||
       SectionName == ".debug_frame") {
     Asm.writeSectionData(W.OS, &Section, Layout);
     return;
   }
 
   assert((MAI->compressDebugSections() == DebugCompressionType::Z ||
           MAI->compressDebugSections() == DebugCompressionType::GNU) &&
          "expected zlib or zlib-gnu style compression");
 
   SmallVector<char, 128> UncompressedData;
   raw_svector_ostream VecOS(UncompressedData);
   Asm.writeSectionData(VecOS, &Section, Layout);
 
   SmallVector<char, 128> CompressedContents;
   if (Error E = zlib::compress(
           StringRef(UncompressedData.data(), UncompressedData.size()),
           CompressedContents)) {
     consumeError(std::move(E));
     W.OS << UncompressedData;
     return;
   }
 
   bool ZlibStyle = MAI->compressDebugSections() == DebugCompressionType::Z;
   if (!maybeWriteCompression(UncompressedData.size(), CompressedContents,
                              ZlibStyle, Sec.getAlignment())) {
     W.OS << UncompressedData;
     return;
   }
 
   if (ZlibStyle)
     // Set the compressed flag. That is zlib style.
     Section.setFlags(Section.getFlags() | ELF::SHF_COMPRESSED);
   else
     // Add "z" prefix to section name. This is zlib-gnu style.
     MC.renameELFSection(&Section, (".z" + SectionName.drop_front(1)).str());
   W.OS << CompressedContents;
 }
 
 void ELFWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
                                  uint64_t Address, uint64_t Offset,
                                  uint64_t Size, uint32_t Link, uint32_t Info,
                                  uint64_t Alignment, uint64_t EntrySize) {
   W.write<uint32_t>(Name);        // sh_name: index into string table
   W.write<uint32_t>(Type);        // sh_type
   WriteWord(Flags);     // sh_flags
   WriteWord(Address);   // sh_addr
   WriteWord(Offset);    // sh_offset
   WriteWord(Size);      // sh_size
   W.write<uint32_t>(Link);        // sh_link
   W.write<uint32_t>(Info);        // sh_info
   WriteWord(Alignment); // sh_addralign
   WriteWord(EntrySize); // sh_entsize
 }
 
 void ELFWriter::writeRelocations(const MCAssembler &Asm,
                                        const MCSectionELF &Sec) {
   std::vector<ELFRelocationEntry> &Relocs = OWriter.Relocations[&Sec];
 
   // We record relocations by pushing to the end of a vector. Reverse the vector
   // to get the relocations in the order they were created.
   // In most cases that is not important, but it can be for special sections
   // (.eh_frame) or specific relocations (TLS optimizations on SystemZ).
   std::reverse(Relocs.begin(), Relocs.end());
 
   // Sort the relocation entries. MIPS needs this.
   OWriter.TargetObjectWriter->sortRelocs(Asm, Relocs);
 
   for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
     const ELFRelocationEntry &Entry = Relocs[e - i - 1];
     unsigned Index = Entry.Symbol ? Entry.Symbol->getIndex() : 0;
 
     if (is64Bit()) {
       write(Entry.Offset);
       if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {
         write(uint32_t(Index));
 
         write(OWriter.TargetObjectWriter->getRSsym(Entry.Type));
         write(OWriter.TargetObjectWriter->getRType3(Entry.Type));
         write(OWriter.TargetObjectWriter->getRType2(Entry.Type));
         write(OWriter.TargetObjectWriter->getRType(Entry.Type));
       } else {
         struct ELF::Elf64_Rela ERE64;
         ERE64.setSymbolAndType(Index, Entry.Type);
         write(ERE64.r_info);
       }
       if (hasRelocationAddend())
         write(Entry.Addend);
     } else {
       write(uint32_t(Entry.Offset));
 
       struct ELF::Elf32_Rela ERE32;
       ERE32.setSymbolAndType(Index, Entry.Type);
       write(ERE32.r_info);
 
       if (hasRelocationAddend())
         write(uint32_t(Entry.Addend));
 
       if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {
         if (uint32_t RType =
                 OWriter.TargetObjectWriter->getRType2(Entry.Type)) {
           write(uint32_t(Entry.Offset));
 
           ERE32.setSymbolAndType(0, RType);
           write(ERE32.r_info);
           write(uint32_t(0));
         }
         if (uint32_t RType =
                 OWriter.TargetObjectWriter->getRType3(Entry.Type)) {
           write(uint32_t(Entry.Offset));
 
           ERE32.setSymbolAndType(0, RType);
           write(ERE32.r_info);
           write(uint32_t(0));
         }
       }
     }
   }
 }
 
 const MCSectionELF *ELFWriter::createStringTable(MCContext &Ctx) {
   const MCSectionELF *StrtabSection = SectionTable[StringTableIndex - 1];
   StrTabBuilder.write(W.OS);
   return StrtabSection;
 }
 
 void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
                              uint32_t GroupSymbolIndex, uint64_t Offset,
                              uint64_t Size, const MCSectionELF &Section) {
   uint64_t sh_link = 0;
   uint64_t sh_info = 0;
 
   switch(Section.getType()) {
   default:
     // Nothing to do.
     break;
 
   case ELF::SHT_DYNAMIC:
     llvm_unreachable("SHT_DYNAMIC in a relocatable object");
 
   case ELF::SHT_REL:
   case ELF::SHT_RELA: {
     sh_link = SymbolTableIndex;
     assert(sh_link && ".symtab not found");
     const MCSection *InfoSection = Section.getAssociatedSection();
     sh_info = SectionIndexMap.lookup(cast<MCSectionELF>(InfoSection));
     break;
   }
 
   case ELF::SHT_SYMTAB:
     sh_link = StringTableIndex;
     sh_info = LastLocalSymbolIndex;
     break;
 
   case ELF::SHT_SYMTAB_SHNDX:
   case ELF::SHT_LLVM_CALL_GRAPH_PROFILE:
   case ELF::SHT_LLVM_ADDRSIG:
     sh_link = SymbolTableIndex;
     break;
 
   case ELF::SHT_GROUP:
     sh_link = SymbolTableIndex;
     sh_info = GroupSymbolIndex;
     break;
   }
 
   if (Section.getFlags() & ELF::SHF_LINK_ORDER) {
     const MCSymbol *Sym = Section.getAssociatedSymbol();
     const MCSectionELF *Sec = cast<MCSectionELF>(&Sym->getSection());
     sh_link = SectionIndexMap.lookup(Sec);
   }
 
   WriteSecHdrEntry(StrTabBuilder.getOffset(Section.getSectionName()),
                    Section.getType(), Section.getFlags(), 0, Offset, Size,
                    sh_link, sh_info, Section.getAlignment(),
                    Section.getEntrySize());
 }
 
 void ELFWriter::writeSectionHeader(
     const MCAsmLayout &Layout, const SectionIndexMapTy &SectionIndexMap,
     const SectionOffsetsTy &SectionOffsets) {
   const unsigned NumSections = SectionTable.size();
 
   // Null section first.
   uint64_t FirstSectionSize =
       (NumSections + 1) >= ELF::SHN_LORESERVE ? NumSections + 1 : 0;
   WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, 0, 0, 0, 0);
 
   for (const MCSectionELF *Section : SectionTable) {
     uint32_t GroupSymbolIndex;
     unsigned Type = Section->getType();
     if (Type != ELF::SHT_GROUP)
       GroupSymbolIndex = 0;
     else
       GroupSymbolIndex = Section->getGroup()->getIndex();
 
     const std::pair<uint64_t, uint64_t> &Offsets =
         SectionOffsets.find(Section)->second;
     uint64_t Size;
     if (Type == ELF::SHT_NOBITS)
       Size = Layout.getSectionAddressSize(Section);
     else
       Size = Offsets.second - Offsets.first;
 
     writeSection(SectionIndexMap, GroupSymbolIndex, Offsets.first, Size,
                  *Section);
   }
 }
 
 uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
   uint64_t StartOffset = W.OS.tell();
 
   MCContext &Ctx = Asm.getContext();
   MCSectionELF *StrtabSection =
       Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
   StringTableIndex = addToSectionTable(StrtabSection);
 
   RevGroupMapTy RevGroupMap;
   SectionIndexMapTy SectionIndexMap;
 
   std::map<const MCSymbol *, std::vector<const MCSectionELF *>> GroupMembers;
 
   // Write out the ELF header ...
   writeHeader(Asm);
 
   // ... then the sections ...
   SectionOffsetsTy SectionOffsets;
   std::vector<MCSectionELF *> Groups;
   std::vector<MCSectionELF *> Relocations;
   for (MCSection &Sec : Asm) {
     MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
     if (Mode == NonDwoOnly && isDwoSection(Section))
       continue;
     if (Mode == DwoOnly && !isDwoSection(Section))
       continue;
 
     align(Section.getAlignment());
 
     // Remember the offset into the file for this section.
     uint64_t SecStart = W.OS.tell();
 
     const MCSymbolELF *SignatureSymbol = Section.getGroup();
     writeSectionData(Asm, Section, Layout);
 
     uint64_t SecEnd = W.OS.tell();
     SectionOffsets[&Section] = std::make_pair(SecStart, SecEnd);
 
     MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
 
     if (SignatureSymbol) {
       Asm.registerSymbol(*SignatureSymbol);
       unsigned &GroupIdx = RevGroupMap[SignatureSymbol];
       if (!GroupIdx) {
         MCSectionELF *Group = Ctx.createELFGroupSection(SignatureSymbol);
         GroupIdx = addToSectionTable(Group);
         Group->setAlignment(4);
         Groups.push_back(Group);
       }
       std::vector<const MCSectionELF *> &Members =
           GroupMembers[SignatureSymbol];
       Members.push_back(&Section);
       if (RelSection)
         Members.push_back(RelSection);
     }
 
     SectionIndexMap[&Section] = addToSectionTable(&Section);
     if (RelSection) {
       SectionIndexMap[RelSection] = addToSectionTable(RelSection);
       Relocations.push_back(RelSection);
     }
   }
 
   MCSectionELF *CGProfileSection = nullptr;
   if (!Asm.CGProfile.empty()) {
     CGProfileSection = Ctx.getELFSection(".llvm.call-graph-profile",
                                          ELF::SHT_LLVM_CALL_GRAPH_PROFILE,
                                          ELF::SHF_EXCLUDE, 16, "");
     SectionIndexMap[CGProfileSection] = addToSectionTable(CGProfileSection);
   }
 
   for (MCSectionELF *Group : Groups) {
     align(Group->getAlignment());
 
     // Remember the offset into the file for this section.
     uint64_t SecStart = W.OS.tell();
 
     const MCSymbol *SignatureSymbol = Group->getGroup();
     assert(SignatureSymbol);
     write(uint32_t(ELF::GRP_COMDAT));
     for (const MCSectionELF *Member : GroupMembers[SignatureSymbol]) {
       uint32_t SecIndex = SectionIndexMap.lookup(Member);
       write(SecIndex);
     }
 
     uint64_t SecEnd = W.OS.tell();
     SectionOffsets[Group] = std::make_pair(SecStart, SecEnd);
   }
 
   if (Mode == DwoOnly) {
     // dwo files don't have symbol tables or relocations, but they do have
     // string tables.
     StrTabBuilder.finalize();
   } else {
     MCSectionELF *AddrsigSection;
     if (OWriter.EmitAddrsigSection) {
       AddrsigSection = Ctx.getELFSection(".llvm_addrsig", ELF::SHT_LLVM_ADDRSIG,
                                          ELF::SHF_EXCLUDE);
       addToSectionTable(AddrsigSection);
     }
 
     // Compute symbol table information.
     computeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap,
                        SectionOffsets);
 
     for (MCSectionELF *RelSection : Relocations) {
       align(RelSection->getAlignment());
 
       // Remember the offset into the file for this section.
       uint64_t SecStart = W.OS.tell();
 
       writeRelocations(Asm,
                        cast<MCSectionELF>(*RelSection->getAssociatedSection()));
 
       uint64_t SecEnd = W.OS.tell();
       SectionOffsets[RelSection] = std::make_pair(SecStart, SecEnd);
     }
 
     if (OWriter.EmitAddrsigSection) {
       uint64_t SecStart = W.OS.tell();
       writeAddrsigSection();
       uint64_t SecEnd = W.OS.tell();
       SectionOffsets[AddrsigSection] = std::make_pair(SecStart, SecEnd);
     }
   }
 
   if (CGProfileSection) {
     uint64_t SecStart = W.OS.tell();
     for (const MCAssembler::CGProfileEntry &CGPE : Asm.CGProfile) {
       W.write<uint32_t>(CGPE.From->getSymbol().getIndex());
       W.write<uint32_t>(CGPE.To->getSymbol().getIndex());
       W.write<uint64_t>(CGPE.Count);
     }
     uint64_t SecEnd = W.OS.tell();
     SectionOffsets[CGProfileSection] = std::make_pair(SecStart, SecEnd);
   }
 
   {
     uint64_t SecStart = W.OS.tell();
     const MCSectionELF *Sec = createStringTable(Ctx);
     uint64_t SecEnd = W.OS.tell();
     SectionOffsets[Sec] = std::make_pair(SecStart, SecEnd);
   }
 
   uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
   align(NaturalAlignment);
 
   const uint64_t SectionHeaderOffset = W.OS.tell();
 
   // ... then the section header table ...
   writeSectionHeader(Layout, SectionIndexMap, SectionOffsets);
 
   uint16_t NumSections = support::endian::byte_swap<uint16_t>(
       (SectionTable.size() + 1 >= ELF::SHN_LORESERVE) ? (uint16_t)ELF::SHN_UNDEF
                                                       : SectionTable.size() + 1,
       W.Endian);
   unsigned NumSectionsOffset;
 
   auto &Stream = static_cast<raw_pwrite_stream &>(W.OS);
   if (is64Bit()) {
     uint64_t Val =
         support::endian::byte_swap<uint64_t>(SectionHeaderOffset, W.Endian);
     Stream.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
                   offsetof(ELF::Elf64_Ehdr, e_shoff));
     NumSectionsOffset = offsetof(ELF::Elf64_Ehdr, e_shnum);
   } else {
     uint32_t Val =
         support::endian::byte_swap<uint32_t>(SectionHeaderOffset, W.Endian);
     Stream.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
                   offsetof(ELF::Elf32_Ehdr, e_shoff));
     NumSectionsOffset = offsetof(ELF::Elf32_Ehdr, e_shnum);
   }
   Stream.pwrite(reinterpret_cast<char *>(&NumSections), sizeof(NumSections),
                 NumSectionsOffset);
 
   return W.OS.tell() - StartOffset;
 }
 
 bool ELFObjectWriter::hasRelocationAddend() const {
   return TargetObjectWriter->hasRelocationAddend();
 }
 
 void ELFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
                                                const MCAsmLayout &Layout) {
   // The presence of symbol versions causes undefined symbols and
   // versions declared with @@@ to be renamed.
   for (const std::pair<StringRef, const MCSymbol *> &P : Asm.Symvers) {
     StringRef AliasName = P.first;
     const auto &Symbol = cast<MCSymbolELF>(*P.second);
     size_t Pos = AliasName.find('@');
     assert(Pos != StringRef::npos);
 
     StringRef Prefix = AliasName.substr(0, Pos);
     StringRef Rest = AliasName.substr(Pos);
     StringRef Tail = Rest;
     if (Rest.startswith("@@@"))
       Tail = Rest.substr(Symbol.isUndefined() ? 2 : 1);
 
     auto *Alias =
         cast<MCSymbolELF>(Asm.getContext().getOrCreateSymbol(Prefix + Tail));
     Asm.registerSymbol(*Alias);
     const MCExpr *Value = MCSymbolRefExpr::create(&Symbol, Asm.getContext());
     Alias->setVariableValue(Value);
 
     // Aliases defined with .symvar copy the binding from the symbol they alias.
     // This is the first place we are able to copy this information.
     Alias->setExternal(Symbol.isExternal());
     Alias->setBinding(Symbol.getBinding());
 
     if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
       continue;
 
-    // FIXME: produce a better error message.
+    // FIXME: Get source locations for these errors or diagnose them earlier.
     if (Symbol.isUndefined() && Rest.startswith("@@") &&
-        !Rest.startswith("@@@"))
-      report_fatal_error("A @@ version cannot be undefined");
+        !Rest.startswith("@@@")) {
+      Asm.getContext().reportError(SMLoc(), "versioned symbol " + AliasName +
+                                                " must be defined");
+      continue;
+    }
 
-    if (Renames.count(&Symbol) && Renames[&Symbol] != Alias)
-      report_fatal_error(llvm::Twine("Multiple symbol versions defined for ") +
-                         Symbol.getName());
+    if (Renames.count(&Symbol) && Renames[&Symbol] != Alias) {
+      Asm.getContext().reportError(
+          SMLoc(), llvm::Twine("multiple symbol versions defined for ") +
+                       Symbol.getName());
+      continue;
+    }
 
     Renames.insert(std::make_pair(&Symbol, Alias));
   }
 
   for (const MCSymbol *&Sym : AddrsigSyms) {
     if (const MCSymbol *R = Renames.lookup(cast<MCSymbolELF>(Sym)))
       Sym = R;
     Sym->setUsedInReloc();
   }
 }
 
 // It is always valid to create a relocation with a symbol. It is preferable
 // to use a relocation with a section if that is possible. Using the section
 // allows us to omit some local symbols from the symbol table.
 bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
                                                const MCSymbolRefExpr *RefA,
                                                const MCSymbolELF *Sym,
                                                uint64_t C,
                                                unsigned Type) const {
   // A PCRel relocation to an absolute value has no symbol (or section). We
   // represent that with a relocation to a null section.
   if (!RefA)
     return false;
 
   MCSymbolRefExpr::VariantKind Kind = RefA->getKind();
   switch (Kind) {
   default:
     break;
   // The .odp creation emits a relocation against the symbol ".TOC." which
   // create a R_PPC64_TOC relocation. However the relocation symbol name
   // in final object creation should be NULL, since the symbol does not
   // really exist, it is just the reference to TOC base for the current
   // object file. Since the symbol is undefined, returning false results
   // in a relocation with a null section which is the desired result.
   case MCSymbolRefExpr::VK_PPC_TOCBASE:
     return false;
 
   // These VariantKind cause the relocation to refer to something other than
   // the symbol itself, like a linker generated table. Since the address of
   // symbol is not relevant, we cannot replace the symbol with the
   // section and patch the difference in the addend.
   case MCSymbolRefExpr::VK_GOT:
   case MCSymbolRefExpr::VK_PLT:
   case MCSymbolRefExpr::VK_GOTPCREL:
   case MCSymbolRefExpr::VK_PPC_GOT_LO:
   case MCSymbolRefExpr::VK_PPC_GOT_HI:
   case MCSymbolRefExpr::VK_PPC_GOT_HA:
     return true;
   }
 
   // An undefined symbol is not in any section, so the relocation has to point
   // to the symbol itself.
   assert(Sym && "Expected a symbol");
   if (Sym->isUndefined())
     return true;
 
   unsigned Binding = Sym->getBinding();
   switch(Binding) {
   default:
     llvm_unreachable("Invalid Binding");
   case ELF::STB_LOCAL:
     break;
   case ELF::STB_WEAK:
     // If the symbol is weak, it might be overridden by a symbol in another
     // file. The relocation has to point to the symbol so that the linker
     // can update it.
     return true;
   case ELF::STB_GLOBAL:
     // Global ELF symbols can be preempted by the dynamic linker. The relocation
     // has to point to the symbol for a reason analogous to the STB_WEAK case.
     return true;
   }
 
   // If a relocation points to a mergeable section, we have to be careful.
   // If the offset is zero, a relocation with the section will encode the
   // same information. With a non-zero offset, the situation is different.
   // For example, a relocation can point 42 bytes past the end of a string.
   // If we change such a relocation to use the section, the linker would think
   // that it pointed to another string and subtracting 42 at runtime will
   // produce the wrong value.
   if (Sym->isInSection()) {
     auto &Sec = cast<MCSectionELF>(Sym->getSection());
     unsigned Flags = Sec.getFlags();
     if (Flags & ELF::SHF_MERGE) {
       if (C != 0)
         return true;
 
       // It looks like gold has a bug (http://sourceware.org/PR16794) and can
       // only handle section relocations to mergeable sections if using RELA.
       if (!hasRelocationAddend())
         return true;
     }
 
     // Most TLS relocations use a got, so they need the symbol. Even those that
     // are just an offset (@tpoff), require a symbol in gold versions before
     // 5efeedf61e4fe720fd3e9a08e6c91c10abb66d42 (2014-09-26) which fixed
     // http://sourceware.org/PR16773.
     if (Flags & ELF::SHF_TLS)
       return true;
   }
 
   // If the symbol is a thumb function the final relocation must set the lowest
   // bit. With a symbol that is done by just having the symbol have that bit
   // set, so we would lose the bit if we relocated with the section.
   // FIXME: We could use the section but add the bit to the relocation value.
   if (Asm.isThumbFunc(Sym))
     return true;
 
   if (TargetObjectWriter->needsRelocateWithSymbol(*Sym, Type))
     return true;
   return false;
 }
 
 void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
                                        const MCAsmLayout &Layout,
                                        const MCFragment *Fragment,
                                        const MCFixup &Fixup, MCValue Target,
                                        uint64_t &FixedValue) {
   MCAsmBackend &Backend = Asm.getBackend();
   bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
                  MCFixupKindInfo::FKF_IsPCRel;
   const MCSectionELF &FixupSection = cast<MCSectionELF>(*Fragment->getParent());
   uint64_t C = Target.getConstant();
   uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
   MCContext &Ctx = Asm.getContext();
 
   if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
     // Let A, B and C being the components of Target and R be the location of
     // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
     // If it is pcrel, we want to compute (A - B + C - R).
 
     // In general, ELF has no relocations for -B. It can only represent (A + C)
     // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
     // replace B to implement it: (A - R - K + C)
     if (IsPCRel) {
       Ctx.reportError(
           Fixup.getLoc(),
           "No relocation available to represent this relative expression");
       return;
     }
 
     const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol());
 
     if (SymB.isUndefined()) {
       Ctx.reportError(Fixup.getLoc(),
                       Twine("symbol '") + SymB.getName() +
                           "' can not be undefined in a subtraction expression");
       return;
     }
 
     assert(!SymB.isAbsolute() && "Should have been folded");
     const MCSection &SecB = SymB.getSection();
     if (&SecB != &FixupSection) {
       Ctx.reportError(Fixup.getLoc(),
                       "Cannot represent a difference across sections");
       return;
     }
 
     uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
     uint64_t K = SymBOffset - FixupOffset;
     IsPCRel = true;
     C -= K;
   }
 
   // We either rejected the fixup or folded B into C at this point.
   const MCSymbolRefExpr *RefA = Target.getSymA();
   const auto *SymA = RefA ? cast<MCSymbolELF>(&RefA->getSymbol()) : nullptr;
 
   bool ViaWeakRef = false;
   if (SymA && SymA->isVariable()) {
     const MCExpr *Expr = SymA->getVariableValue();
     if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) {
       if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) {
         SymA = cast<MCSymbolELF>(&Inner->getSymbol());
         ViaWeakRef = true;
       }
     }
   }
 
   unsigned Type = TargetObjectWriter->getRelocType(Ctx, Target, Fixup, IsPCRel);
   uint64_t OriginalC = C;
   bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type);
   if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
     C += Layout.getSymbolOffset(*SymA);
 
   uint64_t Addend = 0;
   if (hasRelocationAddend()) {
     Addend = C;
     C = 0;
   }
 
   FixedValue = C;
 
   const MCSectionELF *SecA = (SymA && SymA->isInSection())
                                  ? cast<MCSectionELF>(&SymA->getSection())
                                  : nullptr;
   if (!checkRelocation(Ctx, Fixup.getLoc(), &FixupSection, SecA))
     return;
 
   if (!RelocateWithSymbol) {
     const auto *SectionSymbol =
         SecA ? cast<MCSymbolELF>(SecA->getBeginSymbol()) : nullptr;
     if (SectionSymbol)
       SectionSymbol->setUsedInReloc();
     ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend, SymA,
                            OriginalC);
     Relocations[&FixupSection].push_back(Rec);
     return;
   }
 
   const auto *RenamedSymA = SymA;
   if (SymA) {
     if (const MCSymbolELF *R = Renames.lookup(SymA))
       RenamedSymA = R;
 
     if (ViaWeakRef)
       RenamedSymA->setIsWeakrefUsedInReloc();
     else
       RenamedSymA->setUsedInReloc();
   }
   ELFRelocationEntry Rec(FixupOffset, RenamedSymA, Type, Addend, SymA,
                          OriginalC);
   Relocations[&FixupSection].push_back(Rec);
 }
 
 bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
     const MCAssembler &Asm, const MCSymbol &SA, const MCFragment &FB,
     bool InSet, bool IsPCRel) const {
   const auto &SymA = cast<MCSymbolELF>(SA);
   if (IsPCRel) {
     assert(!InSet);
     if (isWeak(SymA))
       return false;
   }
   return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
                                                                 InSet, IsPCRel);
 }
 
 std::unique_ptr<MCObjectWriter>
 llvm::createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
                             raw_pwrite_stream &OS, bool IsLittleEndian) {
   return llvm::make_unique<ELFSingleObjectWriter>(std::move(MOTW), OS,
                                                   IsLittleEndian);
 }
 
 std::unique_ptr<MCObjectWriter>
 llvm::createELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
                                raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS,
                                bool IsLittleEndian) {
   return llvm::make_unique<ELFDwoObjectWriter>(std::move(MOTW), OS, DwoOS,
                                                IsLittleEndian);
 }
Index: stable/11
===================================================================
--- stable/11	(revision 344216)
+++ stable/11	(revision 344217)

Property changes on: stable/11
___________________________________________________________________
Modified: svn:mergeinfo
## -0,0 +0,1 ##
   Merged /head:r344112
Index: stable/12/contrib/llvm/lib/MC/ELFObjectWriter.cpp
===================================================================
--- stable/12/contrib/llvm/lib/MC/ELFObjectWriter.cpp	(revision 344216)
+++ stable/12/contrib/llvm/lib/MC/ELFObjectWriter.cpp	(revision 344217)
@@ -1,1520 +1,1526 @@
 //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements ELF object file writer information.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCFixup.h"
 #include "llvm/MC/MCFixupKindInfo.h"
 #include "llvm/MC/MCFragment.h"
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/MC/MCSymbolELF.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Host.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/SMLoc.h"
 #include "llvm/Support/StringSaver.h"
 #include "llvm/Support/SwapByteOrder.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <map>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
 
 #undef  DEBUG_TYPE
 #define DEBUG_TYPE "reloc-info"
 
 namespace {
 
 using SectionIndexMapTy = DenseMap<const MCSectionELF *, uint32_t>;
 
 class ELFObjectWriter;
 struct ELFWriter;
 
 bool isDwoSection(const MCSectionELF &Sec) {
   return Sec.getSectionName().endswith(".dwo");
 }
 
 class SymbolTableWriter {
   ELFWriter &EWriter;
   bool Is64Bit;
 
   // indexes we are going to write to .symtab_shndx.
   std::vector<uint32_t> ShndxIndexes;
 
   // The numbel of symbols written so far.
   unsigned NumWritten;
 
   void createSymtabShndx();
 
   template <typename T> void write(T Value);
 
 public:
   SymbolTableWriter(ELFWriter &EWriter, bool Is64Bit);
 
   void writeSymbol(uint32_t name, uint8_t info, uint64_t value, uint64_t size,
                    uint8_t other, uint32_t shndx, bool Reserved);
 
   ArrayRef<uint32_t> getShndxIndexes() const { return ShndxIndexes; }
 };
 
 struct ELFWriter {
   ELFObjectWriter &OWriter;
   support::endian::Writer W;
 
   enum DwoMode {
     AllSections,
     NonDwoOnly,
     DwoOnly,
   } Mode;
 
   static uint64_t SymbolValue(const MCSymbol &Sym, const MCAsmLayout &Layout);
   static bool isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
                          bool Used, bool Renamed);
 
   /// Helper struct for containing some precomputed information on symbols.
   struct ELFSymbolData {
     const MCSymbolELF *Symbol;
     uint32_t SectionIndex;
     StringRef Name;
 
     // Support lexicographic sorting.
     bool operator<(const ELFSymbolData &RHS) const {
       unsigned LHSType = Symbol->getType();
       unsigned RHSType = RHS.Symbol->getType();
       if (LHSType == ELF::STT_SECTION && RHSType != ELF::STT_SECTION)
         return false;
       if (LHSType != ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
         return true;
       if (LHSType == ELF::STT_SECTION && RHSType == ELF::STT_SECTION)
         return SectionIndex < RHS.SectionIndex;
       return Name < RHS.Name;
     }
   };
 
   /// @}
   /// @name Symbol Table Data
   /// @{
 
   StringTableBuilder StrTabBuilder{StringTableBuilder::ELF};
 
   /// @}
 
   // This holds the symbol table index of the last local symbol.
   unsigned LastLocalSymbolIndex;
   // This holds the .strtab section index.
   unsigned StringTableIndex;
   // This holds the .symtab section index.
   unsigned SymbolTableIndex;
 
   // Sections in the order they are to be output in the section table.
   std::vector<const MCSectionELF *> SectionTable;
   unsigned addToSectionTable(const MCSectionELF *Sec);
 
   // TargetObjectWriter wrappers.
   bool is64Bit() const;
   bool hasRelocationAddend() const;
 
   void align(unsigned Alignment);
 
   bool maybeWriteCompression(uint64_t Size,
                              SmallVectorImpl<char> &CompressedContents,
                              bool ZLibStyle, unsigned Alignment);
 
 public:
   ELFWriter(ELFObjectWriter &OWriter, raw_pwrite_stream &OS,
             bool IsLittleEndian, DwoMode Mode)
       : OWriter(OWriter),
         W(OS, IsLittleEndian ? support::little : support::big), Mode(Mode) {}
 
   void WriteWord(uint64_t Word) {
     if (is64Bit())
       W.write<uint64_t>(Word);
     else
       W.write<uint32_t>(Word);
   }
 
   template <typename T> void write(T Val) {
     W.write(Val);
   }
 
   void writeHeader(const MCAssembler &Asm);
 
   void writeSymbol(SymbolTableWriter &Writer, uint32_t StringIndex,
                    ELFSymbolData &MSD, const MCAsmLayout &Layout);
 
   // Start and end offset of each section
   using SectionOffsetsTy =
       std::map<const MCSectionELF *, std::pair<uint64_t, uint64_t>>;
 
   // Map from a signature symbol to the group section index
   using RevGroupMapTy = DenseMap<const MCSymbol *, unsigned>;
 
   /// Compute the symbol table data
   ///
   /// \param Asm - The assembler.
   /// \param SectionIndexMap - Maps a section to its index.
   /// \param RevGroupMap - Maps a signature symbol to the group section.
   void computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
                           const SectionIndexMapTy &SectionIndexMap,
                           const RevGroupMapTy &RevGroupMap,
                           SectionOffsetsTy &SectionOffsets);
 
   void writeAddrsigSection();
 
   MCSectionELF *createRelocationSection(MCContext &Ctx,
                                         const MCSectionELF &Sec);
 
   const MCSectionELF *createStringTable(MCContext &Ctx);
 
   void writeSectionHeader(const MCAsmLayout &Layout,
                           const SectionIndexMapTy &SectionIndexMap,
                           const SectionOffsetsTy &SectionOffsets);
 
   void writeSectionData(const MCAssembler &Asm, MCSection &Sec,
                         const MCAsmLayout &Layout);
 
   void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
                         uint64_t Address, uint64_t Offset, uint64_t Size,
                         uint32_t Link, uint32_t Info, uint64_t Alignment,
                         uint64_t EntrySize);
 
   void writeRelocations(const MCAssembler &Asm, const MCSectionELF &Sec);
 
   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout);
   void writeSection(const SectionIndexMapTy &SectionIndexMap,
                     uint32_t GroupSymbolIndex, uint64_t Offset, uint64_t Size,
                     const MCSectionELF &Section);
 };
 
 class ELFObjectWriter : public MCObjectWriter {
   /// The target specific ELF writer instance.
   std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
 
   DenseMap<const MCSectionELF *, std::vector<ELFRelocationEntry>> Relocations;
 
   DenseMap<const MCSymbolELF *, const MCSymbolELF *> Renames;
 
   bool EmitAddrsigSection = false;
   std::vector<const MCSymbol *> AddrsigSyms;
 
   bool hasRelocationAddend() const;
 
   bool shouldRelocateWithSymbol(const MCAssembler &Asm,
                                 const MCSymbolRefExpr *RefA,
                                 const MCSymbolELF *Sym, uint64_t C,
                                 unsigned Type) const;
 
 public:
   ELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW)
       : TargetObjectWriter(std::move(MOTW)) {}
 
   void reset() override {
     Relocations.clear();
     Renames.clear();
     MCObjectWriter::reset();
   }
 
   bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
                                               const MCSymbol &SymA,
                                               const MCFragment &FB, bool InSet,
                                               bool IsPCRel) const override;
 
   virtual bool checkRelocation(MCContext &Ctx, SMLoc Loc,
                                const MCSectionELF *From,
                                const MCSectionELF *To) {
     return true;
   }
 
   void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
                         const MCFragment *Fragment, const MCFixup &Fixup,
                         MCValue Target, uint64_t &FixedValue) override;
 
   void executePostLayoutBinding(MCAssembler &Asm,
                                 const MCAsmLayout &Layout) override;
 
   void emitAddrsigSection() override { EmitAddrsigSection = true; }
   void addAddrsigSymbol(const MCSymbol *Sym) override {
     AddrsigSyms.push_back(Sym);
   }
 
   friend struct ELFWriter;
 };
 
 class ELFSingleObjectWriter : public ELFObjectWriter {
   raw_pwrite_stream &OS;
   bool IsLittleEndian;
 
 public:
   ELFSingleObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
                         raw_pwrite_stream &OS, bool IsLittleEndian)
       : ELFObjectWriter(std::move(MOTW)), OS(OS),
         IsLittleEndian(IsLittleEndian) {}
 
   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override {
     return ELFWriter(*this, OS, IsLittleEndian, ELFWriter::AllSections)
         .writeObject(Asm, Layout);
   }
 
   friend struct ELFWriter;
 };
 
 class ELFDwoObjectWriter : public ELFObjectWriter {
   raw_pwrite_stream &OS, &DwoOS;
   bool IsLittleEndian;
 
 public:
   ELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
                      raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS,
                      bool IsLittleEndian)
       : ELFObjectWriter(std::move(MOTW)), OS(OS), DwoOS(DwoOS),
         IsLittleEndian(IsLittleEndian) {}
 
   virtual bool checkRelocation(MCContext &Ctx, SMLoc Loc,
                                const MCSectionELF *From,
                                const MCSectionELF *To) override {
     if (isDwoSection(*From)) {
       Ctx.reportError(Loc, "A dwo section may not contain relocations");
       return false;
     }
     if (To && isDwoSection(*To)) {
       Ctx.reportError(Loc, "A relocation may not refer to a dwo section");
       return false;
     }
     return true;
   }
 
   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override {
     uint64_t Size = ELFWriter(*this, OS, IsLittleEndian, ELFWriter::NonDwoOnly)
                         .writeObject(Asm, Layout);
     Size += ELFWriter(*this, DwoOS, IsLittleEndian, ELFWriter::DwoOnly)
                 .writeObject(Asm, Layout);
     return Size;
   }
 };
 
 } // end anonymous namespace
 
 void ELFWriter::align(unsigned Alignment) {
   uint64_t Padding = OffsetToAlignment(W.OS.tell(), Alignment);
   W.OS.write_zeros(Padding);
 }
 
 unsigned ELFWriter::addToSectionTable(const MCSectionELF *Sec) {
   SectionTable.push_back(Sec);
   StrTabBuilder.add(Sec->getSectionName());
   return SectionTable.size();
 }
 
 void SymbolTableWriter::createSymtabShndx() {
   if (!ShndxIndexes.empty())
     return;
 
   ShndxIndexes.resize(NumWritten);
 }
 
 template <typename T> void SymbolTableWriter::write(T Value) {
   EWriter.write(Value);
 }
 
 SymbolTableWriter::SymbolTableWriter(ELFWriter &EWriter, bool Is64Bit)
     : EWriter(EWriter), Is64Bit(Is64Bit), NumWritten(0) {}
 
 void SymbolTableWriter::writeSymbol(uint32_t name, uint8_t info, uint64_t value,
                                     uint64_t size, uint8_t other,
                                     uint32_t shndx, bool Reserved) {
   bool LargeIndex = shndx >= ELF::SHN_LORESERVE && !Reserved;
 
   if (LargeIndex)
     createSymtabShndx();
 
   if (!ShndxIndexes.empty()) {
     if (LargeIndex)
       ShndxIndexes.push_back(shndx);
     else
       ShndxIndexes.push_back(0);
   }
 
   uint16_t Index = LargeIndex ? uint16_t(ELF::SHN_XINDEX) : shndx;
 
   if (Is64Bit) {
     write(name);  // st_name
     write(info);  // st_info
     write(other); // st_other
     write(Index); // st_shndx
     write(value); // st_value
     write(size);  // st_size
   } else {
     write(name);            // st_name
     write(uint32_t(value)); // st_value
     write(uint32_t(size));  // st_size
     write(info);            // st_info
     write(other);           // st_other
     write(Index);           // st_shndx
   }
 
   ++NumWritten;
 }
 
 bool ELFWriter::is64Bit() const {
   return OWriter.TargetObjectWriter->is64Bit();
 }
 
 bool ELFWriter::hasRelocationAddend() const {
   return OWriter.hasRelocationAddend();
 }
 
 // Emit the ELF header.
 void ELFWriter::writeHeader(const MCAssembler &Asm) {
   // ELF Header
   // ----------
   //
   // Note
   // ----
   // emitWord method behaves differently for ELF32 and ELF64, writing
   // 4 bytes in the former and 8 in the latter.
 
   W.OS << ELF::ElfMagic; // e_ident[EI_MAG0] to e_ident[EI_MAG3]
 
   W.OS << char(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
 
   // e_ident[EI_DATA]
   W.OS << char(W.Endian == support::little ? ELF::ELFDATA2LSB
                                            : ELF::ELFDATA2MSB);
 
   W.OS << char(ELF::EV_CURRENT);        // e_ident[EI_VERSION]
   // e_ident[EI_OSABI]
   W.OS << char(OWriter.TargetObjectWriter->getOSABI());
   W.OS << char(0);                  // e_ident[EI_ABIVERSION]
 
   W.OS.write_zeros(ELF::EI_NIDENT - ELF::EI_PAD);
 
   W.write<uint16_t>(ELF::ET_REL);             // e_type
 
   W.write<uint16_t>(OWriter.TargetObjectWriter->getEMachine()); // e_machine = target
 
   W.write<uint32_t>(ELF::EV_CURRENT);         // e_version
   WriteWord(0);                    // e_entry, no entry point in .o file
   WriteWord(0);                    // e_phoff, no program header for .o
   WriteWord(0);                     // e_shoff = sec hdr table off in bytes
 
   // e_flags = whatever the target wants
   W.write<uint32_t>(Asm.getELFHeaderEFlags());
 
   // e_ehsize = ELF header size
   W.write<uint16_t>(is64Bit() ? sizeof(ELF::Elf64_Ehdr)
                               : sizeof(ELF::Elf32_Ehdr));
 
   W.write<uint16_t>(0);                  // e_phentsize = prog header entry size
   W.write<uint16_t>(0);                  // e_phnum = # prog header entries = 0
 
   // e_shentsize = Section header entry size
   W.write<uint16_t>(is64Bit() ? sizeof(ELF::Elf64_Shdr)
                               : sizeof(ELF::Elf32_Shdr));
 
   // e_shnum     = # of section header ents
   W.write<uint16_t>(0);
 
   // e_shstrndx  = Section # of '.shstrtab'
   assert(StringTableIndex < ELF::SHN_LORESERVE);
   W.write<uint16_t>(StringTableIndex);
 }
 
 uint64_t ELFWriter::SymbolValue(const MCSymbol &Sym,
                                 const MCAsmLayout &Layout) {
   if (Sym.isCommon() && Sym.isExternal())
     return Sym.getCommonAlignment();
 
   uint64_t Res;
   if (!Layout.getSymbolOffset(Sym, Res))
     return 0;
 
   if (Layout.getAssembler().isThumbFunc(&Sym))
     Res |= 1;
 
   return Res;
 }
 
 static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
   uint8_t Type = newType;
 
   // Propagation rules:
   // IFUNC > FUNC > OBJECT > NOTYPE
   // TLS_OBJECT > OBJECT > NOTYPE
   //
   // dont let the new type degrade the old type
   switch (origType) {
   default:
     break;
   case ELF::STT_GNU_IFUNC:
     if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
         Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
       Type = ELF::STT_GNU_IFUNC;
     break;
   case ELF::STT_FUNC:
     if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
         Type == ELF::STT_TLS)
       Type = ELF::STT_FUNC;
     break;
   case ELF::STT_OBJECT:
     if (Type == ELF::STT_NOTYPE)
       Type = ELF::STT_OBJECT;
     break;
   case ELF::STT_TLS:
     if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
         Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
       Type = ELF::STT_TLS;
     break;
   }
 
   return Type;
 }
 
 void ELFWriter::writeSymbol(SymbolTableWriter &Writer, uint32_t StringIndex,
                             ELFSymbolData &MSD, const MCAsmLayout &Layout) {
   const auto &Symbol = cast<MCSymbolELF>(*MSD.Symbol);
   const MCSymbolELF *Base =
       cast_or_null<MCSymbolELF>(Layout.getBaseSymbol(Symbol));
 
   // This has to be in sync with when computeSymbolTable uses SHN_ABS or
   // SHN_COMMON.
   bool IsReserved = !Base || Symbol.isCommon();
 
   // Binding and Type share the same byte as upper and lower nibbles
   uint8_t Binding = Symbol.getBinding();
   uint8_t Type = Symbol.getType();
   if (Base) {
     Type = mergeTypeForSet(Type, Base->getType());
   }
   uint8_t Info = (Binding << 4) | Type;
 
   // Other and Visibility share the same byte with Visibility using the lower
   // 2 bits
   uint8_t Visibility = Symbol.getVisibility();
   uint8_t Other = Symbol.getOther() | Visibility;
 
   uint64_t Value = SymbolValue(*MSD.Symbol, Layout);
   uint64_t Size = 0;
 
   const MCExpr *ESize = MSD.Symbol->getSize();
   if (!ESize && Base)
     ESize = Base->getSize();
 
   if (ESize) {
     int64_t Res;
     if (!ESize->evaluateKnownAbsolute(Res, Layout))
       report_fatal_error("Size expression must be absolute.");
     Size = Res;
   }
 
   // Write out the symbol table entry
   Writer.writeSymbol(StringIndex, Info, Value, Size, Other, MSD.SectionIndex,
                      IsReserved);
 }
 
 // True if the assembler knows nothing about the final value of the symbol.
 // This doesn't cover the comdat issues, since in those cases the assembler
 // can at least know that all symbols in the section will move together.
 static bool isWeak(const MCSymbolELF &Sym) {
   if (Sym.getType() == ELF::STT_GNU_IFUNC)
     return true;
 
   switch (Sym.getBinding()) {
   default:
     llvm_unreachable("Unknown binding");
   case ELF::STB_LOCAL:
     return false;
   case ELF::STB_GLOBAL:
     return false;
   case ELF::STB_WEAK:
   case ELF::STB_GNU_UNIQUE:
     return true;
   }
 }
 
 bool ELFWriter::isInSymtab(const MCAsmLayout &Layout, const MCSymbolELF &Symbol,
                            bool Used, bool Renamed) {
   if (Symbol.isVariable()) {
     const MCExpr *Expr = Symbol.getVariableValue();
     if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) {
       if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF)
         return false;
     }
   }
 
   if (Used)
     return true;
 
   if (Renamed)
     return false;
 
   if (Symbol.isVariable() && Symbol.isUndefined()) {
     // FIXME: this is here just to diagnose the case of a var = commmon_sym.
     Layout.getBaseSymbol(Symbol);
     return false;
   }
 
   if (Symbol.isUndefined() && !Symbol.isBindingSet())
     return false;
 
   if (Symbol.isTemporary())
     return false;
 
   if (Symbol.getType() == ELF::STT_SECTION)
     return false;
 
   return true;
 }
 
 void ELFWriter::computeSymbolTable(
     MCAssembler &Asm, const MCAsmLayout &Layout,
     const SectionIndexMapTy &SectionIndexMap, const RevGroupMapTy &RevGroupMap,
     SectionOffsetsTy &SectionOffsets) {
   MCContext &Ctx = Asm.getContext();
   SymbolTableWriter Writer(*this, is64Bit());
 
   // Symbol table
   unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
   MCSectionELF *SymtabSection =
       Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, EntrySize, "");
   SymtabSection->setAlignment(is64Bit() ? 8 : 4);
   SymbolTableIndex = addToSectionTable(SymtabSection);
 
   align(SymtabSection->getAlignment());
   uint64_t SecStart = W.OS.tell();
 
   // The first entry is the undefined symbol entry.
   Writer.writeSymbol(0, 0, 0, 0, 0, 0, false);
 
   std::vector<ELFSymbolData> LocalSymbolData;
   std::vector<ELFSymbolData> ExternalSymbolData;
 
   // Add the data for the symbols.
   bool HasLargeSectionIndex = false;
   for (const MCSymbol &S : Asm.symbols()) {
     const auto &Symbol = cast<MCSymbolELF>(S);
     bool Used = Symbol.isUsedInReloc();
     bool WeakrefUsed = Symbol.isWeakrefUsedInReloc();
     bool isSignature = Symbol.isSignature();
 
     if (!isInSymtab(Layout, Symbol, Used || WeakrefUsed || isSignature,
                     OWriter.Renames.count(&Symbol)))
       continue;
 
     if (Symbol.isTemporary() && Symbol.isUndefined()) {
       Ctx.reportError(SMLoc(), "Undefined temporary symbol");
       continue;
     }
 
     ELFSymbolData MSD;
     MSD.Symbol = cast<MCSymbolELF>(&Symbol);
 
     bool Local = Symbol.getBinding() == ELF::STB_LOCAL;
     assert(Local || !Symbol.isTemporary());
 
     if (Symbol.isAbsolute()) {
       MSD.SectionIndex = ELF::SHN_ABS;
     } else if (Symbol.isCommon()) {
       assert(!Local);
       MSD.SectionIndex = ELF::SHN_COMMON;
     } else if (Symbol.isUndefined()) {
       if (isSignature && !Used) {
         MSD.SectionIndex = RevGroupMap.lookup(&Symbol);
         if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
           HasLargeSectionIndex = true;
       } else {
         MSD.SectionIndex = ELF::SHN_UNDEF;
       }
     } else {
       const MCSectionELF &Section =
           static_cast<const MCSectionELF &>(Symbol.getSection());
       if (Mode == NonDwoOnly && isDwoSection(Section))
         continue;
       MSD.SectionIndex = SectionIndexMap.lookup(&Section);
       assert(MSD.SectionIndex && "Invalid section index!");
       if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
         HasLargeSectionIndex = true;
     }
 
     StringRef Name = Symbol.getName();
 
     // Sections have their own string table
     if (Symbol.getType() != ELF::STT_SECTION) {
       MSD.Name = Name;
       StrTabBuilder.add(Name);
     }
 
     if (Local)
       LocalSymbolData.push_back(MSD);
     else
       ExternalSymbolData.push_back(MSD);
   }
 
   // This holds the .symtab_shndx section index.
   unsigned SymtabShndxSectionIndex = 0;
 
   if (HasLargeSectionIndex) {
     MCSectionELF *SymtabShndxSection =
         Ctx.getELFSection(".symtab_shndxr", ELF::SHT_SYMTAB_SHNDX, 0, 4, "");
     SymtabShndxSectionIndex = addToSectionTable(SymtabShndxSection);
     SymtabShndxSection->setAlignment(4);
   }
 
   ArrayRef<std::string> FileNames = Asm.getFileNames();
   for (const std::string &Name : FileNames)
     StrTabBuilder.add(Name);
 
   StrTabBuilder.finalize();
 
   // File symbols are emitted first and handled separately from normal symbols,
   // i.e. a non-STT_FILE symbol with the same name may appear.
   for (const std::string &Name : FileNames)
     Writer.writeSymbol(StrTabBuilder.getOffset(Name),
                        ELF::STT_FILE | ELF::STB_LOCAL, 0, 0, ELF::STV_DEFAULT,
                        ELF::SHN_ABS, true);
 
   // Symbols are required to be in lexicographic order.
   array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
   array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
 
   // Set the symbol indices. Local symbols must come before all other
   // symbols with non-local bindings.
   unsigned Index = FileNames.size() + 1;
 
   for (ELFSymbolData &MSD : LocalSymbolData) {
     unsigned StringIndex = MSD.Symbol->getType() == ELF::STT_SECTION
                                ? 0
                                : StrTabBuilder.getOffset(MSD.Name);
     MSD.Symbol->setIndex(Index++);
     writeSymbol(Writer, StringIndex, MSD, Layout);
   }
 
   // Write the symbol table entries.
   LastLocalSymbolIndex = Index;
 
   for (ELFSymbolData &MSD : ExternalSymbolData) {
     unsigned StringIndex = StrTabBuilder.getOffset(MSD.Name);
     MSD.Symbol->setIndex(Index++);
     writeSymbol(Writer, StringIndex, MSD, Layout);
     assert(MSD.Symbol->getBinding() != ELF::STB_LOCAL);
   }
 
   uint64_t SecEnd = W.OS.tell();
   SectionOffsets[SymtabSection] = std::make_pair(SecStart, SecEnd);
 
   ArrayRef<uint32_t> ShndxIndexes = Writer.getShndxIndexes();
   if (ShndxIndexes.empty()) {
     assert(SymtabShndxSectionIndex == 0);
     return;
   }
   assert(SymtabShndxSectionIndex != 0);
 
   SecStart = W.OS.tell();
   const MCSectionELF *SymtabShndxSection =
       SectionTable[SymtabShndxSectionIndex - 1];
   for (uint32_t Index : ShndxIndexes)
     write(Index);
   SecEnd = W.OS.tell();
   SectionOffsets[SymtabShndxSection] = std::make_pair(SecStart, SecEnd);
 }
 
 void ELFWriter::writeAddrsigSection() {
   for (const MCSymbol *Sym : OWriter.AddrsigSyms)
     encodeULEB128(Sym->getIndex(), W.OS);
 }
 
 MCSectionELF *ELFWriter::createRelocationSection(MCContext &Ctx,
                                                  const MCSectionELF &Sec) {
   if (OWriter.Relocations[&Sec].empty())
     return nullptr;
 
   const StringRef SectionName = Sec.getSectionName();
   std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
   RelaSectionName += SectionName;
 
   unsigned EntrySize;
   if (hasRelocationAddend())
     EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
   else
     EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
 
   unsigned Flags = 0;
   if (Sec.getFlags() & ELF::SHF_GROUP)
     Flags = ELF::SHF_GROUP;
 
   MCSectionELF *RelaSection = Ctx.createELFRelSection(
       RelaSectionName, hasRelocationAddend() ? ELF::SHT_RELA : ELF::SHT_REL,
       Flags, EntrySize, Sec.getGroup(), &Sec);
   RelaSection->setAlignment(is64Bit() ? 8 : 4);
   return RelaSection;
 }
 
 // Include the debug info compression header.
 bool ELFWriter::maybeWriteCompression(
     uint64_t Size, SmallVectorImpl<char> &CompressedContents, bool ZLibStyle,
     unsigned Alignment) {
   if (ZLibStyle) {
     uint64_t HdrSize =
         is64Bit() ? sizeof(ELF::Elf32_Chdr) : sizeof(ELF::Elf64_Chdr);
     if (Size <= HdrSize + CompressedContents.size())
       return false;
     // Platform specific header is followed by compressed data.
     if (is64Bit()) {
       // Write Elf64_Chdr header.
       write(static_cast<ELF::Elf64_Word>(ELF::ELFCOMPRESS_ZLIB));
       write(static_cast<ELF::Elf64_Word>(0)); // ch_reserved field.
       write(static_cast<ELF::Elf64_Xword>(Size));
       write(static_cast<ELF::Elf64_Xword>(Alignment));
     } else {
       // Write Elf32_Chdr header otherwise.
       write(static_cast<ELF::Elf32_Word>(ELF::ELFCOMPRESS_ZLIB));
       write(static_cast<ELF::Elf32_Word>(Size));
       write(static_cast<ELF::Elf32_Word>(Alignment));
     }
     return true;
   }
 
   // "ZLIB" followed by 8 bytes representing the uncompressed size of the section,
   // useful for consumers to preallocate a buffer to decompress into.
   const StringRef Magic = "ZLIB";
   if (Size <= Magic.size() + sizeof(Size) + CompressedContents.size())
     return false;
   W.OS << Magic;
   support::endian::write(W.OS, Size, support::big);
   return true;
 }
 
 void ELFWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
                                  const MCAsmLayout &Layout) {
   MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
   StringRef SectionName = Section.getSectionName();
 
   auto &MC = Asm.getContext();
   const auto &MAI = MC.getAsmInfo();
 
   // Compressing debug_frame requires handling alignment fragments which is
   // more work (possibly generalizing MCAssembler.cpp:writeFragment to allow
   // for writing to arbitrary buffers) for little benefit.
   bool CompressionEnabled =
       MAI->compressDebugSections() != DebugCompressionType::None;
   if (!CompressionEnabled || !SectionName.startswith(".debug_") ||
       SectionName == ".debug_frame") {
     Asm.writeSectionData(W.OS, &Section, Layout);
     return;
   }
 
   assert((MAI->compressDebugSections() == DebugCompressionType::Z ||
           MAI->compressDebugSections() == DebugCompressionType::GNU) &&
          "expected zlib or zlib-gnu style compression");
 
   SmallVector<char, 128> UncompressedData;
   raw_svector_ostream VecOS(UncompressedData);
   Asm.writeSectionData(VecOS, &Section, Layout);
 
   SmallVector<char, 128> CompressedContents;
   if (Error E = zlib::compress(
           StringRef(UncompressedData.data(), UncompressedData.size()),
           CompressedContents)) {
     consumeError(std::move(E));
     W.OS << UncompressedData;
     return;
   }
 
   bool ZlibStyle = MAI->compressDebugSections() == DebugCompressionType::Z;
   if (!maybeWriteCompression(UncompressedData.size(), CompressedContents,
                              ZlibStyle, Sec.getAlignment())) {
     W.OS << UncompressedData;
     return;
   }
 
   if (ZlibStyle)
     // Set the compressed flag. That is zlib style.
     Section.setFlags(Section.getFlags() | ELF::SHF_COMPRESSED);
   else
     // Add "z" prefix to section name. This is zlib-gnu style.
     MC.renameELFSection(&Section, (".z" + SectionName.drop_front(1)).str());
   W.OS << CompressedContents;
 }
 
 void ELFWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
                                  uint64_t Address, uint64_t Offset,
                                  uint64_t Size, uint32_t Link, uint32_t Info,
                                  uint64_t Alignment, uint64_t EntrySize) {
   W.write<uint32_t>(Name);        // sh_name: index into string table
   W.write<uint32_t>(Type);        // sh_type
   WriteWord(Flags);     // sh_flags
   WriteWord(Address);   // sh_addr
   WriteWord(Offset);    // sh_offset
   WriteWord(Size);      // sh_size
   W.write<uint32_t>(Link);        // sh_link
   W.write<uint32_t>(Info);        // sh_info
   WriteWord(Alignment); // sh_addralign
   WriteWord(EntrySize); // sh_entsize
 }
 
 void ELFWriter::writeRelocations(const MCAssembler &Asm,
                                        const MCSectionELF &Sec) {
   std::vector<ELFRelocationEntry> &Relocs = OWriter.Relocations[&Sec];
 
   // We record relocations by pushing to the end of a vector. Reverse the vector
   // to get the relocations in the order they were created.
   // In most cases that is not important, but it can be for special sections
   // (.eh_frame) or specific relocations (TLS optimizations on SystemZ).
   std::reverse(Relocs.begin(), Relocs.end());
 
   // Sort the relocation entries. MIPS needs this.
   OWriter.TargetObjectWriter->sortRelocs(Asm, Relocs);
 
   for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
     const ELFRelocationEntry &Entry = Relocs[e - i - 1];
     unsigned Index = Entry.Symbol ? Entry.Symbol->getIndex() : 0;
 
     if (is64Bit()) {
       write(Entry.Offset);
       if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {
         write(uint32_t(Index));
 
         write(OWriter.TargetObjectWriter->getRSsym(Entry.Type));
         write(OWriter.TargetObjectWriter->getRType3(Entry.Type));
         write(OWriter.TargetObjectWriter->getRType2(Entry.Type));
         write(OWriter.TargetObjectWriter->getRType(Entry.Type));
       } else {
         struct ELF::Elf64_Rela ERE64;
         ERE64.setSymbolAndType(Index, Entry.Type);
         write(ERE64.r_info);
       }
       if (hasRelocationAddend())
         write(Entry.Addend);
     } else {
       write(uint32_t(Entry.Offset));
 
       struct ELF::Elf32_Rela ERE32;
       ERE32.setSymbolAndType(Index, Entry.Type);
       write(ERE32.r_info);
 
       if (hasRelocationAddend())
         write(uint32_t(Entry.Addend));
 
       if (OWriter.TargetObjectWriter->getEMachine() == ELF::EM_MIPS) {
         if (uint32_t RType =
                 OWriter.TargetObjectWriter->getRType2(Entry.Type)) {
           write(uint32_t(Entry.Offset));
 
           ERE32.setSymbolAndType(0, RType);
           write(ERE32.r_info);
           write(uint32_t(0));
         }
         if (uint32_t RType =
                 OWriter.TargetObjectWriter->getRType3(Entry.Type)) {
           write(uint32_t(Entry.Offset));
 
           ERE32.setSymbolAndType(0, RType);
           write(ERE32.r_info);
           write(uint32_t(0));
         }
       }
     }
   }
 }
 
 const MCSectionELF *ELFWriter::createStringTable(MCContext &Ctx) {
   const MCSectionELF *StrtabSection = SectionTable[StringTableIndex - 1];
   StrTabBuilder.write(W.OS);
   return StrtabSection;
 }
 
 void ELFWriter::writeSection(const SectionIndexMapTy &SectionIndexMap,
                              uint32_t GroupSymbolIndex, uint64_t Offset,
                              uint64_t Size, const MCSectionELF &Section) {
   uint64_t sh_link = 0;
   uint64_t sh_info = 0;
 
   switch(Section.getType()) {
   default:
     // Nothing to do.
     break;
 
   case ELF::SHT_DYNAMIC:
     llvm_unreachable("SHT_DYNAMIC in a relocatable object");
 
   case ELF::SHT_REL:
   case ELF::SHT_RELA: {
     sh_link = SymbolTableIndex;
     assert(sh_link && ".symtab not found");
     const MCSection *InfoSection = Section.getAssociatedSection();
     sh_info = SectionIndexMap.lookup(cast<MCSectionELF>(InfoSection));
     break;
   }
 
   case ELF::SHT_SYMTAB:
     sh_link = StringTableIndex;
     sh_info = LastLocalSymbolIndex;
     break;
 
   case ELF::SHT_SYMTAB_SHNDX:
   case ELF::SHT_LLVM_CALL_GRAPH_PROFILE:
   case ELF::SHT_LLVM_ADDRSIG:
     sh_link = SymbolTableIndex;
     break;
 
   case ELF::SHT_GROUP:
     sh_link = SymbolTableIndex;
     sh_info = GroupSymbolIndex;
     break;
   }
 
   if (Section.getFlags() & ELF::SHF_LINK_ORDER) {
     const MCSymbol *Sym = Section.getAssociatedSymbol();
     const MCSectionELF *Sec = cast<MCSectionELF>(&Sym->getSection());
     sh_link = SectionIndexMap.lookup(Sec);
   }
 
   WriteSecHdrEntry(StrTabBuilder.getOffset(Section.getSectionName()),
                    Section.getType(), Section.getFlags(), 0, Offset, Size,
                    sh_link, sh_info, Section.getAlignment(),
                    Section.getEntrySize());
 }
 
 void ELFWriter::writeSectionHeader(
     const MCAsmLayout &Layout, const SectionIndexMapTy &SectionIndexMap,
     const SectionOffsetsTy &SectionOffsets) {
   const unsigned NumSections = SectionTable.size();
 
   // Null section first.
   uint64_t FirstSectionSize =
       (NumSections + 1) >= ELF::SHN_LORESERVE ? NumSections + 1 : 0;
   WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, 0, 0, 0, 0);
 
   for (const MCSectionELF *Section : SectionTable) {
     uint32_t GroupSymbolIndex;
     unsigned Type = Section->getType();
     if (Type != ELF::SHT_GROUP)
       GroupSymbolIndex = 0;
     else
       GroupSymbolIndex = Section->getGroup()->getIndex();
 
     const std::pair<uint64_t, uint64_t> &Offsets =
         SectionOffsets.find(Section)->second;
     uint64_t Size;
     if (Type == ELF::SHT_NOBITS)
       Size = Layout.getSectionAddressSize(Section);
     else
       Size = Offsets.second - Offsets.first;
 
     writeSection(SectionIndexMap, GroupSymbolIndex, Offsets.first, Size,
                  *Section);
   }
 }
 
 uint64_t ELFWriter::writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
   uint64_t StartOffset = W.OS.tell();
 
   MCContext &Ctx = Asm.getContext();
   MCSectionELF *StrtabSection =
       Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0);
   StringTableIndex = addToSectionTable(StrtabSection);
 
   RevGroupMapTy RevGroupMap;
   SectionIndexMapTy SectionIndexMap;
 
   std::map<const MCSymbol *, std::vector<const MCSectionELF *>> GroupMembers;
 
   // Write out the ELF header ...
   writeHeader(Asm);
 
   // ... then the sections ...
   SectionOffsetsTy SectionOffsets;
   std::vector<MCSectionELF *> Groups;
   std::vector<MCSectionELF *> Relocations;
   for (MCSection &Sec : Asm) {
     MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
     if (Mode == NonDwoOnly && isDwoSection(Section))
       continue;
     if (Mode == DwoOnly && !isDwoSection(Section))
       continue;
 
     align(Section.getAlignment());
 
     // Remember the offset into the file for this section.
     uint64_t SecStart = W.OS.tell();
 
     const MCSymbolELF *SignatureSymbol = Section.getGroup();
     writeSectionData(Asm, Section, Layout);
 
     uint64_t SecEnd = W.OS.tell();
     SectionOffsets[&Section] = std::make_pair(SecStart, SecEnd);
 
     MCSectionELF *RelSection = createRelocationSection(Ctx, Section);
 
     if (SignatureSymbol) {
       Asm.registerSymbol(*SignatureSymbol);
       unsigned &GroupIdx = RevGroupMap[SignatureSymbol];
       if (!GroupIdx) {
         MCSectionELF *Group = Ctx.createELFGroupSection(SignatureSymbol);
         GroupIdx = addToSectionTable(Group);
         Group->setAlignment(4);
         Groups.push_back(Group);
       }
       std::vector<const MCSectionELF *> &Members =
           GroupMembers[SignatureSymbol];
       Members.push_back(&Section);
       if (RelSection)
         Members.push_back(RelSection);
     }
 
     SectionIndexMap[&Section] = addToSectionTable(&Section);
     if (RelSection) {
       SectionIndexMap[RelSection] = addToSectionTable(RelSection);
       Relocations.push_back(RelSection);
     }
   }
 
   MCSectionELF *CGProfileSection = nullptr;
   if (!Asm.CGProfile.empty()) {
     CGProfileSection = Ctx.getELFSection(".llvm.call-graph-profile",
                                          ELF::SHT_LLVM_CALL_GRAPH_PROFILE,
                                          ELF::SHF_EXCLUDE, 16, "");
     SectionIndexMap[CGProfileSection] = addToSectionTable(CGProfileSection);
   }
 
   for (MCSectionELF *Group : Groups) {
     align(Group->getAlignment());
 
     // Remember the offset into the file for this section.
     uint64_t SecStart = W.OS.tell();
 
     const MCSymbol *SignatureSymbol = Group->getGroup();
     assert(SignatureSymbol);
     write(uint32_t(ELF::GRP_COMDAT));
     for (const MCSectionELF *Member : GroupMembers[SignatureSymbol]) {
       uint32_t SecIndex = SectionIndexMap.lookup(Member);
       write(SecIndex);
     }
 
     uint64_t SecEnd = W.OS.tell();
     SectionOffsets[Group] = std::make_pair(SecStart, SecEnd);
   }
 
   if (Mode == DwoOnly) {
     // dwo files don't have symbol tables or relocations, but they do have
     // string tables.
     StrTabBuilder.finalize();
   } else {
     MCSectionELF *AddrsigSection;
     if (OWriter.EmitAddrsigSection) {
       AddrsigSection = Ctx.getELFSection(".llvm_addrsig", ELF::SHT_LLVM_ADDRSIG,
                                          ELF::SHF_EXCLUDE);
       addToSectionTable(AddrsigSection);
     }
 
     // Compute symbol table information.
     computeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap,
                        SectionOffsets);
 
     for (MCSectionELF *RelSection : Relocations) {
       align(RelSection->getAlignment());
 
       // Remember the offset into the file for this section.
       uint64_t SecStart = W.OS.tell();
 
       writeRelocations(Asm,
                        cast<MCSectionELF>(*RelSection->getAssociatedSection()));
 
       uint64_t SecEnd = W.OS.tell();
       SectionOffsets[RelSection] = std::make_pair(SecStart, SecEnd);
     }
 
     if (OWriter.EmitAddrsigSection) {
       uint64_t SecStart = W.OS.tell();
       writeAddrsigSection();
       uint64_t SecEnd = W.OS.tell();
       SectionOffsets[AddrsigSection] = std::make_pair(SecStart, SecEnd);
     }
   }
 
   if (CGProfileSection) {
     uint64_t SecStart = W.OS.tell();
     for (const MCAssembler::CGProfileEntry &CGPE : Asm.CGProfile) {
       W.write<uint32_t>(CGPE.From->getSymbol().getIndex());
       W.write<uint32_t>(CGPE.To->getSymbol().getIndex());
       W.write<uint64_t>(CGPE.Count);
     }
     uint64_t SecEnd = W.OS.tell();
     SectionOffsets[CGProfileSection] = std::make_pair(SecStart, SecEnd);
   }
 
   {
     uint64_t SecStart = W.OS.tell();
     const MCSectionELF *Sec = createStringTable(Ctx);
     uint64_t SecEnd = W.OS.tell();
     SectionOffsets[Sec] = std::make_pair(SecStart, SecEnd);
   }
 
   uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
   align(NaturalAlignment);
 
   const uint64_t SectionHeaderOffset = W.OS.tell();
 
   // ... then the section header table ...
   writeSectionHeader(Layout, SectionIndexMap, SectionOffsets);
 
   uint16_t NumSections = support::endian::byte_swap<uint16_t>(
       (SectionTable.size() + 1 >= ELF::SHN_LORESERVE) ? (uint16_t)ELF::SHN_UNDEF
                                                       : SectionTable.size() + 1,
       W.Endian);
   unsigned NumSectionsOffset;
 
   auto &Stream = static_cast<raw_pwrite_stream &>(W.OS);
   if (is64Bit()) {
     uint64_t Val =
         support::endian::byte_swap<uint64_t>(SectionHeaderOffset, W.Endian);
     Stream.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
                   offsetof(ELF::Elf64_Ehdr, e_shoff));
     NumSectionsOffset = offsetof(ELF::Elf64_Ehdr, e_shnum);
   } else {
     uint32_t Val =
         support::endian::byte_swap<uint32_t>(SectionHeaderOffset, W.Endian);
     Stream.pwrite(reinterpret_cast<char *>(&Val), sizeof(Val),
                   offsetof(ELF::Elf32_Ehdr, e_shoff));
     NumSectionsOffset = offsetof(ELF::Elf32_Ehdr, e_shnum);
   }
   Stream.pwrite(reinterpret_cast<char *>(&NumSections), sizeof(NumSections),
                 NumSectionsOffset);
 
   return W.OS.tell() - StartOffset;
 }
 
 bool ELFObjectWriter::hasRelocationAddend() const {
   return TargetObjectWriter->hasRelocationAddend();
 }
 
 void ELFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
                                                const MCAsmLayout &Layout) {
   // The presence of symbol versions causes undefined symbols and
   // versions declared with @@@ to be renamed.
   for (const std::pair<StringRef, const MCSymbol *> &P : Asm.Symvers) {
     StringRef AliasName = P.first;
     const auto &Symbol = cast<MCSymbolELF>(*P.second);
     size_t Pos = AliasName.find('@');
     assert(Pos != StringRef::npos);
 
     StringRef Prefix = AliasName.substr(0, Pos);
     StringRef Rest = AliasName.substr(Pos);
     StringRef Tail = Rest;
     if (Rest.startswith("@@@"))
       Tail = Rest.substr(Symbol.isUndefined() ? 2 : 1);
 
     auto *Alias =
         cast<MCSymbolELF>(Asm.getContext().getOrCreateSymbol(Prefix + Tail));
     Asm.registerSymbol(*Alias);
     const MCExpr *Value = MCSymbolRefExpr::create(&Symbol, Asm.getContext());
     Alias->setVariableValue(Value);
 
     // Aliases defined with .symvar copy the binding from the symbol they alias.
     // This is the first place we are able to copy this information.
     Alias->setExternal(Symbol.isExternal());
     Alias->setBinding(Symbol.getBinding());
 
     if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
       continue;
 
-    // FIXME: produce a better error message.
+    // FIXME: Get source locations for these errors or diagnose them earlier.
     if (Symbol.isUndefined() && Rest.startswith("@@") &&
-        !Rest.startswith("@@@"))
-      report_fatal_error("A @@ version cannot be undefined");
+        !Rest.startswith("@@@")) {
+      Asm.getContext().reportError(SMLoc(), "versioned symbol " + AliasName +
+                                                " must be defined");
+      continue;
+    }
 
-    if (Renames.count(&Symbol) && Renames[&Symbol] != Alias)
-      report_fatal_error(llvm::Twine("Multiple symbol versions defined for ") +
-                         Symbol.getName());
+    if (Renames.count(&Symbol) && Renames[&Symbol] != Alias) {
+      Asm.getContext().reportError(
+          SMLoc(), llvm::Twine("multiple symbol versions defined for ") +
+                       Symbol.getName());
+      continue;
+    }
 
     Renames.insert(std::make_pair(&Symbol, Alias));
   }
 
   for (const MCSymbol *&Sym : AddrsigSyms) {
     if (const MCSymbol *R = Renames.lookup(cast<MCSymbolELF>(Sym)))
       Sym = R;
     Sym->setUsedInReloc();
   }
 }
 
 // It is always valid to create a relocation with a symbol. It is preferable
 // to use a relocation with a section if that is possible. Using the section
 // allows us to omit some local symbols from the symbol table.
 bool ELFObjectWriter::shouldRelocateWithSymbol(const MCAssembler &Asm,
                                                const MCSymbolRefExpr *RefA,
                                                const MCSymbolELF *Sym,
                                                uint64_t C,
                                                unsigned Type) const {
   // A PCRel relocation to an absolute value has no symbol (or section). We
   // represent that with a relocation to a null section.
   if (!RefA)
     return false;
 
   MCSymbolRefExpr::VariantKind Kind = RefA->getKind();
   switch (Kind) {
   default:
     break;
   // The .odp creation emits a relocation against the symbol ".TOC." which
   // create a R_PPC64_TOC relocation. However the relocation symbol name
   // in final object creation should be NULL, since the symbol does not
   // really exist, it is just the reference to TOC base for the current
   // object file. Since the symbol is undefined, returning false results
   // in a relocation with a null section which is the desired result.
   case MCSymbolRefExpr::VK_PPC_TOCBASE:
     return false;
 
   // These VariantKind cause the relocation to refer to something other than
   // the symbol itself, like a linker generated table. Since the address of
   // symbol is not relevant, we cannot replace the symbol with the
   // section and patch the difference in the addend.
   case MCSymbolRefExpr::VK_GOT:
   case MCSymbolRefExpr::VK_PLT:
   case MCSymbolRefExpr::VK_GOTPCREL:
   case MCSymbolRefExpr::VK_PPC_GOT_LO:
   case MCSymbolRefExpr::VK_PPC_GOT_HI:
   case MCSymbolRefExpr::VK_PPC_GOT_HA:
     return true;
   }
 
   // An undefined symbol is not in any section, so the relocation has to point
   // to the symbol itself.
   assert(Sym && "Expected a symbol");
   if (Sym->isUndefined())
     return true;
 
   unsigned Binding = Sym->getBinding();
   switch(Binding) {
   default:
     llvm_unreachable("Invalid Binding");
   case ELF::STB_LOCAL:
     break;
   case ELF::STB_WEAK:
     // If the symbol is weak, it might be overridden by a symbol in another
     // file. The relocation has to point to the symbol so that the linker
     // can update it.
     return true;
   case ELF::STB_GLOBAL:
     // Global ELF symbols can be preempted by the dynamic linker. The relocation
     // has to point to the symbol for a reason analogous to the STB_WEAK case.
     return true;
   }
 
   // If a relocation points to a mergeable section, we have to be careful.
   // If the offset is zero, a relocation with the section will encode the
   // same information. With a non-zero offset, the situation is different.
   // For example, a relocation can point 42 bytes past the end of a string.
   // If we change such a relocation to use the section, the linker would think
   // that it pointed to another string and subtracting 42 at runtime will
   // produce the wrong value.
   if (Sym->isInSection()) {
     auto &Sec = cast<MCSectionELF>(Sym->getSection());
     unsigned Flags = Sec.getFlags();
     if (Flags & ELF::SHF_MERGE) {
       if (C != 0)
         return true;
 
       // It looks like gold has a bug (http://sourceware.org/PR16794) and can
       // only handle section relocations to mergeable sections if using RELA.
       if (!hasRelocationAddend())
         return true;
     }
 
     // Most TLS relocations use a got, so they need the symbol. Even those that
     // are just an offset (@tpoff), require a symbol in gold versions before
     // 5efeedf61e4fe720fd3e9a08e6c91c10abb66d42 (2014-09-26) which fixed
     // http://sourceware.org/PR16773.
     if (Flags & ELF::SHF_TLS)
       return true;
   }
 
   // If the symbol is a thumb function the final relocation must set the lowest
   // bit. With a symbol that is done by just having the symbol have that bit
   // set, so we would lose the bit if we relocated with the section.
   // FIXME: We could use the section but add the bit to the relocation value.
   if (Asm.isThumbFunc(Sym))
     return true;
 
   if (TargetObjectWriter->needsRelocateWithSymbol(*Sym, Type))
     return true;
   return false;
 }
 
 void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
                                        const MCAsmLayout &Layout,
                                        const MCFragment *Fragment,
                                        const MCFixup &Fixup, MCValue Target,
                                        uint64_t &FixedValue) {
   MCAsmBackend &Backend = Asm.getBackend();
   bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
                  MCFixupKindInfo::FKF_IsPCRel;
   const MCSectionELF &FixupSection = cast<MCSectionELF>(*Fragment->getParent());
   uint64_t C = Target.getConstant();
   uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
   MCContext &Ctx = Asm.getContext();
 
   if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
     // Let A, B and C being the components of Target and R be the location of
     // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
     // If it is pcrel, we want to compute (A - B + C - R).
 
     // In general, ELF has no relocations for -B. It can only represent (A + C)
     // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
     // replace B to implement it: (A - R - K + C)
     if (IsPCRel) {
       Ctx.reportError(
           Fixup.getLoc(),
           "No relocation available to represent this relative expression");
       return;
     }
 
     const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol());
 
     if (SymB.isUndefined()) {
       Ctx.reportError(Fixup.getLoc(),
                       Twine("symbol '") + SymB.getName() +
                           "' can not be undefined in a subtraction expression");
       return;
     }
 
     assert(!SymB.isAbsolute() && "Should have been folded");
     const MCSection &SecB = SymB.getSection();
     if (&SecB != &FixupSection) {
       Ctx.reportError(Fixup.getLoc(),
                       "Cannot represent a difference across sections");
       return;
     }
 
     uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
     uint64_t K = SymBOffset - FixupOffset;
     IsPCRel = true;
     C -= K;
   }
 
   // We either rejected the fixup or folded B into C at this point.
   const MCSymbolRefExpr *RefA = Target.getSymA();
   const auto *SymA = RefA ? cast<MCSymbolELF>(&RefA->getSymbol()) : nullptr;
 
   bool ViaWeakRef = false;
   if (SymA && SymA->isVariable()) {
     const MCExpr *Expr = SymA->getVariableValue();
     if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) {
       if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) {
         SymA = cast<MCSymbolELF>(&Inner->getSymbol());
         ViaWeakRef = true;
       }
     }
   }
 
   unsigned Type = TargetObjectWriter->getRelocType(Ctx, Target, Fixup, IsPCRel);
   uint64_t OriginalC = C;
   bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type);
   if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
     C += Layout.getSymbolOffset(*SymA);
 
   uint64_t Addend = 0;
   if (hasRelocationAddend()) {
     Addend = C;
     C = 0;
   }
 
   FixedValue = C;
 
   const MCSectionELF *SecA = (SymA && SymA->isInSection())
                                  ? cast<MCSectionELF>(&SymA->getSection())
                                  : nullptr;
   if (!checkRelocation(Ctx, Fixup.getLoc(), &FixupSection, SecA))
     return;
 
   if (!RelocateWithSymbol) {
     const auto *SectionSymbol =
         SecA ? cast<MCSymbolELF>(SecA->getBeginSymbol()) : nullptr;
     if (SectionSymbol)
       SectionSymbol->setUsedInReloc();
     ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend, SymA,
                            OriginalC);
     Relocations[&FixupSection].push_back(Rec);
     return;
   }
 
   const auto *RenamedSymA = SymA;
   if (SymA) {
     if (const MCSymbolELF *R = Renames.lookup(SymA))
       RenamedSymA = R;
 
     if (ViaWeakRef)
       RenamedSymA->setIsWeakrefUsedInReloc();
     else
       RenamedSymA->setUsedInReloc();
   }
   ELFRelocationEntry Rec(FixupOffset, RenamedSymA, Type, Addend, SymA,
                          OriginalC);
   Relocations[&FixupSection].push_back(Rec);
 }
 
 bool ELFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
     const MCAssembler &Asm, const MCSymbol &SA, const MCFragment &FB,
     bool InSet, bool IsPCRel) const {
   const auto &SymA = cast<MCSymbolELF>(SA);
   if (IsPCRel) {
     assert(!InSet);
     if (isWeak(SymA))
       return false;
   }
   return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
                                                                 InSet, IsPCRel);
 }
 
 std::unique_ptr<MCObjectWriter>
 llvm::createELFObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
                             raw_pwrite_stream &OS, bool IsLittleEndian) {
   return llvm::make_unique<ELFSingleObjectWriter>(std::move(MOTW), OS,
                                                   IsLittleEndian);
 }
 
 std::unique_ptr<MCObjectWriter>
 llvm::createELFDwoObjectWriter(std::unique_ptr<MCELFObjectTargetWriter> MOTW,
                                raw_pwrite_stream &OS, raw_pwrite_stream &DwoOS,
                                bool IsLittleEndian) {
   return llvm::make_unique<ELFDwoObjectWriter>(std::move(MOTW), OS, DwoOS,
                                                IsLittleEndian);
 }
Index: stable/12
===================================================================
--- stable/12	(revision 344216)
+++ stable/12	(revision 344217)

Property changes on: stable/12
___________________________________________________________________
Modified: svn:mergeinfo
## -0,0 +0,1 ##
   Merged /head:r344112