Create a SymbolBody for locals

[• rafael]

rebased

[ruiu]

So a natural question to ask is whether LocalSymbol is an appropriate class or not. Conceptually, being local is orthogonal to the type. There can be an undefined local symbol (and I think some ABI like PPC actually has that for some special use case.) What do you think?

[• rafael]

I is probably orthogonal, but having it in place is very handy to
change one thing at a time.

Note that each patch in the series makes the codebase smaller.
Unifying LocalSymbol is what I want to try in patch 4, which will
hopefully delete even more lines :-)

Cheers,
Rafael

[ruiu]

ELF/InputFiles.h

112–115

For consistency with getSymbols, I'd name getLocalSymbols and getNonLocalSymbols.

[ruiu]

LGTM

I build three more programs with and without the series of patches for local symbols (and in addition to that with GNU gold) and observed that the patch series improved performance in all three cases.

Time is in milliseconds.

Clang (RelWithDebugInfo)

w/o patch  13730
w/patch    13224
gold       15795

Clang (RelWithDebugInfo without -f{function,data}-sections)

w/o patch  13300
w/patch    12790
gold       15185

gold in binutils 2.26

w/o patch  542
w/patch    501
gold       726

(The gap between our linker and gold is getting narrower, but that's not a topic of this patch.)

It cannot describe why there is a case that this patch had a negative impact on performance, but I confirmed that the your test result is correct using the archive file you sent to me. So there must be some hidden condition that this approach is not very good at it. But broadly speaking this seems a good one. This makes things much simpler and seems to improve performance in general.

I hoped you did not change the signature of getSymbol in this patch because that change made this patch a lot larger. You could have done that in a different patch. However, since I have already reviewed all the changes, this overall looks good to me.

[Eugene.Zelenko]

Committed in r263222.

ELF/ICF.cpp

 private:
   uint64_t NextId = 1;
 
   static void setLive(SymbolTable<ELFT> *S);
   static uint64_t relSize(InputSection<ELFT> *S);
   static uint64_t getHash(InputSection<ELFT> *S);
   static bool isEligible(InputSectionBase<ELFT> *Sec);
   static std::vector<InputSection<ELFT> *> getSections(SymbolTable<ELFT> *S);
-  static SymbolBody *getSymbol(const InputSection<ELFT> *Sec,
+  static SymbolBody &getSymbol(const InputSection<ELFT> *Sec,
                                const Elf_Rel *Rel);
 
   void segregate(InputSection<ELFT> **Begin, InputSection<ELFT> **End,
                  Comparator Eq);
 
   void forEachGroup(std::vector<InputSection<ELFT> *> &V, Comparator Eq);
 
   template <class RelTy>
ICF<ELFT>::getSections(SymbolTable<ELFT> *Symtab) {
   for (const std::unique_ptr<ObjectFile<ELFT>> &F : Symtab->getObjectFiles())
     for (InputSectionBase<ELFT> *S : F->getSections())
       if (isEligible(S))
         V.push_back(cast<InputSection<ELFT>>(S));
   return V;
 }
 
 template <class ELFT>
-SymbolBody *ICF<ELFT>::getSymbol(const InputSection<ELFT> *Sec,
+SymbolBody &ICF<ELFT>::getSymbol(const InputSection<ELFT> *Sec,
                                  const Elf_Rel *Rel) {
   uint32_t SymIdx = Rel->getSymbol(Config->Mips64EL);
-  return Sec->File->getSymbolBody(SymIdx);
+  return Sec->File->getSymbolBody(SymIdx).repl();
 }
 
 // All sections between Begin and End must have the same group ID before
 // you call this function. This function compare sections between Begin
 // and End using Eq and assign new group IDs for new groups.
 template <class ELFT>
 void ICF<ELFT>::segregate(InputSection<ELFT> **Begin, InputSection<ELFT> **End,
                           Comparator Eq) {

 bool ICF<ELFT>::variableEq(const InputSection<ELFT> *A,
                            const InputSection<ELFT> *B,
                            iterator_range<const RelTy *> RelsA,
                            iterator_range<const RelTy *> RelsB) {
   const RelTy *IA = RelsA.begin();
   const RelTy *EA = RelsA.end();
   const RelTy *IB = RelsB.begin();
   for (; IA != EA; ++IA, ++IB) {
-    // If both IA and IB are pointing to the same local symbol,
-    // this "if" condition must be true.
-    if (A->File == B->File &&
-        IA->getSymbol(Config->Mips64EL) == IB->getSymbol(Config->Mips64EL))
-      continue;
-
-    // Otherwise, IA and IB must be pointing to the global symbols.
-    SymbolBody *SA = getSymbol(A, (const Elf_Rel *)IA);
-    SymbolBody *SB = getSymbol(B, (const Elf_Rel *)IB);
-    if (!SA || !SB)
-      return false;
-
-    // The global symbols should be simply the same.
-    if (SA->repl() == SB->repl())
+    SymbolBody &SA = getSymbol(A, (const Elf_Rel *)IA);
+    SymbolBody &SB = getSymbol(B, (const Elf_Rel *)IB);
+    if (&SA == &SB)
       continue;
 
     // Or, the symbols should be pointing to the same section
     // in terms of the group ID.
-    auto *DA = dyn_cast<DefinedRegular<ELFT>>(SA->repl());
-    auto *DB = dyn_cast<DefinedRegular<ELFT>>(SB->repl());
+    auto *DA = dyn_cast<DefinedRegular<ELFT>>(&SA);
+    auto *DB = dyn_cast<DefinedRegular<ELFT>>(&SB);
     if (!DA || !DB)
       return false;
     if (DA->Sym.st_value != DB->Sym.st_value)
       return false;
     InputSection<ELFT> *X = dyn_cast<InputSection<ELFT>>(DA->Section);
     InputSection<ELFT> *Y = dyn_cast<InputSection<ELFT>>(DB->Section);
     if (X && Y && X->GroupId && X->GroupId == Y->GroupId)
       continue;

ELF/InputFiles.h

public:
   uint32_t getSectionIndex(const Elf_Sym &Sym) const;
 
 protected:
   llvm::object::ELFFile<ELFT> ELFObj;
   const Elf_Shdr *Symtab = nullptr;
   ArrayRef<Elf_Word> SymtabSHNDX;
   StringRef StringTable;
   void initStringTable();
-  Elf_Sym_Range getNonLocalSymbols();
-  Elf_Sym_Range getSymbolsHelper(bool);
+  Elf_Sym_Range getElfSymbols(bool OnlyGlobals);
 };
 
 // .o file.
 template <class ELFT> class ObjectFile : public ELFFileBase<ELFT> {
   typedef ELFFileBase<ELFT> Base;
   typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
   typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
   typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym_Range Elf_Sym_Range;
   typedef typename llvm::object::ELFFile<ELFT>::Elf_Word Elf_Word;
   typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
 
   // uint32 in ELFT's byte order
   typedef llvm::support::detail::packed_endian_specific_integral<
       uint32_t, ELFT::TargetEndianness, 2>
       uint32_X;
 
   StringRef getShtGroupSignature(const Elf_Shdr &Sec);
   ArrayRef<uint32_X> getShtGroupEntries(const Elf_Shdr &Sec);
 
 public:
   static bool classof(const InputFile *F) {
     return F->kind() == Base::ObjectKind;
   }
 
-  ArrayRef<SymbolBody *> getSymbols() { return SymbolBodies; }
+  ArrayRef<SymbolBody *> getSymbols();
+  ArrayRef<SymbolBody *> getLocalSymbolBodies();
+  ArrayRef<SymbolBody *> getNonLocalSymbolBodies();
 
   explicit ObjectFile(MemoryBufferRef M);
   void parse(llvm::DenseSet<StringRef> &ComdatGroups);
 
   ArrayRef<InputSectionBase<ELFT> *> getSections() const { return Sections; }
   InputSectionBase<ELFT> *getSection(const Elf_Sym &Sym) const;
 
-  SymbolBody *getSymbolBody(uint32_t SymbolIndex) const {
-    uint32_t FirstNonLocal = this->Symtab->sh_info;
-    if (SymbolIndex < FirstNonLocal)
-      return nullptr;
-    return SymbolBodies[SymbolIndex - FirstNonLocal];
+  SymbolBody &getSymbolBody(uint32_t SymbolIndex) const {
+    return *SymbolBodies[SymbolIndex];
   }
 
-  Elf_Sym_Range getLocalSymbols();
-  const Elf_Sym *getLocalSymbol(uintX_t SymIndex);
-
   const Elf_Shdr *getSymbolTable() const { return this->Symtab; };
 
   // Get MIPS GP0 value defined by this file. This value represents the gp value
   // used to create the relocatable object and required to support
   // R_MIPS_GPREL16 / R_MIPS_GPREL32 relocations.
   uint32_t getMipsGp0() const;
 
   // The number is the offset in the string table. It will be used as the

ELF/InputFiles.cpp

 ELFKind ELFFileBase<ELFT>::getELFKind() {
   if (ELFT::TargetEndianness == support::little)
     return ELFT::Is64Bits ? ELF64LEKind : ELF32LEKind;
   return ELFT::Is64Bits ? ELF64BEKind : ELF32BEKind;
 }
 
 template <class ELFT>
 typename ELFFileBase<ELFT>::Elf_Sym_Range
-ELFFileBase<ELFT>::getSymbolsHelper(bool Local) {
+ELFFileBase<ELFT>::getElfSymbols(bool OnlyGlobals) {
   if (!Symtab)
     return Elf_Sym_Range(nullptr, nullptr);
   Elf_Sym_Range Syms = ELFObj.symbols(Symtab);
   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
   uint32_t FirstNonLocal = Symtab->sh_info;
   if (FirstNonLocal > NumSymbols)
     fatal("Invalid sh_info in symbol table");
-  if (!Local)
+
+  if (OnlyGlobals)
     return make_range(Syms.begin() + FirstNonLocal, Syms.end());
-  // +1 to skip over dummy symbol.
-  return make_range(Syms.begin() + 1, Syms.begin() + FirstNonLocal);
+  return make_range(Syms.begin(), Syms.end());
 }
 
 template <class ELFT>
 uint32_t ELFFileBase<ELFT>::getSectionIndex(const Elf_Sym &Sym) const {
   uint32_t I = Sym.st_shndx;
   if (I == ELF::SHN_XINDEX)
     return ELFObj.getExtendedSymbolTableIndex(&Sym, Symtab, SymtabSHNDX);
   if (I >= ELF::SHN_LORESERVE)
     return 0;
   return I;
 }
 
 template <class ELFT> void ELFFileBase<ELFT>::initStringTable() {
   if (!Symtab)
     return;
   StringTable = check(ELFObj.getStringTableForSymtab(*Symtab));
 }
 
 template <class ELFT>
-typename ELFFileBase<ELFT>::Elf_Sym_Range
-ELFFileBase<ELFT>::getNonLocalSymbols() {
-  return getSymbolsHelper(false);
+elf::ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
+    : ELFFileBase<ELFT>(Base::ObjectKind, M) {}
+
+template <class ELFT>
+ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getNonLocalSymbolBodies() {
+  if (!this->Symtab)
+    return this->SymbolBodies;
+  uint32_t FirstNonLocal = this->Symtab->sh_info;
+  return makeArrayRef(this->SymbolBodies).slice(FirstNonLocal);
 }
 
 template <class ELFT>
-elf::ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
-    : ELFFileBase<ELFT>(Base::ObjectKind, M) {}
+ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getLocalSymbolBodies() {
+  if (!this->Symtab)
+    return this->SymbolBodies;
+  uint32_t FirstNonLocal = this->Symtab->sh_info;
+  return makeArrayRef(this->SymbolBodies).slice(1, FirstNonLocal - 1);
+}
 
 template <class ELFT>
-typename elf::ObjectFile<ELFT>::Elf_Sym_Range
-elf::ObjectFile<ELFT>::getLocalSymbols() {
-  return this->getSymbolsHelper(true);
+ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getSymbols() {
+  if (!this->Symtab)
+    return this->SymbolBodies;
+  return makeArrayRef(this->SymbolBodies).slice(1);
 }
 
 template <class ELFT> uint32_t elf::ObjectFile<ELFT>::getMipsGp0() const {
   if (MipsReginfo)
     return MipsReginfo->Reginfo->ri_gp_value;
   return 0;
 }
 
 template <class ELFT>
-const typename elf::ObjectFile<ELFT>::Elf_Sym *
-elf::ObjectFile<ELFT>::getLocalSymbol(uintX_t SymIndex) {
-  uint32_t FirstNonLocal = this->Symtab->sh_info;
-  if (SymIndex >= FirstNonLocal)
-    return nullptr;
-  Elf_Sym_Range Syms = this->ELFObj.symbols(this->Symtab);
-  return Syms.begin() + SymIndex;
-}
-
-template <class ELFT>
 void elf::ObjectFile<ELFT>::parse(DenseSet<StringRef> &ComdatGroups) {
   // Read section and symbol tables.
   initializeSections(ComdatGroups);
   initializeSymbols();
 }
 
 // Sections with SHT_GROUP and comdat bits define comdat section groups.
 // They are identified and deduplicated by group name. This function
if (!Config->Relocatable && Name == ".eh_frame")
     return new (EHAlloc.Allocate()) EHInputSection<ELFT>(this, &Sec);
   if (shouldMerge<ELFT>(Sec))
     return new (MAlloc.Allocate()) MergeInputSection<ELFT>(this, &Sec);
   return new (Alloc) InputSection<ELFT>(this, &Sec);
 }
 
 template <class ELFT> void elf::ObjectFile<ELFT>::initializeSymbols() {
   this->initStringTable();
-  Elf_Sym_Range Syms = this->getNonLocalSymbols();
+  Elf_Sym_Range Syms = this->getElfSymbols(false);
   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
   SymbolBodies.reserve(NumSymbols);
   for (const Elf_Sym &Sym : Syms)
     SymbolBodies.push_back(createSymbolBody(&Sym));
 }
 
 template <class ELFT>
 InputSectionBase<ELFT> *
 elf::ObjectFile<ELFT>::getSection(const Elf_Sym &Sym) const {
   uint32_t Index = this->getSectionIndex(Sym);
   if (Index == 0)
     return nullptr;
   if (Index >= Sections.size() || !Sections[Index])
     fatal("Invalid section index");
   InputSectionBase<ELFT> *S = Sections[Index];
   if (S == InputSectionBase<ELFT>::Discarded)
     return S;
   return S->Repl;
 }
 
 template <class ELFT>
 SymbolBody *elf::ObjectFile<ELFT>::createSymbolBody(const Elf_Sym *Sym) {
+  unsigned char Binding = Sym->getBinding();
+  if (Binding == STB_LOCAL)
+    return new (Alloc) LocalSymbol<ELFT>(*Sym);
+
   StringRef Name = check(Sym->getName(this->StringTable));
 
   switch (Sym->st_shndx) {
   case SHN_UNDEF:
     return new (Alloc) UndefinedElf<ELFT>(Name, *Sym);
   case SHN_COMMON:
     return new (Alloc) DefinedCommon(Name, Sym->st_size, Sym->st_value,
                                      Sym->getBinding() == llvm::ELF::STB_WEAK,
                                      Sym->getVisibility());
   }
 
-  switch (Sym->getBinding()) {
+  switch (Binding) {
   default:
     fatal("unexpected binding");
   case STB_GLOBAL:
   case STB_WEAK:
   case STB_GNU_UNIQUE: {
     InputSectionBase<ELFT> *Sec = getSection(*Sym);
     if (Sec == InputSection<ELFT>::Discarded)
       return new (Alloc) UndefinedElf<ELFT>(Name, *Sym);
if (Dyn.d_tag == DT_SONAME) {
       SoName = StringRef(this->StringTable.data() + Val);
       return;
     }
   }
 }
 
 // Fully parse the shared object file. This must be called after parseSoName().
 template <class ELFT> void SharedFile<ELFT>::parseRest() {
-  Elf_Sym_Range Syms = this->getNonLocalSymbols();
+  Elf_Sym_Range Syms = this->getElfSymbols(true);
   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
   SymbolBodies.reserve(NumSymbols);
   for (const Elf_Sym &Sym : Syms) {
     StringRef Name = check(Sym.getName(this->StringTable));
     if (Sym.isUndefined())
       Undefs.push_back(Name);
     else
       SymbolBodies.emplace_back(this, Name, Sym);

ELF/InputSection.cpp

 }
 
 // Returns a section that Rel relocation is pointing to.
 template <class ELFT>
 InputSectionBase<ELFT> *
 InputSectionBase<ELFT>::getRelocTarget(const Elf_Rel &Rel) const {
   // Global symbol
   uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
-  if (SymbolBody *B = File->getSymbolBody(SymIndex))
-    if (auto *D = dyn_cast<DefinedRegular<ELFT>>(B->repl()))
-      return D->Section->Repl;
-  // Local symbol
-  if (const Elf_Sym *Sym = File->getLocalSymbol(SymIndex))
-    if (InputSectionBase<ELFT> *Sec = File->getSection(*Sym))
+  SymbolBody &B = File->getSymbolBody(SymIndex).repl();
+  if (auto *D = dyn_cast<DefinedRegular<ELFT>>(&B))
+  if (auto *L = dyn_cast<LocalSymbol<ELFT>>(&B))
+    if (InputSectionBase<ELFT> *Sec = File->getSection(L->Sym))
       return Sec;
   return nullptr;
 }
 
 template <class ELFT>
 InputSectionBase<ELFT> *
 InputSectionBase<ELFT>::getRelocTarget(const Elf_Rela &Rel) const {
   return getRelocTarget(reinterpret_cast<const Elf_Rel &>(Rel));

 void InputSection<ELFT>::copyRelocations(uint8_t *Buf,
                                          RelIteratorRange<isRela> Rels) {
   typedef Elf_Rel_Impl<ELFT, isRela> RelType;
   InputSectionBase<ELFT> *RelocatedSection = getRelocatedSection();
 
   for (const RelType &Rel : Rels) {
     uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
     uint32_t Type = Rel.getType(Config->Mips64EL);
-    const Elf_Shdr *SymTab = this->File->getSymbolTable();
+    SymbolBody &Body = this->File->getSymbolBody(SymIndex).repl();
 
     RelType *P = reinterpret_cast<RelType *>(Buf);
     Buf += sizeof(RelType);
 
-    // Relocation against local symbol here means that it is probably
-    // rel[a].eh_frame section which has references to sections in r_info field.
-    if (SymIndex < SymTab->sh_info) {
-      const Elf_Sym *Sym = this->File->getLocalSymbol(SymIndex);
-      uint32_t Idx = Out<ELFT>::SymTab->Locals[Sym];
-      P->r_offset = RelocatedSection->getOffset(Rel.r_offset);
-      P->setSymbolAndType(Idx, Type, Config->Mips64EL);
-      continue;
-    }
-
-    SymbolBody *Body = this->File->getSymbolBody(SymIndex)->repl();
-    P->r_offset = RelocatedSection->getOffset(Rel.r_offset);
-    P->setSymbolAndType(Body->DynsymIndex, Type, Config->Mips64EL);
+    P->setSymbolAndType(Body.DynsymIndex, Type, Config->Mips64EL);
   }
 }
 
 static uint32_t getMipsPairedRelocType(uint32_t Type) {
   if (Config->EMachine != EM_MIPS)
     return R_MIPS_NONE;
   switch (Type) {
   case R_MIPS_HI16:
for (size_t I = 0; I < Num; ++I) {
     if (Target->pointsToLocalDynamicGotEntry(Type) &&
         !Target->canRelaxTls(Type, nullptr)) {
       Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
                           Out<ELFT>::Got->getTlsIndexVA() +
                               getAddend<ELFT>(RI));
       continue;
     }
 
-    const Elf_Shdr *SymTab = File->getSymbolTable();
-    SymbolBody *Body = nullptr;
-    if (SymIndex >= SymTab->sh_info)
-      Body = File->getSymbolBody(SymIndex)->repl();
+    SymbolBody &Body = File->getSymbolBody(SymIndex).repl();
 
-    if (Target->canRelaxTls(Type, Body)) {
+    if (Target->canRelaxTls(Type, &Body)) {
       uintX_t SymVA;
-      if (!Body)
+      if (Body.isLocal())
         SymVA = getLocalRelTarget(*File, RI, 0);
-      else if (Target->needsGot(Type, *Body))
-        SymVA = Body->getGotVA<ELFT>();
+      else if (Target->needsGot(Type, Body))
+        SymVA = Body.getGotVA<ELFT>();
       else
-        SymVA = Body->getVA<ELFT>();
+        SymVA = Body.getVA<ELFT>();
       // By optimizing TLS relocations, it is sometimes needed to skip
       // relocations that immediately follow TLS relocations. This function
       // knows how many slots we need to skip.
       I += Target->relaxTls(BufLoc, BufEnd, Type, AddrLoc, SymVA, Body);
       continue;
     }
 
     // Handle relocations for local symbols -- they never get
     // resolved so we don't allocate a SymbolBody.
     uintX_t A = getAddend<ELFT>(RI);
-    if (!Body) {
+    if (Body.isLocal()) {
       uintX_t SymVA = getLocalRelTarget(*File, RI, A);
       uint8_t *PairedLoc = nullptr;
       if (Config->EMachine == EM_MIPS) {
         if (Type == R_MIPS_GPREL16 || Type == R_MIPS_GPREL32)
           // We need to adjust SymVA value in case of R_MIPS_GPREL16/32
           // relocations because they use the following expression to calculate
           // the relocation's result for local symbol: S + A + GP0 - G.
           SymVA += File->getMipsGp0();
if (Body.isLocal()) {
           PairedLoc = findMipsPairedReloc(
               Buf, SymIndex, getMipsPairedRelocType(Type), NextRelocs);
       }
       Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA, 0, PairedLoc);
       continue;
     }
 
     if (Target->isTlsGlobalDynamicRel(Type) &&
-        !Target->canRelaxTls(Type, Body)) {
+        !Target->canRelaxTls(Type, &Body)) {
       Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
-                          Out<ELFT>::Got->getGlobalDynAddr(*Body) +
+                          Out<ELFT>::Got->getGlobalDynAddr(Body) +
                               getAddend<ELFT>(RI));
       continue;
     }
 
-    uintX_t SymVA = Body->getVA<ELFT>();
+    uintX_t SymVA = Body.getVA<ELFT>();
     bool CBP = canBePreempted(Body);
-    if (Target->needsPlt<ELFT>(Type, *Body)) {
-      SymVA = Body->getPltVA<ELFT>();
-    } else if (Target->needsGot(Type, *Body)) {
+    if (Target->needsPlt<ELFT>(Type, Body)) {
+      SymVA = Body.getPltVA<ELFT>();
+    } else if (Target->needsGot(Type, Body)) {
       if (Config->EMachine == EM_MIPS && !CBP)
         // Under some conditions relocations against non-local symbols require
         // entries in the local part of MIPS GOT. In that case we need an entry
         // initialized by full address of the symbol.
-        SymVA = Out<ELFT>::Got->getMipsLocalFullAddr(*Body);
+        SymVA = Out<ELFT>::Got->getMipsLocalFullAddr(Body);
       else
-        SymVA = Body->getGotVA<ELFT>();
-      if (Body->IsTls)
+        SymVA = Body.getGotVA<ELFT>();
+      if (Body.IsTls)
         Type = Target->getTlsGotRel(Type);
     } else if (Target->isSizeRel(Type) && CBP) {
       // A SIZE relocation is supposed to set a symbol size, but if a symbol
       // can be preempted, the size at runtime may be different than link time.
       // If that's the case, we leave the field alone rather than filling it
       // with a possibly incorrect value.
       continue;
     } else if (Config->EMachine == EM_MIPS) {
-      if (Type == R_MIPS_HI16 && Body == Config->MipsGpDisp)
+      if (Type == R_MIPS_HI16 && &Body == Config->MipsGpDisp)
         SymVA = getMipsGpAddr<ELFT>() - AddrLoc;
-      else if (Type == R_MIPS_LO16 && Body == Config->MipsGpDisp)
+      else if (Type == R_MIPS_LO16 && &Body == Config->MipsGpDisp)
         SymVA = getMipsGpAddr<ELFT>() - AddrLoc + 4;
-      else if (Body == Config->MipsLocalGp)
+      else if (&Body == Config->MipsLocalGp)
         SymVA = getMipsGpAddr<ELFT>();
-    } else if (!Target->needsCopyRel<ELFT>(Type, *Body) && CBP) {
+    } else if (!Target->needsCopyRel<ELFT>(Type, Body) && CBP) {
       continue;
     }
-    uintX_t Size = Body->getSize<ELFT>();
+    uintX_t Size = Body.getSize<ELFT>();
     Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA + A, Size + A,
                         findMipsPairedReloc(Buf, SymIndex,
                                             getMipsPairedRelocType(Type),
                                             NextRelocs));
   }
 }
 
 template <class ELFT> void InputSection<ELFT>::writeTo(uint8_t *Buf) {

ELF/MarkLive.cpp

if (!Sec || Sec->Live)
       return;
     Sec->Live = true;
     if (InputSection<ELFT> *S = dyn_cast<InputSection<ELFT>>(Sec))
       Q.push_back(S);
   };
 
   auto MarkSymbol = [&](SymbolBody *Sym) {
     if (Sym)
-      if (auto *D = dyn_cast<DefinedRegular<ELFT>>(Sym->repl()))
+      if (auto *D = dyn_cast<DefinedRegular<ELFT>>(&Sym->repl()))
         Enqueue(D->Section);
   };
 
   // Add GC root symbols.
   MarkSymbol(Config->EntrySym);
   MarkSymbol(Symtab->find(Config->Init));
   MarkSymbol(Symtab->find(Config->Fini));
   for (StringRef S : Config->Undefined)

ELF/OutputSections.h

 }
 
 template <class ELFT, bool IsRela>
 typename llvm::object::ELFFile<ELFT>::uintX_t
 getLocalRelTarget(const ObjectFile<ELFT> &File,
                   const llvm::object::Elf_Rel_Impl<ELFT, IsRela> &Rel,
                   typename llvm::object::ELFFile<ELFT>::uintX_t Addend);
 
-bool canBePreempted(const SymbolBody *Body);
+bool canBePreempted(const SymbolBody &Body);
 
 bool isValidCIdentifier(StringRef S);
 
 // This represents a section in an output file.
 // Different sub classes represent different types of sections. Some contain
 // input sections, others are created by the linker.
 // The writer creates multiple OutputSections and assign them unique,
 // non-overlapping file offsets and VAs.

 template <class ELFT> class GotSection final : public OutputSectionBase<ELFT> {
   typedef OutputSectionBase<ELFT> Base;
   typedef typename Base::uintX_t uintX_t;
 
 public:
   GotSection();
   void finalize() override;
   void writeTo(uint8_t *Buf) override;
-  void addEntry(SymbolBody *Sym);
+  void addEntry(SymbolBody &Sym);
   void addMipsLocalEntry();
-  bool addDynTlsEntry(SymbolBody *Sym);
+  bool addDynTlsEntry(SymbolBody &Sym);
   bool addTlsIndex();
   bool empty() const { return MipsLocalEntries == 0 && Entries.empty(); }
   uintX_t getMipsLocalFullAddr(const SymbolBody &B);
   uintX_t getMipsLocalPageAddr(uintX_t Addr);
   uintX_t getGlobalDynAddr(const SymbolBody &B) const;
   uintX_t getNumEntries() const { return Entries.size(); }
 
   // Returns the symbol which corresponds to the first entry of the global part

 template <class ELFT>
 class GotPltSection final : public OutputSectionBase<ELFT> {
   typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
 
 public:
   GotPltSection();
   void finalize() override;
   void writeTo(uint8_t *Buf) override;
-  void addEntry(SymbolBody *Sym);
+  void addEntry(SymbolBody &Sym);
   bool empty() const;
 
 private:
   std::vector<const SymbolBody *> Entries;
 };
 
 template <class ELFT> class PltSection final : public OutputSectionBase<ELFT> {
   typedef OutputSectionBase<ELFT> Base;
   typedef typename Base::uintX_t uintX_t;
 
 public:
   PltSection();
   void finalize() override;
   void writeTo(uint8_t *Buf) override;
-  void addEntry(SymbolBody *Sym);
+  void addEntry(SymbolBody &Sym);
   bool empty() const { return Entries.empty(); }
 
 private:
   std::vector<std::pair<const SymbolBody *, unsigned>> Entries;
 };
 
 template <class ELFT> struct DynamicReloc {
   typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
public:
 
   ArrayRef<std::pair<SymbolBody *, size_t>> getSymbols() const {
     return Symbols;
   }
 
   unsigned NumLocals = 0;
   StringTableSection<ELFT> &StrTabSec;
 
-  // Local symbol -> ID, filled only when producing relocatable output.
-  llvm::DenseMap<const Elf_Sym *, uint32_t> Locals;
-
 private:
   void writeLocalSymbols(uint8_t *&Buf);
   void writeGlobalSymbols(uint8_t *Buf);
 
   const OutputSectionBase<ELFT> *getOutputSection(SymbolBody *Sym);
   static uint8_t getSymbolBinding(SymbolBody *Body);
 
   SymbolTable<ELFT> &Table;

ELF/OutputSections.cpp

 }
 
 template <class ELFT>
 GotPltSection<ELFT>::GotPltSection()
     : OutputSectionBase<ELFT>(".got.plt", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE) {
   this->Header.sh_addralign = sizeof(uintX_t);
 }
 
-template <class ELFT> void GotPltSection<ELFT>::addEntry(SymbolBody *Sym) {
-  Sym->GotPltIndex = Target->GotPltHeaderEntriesNum + Entries.size();
-  Entries.push_back(Sym);
+template <class ELFT> void GotPltSection<ELFT>::addEntry(SymbolBody &Sym) {
+  Sym.GotPltIndex = Target->GotPltHeaderEntriesNum + Entries.size();
+  Entries.push_back(&Sym);
 }
 
 template <class ELFT> bool GotPltSection<ELFT>::empty() const {
   return Entries.empty();
 }
 
 template <class ELFT> void GotPltSection<ELFT>::finalize() {
   this->Header.sh_size =

 template <class ELFT>
 GotSection<ELFT>::GotSection()
     : OutputSectionBase<ELFT>(".got", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE) {
   if (Config->EMachine == EM_MIPS)
     this->Header.sh_flags |= SHF_MIPS_GPREL;
   this->Header.sh_addralign = sizeof(uintX_t);
 }
 
-template <class ELFT> void GotSection<ELFT>::addEntry(SymbolBody *Sym) {
-  Sym->GotIndex = Entries.size();
-  Entries.push_back(Sym);
+template <class ELFT> void GotSection<ELFT>::addEntry(SymbolBody &Sym) {
+  Sym.GotIndex = Entries.size();
+  Entries.push_back(&Sym);
 }
 
 template <class ELFT> void GotSection<ELFT>::addMipsLocalEntry() {
   ++MipsLocalEntries;
 }
 
-template <class ELFT> bool GotSection<ELFT>::addDynTlsEntry(SymbolBody *Sym) {
-  if (Sym->hasGlobalDynIndex())
+template <class ELFT> bool GotSection<ELFT>::addDynTlsEntry(SymbolBody &Sym) {
+  if (Sym.hasGlobalDynIndex())
     return false;
-  Sym->GlobalDynIndex = Target->GotHeaderEntriesNum + Entries.size();
+  Sym.GlobalDynIndex = Target->GotHeaderEntriesNum + Entries.size();
   // Global Dynamic TLS entries take two GOT slots.
-  Entries.push_back(Sym);
+  Entries.push_back(&Sym);
   Entries.push_back(nullptr);
   return true;
 }
 
 // Reserves TLS entries for a TLS module ID and a TLS block offset.
 // In total it takes two GOT slots.
 template <class ELFT> bool GotSection<ELFT>::addTlsIndex() {
   if (TlsIndexOff != uint32_t(-1))
for (const SymbolBody *B : Entries) {
     Buf += sizeof(uintX_t);
     if (!B)
       continue;
     // MIPS has special rules to fill up GOT entries.
     // See "Global Offset Table" in Chapter 5 in the following document
     // for detailed description:
     // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
     // As the first approach, we can just store addresses for all symbols.
-    if (Config->EMachine != EM_MIPS && canBePreempted(B))
+    if (Config->EMachine != EM_MIPS && canBePreempted(*B))
       continue; // The dynamic linker will take care of it.
     uintX_t VA = B->getVA<ELFT>();
     write<uintX_t, ELFT::TargetEndianness, sizeof(uintX_t)>(Entry, VA);
   }
 }
 
 template <class ELFT>
 PltSection<ELFT>::PltSection()
for (auto &I : Entries) {
     uint64_t Got =
         Target->UseLazyBinding ? B->getGotPltVA<ELFT>() : B->getGotVA<ELFT>();
     uint64_t Plt = this->getVA() + Off;
     Target->writePlt(Buf + Off, Got, Plt, B->PltIndex, RelOff);
     Off += Target->PltEntrySize;
   }
 }
 
-template <class ELFT> void PltSection<ELFT>::addEntry(SymbolBody *Sym) {
-  Sym->PltIndex = Entries.size();
+template <class ELFT> void PltSection<ELFT>::addEntry(SymbolBody &Sym) {
+  Sym.PltIndex = Entries.size();
   unsigned RelOff = Target->UseLazyBinding
                         ? Out<ELFT>::RelaPlt->getRelocOffset()
                         : Out<ELFT>::RelaDyn->getRelocOffset();
-  Entries.push_back(std::make_pair(Sym, RelOff));
+  Entries.push_back(std::make_pair(&Sym, RelOff));
 }
 
 template <class ELFT> void PltSection<ELFT>::finalize() {
   this->Header.sh_size =
       Target->PltZeroSize + Entries.size() * Target->PltEntrySize;
 }
 
 template <class ELFT>
if (Sym->getType() == STT_SECTION) {
     Offset += Addend;
     Addend = 0;
   }
   return Section->OutSec->getVA() + Section->getOffset(Offset) + Addend;
 }
 
 // Returns true if a symbol can be replaced at load-time by a symbol
 // with the same name defined in other ELF executable or DSO.
-bool elf::canBePreempted(const SymbolBody *Body) {
-  if (!Body)
-    return false;  // Body is a local symbol.
-  if (Body->isShared())
+bool elf::canBePreempted(const SymbolBody &Body) {
+  if (Body.isLocal())
+    return false;
+
+  if (Body.isShared())
     return true;
 
-  if (Body->isUndefined()) {
-    if (!Body->isWeak())
+  if (Body.isUndefined()) {
+    if (!Body.isWeak())
       return true;
 
     // Ideally the static linker should see a definition for every symbol, but
     // shared object are normally allowed to have undefined references that the
     // static linker never sees a definition for.
     if (Config->Shared)
       return true;
 
     // Otherwise, just resolve to 0.
     return false;
   }
   if (!Config->Shared)
     return false;
-  if (Body->getVisibility() != STV_DEFAULT)
+  if (Body.getVisibility() != STV_DEFAULT)
     return false;
-  if (Config->Bsymbolic || (Config->BsymbolicFunctions && Body->IsFunc))
+  if (Config->Bsymbolic || (Config->BsymbolicFunctions && Body.IsFunc))
     return false;
   return true;
 }
 
 static void fill(uint8_t *Buf, size_t Size, ArrayRef<uint8_t> A) {
   size_t I = 0;
   for (; I + A.size() < Size; I += A.size())
     memcpy(Buf + I, A.data(), A.size());
if (ID == 0) {
       // CIE
       Cie<ELFT> C(S, Index);
       if (Config->EhFrameHdr)
         C.FdeEncoding = getFdeEncoding(D);
 
       SymbolBody *Personality = nullptr;
       if (HasReloc) {
         uint32_t SymIndex = RelI->getSymbol(Config->Mips64EL);
-        Personality = S->getFile()->getSymbolBody(SymIndex)->repl();
+        Personality = &S->getFile()->getSymbolBody(SymIndex).repl();
       }
 
       std::pair<StringRef, SymbolBody *> CieInfo(Entry, Personality);
       auto P = CieMap.insert(std::make_pair(CieInfo, Cies.size()));
       if (P.second) {
         Cies.push_back(C);
         this->Header.sh_size += alignTo(Length, sizeof(uintX_t));
       }

 
 template <class ELFT>
 const OutputSectionBase<ELFT> *
 SymbolTableSection<ELFT>::getOutputSection(SymbolBody *Sym) {
   switch (Sym->kind()) {
   case SymbolBody::DefinedSyntheticKind:
     return &cast<DefinedSynthetic<ELFT>>(Sym)->Section;
   case SymbolBody::DefinedRegularKind: {
-    auto *D = cast<DefinedRegular<ELFT>>(Sym->repl());
-    if (D->Section)
-      return D->Section->OutSec;
+    auto &D = cast<DefinedRegular<ELFT>>(Sym->repl());
+    if (D.Section)
+      return D.Section->OutSec;
     break;
   }
   case SymbolBody::DefinedCommonKind:
     return Out<ELFT>::Bss;
   case SymbolBody::SharedKind:
     if (cast<SharedSymbol<ELFT>>(Sym)->needsCopy())
       return Out<ELFT>::Bss;
     break;
   case SymbolBody::UndefinedElfKind:
   case SymbolBody::UndefinedKind:
   case SymbolBody::LazyKind:
     break;
   case SymbolBody::DefinedBitcodeKind:
     llvm_unreachable("Should have been replaced");
+  case SymbolBody::DefinedLocalKind:
+    llvm_unreachable("Should not be used");
   }
   return nullptr;
 }
 
 template <class ELFT>
 uint8_t SymbolTableSection<ELFT>::getSymbolBinding(SymbolBody *Body) {
   uint8_t Visibility = Body->getVisibility();
   if (Visibility != STV_DEFAULT && Visibility != STV_PROTECTED)

ELF/SymbolTable.cpp

for (SymbolBody *B : F->getSymbols())
       resolve(B);
     return;
   }
 
   // .o file
   auto *F = cast<ObjectFile<ELFT>>(FileP);
   ObjectFiles.emplace_back(cast<ObjectFile<ELFT>>(File.release()));
   F->parse(ComdatGroups);
-  for (SymbolBody *B : F->getSymbols())
+  for (SymbolBody *B : F->getNonLocalSymbolBodies())
     resolve(B);
 }
 
 // This is for use when debugging LTO.
 static void saveLtoObjectFile(StringRef Buffer) {
   std::error_code EC;
   raw_fd_ostream OS(Config->OutputFile.str() + ".lto.o", EC,
                     sys::fs::OpenFlags::F_None);
static void addBitcodeFile(IRMover &Mover, BitcodeFile &F,
                            LLVMContext &Context) {
   std::unique_ptr<MemoryBuffer> Buffer =
       MemoryBuffer::getMemBuffer(F.MB, false);
   std::unique_ptr<Module> M =
       check(getLazyBitcodeModule(std::move(Buffer), Context,
                                  /*ShouldLazyLoadMetadata*/ false));
   std::vector<GlobalValue *> Keep;
   for (SymbolBody *B : F.getSymbols()) {
-    if (B->repl() != B)
+    if (&B->repl() != B)
       continue;
     auto *DB = dyn_cast<DefinedBitcode>(B);
     if (!DB)
       continue;
     GlobalValue *GV = M->getNamedValue(B->getName());
     assert(GV);
     Keep.push_back(GV);
   }

 }
 
 template <class ELFT> void SymbolTable<ELFT>::addCombinedLtoObject() {
   if (BitcodeFiles.empty())
     return;
   ObjectFile<ELFT> *Obj = createCombinedLtoObject();
   llvm::DenseSet<StringRef> DummyGroups;
   Obj->parse(DummyGroups);
-  for (SymbolBody *Body : Obj->getSymbols()) {
+  for (SymbolBody *Body : Obj->getNonLocalSymbolBodies()) {
     Symbol *Sym = insert(Body);
     if (!Sym->Body->isUndefined() && Body->isUndefined())
       continue;
     Sym->Body = Body;
   }
 }
 
 // Add an undefined symbol.

ELF/Symbols.h

 
 // The base class for real symbol classes.
 class SymbolBody {
 public:
   enum Kind {
     DefinedFirst,
     DefinedRegularKind = DefinedFirst,
     SharedKind,
-    DefinedElfLast = SharedKind,
+    DefinedLocalKind,
+    DefinedElfLast = DefinedLocalKind,
     DefinedCommonKind,
     DefinedBitcodeKind,
     DefinedSyntheticKind,
     DefinedLast = DefinedSyntheticKind,
     UndefinedElfKind,
     UndefinedKind,
     LazyKind
   };
 
   Kind kind() const { return static_cast<Kind>(SymbolKind); }
 
   bool isWeak() const { return IsWeak; }
   bool isUndefined() const {
     return SymbolKind == UndefinedKind || SymbolKind == UndefinedElfKind;
   }
   bool isDefined() const { return SymbolKind <= DefinedLast; }
   bool isCommon() const { return SymbolKind == DefinedCommonKind; }
   bool isLazy() const { return SymbolKind == LazyKind; }
   bool isShared() const { return SymbolKind == SharedKind; }
+  bool isLocal() const { return SymbolKind == DefinedLocalKind; }
   bool isUsedInRegularObj() const { return IsUsedInRegularObj; }
 
   // Returns the symbol name.
   StringRef getName() const { return Name; }
 
   uint8_t getVisibility() const { return Visibility; }
 
   unsigned DynsymIndex = 0;
public:
 
   // A SymbolBody has a backreference to a Symbol. Originally they are
   // doubly-linked. A backreference will never change. But the pointer
   // in the Symbol may be mutated by the resolver. If you have a
   // pointer P to a SymbolBody and are not sure whether the resolver
   // has chosen the object among other objects having the same name,
   // you can access P->Backref->Body to get the resolver's result.
   void setBackref(Symbol *P) { Backref = P; }
-  SymbolBody *repl() { return Backref ? Backref->Body : this; }
+  SymbolBody &repl() { return Backref ? *Backref->Body : *this; }
   Symbol *getSymbol() { return Backref; }
 
   // Decides which symbol should "win" in the symbol table, this or
   // the Other. Returns 1 if this wins, -1 if the Other wins, or 0 if
   // they are duplicate (conflicting) symbols.
   template <class ELFT> int compare(SymbolBody *Other);
 
 protected:
public:
   SharedFile<ELFT> *File;
 
   // OffsetInBss is significant only when needsCopy() is true.
   uintX_t OffsetInBss = 0;
 
   bool needsCopy() const { return this->NeedsCopyOrPltAddr && !this->IsFunc; }
 };
 
+template <class ELFT> class LocalSymbol : public DefinedElf<ELFT> {
+  typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
+
+public:
+  LocalSymbol(const Elf_Sym &Sym)
+      : DefinedElf<ELFT>(SymbolBody::DefinedLocalKind, "", Sym) {}
+
+  static bool classof(const SymbolBody *S) {
+    return S->kind() == SymbolBody::DefinedLocalKind;
+  }
+};
+
 // This class represents a symbol defined in an archive file. It is
 // created from an archive file header, and it knows how to load an
 // object file from an archive to replace itself with a defined
 // symbol. If the resolver finds both Undefined and Lazy for
 // the same name, it will ask the Lazy to load a file.
 class Lazy : public SymbolBody {
 public:
   Lazy(ArchiveFile *F, const llvm::object::Archive::Symbol S)

ELF/Symbols.cpp

typename ELFFile<ELFT>::uintX_t SymbolBody::getVA() const {
   case UndefinedElfKind:
   case UndefinedKind:
     return 0;
   case LazyKind:
     assert(isUsedInRegularObj() && "Lazy symbol reached writer");
     return 0;
   case DefinedBitcodeKind:
     llvm_unreachable("Should have been replaced");
+  case DefinedLocalKind:
+    llvm_unreachable("Should not be used");
   }
   llvm_unreachable("Invalid symbol kind");
 }
 
 template <class ELFT>
 typename ELFFile<ELFT>::uintX_t SymbolBody::getGotVA() const {
   return Out<ELFT>::Got->getVA() +
          (Out<ELFT>::Got->getMipsLocalEntriesNum() + GotIndex) *

ELF/Target.h

public:
   virtual void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
                            uint64_t P, uint64_t SA, uint64_t ZA = 0,
                            uint8_t *PairedLoc = nullptr) const = 0;
   virtual bool isGotRelative(uint32_t Type) const;
   bool canRelaxTls(uint32_t Type, const SymbolBody *S) const;
   template <class ELFT>
   bool needsCopyRel(uint32_t Type, const SymbolBody &S) const;
   virtual size_t relaxTls(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
-                          uint64_t P, uint64_t SA, const SymbolBody *S) const;
+                          uint64_t P, uint64_t SA, const SymbolBody &S) const;
   virtual ~TargetInfo();
 
   unsigned PageSize = 4096;
 
   // On freebsd x86_64 the first page cannot be mmaped.
   // On linux that is controled by vm.mmap_min_addr. At least on some x86_64
   // installs that is 65536, so the first 15 pages cannot be used.
   // Given that, the smallest value that can be used in here is 0x10000.

ELF/Target.cpp

public:
   bool needsCopyRelImpl(uint32_t Type) const override;
   bool needsDynRelative(uint32_t Type) const override;
   bool needsGot(uint32_t Type, SymbolBody &S) const override;
   bool needsPltImpl(uint32_t Type) const override;
   void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
                    uint64_t SA, uint64_t ZA = 0,
                    uint8_t *PairedLoc = nullptr) const override;
   size_t relaxTls(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
-                  uint64_t SA, const SymbolBody *S) const override;
+                  uint64_t SA, const SymbolBody &S) const override;
   bool isGotRelative(uint32_t Type) const override;
   bool refersToGotEntry(uint32_t Type) const override;
 
 private:
   void relocateTlsLdToLe(uint8_t *Loc, uint8_t *BufEnd, uint64_t P,
                          uint64_t SA) const;
   void relocateTlsGdToIe(uint8_t *Loc, uint8_t *BufEnd, uint64_t P,
                          uint64_t SA) const;
public:
   bool refersToGotEntry(uint32_t Type) const override;
   bool needsPltImpl(uint32_t Type) const override;
   void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
                    uint64_t SA, uint64_t ZA = 0,
                    uint8_t *PairedLoc = nullptr) const override;
   bool isRelRelative(uint32_t Type) const override;
   bool isSizeRel(uint32_t Type) const override;
   size_t relaxTls(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
-                  uint64_t SA, const SymbolBody *S) const override;
+                  uint64_t SA, const SymbolBody &S) const override;
 
 private:
   void relocateTlsLdToLe(uint8_t *Loc, uint8_t *BufEnd, uint64_t P,
                          uint64_t SA) const;
   void relocateTlsGdToLe(uint8_t *Loc, uint8_t *BufEnd, uint64_t P,
                          uint64_t SA) const;
   void relocateTlsGdToIe(uint8_t *Loc, uint8_t *BufEnd, uint64_t P,
                          uint64_t SA) const;
public:
   bool isRelRelative(uint32_t Type) const override;
   bool needsCopyRelImpl(uint32_t Type) const override;
   bool needsGot(uint32_t Type, SymbolBody &S) const override;
   bool needsPltImpl(uint32_t Type) const override;
   void relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
                    uint64_t SA, uint64_t ZA = 0,
                    uint8_t *PairedLoc = nullptr) const override;
   size_t relaxTls(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type, uint64_t P,
-                  uint64_t SA, const SymbolBody *S) const override;
+                  uint64_t SA, const SymbolBody &S) const override;
 
 private:
   void relocateTlsGdToLe(uint32_t Type, uint8_t *Loc, uint8_t *BufEnd,
                          uint64_t P, uint64_t SA) const;
   void relocateTlsIeToLe(uint32_t Type, uint8_t *Loc, uint8_t *BufEnd,
                          uint64_t P, uint64_t SA) const;
 
   static const uint64_t TcbSize = 16;
bool TargetInfo::canRelaxTls(uint32_t Type, const SymbolBody *S) const {
 
   // Local-Dynamic relocs can be relaxed to Local-Exec.
   if (isTlsLocalDynamicRel(Type))
     return true;
 
   // Initial-Exec relocs can be relaxed to Local-Exec if the symbol is locally
   // defined.
   if (isTlsInitialExecRel(Type))
-    return !canBePreempted(S);
+    return !canBePreempted(*S);
 
   return false;
 }
 
 uint64_t TargetInfo::getVAStart() const { return Config->Shared ? 0 : VAStart; }
 
 bool TargetInfo::needsCopyRelImpl(uint32_t Type) const { return false; }
 

 
 bool TargetInfo::refersToGotEntry(uint32_t Type) const { return false; }
 
 template <class ELFT>
 TargetInfo::PltNeed TargetInfo::needsPlt(uint32_t Type,
                                          const SymbolBody &S) const {
   if (isGnuIFunc<ELFT>(S))
     return Plt_Explicit;
-  if (canBePreempted(&S) && needsPltImpl(Type))
+  if (canBePreempted(S) && needsPltImpl(Type))
     return Plt_Explicit;
 
   // This handles a non PIC program call to function in a shared library.
   // In an ideal world, we could just report an error saying the relocation
   // can overflow at runtime.
   // In the real world with glibc, crt1.o has a R_X86_64_PC32 pointing to
   // libc.so.
   //

 bool TargetInfo::isTlsLocalDynamicRel(uint32_t Type) const { return false; }
 
 bool TargetInfo::isTlsGlobalDynamicRel(uint32_t Type) const {
   return false;
 }
 
 size_t TargetInfo::relaxTls(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
                             uint64_t P, uint64_t SA,
-                            const SymbolBody *S) const {
+                            const SymbolBody &S) const {
   return 0;
 }
 
 X86TargetInfo::X86TargetInfo() {
   CopyRel = R_386_COPY;
   GotRel = R_386_GLOB_DAT;
   PltRel = R_386_JUMP_SLOT;
   IRelativeRel = R_386_IRELATIVE;

 }
 
 bool X86TargetInfo::needsCopyRelImpl(uint32_t Type) const {
   return Type == R_386_32 || Type == R_386_16 || Type == R_386_8;
 }
 
 bool X86TargetInfo::needsGot(uint32_t Type, SymbolBody &S) const {
   if (S.IsTls && Type == R_386_TLS_GD)
-    return Target->canRelaxTls(Type, &S) && canBePreempted(&S);
+    return Target->canRelaxTls(Type, &S) && canBePreempted(S);
   if (Type == R_386_TLS_GOTIE || Type == R_386_TLS_IE)
     return !canRelaxTls(Type, &S);
   return Type == R_386_GOT32 || needsPlt<ELF32LE>(Type, S);
 }
 
 bool X86TargetInfo::needsPltImpl(uint32_t Type) const {
   return Type == R_386_PLT32;
 }

 }
 
 bool X86TargetInfo::needsDynRelative(uint32_t Type) const {
   return Config->Shared && Type == R_386_TLS_IE;
 }
 
 size_t X86TargetInfo::relaxTls(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
                                uint64_t P, uint64_t SA,
-                               const SymbolBody *S) const {
+                               const SymbolBody &S) const {
   switch (Type) {
   case R_386_TLS_GD:
     if (canBePreempted(S))
       relocateTlsGdToIe(Loc, BufEnd, P, SA);
     else
       relocateTlsGdToLe(Loc, BufEnd, P, SA);
     // The next relocation should be against __tls_get_addr, so skip it
     return 1;

 }
 
 bool X86_64TargetInfo::refersToGotEntry(uint32_t Type) const {
   return Type == R_X86_64_GOTPCREL;
 }
 
 bool X86_64TargetInfo::needsGot(uint32_t Type, SymbolBody &S) const {
   if (Type == R_X86_64_TLSGD)
-    return Target->canRelaxTls(Type, &S) && canBePreempted(&S);
+    return Target->canRelaxTls(Type, &S) && canBePreempted(S);
   if (Type == R_X86_64_GOTTPOFF)
     return !canRelaxTls(Type, &S);
   return refersToGotEntry(Type) || needsPlt<ELF64LE>(Type, S);
 }
 
 uint32_t X86_64TargetInfo::getTlsGotRel(uint32_t Type) const {
   // No other types of TLS relocations requiring GOT should
   // reach here.

 
 // This function applies a TLS relocation with an optimization as described
 // in the Ulrich's document. As a result of rewriting instructions at the
 // relocation target, relocations immediately follow the TLS relocation (which
 // would be applied to rewritten instructions) may have to be skipped.
 // This function returns a number of relocations that need to be skipped.
 size_t X86_64TargetInfo::relaxTls(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
                                   uint64_t P, uint64_t SA,
-                                  const SymbolBody *S) const {
+                                  const SymbolBody &S) const {
   switch (Type) {
   case R_X86_64_DTPOFF32:
     relocateOne(Loc, BufEnd, R_X86_64_TPOFF32, P, SA);
     return 0;
   case R_X86_64_GOTTPOFF:
     relocateTlsIeToLe(Loc, BufEnd, P, SA);
     return 0;
   case R_X86_64_TLSGD: {
void AArch64TargetInfo::relocateOne(uint8_t *Loc, uint8_t *BufEnd,
   }
   default:
     fatal("unrecognized reloc " + Twine(Type));
   }
 }
 
 size_t AArch64TargetInfo::relaxTls(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
                                    uint64_t P, uint64_t SA,
-                                   const SymbolBody *S) const {
+                                   const SymbolBody &S) const {
   switch (Type) {
   case R_AARCH64_TLSDESC_ADR_PAGE21:
   case R_AARCH64_TLSDESC_LD64_LO12_NC:
   case R_AARCH64_TLSDESC_ADD_LO12_NC:
   case R_AARCH64_TLSDESC_CALL: {
     if (canBePreempted(S))
       fatal("Unsupported TLS optimization");
-    uint64_t X = S ? S->getVA<ELF64LE>() : SA;
+    uint64_t X = S.getVA<ELF64LE>();
     relocateTlsGdToLe(Type, Loc, BufEnd, P, X);
     return 0;
   }
   case R_AARCH64_TLSIE_ADR_GOTTPREL_PAGE21:
   case R_AARCH64_TLSIE_LD64_GOTTPREL_LO12_NC:
-    relocateTlsIeToLe(Type, Loc, BufEnd, P, S->getVA<ELF64LE>());
+    relocateTlsIeToLe(Type, Loc, BufEnd, P, S.getVA<ELF64LE>());
     return 0;
   }
   llvm_unreachable("Unknown TLS optimization");
 }
 
 // Global-Dynamic relocations can be relaxed to Local-Exec if both binary is
 // an executable and target is final (can notbe preempted).
 void AArch64TargetInfo::relocateTlsGdToLe(uint32_t Type, uint8_t *Loc,

ELF/Writer.cpp

static bool isEqual(const SectionKey<Is64Bits> &LHS,
     return DenseMapInfo<StringRef>::isEqual(LHS.Name, RHS.Name) &&
            LHS.Type == RHS.Type && LHS.Flags == RHS.Flags &&
            LHS.Alignment == RHS.Alignment;
   }
 };
 }
 
 template <class ELFT, class RelT>
-static bool handleTlsRelocation(uint32_t Type, SymbolBody *Body,
+static bool handleTlsRelocation(uint32_t Type, SymbolBody &Body,
                                 InputSectionBase<ELFT> &C, RelT &RI) {
   if (Target->pointsToLocalDynamicGotEntry(Type)) {
     if (Target->canRelaxTls(Type, nullptr))
       return true;
     if (Out<ELFT>::Got->addTlsIndex())
       Out<ELFT>::RelaDyn->addReloc({Target->TlsModuleIndexRel,
                                     DynamicReloc<ELFT>::Off_LTlsIndex,
                                     nullptr});
     return true;
   }
 
-  if (!Body || !Body->IsTls)
+  if (!Body.IsTls)
     return false;
 
   if (Target->isTlsGlobalDynamicRel(Type)) {
-    if (!Target->canRelaxTls(Type, Body)) {
+    if (!Target->canRelaxTls(Type, &Body)) {
       if (Out<ELFT>::Got->addDynTlsEntry(Body)) {
         Out<ELFT>::RelaDyn->addReloc({Target->TlsModuleIndexRel,
-                                      DynamicReloc<ELFT>::Off_GTlsIndex, Body});
+                                      DynamicReloc<ELFT>::Off_GTlsIndex,
+                                      &Body});
         Out<ELFT>::RelaDyn->addReloc(
-            {Target->TlsOffsetRel, DynamicReloc<ELFT>::Off_GTlsOffset, Body});
+            {Target->TlsOffsetRel, DynamicReloc<ELFT>::Off_GTlsOffset, &Body});
       }
       return true;
     }
     if (!canBePreempted(Body))
       return true;
   }
   return false;
 }

 template <bool isRela>
 void Writer<ELFT>::scanRelocs(
     InputSectionBase<ELFT> &C,
     iterator_range<const Elf_Rel_Impl<ELFT, isRela> *> Rels) {
   typedef Elf_Rel_Impl<ELFT, isRela> RelType;
   const ObjectFile<ELFT> &File = *C.getFile();
   for (const RelType &RI : Rels) {
     uint32_t SymIndex = RI.getSymbol(Config->Mips64EL);
-    SymbolBody *Body = File.getSymbolBody(SymIndex);
+    SymbolBody &OrigBody = File.getSymbolBody(SymIndex);
+    SymbolBody &Body = OrigBody.repl();
     uint32_t Type = RI.getType(Config->Mips64EL);
 
     // Ignore "hint" relocation because it is for optional code optimization.
     if (Target->isHintRel(Type))
       continue;
 
     if (Target->isGotRelative(Type))
       HasGotOffRel = true;
 
     // Set "used" bit for --as-needed.
-    if (Body && Body->isUndefined() && !Body->isWeak())
-      if (auto *S = dyn_cast<SharedSymbol<ELFT>>(Body->repl()))
+    if (OrigBody.isUndefined() && !OrigBody.isWeak())
+      if (auto *S = dyn_cast<SharedSymbol<ELFT>>(&Body))
         S->File->IsUsed = true;
 
-    if (Body)
-      Body = Body->repl();
-
     bool CBP = canBePreempted(Body);
     if (handleTlsRelocation<ELFT>(Type, Body, C, RI))
       continue;
 
     if (Target->needsDynRelative(Type))
       Out<ELFT>::RelaDyn->addReloc({Target->RelativeRel, &C, RI.r_offset, true,
-                                    Body, getAddend<ELFT>(RI)});
+                                    &Body, getAddend<ELFT>(RI)});
 
     // MIPS has a special rule to create GOTs for local symbols.
     if (Config->EMachine == EM_MIPS && !CBP &&
         (Type == R_MIPS_GOT16 || Type == R_MIPS_CALL16)) {
       // FIXME (simon): Do not add so many redundant entries.
       Out<ELFT>::Got->addMipsLocalEntry();
       continue;
     }
 
     // If a symbol in a DSO is referenced directly instead of through GOT,
     // we need to create a copy relocation for the symbol.
-    if (auto *B = dyn_cast_or_null<SharedSymbol<ELFT>>(Body)) {
+    if (auto *B = dyn_cast_or_null<SharedSymbol<ELFT>>(&Body)) {
       if (B->needsCopy())
         continue;
       if (Target->needsCopyRel<ELFT>(Type, *B)) {
         B->NeedsCopyOrPltAddr = true;
         Out<ELFT>::RelaDyn->addReloc(
             {Target->CopyRel, DynamicReloc<ELFT>::Off_Bss, B});
         continue;
       }
     }
 
     // An STT_GNU_IFUNC symbol always uses a PLT entry, and all references
     // to the symbol go through the PLT. This is true even for a local
     // symbol, although local symbols normally do not require PLT entries.
-    if (Body && isGnuIFunc<ELFT>(*Body)) {
-      if (Body->isInPlt())
+    if (isGnuIFunc<ELFT>(Body)) {
+      if (Body.isInPlt())
         continue;
       Out<ELFT>::Plt->addEntry(Body);
       if (Target->UseLazyBinding) {
         Out<ELFT>::GotPlt->addEntry(Body);
         Out<ELFT>::RelaPlt->addReloc(
             {CBP ? Target->PltRel : Target->IRelativeRel,
-             DynamicReloc<ELFT>::Off_GotPlt, !CBP, Body});
+             DynamicReloc<ELFT>::Off_GotPlt, !CBP, &Body});
       } else {
         Out<ELFT>::Got->addEntry(Body);
         Out<ELFT>::RelaDyn->addReloc(
             {CBP ? Target->PltRel : Target->IRelativeRel,
-             DynamicReloc<ELFT>::Off_Got, !CBP, Body});
+             DynamicReloc<ELFT>::Off_Got, !CBP, &Body});
       }
       continue;
     }
 
     // If a relocation needs PLT, we create a PLT and a GOT slot
     // for the symbol.
-    TargetInfo::PltNeed NeedPlt = TargetInfo::Plt_No;
-    if (Body)
-      NeedPlt = Target->needsPlt<ELFT>(Type, *Body);
+    TargetInfo::PltNeed NeedPlt = Target->needsPlt<ELFT>(Type, Body);
     if (NeedPlt) {
       if (NeedPlt == TargetInfo::Plt_Implicit)
-        Body->NeedsCopyOrPltAddr = true;
-      if (Body->isInPlt())
+        Body.NeedsCopyOrPltAddr = true;
+      if (Body.isInPlt())
         continue;
       Out<ELFT>::Plt->addEntry(Body);
 
       if (Target->UseLazyBinding) {
         Out<ELFT>::GotPlt->addEntry(Body);
         Out<ELFT>::RelaPlt->addReloc(
-            {Target->PltRel, DynamicReloc<ELFT>::Off_GotPlt, Body});
+            {Target->PltRel, DynamicReloc<ELFT>::Off_GotPlt, &Body});
       } else {
-        if (Body->isInGot())
+        if (Body.isInGot())
           continue;
         Out<ELFT>::Got->addEntry(Body);
         Out<ELFT>::RelaDyn->addReloc(
-            {Target->GotRel, DynamicReloc<ELFT>::Off_Got, Body});
+            {Target->GotRel, DynamicReloc<ELFT>::Off_Got, &Body});
       }
       continue;
     }
 
     // If a relocation needs GOT, we create a GOT slot for the symbol.
-    if (Body && Target->needsGot(Type, *Body)) {
-      if (Body->isInGot())
+    if (Target->needsGot(Type, Body)) {
+      if (Body.isInGot())
         continue;
       Out<ELFT>::Got->addEntry(Body);
 
       if (Config->EMachine == EM_MIPS) {
         // MIPS ABI has special rules to process GOT entries
         // and doesn't require relocation entries for them.
         // See "Global Offset Table" in Chapter 5 in the following document
         // for detailed description:
         // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
-        Body->MustBeInDynSym = true;
+        Body.MustBeInDynSym = true;
         continue;
       }
 
       bool Dynrel = Config->Shared && !Target->isRelRelative(Type) &&
                     !Target->isSizeRel(Type);
       if (CBP || Dynrel) {
         uint32_t DynType;
         if (CBP)
-          DynType = Body->IsTls ? Target->TlsGotRel : Target->GotRel;
+          DynType = Body.IsTls ? Target->TlsGotRel : Target->GotRel;
         else
           DynType = Target->RelativeRel;
         Out<ELFT>::RelaDyn->addReloc(
-            {DynType, DynamicReloc<ELFT>::Off_Got, !CBP, Body});
+            {DynType, DynamicReloc<ELFT>::Off_Got, !CBP, &Body});
       }
       continue;
     }
 
     if (Config->EMachine == EM_MIPS) {
       if (Type == R_MIPS_LO16)
         // Ignore R_MIPS_LO16 relocation. If it is a pair for R_MIPS_GOT16 we
         // already completed all required action (GOT entry allocation) when
         // handle R_MIPS_GOT16a. If it is a pair for R_MIPS_HI16 against
         // _gp_disp it does not require dynamic relocation. If its a pair for
         // R_MIPS_HI16 against a regular symbol it does not require dynamic
         // relocation too because that case is possible for executable file
         // linking only.
         continue;
-      if (Body == Config->MipsGpDisp || Body == Config->MipsLocalGp)
+      if (&Body == Config->MipsGpDisp || &Body == Config->MipsLocalGp)
         // MIPS _gp_disp designates offset between start of function and 'gp'
         // pointer into GOT. __gnu_local_gp is equal to the current value of
         // the 'gp'. Therefore any relocations against them do not require
         // dynamic relocation.
         continue;
     }
 
     if (CBP) {
       // We don't know anything about the finaly symbol. Just ask the dynamic
       // linker to handle the relocation for us.
       Out<ELFT>::RelaDyn->addReloc({Target->getDynRel(Type), &C, RI.r_offset,
-                                    false, Body, getAddend<ELFT>(RI)});
+                                    false, &Body, getAddend<ELFT>(RI)});
       continue;
     }
 
     // We know that this is the final symbol. If the program being produced
     // is position independent, the final value is still not known.
     // If the relocation depends on the symbol value (not the size or distances
     // in the output), we still need some help from the dynamic linker.
     // We can however do better than just copying the incoming relocation. We
     // can process some of it and and just ask the dynamic linker to add the
     // load address.
     if (!Config->Shared || Target->isRelRelative(Type) ||
         Target->isSizeRel(Type))
       continue;
 
     uintX_t Addend = getAddend<ELFT>(RI);
     if (Config->EMachine == EM_PPC64 && RI.getType(false) == R_PPC64_TOC) {
       Out<ELFT>::RelaDyn->addReloc({R_PPC64_RELATIVE, &C, RI.r_offset, false,
                                     nullptr,
                                     (uintX_t)getPPC64TocBase() + Addend});
       continue;
     }
-    if (Body) {
+    if (!Body.isLocal()) {
       Out<ELFT>::RelaDyn->addReloc(
-          {Target->RelativeRel, &C, RI.r_offset, true, Body, Addend});
+          {Target->RelativeRel, &C, RI.r_offset, true, &Body, Addend});
       continue;
     }
-    const Elf_Sym *Sym =
-        File.getObj().getRelocationSymbol(&RI, File.getSymbolTable());
-    InputSectionBase<ELFT> *Section = File.getSection(*Sym);
-    uintX_t Offset = Sym->st_value;
-    if (Sym->getType() == STT_SECTION) {
+    const Elf_Sym &Sym = cast<LocalSymbol<ELFT>>(Body).Sym;
+    InputSectionBase<ELFT> *Section = File.getSection(Sym);
+    uintX_t Offset = Sym.st_value;
+    if (Sym.getType() == STT_SECTION) {
       Offset += Addend;
       Addend = 0;
     }
     Out<ELFT>::RelaDyn->addReloc(
         {Target->RelativeRel, &C, RI.r_offset, Section, Offset, Addend});
   }
 }
 

 }
 
 // Local symbols are not in the linker's symbol table. This function scans
 // each object file's symbol table to copy local symbols to the output.
 template <class ELFT> void Writer<ELFT>::copyLocalSymbols() {
   if (!Out<ELFT>::SymTab)
     return;
   for (const std::unique_ptr<ObjectFile<ELFT>> &F : Symtab.getObjectFiles()) {
-    for (const Elf_Sym &Sym : F->getLocalSymbols()) {
+    for (SymbolBody *B : F->getLocalSymbolBodies()) {
+      auto *L = dyn_cast<LocalSymbol<ELFT>>(B);
+      const Elf_Sym &Sym = cast<LocalSymbol<ELFT>>(B)->Sym;
       StringRef SymName = check(Sym.getName(F->getStringTable()));
       if (!shouldKeepInSymtab<ELFT>(*F, SymName, Sym))
         continue;
       if (Sym.st_shndx != SHN_ABS) {
         InputSectionBase<ELFT> *Section = F->getSection(Sym);
         if (!Section->Live)
           continue;
         // That can happen if creating relocatable output.
         if (Sym.getType() == STT_SECTION)
           SymName = Section->getSectionName();
       }
       ++Out<ELFT>::SymTab->NumLocals;
       if (Config->Relocatable)
-        Out<ELFT>::SymTab->Locals[&Sym] = Out<ELFT>::SymTab->NumLocals;
+        L->DynsymIndex = Out<ELFT>::SymTab->NumLocals;
       F->KeptLocalSyms.push_back(std::make_pair(
           &Sym, Out<ELFT>::SymTab->StrTabSec.addString(SymName)));
     }
   }
 }
 
 // PPC64 has a number of special SHT_PROGBITS+SHF_ALLOC+SHF_WRITE sections that
 // we would like to make sure appear is a specific order to maximize their
static uint32_t getELFFlags() {
   uint32_t V = EF_MIPS_ABI_O32 | EF_MIPS_CPIC | EF_MIPS_ARCH_32R2;
   if (Config->Shared)
     V |= EF_MIPS_PIC;
   return V;
 }
 
 template <class ELFT>
 static typename ELFFile<ELFT>::uintX_t getEntryAddr() {
-  if (Config->EntrySym) {
-    if (SymbolBody *B = Config->EntrySym->repl())
-      return B->getVA<ELFT>();
-    return 0;
-  }
+  if (SymbolBody *B = Config->EntrySym)
+    return B->repl().getVA<ELFT>();
   if (Config->EntryAddr != uint64_t(-1))
     return Config->EntryAddr;
   return 0;
 }
 
 template <class ELFT> static uint8_t getELFEncoding() {
   if (ELFT::TargetEndianness == llvm::support::little)
     return ELFDATA2LSB;