[lld] r289280 - COFF: New symbol table design.

Mike Aizatsky via llvm-commits llvm-commits at lists.llvm.org
Mon Dec 12 09:36:56 PST 2016


Peter,

I think this breaks asan bot:

http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/builds/414/steps/check-lld%20asan/logs/stdio

=================================================================
==6557==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 56 byte(s) in 1 object(s) allocated from:
    #0 0x706540 in operator new(unsigned long)
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/projects/compiler-rt/lib/asan/asan_new_delete.cc:82
    #1 0x7a7b39 in
lld::coff::DefinedImportThunk::DefinedImportThunk(llvm::StringRef,
lld::coff::DefinedImportData*, unsigned short)
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/Symbols.cpp:64:26
    #2 0x79e014 in replaceBody<lld::coff::DefinedImportThunk,
llvm::StringRef &, lld::coff::DefinedImportData *&, unsigned short &>
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/Symbols.h:417:24
    #3 0x79e014 in
lld::coff::SymbolTable::addImportThunk(llvm::StringRef,
lld::coff::DefinedImportData*, unsigned short)
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/SymbolTable.cpp:276
    #4 0x780413 in lld::coff::ImportFile::parse()
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/InputFiles.cpp:349:15
    #5 0x79719b in
lld::coff::SymbolTable::addFile(lld::coff::InputFile*)
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/SymbolTable.cpp:32:9
    #6 0x79b35e in
lld::coff::SymbolTable::addMemberFile(lld::coff::ArchiveFile*,
llvm::object::Archive::Symbol)
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/SymbolTable.cpp:292:3
    #7 0x79b715 in
lld::coff::SymbolTable::addLazy(lld::coff::ArchiveFile*,
llvm::object::Archive::Symbol)
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/SymbolTable.cpp:156:3
    #8 0x775f2c in lld::coff::ArchiveFile::parse()
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/InputFiles.cpp:60:13
    #9 0x79719b in
lld::coff::SymbolTable::addFile(lld::coff::InputFile*)
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/SymbolTable.cpp:32:9
    #10 0x735c7b in lld::coff::LinkerDriver::link(llvm::ArrayRef<char
const*>) /mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/Driver.cpp:580:12
    #11 0x72eaa6 in lld::coff::link(llvm::ArrayRef<char const*>)
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/COFF/Driver.cpp:49:11
    #12 0x70adfd in main
/mnt/b/sanitizer-buildbot2/sanitizer-x86_64-linux-bootstrap/build/llvm/tools/lld/tools/lld/lld.cpp:106:13
    #13 0x7f899f22af44 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x21f44)

SUMMARY: AddressSanitizer: 56 byte(s) leaked in 1 allocation(s).



On Fri, Dec 9, 2016 at 2:05 PM Peter Collingbourne via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: pcc
> Date: Fri Dec  9 15:55:24 2016
> New Revision: 289280
>
> URL: http://llvm.org/viewvc/llvm-project?rev=289280&view=rev
> Log:
> COFF: New symbol table design.
>
> This ports the ELF linker's symbol table design, introduced in r268178,
> to the COFF linker.
>
> Differential Revision: http://reviews.llvm.org/D21166
>
> Modified:
>     lld/trunk/COFF/Chunks.cpp
>     lld/trunk/COFF/Chunks.h
>     lld/trunk/COFF/Config.h
>     lld/trunk/COFF/DLL.cpp
>     lld/trunk/COFF/Driver.cpp
>     lld/trunk/COFF/Driver.h
>     lld/trunk/COFF/DriverUtils.cpp
>     lld/trunk/COFF/ICF.cpp
>     lld/trunk/COFF/InputFiles.cpp
>     lld/trunk/COFF/InputFiles.h
>     lld/trunk/COFF/MarkLive.cpp
>     lld/trunk/COFF/SymbolTable.cpp
>     lld/trunk/COFF/SymbolTable.h
>     lld/trunk/COFF/Symbols.cpp
>     lld/trunk/COFF/Symbols.h
>     lld/trunk/COFF/Writer.cpp
>     lld/trunk/test/COFF/include2.test
>     lld/trunk/test/COFF/order.test
>     lld/trunk/test/COFF/symtab.test
>
> Modified: lld/trunk/COFF/Chunks.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Chunks.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Chunks.cpp (original)
> +++ lld/trunk/COFF/Chunks.cpp Fri Dec  9 15:55:24 2016
> @@ -150,7 +150,7 @@ void SectionChunk::writeTo(uint8_t *Buf)
>    // Apply relocations.
>    for (const coff_relocation &Rel : Relocs) {
>      uint8_t *Off = Buf + OutputSectionOff + Rel.VirtualAddress;
> -    SymbolBody *Body = File->getSymbolBody(Rel.SymbolTableIndex)->repl();
> +    SymbolBody *Body = File->getSymbolBody(Rel.SymbolTableIndex);
>      Defined *Sym = cast<Defined>(Body);
>      uint64_t P = RVA + Rel.VirtualAddress;
>      switch (Config->Machine) {
> @@ -203,7 +203,7 @@ void SectionChunk::getBaserels(std::vect
>      uint8_t Ty = getBaserelType(Rel);
>      if (Ty == IMAGE_REL_BASED_ABSOLUTE)
>        continue;
> -    SymbolBody *Body = File->getSymbolBody(Rel.SymbolTableIndex)->repl();
> +    SymbolBody *Body = File->getSymbolBody(Rel.SymbolTableIndex);
>      if (isa<DefinedAbsolute>(Body))
>        continue;
>      Res->emplace_back(RVA + Rel.VirtualAddress, Ty);
>
> Modified: lld/trunk/COFF/Chunks.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Chunks.h?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Chunks.h (original)
> +++ lld/trunk/COFF/Chunks.h Fri Dec  9 15:55:24 2016
> @@ -28,7 +28,6 @@ using llvm::object::COFFSymbolRef;
>  using llvm::object::SectionRef;
>  using llvm::object::coff_relocation;
>  using llvm::object::coff_section;
> -using llvm::sys::fs::file_magic;
>
>  class Baserel;
>  class Defined;
>
> Modified: lld/trunk/COFF/Config.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Config.h?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Config.h (original)
> +++ lld/trunk/COFF/Config.h Fri Dec  9 15:55:24 2016
> @@ -26,7 +26,8 @@ using llvm::StringRef;
>  class DefinedAbsolute;
>  class DefinedRelative;
>  class StringChunk;
> -class Undefined;
> +struct Symbol;
> +class SymbolBody;
>
>  // Short aliases.
>  static const auto AMD64 = llvm::COFF::IMAGE_FILE_MACHINE_AMD64;
> @@ -37,7 +38,7 @@ static const auto I386 = llvm::COFF::IMA
>  struct Export {
>    StringRef Name;       // N in /export:N or /export:E=N
>    StringRef ExtName;    // E in /export:E=N
> -  Undefined *Sym = nullptr;
> +  SymbolBody *Sym = nullptr;
>    uint16_t Ordinal = 0;
>    bool Noname = false;
>    bool Data = false;
> @@ -76,7 +77,7 @@ struct Configuration {
>    llvm::COFF::MachineTypes Machine = IMAGE_FILE_MACHINE_UNKNOWN;
>    bool Verbose = false;
>    WindowsSubsystem Subsystem = llvm::COFF::IMAGE_SUBSYSTEM_UNKNOWN;
> -  Undefined *Entry = nullptr;
> +  SymbolBody *Entry = nullptr;
>    bool NoEntry = false;
>    std::string OutputFile;
>    bool DoGC = true;
> @@ -89,7 +90,7 @@ struct Configuration {
>    StringRef PDBPath;
>
>    // Symbols in this set are considered as live by the garbage collector.
> -  std::set<Undefined *> GCRoot;
> +  std::set<SymbolBody *> GCRoot;
>
>    std::set<StringRef> NoDefaultLibs;
>    bool NoDefaultLibAll = false;
> @@ -100,11 +101,11 @@ struct Configuration {
>    std::vector<Export> Exports;
>    std::set<std::string> DelayLoads;
>    std::map<std::string, int> DLLOrder;
> -  Undefined *DelayLoadHelper = nullptr;
> +  SymbolBody *DelayLoadHelper = nullptr;
>
>    // Used for SafeSEH.
> -  DefinedRelative *SEHTable = nullptr;
> -  DefinedAbsolute *SEHCount = nullptr;
> +  Symbol *SEHTable = nullptr;
> +  Symbol *SEHCount = nullptr;
>
>    // Used for /opt:lldlto=N
>    unsigned LTOOptLevel = 2;
>
> Modified: lld/trunk/COFF/DLL.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/DLL.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/DLL.cpp (original)
> +++ lld/trunk/COFF/DLL.cpp Fri Dec  9 15:55:24 2016
> @@ -324,7 +324,7 @@ public:
>        if (E.ForwardChunk) {
>          write32le(P, E.ForwardChunk->getRVA());
>        } else {
> -        write32le(P, cast<Defined>(E.Sym->repl())->getRVA());
> +        write32le(P, cast<Defined>(E.Sym)->getRVA());
>        }
>      }
>    }
>
> Modified: lld/trunk/COFF/Driver.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Driver.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Driver.cpp (original)
> +++ lld/trunk/COFF/Driver.cpp Fri Dec  9 15:55:24 2016
> @@ -207,10 +207,10 @@ void LinkerDriver::addLibSearchPaths() {
>    }
>  }
>
> -Undefined *LinkerDriver::addUndefined(StringRef Name) {
> -  Undefined *U = Symtab.addUndefined(Name);
> -  Config->GCRoot.insert(U);
> -  return U;
> +SymbolBody *LinkerDriver::addUndefined(StringRef Name) {
> +  SymbolBody *B = Symtab.addUndefined(Name);
> +  Config->GCRoot.insert(B);
> +  return B;
>  }
>
>  // Symbol names are mangled by appending "_" prefix on x86.
> @@ -232,7 +232,7 @@ StringRef LinkerDriver::findDefaultEntry
>    };
>    for (auto E : Entries) {
>      StringRef Entry = Symtab.findMangle(mangle(E[0]));
> -    if (!Entry.empty() && !isa<Undefined>(Symtab.find(Entry)->Body))
> +    if (!Entry.empty() && !isa<Undefined>(Symtab.find(Entry)->body()))
>        return mangle(E[1]);
>    }
>    return "";
> @@ -715,7 +715,7 @@ void LinkerDriver::link(ArrayRef<const c
>        Symbol *Sym = Symtab.find(From);
>        if (!Sym)
>          continue;
> -      if (auto *U = dyn_cast<Undefined>(Sym->Body))
> +      if (auto *U = dyn_cast<Undefined>(Sym->body()))
>          if (!U->WeakAlias)
>            U->WeakAlias = Symtab.addUndefined(To);
>      }
> @@ -734,7 +734,7 @@ void LinkerDriver::link(ArrayRef<const c
>    Symtab.addCombinedLTOObjects();
>
>    // Make sure we have resolved all symbols.
> -  Symtab.reportRemainingUndefines(/*Resolve=*/true);
> +  Symtab.reportRemainingUndefines();
>
>    // Windows specific -- if no /subsystem is given, we need to infer
>    // that from entry point name.
>
> Modified: lld/trunk/COFF/Driver.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Driver.h?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Driver.h (original)
> +++ lld/trunk/COFF/Driver.h Fri Dec  9 15:55:24 2016
> @@ -59,6 +59,7 @@ private:
>
>  class LinkerDriver {
>  public:
> +  LinkerDriver() { coff::Symtab = &Symtab; }
>    void link(llvm::ArrayRef<const char *> Args);
>
>    // Used by the resolver to parse .drectve section contents.
> @@ -86,7 +87,7 @@ private:
>    std::vector<StringRef> SearchPaths;
>    std::set<std::string> VisitedFiles;
>
> -  Undefined *addUndefined(StringRef Sym);
> +  SymbolBody *addUndefined(StringRef Sym);
>    StringRef mangle(StringRef Sym);
>
>    // Windows specific -- "main" is not the only main function in Windows.
>
> Modified: lld/trunk/COFF/DriverUtils.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/DriverUtils.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/DriverUtils.cpp (original)
> +++ lld/trunk/COFF/DriverUtils.cpp Fri Dec  9 15:55:24 2016
> @@ -510,13 +510,13 @@ void fixupExports() {
>    }
>
>    for (Export &E : Config->Exports) {
> +    SymbolBody *Sym = E.Sym;
>      if (!E.ForwardTo.empty()) {
>        E.SymbolName = E.Name;
> -    } else if (Undefined *U = cast_or_null<Undefined>(E.Sym->WeakAlias)) {
> -      E.SymbolName = U->getName();
> -    } else {
> -      E.SymbolName = E.Sym->getName();
> -    }
> +    } else if (auto *U = dyn_cast<Undefined>(Sym))
> +      if (U->WeakAlias)
> +        Sym = U->WeakAlias;
> +    E.SymbolName = Sym->getName();
>    }
>
>    for (Export &E : Config->Exports) {
>
> Modified: lld/trunk/COFF/ICF.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/ICF.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/ICF.cpp (original)
> +++ lld/trunk/COFF/ICF.cpp Fri Dec  9 15:55:24 2016
> @@ -115,8 +115,8 @@ bool ICF::equalsConstant(const SectionCh
>          R1.VirtualAddress != R2.VirtualAddress) {
>        return false;
>      }
> -    SymbolBody *B1 = A->File->getSymbolBody(R1.SymbolTableIndex)->repl();
> -    SymbolBody *B2 = B->File->getSymbolBody(R2.SymbolTableIndex)->repl();
> +    SymbolBody *B1 = A->File->getSymbolBody(R1.SymbolTableIndex);
> +    SymbolBody *B2 = B->File->getSymbolBody(R2.SymbolTableIndex);
>      if (B1 == B2)
>        return true;
>      if (auto *D1 = dyn_cast<DefinedRegular>(B1))
> @@ -141,8 +141,8 @@ bool ICF::equalsConstant(const SectionCh
>  bool ICF::equalsVariable(const SectionChunk *A, const SectionChunk *B) {
>    // Compare relocations.
>    auto Eq = [&](const coff_relocation &R1, const coff_relocation &R2) {
> -    SymbolBody *B1 = A->File->getSymbolBody(R1.SymbolTableIndex)->repl();
> -    SymbolBody *B2 = B->File->getSymbolBody(R2.SymbolTableIndex)->repl();
> +    SymbolBody *B1 = A->File->getSymbolBody(R1.SymbolTableIndex);
> +    SymbolBody *B2 = B->File->getSymbolBody(R2.SymbolTableIndex);
>      if (B1 == B2)
>        return true;
>      if (auto *D1 = dyn_cast<DefinedRegular>(B1))
>
> Modified: lld/trunk/COFF/InputFiles.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/InputFiles.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/InputFiles.cpp (original)
> +++ lld/trunk/COFF/InputFiles.cpp Fri Dec  9 15:55:24 2016
> @@ -12,7 +12,9 @@
>  #include "Driver.h"
>  #include "Error.h"
>  #include "InputFiles.h"
> +#include "SymbolTable.h"
>  #include "Symbols.h"
> +#include "lld/Support/Memory.h"
>  #include "llvm/ADT/SmallVector.h"
>  #include "llvm/ADT/Triple.h"
>  #include "llvm/ADT/Twine.h"
> @@ -39,13 +41,13 @@ using namespace llvm::support::endian;
>
>  using llvm::Triple;
>  using llvm::support::ulittle32_t;
> +using llvm::sys::fs::file_magic;
> +using llvm::sys::fs::identify_magic;
>
>  namespace lld {
>  namespace coff {
>
> -int InputFile::NextIndex = 0;
>  LLVMContext BitcodeFile::Context;
> -std::mutex BitcodeFile::Mu;
>
>  ArchiveFile::ArchiveFile(MemoryBufferRef M) : InputFile(ArchiveKind, M) {}
>
> @@ -53,14 +55,6 @@ void ArchiveFile::parse() {
>    // Parse a MemoryBufferRef as an archive file.
>    File = check(Archive::create(MB), toString(this));
>
> -  // Allocate a buffer for Lazy objects.
> -  size_t NumSyms = File->getNumberOfSymbols();
> -  LazySymbols.reserve(NumSyms);
> -
> -  // Read the symbol table to construct Lazy objects.
> -  for (const Archive::Symbol &Sym : File->symbols())
> -    LazySymbols.emplace_back(this, Sym);
> -
>    // Seen is a map from member files to boolean values. Initially
>    // all members are mapped to false, which indicates all these files
>    // are not read yet.
> @@ -69,18 +63,22 @@ void ArchiveFile::parse() {
>      Seen[Child.getChildOffset()].clear();
>    if (Err)
>      fatal(Err, toString(this));
> +
> +  // Read the symbol table to construct Lazy objects.
> +  for (const Archive::Symbol &Sym : File->symbols())
> +    Symtab->addLazy(this, Sym);
>  }
>
>  // Returns a buffer pointing to a member file containing a given symbol.
>  // This function is thread-safe.
> -MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
> +InputFile *ArchiveFile::getMember(const Archive::Symbol *Sym) {
>    const Archive::Child &C =
>        check(Sym->getMember(),
>              "could not get the member for symbol " + Sym->getName());
>
>    // Return an empty buffer if we have already returned the same buffer.
>    if (Seen[C.getChildOffset()].test_and_set())
> -    return MemoryBufferRef();
> +    return nullptr;
>
>    MemoryBufferRef MB =
>        check(C.getMemoryBufferRef(),
> @@ -90,10 +88,21 @@ MemoryBufferRef ArchiveFile::getMember(c
>      Driver->Cpio->append(relativeToRoot(check(C.getFullName())),
>                           MB.getBuffer());
>
> -  return MB;
> -}
> +  file_magic Magic = identify_magic(MB.getBuffer());
> +  if (Magic == file_magic::coff_import_library)
> +    return make<ImportFile>(MB);
> +
> +  InputFile *Obj;
> +  if (Magic == file_magic::coff_object)
> +    Obj = make<ObjectFile>(MB);
> +  else if (Magic == file_magic::bitcode)
> +    Obj = make<BitcodeFile>(MB);
> +  else
> +    fatal("unknown file type: " + MB.getBufferIdentifier());
>
> -MutableArrayRef<Lazy> ArchiveFile::getLazySymbols() { return LazySymbols;
> }
> +  Obj->ParentName = getName();
> +  return Obj;
> +}
>
>  void ObjectFile::parse() {
>    // Parse a memory buffer as a COFF file.
> @@ -167,7 +176,7 @@ void ObjectFile::initializeSymbols() {
>    uint32_t NumSymbols = COFFObj->getNumberOfSymbols();
>    SymbolBodies.reserve(NumSymbols);
>    SparseSymbolBodies.resize(NumSymbols);
> -  SmallVector<std::pair<Undefined *, uint32_t>, 8> WeakAliases;
> +  SmallVector<std::pair<SymbolBody *, uint32_t>, 8> WeakAliases;
>    int32_t LastSectionNumber = 0;
>    for (uint32_t I = 0; I < NumSymbols; ++I) {
>      // Get a COFFSymbolRef object.
> @@ -188,7 +197,7 @@ void ObjectFile::initializeSymbols() {
>        Body = createUndefined(Sym);
>        uint32_t TagIndex =
>            static_cast<const coff_aux_weak_external *>(AuxP)->TagIndex;
> -      WeakAliases.emplace_back((Undefined *)Body, TagIndex);
> +      WeakAliases.emplace_back(Body, TagIndex);
>      } else {
>        Body = createDefined(Sym, AuxP, IsFirst);
>      }
> @@ -199,23 +208,30 @@ void ObjectFile::initializeSymbols() {
>      I += Sym.getNumberOfAuxSymbols();
>      LastSectionNumber = Sym.getSectionNumber();
>    }
> -  for (auto WeakAlias : WeakAliases)
> -    WeakAlias.first->WeakAlias = SparseSymbolBodies[WeakAlias.second];
> +  for (auto WeakAlias : WeakAliases) {
> +    auto *U = dyn_cast<Undefined>(WeakAlias.first);
> +    if (!U)
> +      continue;
> +    // Report an error if two undefined symbols have different weak
> aliases.
> +    if (U->WeakAlias && U->WeakAlias !=
> SparseSymbolBodies[WeakAlias.second])
> +      Symtab->reportDuplicate(U->symbol(), this);
> +    U->WeakAlias = SparseSymbolBodies[WeakAlias.second];
> +  }
>  }
>
> -Undefined *ObjectFile::createUndefined(COFFSymbolRef Sym) {
> +SymbolBody *ObjectFile::createUndefined(COFFSymbolRef Sym) {
>    StringRef Name;
>    COFFObj->getSymbolName(Sym, Name);
> -  return new (Alloc) Undefined(Name);
> +  return Symtab->addUndefined(Name, this, Sym.isWeakExternal())->body();
>  }
>
> -Defined *ObjectFile::createDefined(COFFSymbolRef Sym, const void *AuxP,
> -                                   bool IsFirst) {
> +SymbolBody *ObjectFile::createDefined(COFFSymbolRef Sym, const void *AuxP,
> +                                      bool IsFirst) {
>    StringRef Name;
>    if (Sym.isCommon()) {
>      auto *C = new (Alloc) CommonChunk(Sym);
>      Chunks.push_back(C);
> -    return new (Alloc) DefinedCommon(this, Sym, C);
> +    return Symtab->addCommon(this, Sym, C)->body();
>    }
>    if (Sym.isAbsolute()) {
>      COFFObj->getSymbolName(Sym, Name);
> @@ -228,7 +244,10 @@ Defined *ObjectFile::createDefined(COFFS
>          SEHCompat = true;
>        return nullptr;
>      }
> -    return new (Alloc) DefinedAbsolute(Name, Sym);
> +    if (Sym.isExternal())
> +      return Symtab->addAbsolute(Name, Sym)->body();
> +    else
> +      return new (Alloc) DefinedAbsolute(Name, Sym);
>    }
>    int32_t SectionNumber = Sym.getSectionNumber();
>    if (SectionNumber == llvm::COFF::IMAGE_SYM_DEBUG)
> @@ -258,7 +277,11 @@ Defined *ObjectFile::createDefined(COFFS
>      SC->Checksum = Aux->CheckSum;
>    }
>
> -  auto *B = new (Alloc) DefinedRegular(this, Sym, SC);
> +  DefinedRegular *B;
> +  if (Sym.isExternal())
> +    B = cast<DefinedRegular>(Symtab->addRegular(this, Sym, SC)->body());
> +  else
> +    B = new (Alloc) DefinedRegular(this, Sym, SC);
>    if (SC->isCOMDAT() && Sym.getValue() == 0 && !AuxP)
>      SC->setSymbol(B);
>
> @@ -320,22 +343,23 @@ void ImportFile::parse() {
>      ExtName = ExtName.substr(0, ExtName.find('@'));
>      break;
>    }
> -  ImpSym = new (Alloc) DefinedImportData(DLLName, ImpName, ExtName, Hdr);
> -  SymbolBodies.push_back(ImpSym);
> +
> +  this->Hdr = Hdr;
> +  ExternalName = ExtName;
> +
> +  ImpSym = cast<DefinedImportData>(
> +      Symtab->addImportData(ImpName, this)->body());
>
>    // If type is function, we need to create a thunk which jump to an
>    // address pointed by the __imp_ symbol. (This allows you to call
>    // DLL functions just like regular non-DLL functions.)
>    if (Hdr->getType() != llvm::COFF::IMPORT_CODE)
>      return;
> -  ThunkSym = new (Alloc) DefinedImportThunk(Name, ImpSym, Hdr->Machine);
> -  SymbolBodies.push_back(ThunkSym);
> +  ThunkSym = cast<DefinedImportThunk>(
> +      Symtab->addImportThunk(Name, ImpSym, Hdr->Machine)->body());
>  }
>
>  void BitcodeFile::parse() {
> -  // Usually parse() is thread-safe, but bitcode file is an exception.
> -  std::lock_guard<std::mutex> Lock(Mu);
> -
>    Context.enableDebugTypeODRUniquing();
>    ErrorOr<std::unique_ptr<LTOModule>> ModOrErr =
> LTOModule::createFromBuffer(
>        Context, MB.getBufferStart(), MB.getBufferSize(),
> llvm::TargetOptions());
> @@ -350,15 +374,15 @@ void BitcodeFile::parse() {
>      StringRef SymName = Saver.save(M->getSymbolName(I));
>      int SymbolDef = Attrs & LTO_SYMBOL_DEFINITION_MASK;
>      if (SymbolDef == LTO_SYMBOL_DEFINITION_UNDEFINED) {
> -      SymbolBodies.push_back(new (Alloc) Undefined(SymName));
> +      SymbolBodies.push_back(Symtab->addUndefined(SymName, this,
> false)->body());
>      } else {
>        bool Replaceable =
>            (SymbolDef == LTO_SYMBOL_DEFINITION_TENTATIVE || // common
>             (Attrs & LTO_SYMBOL_COMDAT) ||                  // comdat
>             (SymbolDef == LTO_SYMBOL_DEFINITION_WEAK &&     // weak
> external
>              (Attrs & LTO_SYMBOL_ALIAS)));
> -      SymbolBodies.push_back(new (Alloc) DefinedBitcode(this, SymName,
> -                                                        Replaceable));
> +      SymbolBodies.push_back(
> +          Symtab->addBitcode(this, SymName, Replaceable)->body());
>      }
>    }
>
>
> Modified: lld/trunk/COFF/InputFiles.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/InputFiles.h?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/InputFiles.h (original)
> +++ lld/trunk/COFF/InputFiles.h Fri Dec  9 15:55:24 2016
> @@ -31,6 +31,7 @@ using llvm::COFF::MachineTypes;
>  using llvm::object::Archive;
>  using llvm::object::COFFObjectFile;
>  using llvm::object::COFFSymbolRef;
> +using llvm::object::coff_import_header;
>  using llvm::object::coff_section;
>
>  class Chunk;
> @@ -39,6 +40,7 @@ class DefinedImportData;
>  class DefinedImportThunk;
>  class Lazy;
>  class SectionChunk;
> +struct Symbol;
>  class SymbolBody;
>  class Undefined;
>
> @@ -52,9 +54,6 @@ public:
>    // Returns the filename.
>    StringRef getName() { return MB.getBufferIdentifier(); }
>
> -  // Returns symbols defined by this file.
> -  virtual std::vector<SymbolBody *> &getSymbols() = 0;
> -
>    // Reads a file (the constructor doesn't do that).
>    virtual void parse() = 0;
>
> @@ -67,14 +66,8 @@ public:
>    // Returns .drectve section contents if exist.
>    StringRef getDirectives() { return StringRef(Directives).trim(); }
>
> -  // Each file has a unique index. The index number is used to
> -  // resolve ties in symbol resolution.
> -  int Index;
> -  static int NextIndex;
> -
>  protected:
> -  InputFile(Kind K, MemoryBufferRef M)
> -      : Index(NextIndex++), MB(M), FileKind(K) {}
> +  InputFile(Kind K, MemoryBufferRef M) : MB(M), FileKind(K) {}
>
>    MemoryBufferRef MB;
>    std::string Directives;
> @@ -90,22 +83,14 @@ public:
>    static bool classof(const InputFile *F) { return F->kind() ==
> ArchiveKind; }
>    void parse() override;
>
> -  // Returns a memory buffer for a given symbol. An empty memory buffer
> -  // is returned if we have already returned the same memory buffer.
> -  // (So that we don't instantiate same members more than once.)
> -  MemoryBufferRef getMember(const Archive::Symbol *Sym);
> -
> -  llvm::MutableArrayRef<Lazy> getLazySymbols();
> -
> -  // All symbols returned by ArchiveFiles are of Lazy type.
> -  std::vector<SymbolBody *> &getSymbols() override {
> -    llvm_unreachable("internal fatal");
> -  }
> +  // Returns an input file for a given symbol. A null pointer is returned
> if we
> +  // have already returned the same input file. (So that we don't
> instantiate
> +  // the same member more than once.)
> +  InputFile *getMember(const Archive::Symbol *Sym);
>
>  private:
>    std::unique_ptr<Archive> File;
>    std::string Filename;
> -  std::vector<Lazy> LazySymbols;
>    std::map<uint64_t, std::atomic_flag> Seen;
>  };
>
> @@ -118,7 +103,7 @@ public:
>    MachineTypes getMachineType() override;
>    std::vector<Chunk *> &getChunks() { return Chunks; }
>    std::vector<SectionChunk *> &getDebugChunks() { return DebugChunks; }
> -  std::vector<SymbolBody *> &getSymbols() override { return SymbolBodies;
> }
> +  std::vector<SymbolBody *> &getSymbols() { return SymbolBodies; }
>
>    // Returns a SymbolBody object for the SymbolIndex'th symbol in the
>    // underlying object file.
> @@ -142,8 +127,8 @@ private:
>    void initializeSymbols();
>    void initializeSEH();
>
> -  Defined *createDefined(COFFSymbolRef Sym, const void *Aux, bool
> IsFirst);
> -  Undefined *createUndefined(COFFSymbolRef Sym);
> +  SymbolBody *createDefined(COFFSymbolRef Sym, const void *Aux, bool
> IsFirst);
> +  SymbolBody *createUndefined(COFFSymbolRef Sym);
>
>    std::unique_ptr<COFFObjectFile> COFFObj;
>    llvm::BumpPtrAllocator Alloc;
> @@ -181,7 +166,6 @@ public:
>    explicit ImportFile(MemoryBufferRef M)
>        : InputFile(ImportKind, M), StringAlloc(StringAllocAux) {}
>    static bool classof(const InputFile *F) { return F->kind() ==
> ImportKind; }
> -  std::vector<SymbolBody *> &getSymbols() override { return SymbolBodies;
> }
>
>    DefinedImportData *ImpSym = nullptr;
>    DefinedImportThunk *ThunkSym = nullptr;
> @@ -190,10 +174,14 @@ public:
>  private:
>    void parse() override;
>
> -  std::vector<SymbolBody *> SymbolBodies;
>    llvm::BumpPtrAllocator Alloc;
>    llvm::BumpPtrAllocator StringAllocAux;
>    llvm::StringSaver StringAlloc;
> +
> +public:
> +  StringRef ExternalName;
> +  const coff_import_header *Hdr;
> +  Chunk *Location = nullptr;
>  };
>
>  // Used for LTO.
> @@ -201,7 +189,7 @@ class BitcodeFile : public InputFile {
>  public:
>    explicit BitcodeFile(MemoryBufferRef M) : InputFile(BitcodeKind, M) {}
>    static bool classof(const InputFile *F) { return F->kind() ==
> BitcodeKind; }
> -  std::vector<SymbolBody *> &getSymbols() override { return SymbolBodies;
> }
> +  std::vector<SymbolBody *> &getSymbols() { return SymbolBodies; }
>    MachineTypes getMachineType() override;
>    std::unique_ptr<LTOModule> takeModule() { return std::move(M); }
>
>
> Modified: lld/trunk/COFF/MarkLive.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/MarkLive.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/MarkLive.cpp (original)
> +++ lld/trunk/COFF/MarkLive.cpp Fri Dec  9 15:55:24 2016
> @@ -38,8 +38,8 @@ void markLive(const std::vector<Chunk *>
>    };
>
>    // Add GC root chunks.
> -  for (Undefined *U : Config->GCRoot)
> -    if (auto *D = dyn_cast<DefinedRegular>(U->repl()))
> +  for (SymbolBody *B : Config->GCRoot)
> +    if (auto *D = dyn_cast<DefinedRegular>(B))
>        Enqueue(D->getChunk());
>
>    while (!Worklist.empty()) {
> @@ -48,7 +48,7 @@ void markLive(const std::vector<Chunk *>
>
>      // Mark all symbols listed in the relocation table for this section.
>      for (SymbolBody *S : SC->symbols())
> -      if (auto *D = dyn_cast<DefinedRegular>(S->repl()))
> +      if (auto *D = dyn_cast<DefinedRegular>(S))
>          Enqueue(D->getChunk());
>
>      // Mark associative sections if any.
>
> Modified: lld/trunk/COFF/SymbolTable.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/SymbolTable.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/SymbolTable.cpp (original)
> +++ lld/trunk/COFF/SymbolTable.cpp Fri Dec  9 15:55:24 2016
> @@ -12,7 +12,6 @@
>  #include "Driver.h"
>  #include "Error.h"
>  #include "Symbols.h"
> -#include "lld/Core/Parallel.h"
>  #include "lld/Support/Memory.h"
>  #include "llvm/IR/LLVMContext.h"
>  #include "llvm/LTO/legacy/LTOCodeGenerator.h"
> @@ -25,21 +24,15 @@ using namespace llvm;
>  namespace lld {
>  namespace coff {
>
> -void SymbolTable::addFile(InputFile *File) {
> -#if LLVM_ENABLE_THREADS
> -  std::launch Policy = std::launch::async;
> -#else
> -  std::launch Policy = std::launch::deferred;
> -#endif
> +SymbolTable *Symtab;
>
> +void SymbolTable::addFile(InputFile *File) {
>    Files.push_back(File);
>    if (auto *F = dyn_cast<ArchiveFile>(File)) {
> -    ArchiveQueue.push_back(
> -        std::async(Policy, [=]() { F->parse(); return F; }));
> +    ArchiveQueue.push_back(F);
>      return;
>    }
> -  ObjectQueue.push_back(
> -      std::async(Policy, [=]() { File->parse(); return File; }));
> +  ObjectQueue.push_back(File);
>    if (auto *F = dyn_cast<ObjectFile>(File)) {
>      ObjectFiles.push_back(F);
>    } else if (auto *F = dyn_cast<BitcodeFile>(File)) {
> @@ -53,7 +46,7 @@ void SymbolTable::step() {
>    if (queueEmpty())
>      return;
>    readObjects();
> -  readArchives();
> +  readArchive();
>  }
>
>  void SymbolTable::run() {
> @@ -61,26 +54,17 @@ void SymbolTable::run() {
>      step();
>  }
>
> -void SymbolTable::readArchives() {
> +void SymbolTable::readArchive() {
>    if (ArchiveQueue.empty())
>      return;
>
>    // Add lazy symbols to the symbol table. Lazy symbols that conflict
>    // with existing undefined symbols are accumulated in LazySyms.
> -  std::vector<Symbol *> LazySyms;
> -  for (std::future<ArchiveFile *> &Future : ArchiveQueue) {
> -    ArchiveFile *File = Future.get();
> -    if (Config->Verbose)
> -      outs() << "Reading " << toString(File) << "\n";
> -    for (Lazy &Sym : File->getLazySymbols())
> -      addLazy(&Sym, &LazySyms);
> -  }
> -  ArchiveQueue.clear();
> -
> -  // Add archive member files to ObjectQueue that should resolve
> -  // existing undefined symbols.
> -  for (Symbol *Sym : LazySyms)
> -    addMemberFile(cast<Lazy>(Sym->Body));
> +  ArchiveFile *File = ArchiveQueue.front();
> +  ArchiveQueue.pop_front();
> +  if (Config->Verbose)
> +    outs() << "Reading " << toString(File) << "\n";
> +  File->parse();
>  }
>
>  void SymbolTable::readObjects() {
> @@ -90,14 +74,12 @@ void SymbolTable::readObjects() {
>    // Add defined and undefined symbols to the symbol table.
>    std::vector<StringRef> Directives;
>    for (size_t I = 0; I < ObjectQueue.size(); ++I) {
> -    InputFile *File = ObjectQueue[I].get();
> +    InputFile *File = ObjectQueue[I];
>      if (Config->Verbose)
>        outs() << "Reading " << toString(File) << "\n";
> +    File->parse();
>      // Adding symbols may add more files to ObjectQueue
>      // (but not to ArchiveQueue).
> -    for (SymbolBody *Sym : File->getSymbols())
> -      if (Sym->isExternal())
> -        addSymbol(Sym);
>      StringRef S = File->getDirectives();
>      if (!S.empty()) {
>        Directives.push_back(S);
> @@ -117,127 +99,239 @@ bool SymbolTable::queueEmpty() {
>    return ArchiveQueue.empty() && ObjectQueue.empty();
>  }
>
> -void SymbolTable::reportRemainingUndefines(bool Resolve) {
> +void SymbolTable::reportRemainingUndefines() {
>    SmallPtrSet<SymbolBody *, 8> Undefs;
>    for (auto &I : Symtab) {
>      Symbol *Sym = I.second;
> -    auto *Undef = dyn_cast<Undefined>(Sym->Body);
> +    auto *Undef = dyn_cast<Undefined>(Sym->body());
>      if (!Undef)
>        continue;
> +    if (!Sym->IsUsedInRegularObj)
> +      continue;
>      StringRef Name = Undef->getName();
>      // A weak alias may have been resolved, so check for that.
>      if (Defined *D = Undef->getWeakAlias()) {
> -      if (Resolve)
> -        Sym->Body = D;
> +      // We resolve weak aliases by replacing the alias's SymbolBody with
> the
> +      // target's SymbolBody. This causes all SymbolBody pointers
> referring to
> +      // the old symbol to instead refer to the new symbol. However, we
> can't
> +      // just blindly copy sizeof(Symbol::Body) bytes from D to Sym->Body
> +      // because D may be an internal symbol, and internal symbols are
> stored as
> +      // "unparented" SymbolBodies. For that reason we need to check
> which type
> +      // of symbol we are dealing with and copy the correct number of
> bytes.
> +      if (isa<DefinedRegular>(D))
> +        memcpy(Sym->Body.buffer, D, sizeof(DefinedRegular));
> +      else if (isa<DefinedAbsolute>(D))
> +        memcpy(Sym->Body.buffer, D, sizeof(DefinedAbsolute));
> +      else
> +        // No other internal symbols are possible.
> +        Sym->Body = D->symbol()->Body;
>        continue;
>      }
>      // If we can resolve a symbol by removing __imp_ prefix, do that.
>      // This odd rule is for compatibility with MSVC linker.
>      if (Name.startswith("__imp_")) {
>        Symbol *Imp = find(Name.substr(strlen("__imp_")));
> -      if (Imp && isa<Defined>(Imp->Body)) {
> -        if (!Resolve)
> -          continue;
> -        auto *D = cast<Defined>(Imp->Body);
> -        auto *S = make<DefinedLocalImport>(Name, D);
> -        LocalImportChunks.push_back(S->getChunk());
> -        Sym->Body = S;
> +      if (Imp && isa<Defined>(Imp->body())) {
> +        auto *D = cast<Defined>(Imp->body());
> +        replaceBody<DefinedLocalImport>(Sym, Name, D);
> +        LocalImportChunks.push_back(
> +            cast<DefinedLocalImport>(Sym->body())->getChunk());
>          continue;
>        }
>      }
>      // Remaining undefined symbols are not fatal if /force is specified.
>      // They are replaced with dummy defined symbols.
> -    if (Config->Force && Resolve)
> -      Sym->Body = make<DefinedAbsolute>(Name, 0);
> -    Undefs.insert(Sym->Body);
> +    if (Config->Force)
> +      replaceBody<DefinedAbsolute>(Sym, Name, 0);
> +    Undefs.insert(Sym->body());
>    }
>    if (Undefs.empty())
>      return;
> -  for (Undefined *U : Config->GCRoot)
> -    if (Undefs.count(U->repl()))
> -      errs() << "<root>: undefined symbol: " << U->getName() << "\n";
> -  for (InputFile *File : Files)
> -    if (!isa<ArchiveFile>(File))
> -      for (SymbolBody *Sym : File->getSymbols())
> -        if (Undefs.count(Sym->repl()))
> -          errs() << toString(File) << ": undefined symbol: " <<
> Sym->getName()
> -                 << "\n";
> +  for (SymbolBody *B : Config->GCRoot)
> +    if (Undefs.count(B))
> +      errs() << "<root>: undefined symbol: " << B->getName() << "\n";
> +  for (ObjectFile *File : ObjectFiles)
> +    for (SymbolBody *Sym : File->getSymbols())
> +      if (Undefs.count(Sym))
> +        errs() << toString(File) << ": undefined symbol: " <<
> Sym->getName()
> +               << "\n";
>    if (!Config->Force)
>      fatal("link failed");
>  }
>
> -void SymbolTable::addLazy(Lazy *New, std::vector<Symbol *> *Accum) {
> -  Symbol *Sym = insert(New);
> -  if (Sym->Body == New)
> -    return;
> -  SymbolBody *Existing = Sym->Body;
> -  if (isa<Defined>(Existing))
> -    return;
> -  if (Lazy *L = dyn_cast<Lazy>(Existing))
> -    if (L->getFileIndex() < New->getFileIndex())
> -      return;
> -  Sym->Body = New;
> -  New->setBackref(Sym);
> -  if (isa<Undefined>(Existing))
> -    Accum->push_back(Sym);
> -}
> -
> -void SymbolTable::addSymbol(SymbolBody *New) {
> -  // Find an existing symbol or create and insert a new one.
> -  assert(isa<Defined>(New) || isa<Undefined>(New));
> -  Symbol *Sym = insert(New);
> -  if (Sym->Body == New)
> -    return;
> -  SymbolBody *Existing = Sym->Body;
> -
> -  // If we have an undefined symbol and a lazy symbol,
> -  // let the lazy symbol to read a member file.
> -  if (auto *L = dyn_cast<Lazy>(Existing)) {
> -    // Undefined symbols with weak aliases need not to be resolved,
> -    // since they would be replaced with weak aliases if they remain
> -    // undefined.
> -    if (auto *U = dyn_cast<Undefined>(New)) {
> -      if (!U->WeakAlias) {
> -        addMemberFile(L);
> -        return;
> -      }
> -    }
> -    Sym->Body = New;
> -    return;
> +std::pair<Symbol *, bool> SymbolTable::insert(StringRef Name) {
> +  Symbol *&Sym = Symtab[Name];
> +  if (Sym)
> +    return {Sym, false};
> +  Sym = make<Symbol>();
> +  Sym->IsUsedInRegularObj = false;
> +  return {Sym, true};
> +}
> +
> +Symbol *SymbolTable::addUndefined(StringRef Name, InputFile *F,
> +                                  bool IsWeakAlias) {
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(Name);
> +  if (!F || !isa<BitcodeFile>(F))
> +    S->IsUsedInRegularObj = true;
> +  if (WasInserted || (isa<Lazy>(S->body()) && IsWeakAlias)) {
> +    replaceBody<Undefined>(S, Name);
> +    return S;
>    }
> -
> -  // compare() returns -1, 0, or 1 if the lhs symbol is less preferable,
> -  // equivalent (conflicting), or more preferable, respectively.
> -  int Comp = Existing->compare(New);
> -  if (Comp == 0)
> -    fatal("duplicate symbol: " + toString(*Existing) + " in " +
> -          toString(Existing->getFile()) + " and in " +
> -          toString(New->getFile()));
> -  if (Comp < 0)
> -    Sym->Body = New;
> -}
> -
> -Symbol *SymbolTable::insert(SymbolBody *New) {
> -  Symbol *&Sym = Symtab[New->getName()];
> -  if (Sym) {
> -    New->setBackref(Sym);
> -    return Sym;
> -  }
> -  Sym = make<Symbol>(New);
> -  New->setBackref(Sym);
> -  return Sym;
> +  if (auto *L = dyn_cast<Lazy>(S->body()))
> +    addMemberFile(L->File, L->Sym);
> +  return S;
> +}
> +
> +void SymbolTable::addLazy(ArchiveFile *F, const Archive::Symbol Sym) {
> +  StringRef Name = Sym.getName();
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(Name);
> +  if (WasInserted) {
> +    replaceBody<Lazy>(S, F, Sym);
> +    return;
> +  }
> +  auto *U = dyn_cast<Undefined>(S->body());
> +  if (!U || U->WeakAlias)
> +    return;
> +  addMemberFile(F, Sym);
> +}
> +
> +void SymbolTable::reportDuplicate(Symbol *Existing, InputFile *NewFile) {
> +  fatal("duplicate symbol: " + toString(*Existing->body()) + " in " +
> +        toString(Existing->body()->getFile()) + " and in " +
> +        (NewFile ? toString(NewFile) : "(internal)"));
> +}
> +
> +Symbol *SymbolTable::addAbsolute(StringRef N, COFFSymbolRef Sym) {
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(N);
> +  S->IsUsedInRegularObj = true;
> +  if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
> +    replaceBody<DefinedAbsolute>(S, N, Sym);
> +  else if (!isa<DefinedCOFF>(S->body()))
> +    reportDuplicate(S, nullptr);
> +  return S;
> +}
> +
> +Symbol *SymbolTable::addAbsolute(StringRef N, uint64_t VA) {
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(N);
> +  S->IsUsedInRegularObj = true;
> +  if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
> +    replaceBody<DefinedAbsolute>(S, N, VA);
> +  else if (!isa<DefinedCOFF>(S->body()))
> +    reportDuplicate(S, nullptr);
> +  return S;
> +}
> +
> +Symbol *SymbolTable::addRelative(StringRef N, uint64_t VA) {
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(N);
> +  S->IsUsedInRegularObj = true;
> +  if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
> +    replaceBody<DefinedRelative>(S, N, VA);
> +  else if (!isa<DefinedCOFF>(S->body()))
> +    reportDuplicate(S, nullptr);
> +  return S;
> +}
> +
> +Symbol *SymbolTable::addRegular(ObjectFile *F, COFFSymbolRef Sym,
> +                                SectionChunk *C) {
> +  StringRef Name;
> +  F->getCOFFObj()->getSymbolName(Sym, Name);
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(Name);
> +  S->IsUsedInRegularObj = true;
> +  if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
> +    replaceBody<DefinedRegular>(S, F, Sym, C);
> +  else if (auto *R = dyn_cast<DefinedRegular>(S->body())) {
> +    if (!C->isCOMDAT() || !R->isCOMDAT())
> +      reportDuplicate(S, F);
> +  } else if (auto *B = dyn_cast<DefinedBitcode>(S->body())) {
> +    if (B->IsReplaceable)
> +      replaceBody<DefinedRegular>(S, F, Sym, C);
> +    else if (!C->isCOMDAT())
> +      reportDuplicate(S, F);
> +  } else
> +    replaceBody<DefinedRegular>(S, F, Sym, C);
> +  return S;
> +}
> +
> +Symbol *SymbolTable::addBitcode(BitcodeFile *F, StringRef N, bool
> IsReplaceable) {
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(N);
> +  if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body())) {
> +    replaceBody<DefinedBitcode>(S, F, N, IsReplaceable);
> +    return S;
> +  }
> +  if (isa<DefinedCommon>(S->body()))
> +    return S;
> +  if (IsReplaceable)
> +    if (isa<DefinedRegular>(S->body()) || isa<DefinedBitcode>(S->body()))
> +      return S;
> +  reportDuplicate(S, F);
> +  return S;
> +}
> +
> +Symbol *SymbolTable::addCommon(ObjectFile *F, COFFSymbolRef Sym,
> +                               CommonChunk *C) {
> +  StringRef Name;
> +  F->getCOFFObj()->getSymbolName(Sym, Name);
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(Name);
> +  S->IsUsedInRegularObj = true;
> +  if (WasInserted || !isa<DefinedCOFF>(S->body()))
> +    replaceBody<DefinedCommon>(S, F, Sym, C);
> +  else if (auto *DC = dyn_cast<DefinedCommon>(S->body()))
> +    if (Sym.getValue() > DC->getSize())
> +      replaceBody<DefinedCommon>(S, F, Sym, C);
> +  return S;
> +}
> +
> +Symbol *SymbolTable::addImportData(StringRef N, ImportFile *F) {
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(N);
> +  S->IsUsedInRegularObj = true;
> +  if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
> +    replaceBody<DefinedImportData>(S, N, F);
> +  else if (!isa<DefinedCOFF>(S->body()))
> +    reportDuplicate(S, nullptr);
> +  return S;
> +}
> +
> +Symbol *SymbolTable::addImportThunk(StringRef Name, DefinedImportData *ID,
> +                                    uint16_t Machine) {
> +  Symbol *S;
> +  bool WasInserted;
> +  std::tie(S, WasInserted) = insert(Name);
> +  S->IsUsedInRegularObj = true;
> +  if (WasInserted || isa<Undefined>(S->body()) || isa<Lazy>(S->body()))
> +    replaceBody<DefinedImportThunk>(S, Name, ID, Machine);
> +  else if (!isa<DefinedCOFF>(S->body()))
> +    reportDuplicate(S, nullptr);
> +  return S;
>  }
>
>  // Reads an archive member file pointed by a given symbol.
> -void SymbolTable::addMemberFile(Lazy *Body) {
> -  InputFile *File = Body->getMember();
> +void SymbolTable::addMemberFile(ArchiveFile *F, const Archive::Symbol
> Sym) {
> +  InputFile *File = F->getMember(&Sym);
>
>    // getMember returns an empty buffer if the member was already
>    // read from the library.
>    if (!File)
>      return;
>    if (Config->Verbose)
> -    outs() << "Loaded " << toString(File) << " for " << Body->getName()
> << "\n";
> +    outs() << "Loaded " << toString(File) << " for " << Sym.getName() <<
> "\n";
>    addFile(File);
>  }
>
> @@ -274,7 +368,7 @@ StringRef SymbolTable::findByPrefix(Stri
>
>  StringRef SymbolTable::findMangle(StringRef Name) {
>    if (Symbol *Sym = find(Name))
> -    if (!isa<Undefined>(Sym->Body))
> +    if (!isa<Undefined>(Sym->body()))
>        return Name;
>    if (Config->Machine != I386)
>      return findByPrefix(("?" + Name + "@@Y").str());
> @@ -288,34 +382,17 @@ StringRef SymbolTable::findMangle(String
>    return findByPrefix(("?" + Name.substr(1) + "@@Y").str());
>  }
>
> -void SymbolTable::mangleMaybe(Undefined *U) {
> -  if (U->WeakAlias)
> -    return;
> -  if (!isa<Undefined>(U->repl()))
> +void SymbolTable::mangleMaybe(SymbolBody *B) {
> +  auto *U = dyn_cast<Undefined>(B);
> +  if (!U || U->WeakAlias)
>      return;
>    StringRef Alias = findMangle(U->getName());
>    if (!Alias.empty())
>      U->WeakAlias = addUndefined(Alias);
>  }
>
> -Undefined *SymbolTable::addUndefined(StringRef Name) {
> -  auto *New = make<Undefined>(Name);
> -  addSymbol(New);
> -  if (auto *U = dyn_cast<Undefined>(New->repl()))
> -    return U;
> -  return New;
> -}
> -
> -DefinedRelative *SymbolTable::addRelative(StringRef Name, uint64_t VA) {
> -  auto *New = make<DefinedRelative>(Name, VA);
> -  addSymbol(New);
> -  return New;
> -}
> -
> -DefinedAbsolute *SymbolTable::addAbsolute(StringRef Name, uint64_t VA) {
> -  auto *New = make<DefinedAbsolute>(Name, VA);
> -  addSymbol(New);
> -  return New;
> +SymbolBody *SymbolTable::addUndefined(StringRef Name) {
> +  return addUndefined(Name, nullptr, false)->body();
>  }
>
>  void SymbolTable::printMap(llvm::raw_ostream &OS) {
> @@ -329,59 +406,19 @@ void SymbolTable::printMap(llvm::raw_ost
>    }
>  }
>
> -void SymbolTable::addCombinedLTOObject(ObjectFile *Obj) {
> -  for (SymbolBody *Body : Obj->getSymbols()) {
> -    if (!Body->isExternal())
> -      continue;
> -    // We should not see any new undefined symbols at this point, but
> we'll
> -    // diagnose them later in reportRemainingUndefines().
> -    StringRef Name = Body->getName();
> -    Symbol *Sym = insert(Body);
> -    SymbolBody *Existing = Sym->Body;
> -
> -    if (Existing == Body)
> -      continue;
> -
> -    if (isa<DefinedBitcode>(Existing)) {
> -      Sym->Body = Body;
> -      continue;
> -    }
> -    if (isa<Undefined>(Body)) {
> -      if (auto *L = dyn_cast<Lazy>(Existing)) {
> -        // We may see new references to runtime library symbols such as
> __chkstk
> -        // here. These symbols must be wholly defined in non-bitcode
> files.
> -        addMemberFile(L);
> -        continue;
> -      }
> -    }
> -
> -    int Comp = Existing->compare(Body);
> -    if (Comp == 0)
> -      fatal("LTO: unexpected duplicate symbol: " + Name);
> -    if (Comp < 0)
> -      Sym->Body = Body;
> -  }
> -}
> -
>  void SymbolTable::addCombinedLTOObjects() {
>    if (BitcodeFiles.empty())
>      return;
>
> -  // Diagnose any undefined symbols early, but do not resolve weak
> externals,
> -  // as resolution breaks the invariant that each Symbol points to a
> unique
> -  // SymbolBody, which we rely on to replace DefinedBitcode symbols
> correctly.
> -  reportRemainingUndefines(/*Resolve=*/false);
> -
>    // Create an object file and add it to the symbol table by replacing any
>    // DefinedBitcode symbols with the definitions in the object file.
>    LTOCodeGenerator CG(BitcodeFile::Context);
>    CG.setOptLevel(Config->LTOOptLevel);
>    std::vector<ObjectFile *> Objs = createLTOObjects(&CG);
>
> -  for (ObjectFile *Obj : Objs)
> -    addCombinedLTOObject(Obj);
> -
>    size_t NumBitcodeFiles = BitcodeFiles.size();
> +  for (ObjectFile *Obj : Objs)
> +    Obj->parse();
>    run();
>    if (BitcodeFiles.size() != NumBitcodeFiles)
>      fatal("LTO: late loaded symbol created new bitcode reference");
> @@ -390,25 +427,17 @@ void SymbolTable::addCombinedLTOObjects(
>  // Combine and compile bitcode files and then return the result
>  // as a vector of regular COFF object files.
>  std::vector<ObjectFile *> SymbolTable::createLTOObjects(LTOCodeGenerator
> *CG) {
> -  // All symbols referenced by non-bitcode objects must be preserved.
> -  for (ObjectFile *File : ObjectFiles)
> -    for (SymbolBody *Body : File->getSymbols())
> -      if (auto *S = dyn_cast<DefinedBitcode>(Body->repl()))
> -        CG->addMustPreserveSymbol(S->getName());
> -
> -  // Likewise for bitcode symbols which we initially resolved to
> non-bitcode.
> +  // All symbols referenced by non-bitcode objects, including GC roots,
> must be
> +  // preserved. We must also replace bitcode symbols with undefined
> symbols so
> +  // that they may be replaced with real definitions without conflicting.
>    for (BitcodeFile *File : BitcodeFiles)
> -    for (SymbolBody *Body : File->getSymbols())
> -      if (isa<DefinedBitcode>(Body) && !isa<DefinedBitcode>(Body->repl()))
> +    for (SymbolBody *Body : File->getSymbols()) {
> +      if (!isa<DefinedBitcode>(Body))
> +        continue;
> +      if (Body->symbol()->IsUsedInRegularObj)
>          CG->addMustPreserveSymbol(Body->getName());
> -
> -  // Likewise for other symbols that must be preserved.
> -  for (Undefined *U : Config->GCRoot) {
> -    if (auto *S = dyn_cast<DefinedBitcode>(U->repl()))
> -      CG->addMustPreserveSymbol(S->getName());
> -    else if (auto *S =
> dyn_cast_or_null<DefinedBitcode>(U->getWeakAlias()))
> -      CG->addMustPreserveSymbol(S->getName());
> -  }
> +      replaceBody<Undefined>(Body->symbol(), Body->getName());
> +    }
>
>    CG->setModule(BitcodeFiles[0]->takeModule());
>    for (unsigned I = 1, E = BitcodeFiles.size(); I != E; ++I)
> @@ -438,7 +467,6 @@ std::vector<ObjectFile *> SymbolTable::c
>      auto *ObjFile = new ObjectFile(MemoryBufferRef(Obj, "<LTO object>"));
>      Files.emplace_back(ObjFile);
>      ObjectFiles.push_back(ObjFile);
> -    ObjFile->parse();
>      ObjFiles.push_back(ObjFile);
>    }
>
>
> Modified: lld/trunk/COFF/SymbolTable.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/SymbolTable.h?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/SymbolTable.h (original)
> +++ lld/trunk/COFF/SymbolTable.h Fri Dec  9 15:55:24 2016
> @@ -22,6 +22,7 @@
>  #endif
>
>  #include <future>
> +#include <list>
>
>  namespace llvm {
>  struct LTOCodeGenerator;
> @@ -31,6 +32,7 @@ namespace lld {
>  namespace coff {
>
>  class Chunk;
> +class CommonChunk;
>  class Defined;
>  class DefinedAbsolute;
>  class DefinedRelative;
> @@ -48,7 +50,9 @@ struct Symbol;
>  // conflicts. For example, obviously, a defined symbol is better than
>  // an undefined symbol. Or, if there's a conflict between a lazy and a
>  // undefined, it'll read an archive member to read a real definition
> -// to replace the lazy symbol. The logic is implemented in resolve().
> +// to replace the lazy symbol. The logic is implemented in the
> +// add*() functions, which are called by input files as they are parsed.
> +// There is one add* function per symbol type.
>  class SymbolTable {
>  public:
>    void addFile(InputFile *File);
> @@ -57,9 +61,10 @@ public:
>    void run();
>    bool queueEmpty();
>
> -  // Print an error message on undefined symbols. If Resolve is true, try
> to
> -  // resolve any undefined symbols and update the symbol table
> accordingly.
> -  void reportRemainingUndefines(bool Resolve);
> +  // Try to resolve any undefined symbols and update the symbol table
> +  // accordingly, then print an error message for any remaining undefined
> +  // symbols.
> +  void reportRemainingUndefines();
>
>    // Returns a list of chunks of selected symbols.
>    std::vector<Chunk *> getChunks();
> @@ -72,7 +77,7 @@ public:
>    // mangled symbol. This function tries to find a mangled name
>    // for U from the symbol table, and if found, set the symbol as
>    // a weak alias for U.
> -  void mangleMaybe(Undefined *U);
> +  void mangleMaybe(SymbolBody *B);
>    StringRef findMangle(StringRef Name);
>
>    // Print a layout map to OS.
> @@ -91,36 +96,49 @@ public:
>    std::vector<ObjectFile *> ObjectFiles;
>
>    // Creates an Undefined symbol for a given name.
> -  Undefined *addUndefined(StringRef Name);
> -  DefinedRelative *addRelative(StringRef Name, uint64_t VA);
> -  DefinedAbsolute *addAbsolute(StringRef Name, uint64_t VA);
> +  SymbolBody *addUndefined(StringRef Name);
> +
> +  Symbol *addRelative(StringRef N, uint64_t VA);
> +  Symbol *addAbsolute(StringRef N, uint64_t VA);
> +
> +  Symbol *addUndefined(StringRef Name, InputFile *F, bool IsWeakAlias);
> +  void addLazy(ArchiveFile *F, const Archive::Symbol Sym);
> +  Symbol *addAbsolute(StringRef N, COFFSymbolRef S);
> +  Symbol *addRegular(ObjectFile *F, COFFSymbolRef S, SectionChunk *C);
> +  Symbol *addBitcode(BitcodeFile *F, StringRef N, bool IsReplaceable);
> +  Symbol *addCommon(ObjectFile *F, COFFSymbolRef S, CommonChunk *C);
> +  Symbol *addImportData(StringRef N, ImportFile *F);
> +  Symbol *addImportThunk(StringRef Name, DefinedImportData *S,
> +                         uint16_t Machine);
> +
> +  void reportDuplicate(Symbol *Existing, InputFile *NewFile);
>
>    // A list of chunks which to be added to .rdata.
>    std::vector<Chunk *> LocalImportChunks;
>
>  private:
> -  void readArchives();
> +  void readArchive();
>    void readObjects();
>
> -  void addSymbol(SymbolBody *New);
> -  void addLazy(Lazy *New, std::vector<Symbol *> *Accum);
> -  Symbol *insert(SymbolBody *New);
> +  std::pair<Symbol *, bool> insert(StringRef Name);
>    StringRef findByPrefix(StringRef Prefix);
>
> -  void addMemberFile(Lazy *Body);
> +  void addMemberFile(ArchiveFile *F, const Archive::Symbol Sym);
>    void addCombinedLTOObject(ObjectFile *Obj);
>    std::vector<ObjectFile *> createLTOObjects(llvm::LTOCodeGenerator *CG);
>
>    llvm::DenseMap<StringRef, Symbol *> Symtab;
>
>    std::vector<InputFile *> Files;
> -  std::vector<std::future<ArchiveFile *>> ArchiveQueue;
> -  std::vector<std::future<InputFile *>> ObjectQueue;
> +  std::list<ArchiveFile *> ArchiveQueue;
> +  std::vector<InputFile *> ObjectQueue;
>
>    std::vector<BitcodeFile *> BitcodeFiles;
>    std::vector<SmallString<0>> Objs;
>  };
>
> +extern SymbolTable *Symtab;
> +
>  } // namespace coff
>  } // namespace lld
>
>
> Modified: lld/trunk/COFF/Symbols.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Symbols.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Symbols.cpp (original)
> +++ lld/trunk/COFF/Symbols.cpp Fri Dec  9 15:55:24 2016
> @@ -18,8 +18,6 @@
>
>  using namespace llvm;
>  using namespace llvm::object;
> -using llvm::sys::fs::identify_magic;
> -using llvm::sys::fs::file_magic;
>
>  namespace lld {
>  namespace coff {
> @@ -49,120 +47,6 @@ InputFile *SymbolBody::getFile() {
>    return nullptr;
>  }
>
> -// Returns 1, 0 or -1 if this symbol should take precedence
> -// over the Other, tie or lose, respectively.
> -int SymbolBody::compare(SymbolBody *Other) {
> -  Kind LK = kind(), RK = Other->kind();
> -
> -  // Normalize so that the smaller kind is on the left.
> -  if (LK > RK)
> -    return -Other->compare(this);
> -
> -  // First handle comparisons between two different kinds.
> -  if (LK != RK) {
> -    if (RK > LastDefinedKind) {
> -      if (LK == LazyKind && cast<Undefined>(Other)->WeakAlias)
> -        return -1;
> -
> -      // The LHS is either defined or lazy and so it wins.
> -      assert((LK <= LastDefinedKind || LK == LazyKind) && "Bad kind!");
> -      return 1;
> -    }
> -
> -    // Bitcode has special complexities.
> -    if (RK == DefinedBitcodeKind) {
> -      auto *RHS = cast<DefinedBitcode>(Other);
> -
> -      switch (LK) {
> -      case DefinedCommonKind:
> -        return 1;
> -
> -      case DefinedRegularKind:
> -        // As an approximation, regular symbols win over bitcode symbols,
> -        // but we definitely have a conflict if the regular symbol is not
> -        // replaceable and neither is the bitcode symbol. We do not
> -        // replicate the rest of the symbol resolution logic here; symbol
> -        // resolution will be done accurately after lowering bitcode
> symbols
> -        // to regular symbols in addCombinedLTOObject().
> -        if (cast<DefinedRegular>(this)->isCOMDAT() || RHS->IsReplaceable)
> -          return 1;
> -
> -        // Fallthrough to the default of a tie otherwise.
> -      default:
> -        return 0;
> -      }
> -    }
> -
> -    // Either of the object file kind will trump a higher kind.
> -    if (LK <= LastDefinedCOFFKind)
> -      return 1;
> -
> -    // The remaining kind pairs are ties amongst defined symbols.
> -    return 0;
> -  }
> -
> -  // Now handle the case where the kinds are the same.
> -  switch (LK) {
> -  case DefinedRegularKind: {
> -    auto *LHS = cast<DefinedRegular>(this);
> -    auto *RHS = cast<DefinedRegular>(Other);
> -    if (LHS->isCOMDAT() && RHS->isCOMDAT())
> -      return LHS->getFileIndex() < RHS->getFileIndex() ? 1 : -1;
> -    return 0;
> -  }
> -
> -  case DefinedCommonKind: {
> -    auto *LHS = cast<DefinedCommon>(this);
> -    auto *RHS = cast<DefinedCommon>(Other);
> -    if (LHS->getSize() == RHS->getSize())
> -      return LHS->getFileIndex() < RHS->getFileIndex() ? 1 : -1;
> -    return LHS->getSize() > RHS->getSize() ? 1 : -1;
> -  }
> -
> -  case DefinedBitcodeKind: {
> -    auto *LHS = cast<DefinedBitcode>(this);
> -    auto *RHS = cast<DefinedBitcode>(Other);
> -    // If both are non-replaceable, we have a tie.
> -    if (!LHS->IsReplaceable && !RHS->IsReplaceable)
> -      return 0;
> -
> -    // Non-replaceable symbols win, but even two replaceable symboles
> don't
> -    // tie. If both symbols are replaceable, choice is arbitrary.
> -    if (RHS->IsReplaceable && LHS->IsReplaceable)
> -      return uintptr_t(LHS) < uintptr_t(RHS) ? 1 : -1;
> -    return LHS->IsReplaceable ? -1 : 1;
> -  }
> -
> -  case LazyKind: {
> -    // Don't tie, pick the earliest.
> -    auto *LHS = cast<Lazy>(this);
> -    auto *RHS = cast<Lazy>(Other);
> -    return LHS->getFileIndex() < RHS->getFileIndex() ? 1 : -1;
> -  }
> -
> -  case UndefinedKind: {
> -    auto *LHS = cast<Undefined>(this);
> -    auto *RHS = cast<Undefined>(Other);
> -    // Tie if both undefined symbols have different weak aliases.
> -    if (LHS->WeakAlias && RHS->WeakAlias) {
> -      if (LHS->WeakAlias->getName() != RHS->WeakAlias->getName())
> -        return 0;
> -      return uintptr_t(LHS) < uintptr_t(RHS) ? 1 : -1;
> -    }
> -    return LHS->WeakAlias ? 1 : -1;
> -  }
> -
> -  case DefinedLocalImportKind:
> -  case DefinedImportThunkKind:
> -  case DefinedImportDataKind:
> -  case DefinedAbsoluteKind:
> -  case DefinedRelativeKind:
> -    // These all simply tie.
> -    return 0;
> -  }
> -  llvm_unreachable("unknown symbol kind");
> -}
> -
>  COFFSymbolRef DefinedCOFF::getCOFFSymbol() {
>    size_t SymSize = File->getCOFFObj()->getSymbolTableEntrySize();
>    if (SymSize == sizeof(coff_symbol16))
> @@ -182,34 +66,10 @@ DefinedImportThunk::DefinedImportThunk(S
>    }
>  }
>
> -InputFile *Lazy::getMember() {
> -  MemoryBufferRef MBRef = File->getMember(&Sym);
> -
> -  // getMember returns an empty buffer if the member was already
> -  // read from the library.
> -  if (MBRef.getBuffer().empty())
> -    return nullptr;
> -
> -  file_magic Magic = identify_magic(MBRef.getBuffer());
> -  if (Magic == file_magic::coff_import_library)
> -    return make<ImportFile>(MBRef);
> -
> -  InputFile *Obj;
> -  if (Magic == file_magic::coff_object)
> -    Obj = make<ObjectFile>(MBRef);
> -  else if (Magic == file_magic::bitcode)
> -    Obj = make<BitcodeFile>(MBRef);
> -  else
> -    fatal("unknown file type: " + File->getName());
> -
> -  Obj->ParentName = File->getName();
> -  return Obj;
> -}
> -
>  Defined *Undefined::getWeakAlias() {
>    // A weak alias may be a weak alias to another symbol, so check
> recursively.
>    for (SymbolBody *A = WeakAlias; A; A = cast<Undefined>(A)->WeakAlias)
> -    if (auto *D = dyn_cast<Defined>(A->repl()))
> +    if (auto *D = dyn_cast<Defined>(A))
>        return D;
>    return nullptr;
>  }
>
> Modified: lld/trunk/COFF/Symbols.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Symbols.h?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Symbols.h (original)
> +++ lld/trunk/COFF/Symbols.h Fri Dec  9 15:55:24 2016
> @@ -32,15 +32,8 @@ class ArchiveFile;
>  class BitcodeFile;
>  class InputFile;
>  class ObjectFile;
> -class SymbolBody;
> -
> -// A real symbol object, SymbolBody, is usually accessed indirectly
> -// through a Symbol. There's always one Symbol for each symbol name.
> -// The resolver updates SymbolBody pointers as it resolves symbols.
> -struct Symbol {
> -  explicit Symbol(SymbolBody *P) : Body(P) {}
> -  SymbolBody *Body;
> -};
> +struct Symbol;
> +class SymbolTable;
>
>  // The base class for real symbol classes.
>  class SymbolBody {
> @@ -78,21 +71,13 @@ public:
>    // Returns the file from which this symbol was created.
>    InputFile *getFile();
>
> -  // 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; }
> -
> -  // 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.
> -  int compare(SymbolBody *Other);
> +  Symbol *symbol();
> +  const Symbol *symbol() const {
> +    return const_cast<SymbolBody *>(this)->symbol();
> +  }
>
>  protected:
> +  friend SymbolTable;
>    explicit SymbolBody(Kind K, StringRef N = "")
>        : SymbolKind(K), IsExternal(true), IsCOMDAT(false),
>          IsReplaceable(false), Name(N) {}
> @@ -107,7 +92,6 @@ protected:
>    unsigned IsReplaceable : 1;
>
>    StringRef Name;
> -  Symbol *Backref = nullptr;
>  };
>
>  // The base class for any defined symbols, including absolute symbols,
> @@ -149,7 +133,6 @@ public:
>    }
>
>    ObjectFile *getFile() { return File; }
> -  int getFileIndex() { return File->Index; }
>
>    COFFSymbolRef getCOFFSymbol();
>
> @@ -195,7 +178,7 @@ public:
>    uint64_t getRVA() { return Data->getRVA(); }
>
>  private:
> -  friend SymbolBody;
> +  friend SymbolTable;
>    uint64_t getSize() { return Sym->Value; }
>    CommonChunk *Data;
>  };
> @@ -254,15 +237,12 @@ public:
>
>    static bool classof(const SymbolBody *S) { return S->kind() ==
> LazyKind; }
>
> -  // Returns an object file for this symbol, or a nullptr if the file
> -  // was already returned.
> -  InputFile *getMember();
> -
> -  int getFileIndex() { return File->Index; }
> -
>    ArchiveFile *File;
>
>  private:
> +  friend SymbolTable;
> +
> +private:
>    const Archive::Symbol Sym;
>  };
>
> @@ -295,26 +275,22 @@ public:
>  // table in an output. The former has "__imp_" prefix.
>  class DefinedImportData : public Defined {
>  public:
> -  DefinedImportData(StringRef D, StringRef N, StringRef E,
> -                    const coff_import_header *H)
> -      : Defined(DefinedImportDataKind, N), DLLName(D), ExternalName(E),
> Hdr(H) {
> +  DefinedImportData(StringRef N, ImportFile *F)
> +      : Defined(DefinedImportDataKind, N), File(F) {
>    }
>
>    static bool classof(const SymbolBody *S) {
>      return S->kind() == DefinedImportDataKind;
>    }
>
> -  uint64_t getRVA() { return Location->getRVA(); }
> -  StringRef getDLLName() { return DLLName; }
> -  StringRef getExternalName() { return ExternalName; }
> -  void setLocation(Chunk *AddressTable) { Location = AddressTable; }
> -  uint16_t getOrdinal() { return Hdr->OrdinalHint; }
> +  uint64_t getRVA() { return File->Location->getRVA(); }
> +  StringRef getDLLName() { return File->DLLName; }
> +  StringRef getExternalName() { return File->ExternalName; }
> +  void setLocation(Chunk *AddressTable) { File->Location = AddressTable; }
> +  uint16_t getOrdinal() { return File->Hdr->OrdinalHint; }
>
>  private:
> -  StringRef DLLName;
> -  StringRef ExternalName;
> -  const coff_import_header *Hdr;
> -  Chunk *Location = nullptr;
> +  ImportFile *File;
>  };
>
>  // This class represents a symbol for a jump table entry which jumps
> @@ -345,17 +321,17 @@ private:
>  class DefinedLocalImport : public Defined {
>  public:
>    DefinedLocalImport(StringRef N, Defined *S)
> -      : Defined(DefinedLocalImportKind, N), Data(S) {}
> +      : Defined(DefinedLocalImportKind, N), Data(new LocalImportChunk(S))
> {}
>
>    static bool classof(const SymbolBody *S) {
>      return S->kind() == DefinedLocalImportKind;
>    }
>
> -  uint64_t getRVA() { return Data.getRVA(); }
> -  Chunk *getChunk() { return &Data; }
> +  uint64_t getRVA() { return Data->getRVA(); }
> +  Chunk *getChunk() { return Data.get(); }
>
>  private:
> -  LocalImportChunk Data;
> +  std::unique_ptr<LocalImportChunk> Data;
>  };
>
>  class DefinedBitcode : public Defined {
> @@ -363,6 +339,11 @@ class DefinedBitcode : public Defined {
>  public:
>    DefinedBitcode(BitcodeFile *F, StringRef N, bool IsReplaceable)
>        : Defined(DefinedBitcodeKind, N), File(F) {
> +    // IsReplaceable tracks whether the bitcode symbol may be replaced
> with some
> +    // other (defined, common or bitcode) symbol. This is the case for
> common,
> +    // comdat and weak external symbols. We try to replace bitcode
> symbols with
> +    // "real" symbols (see SymbolTable::add{Regular,Bitcode}), and
> resolve the
> +    // result against the real symbol from the combined LTO object.
>      this->IsReplaceable = IsReplaceable;
>    }
>
> @@ -398,6 +379,45 @@ inline uint64_t Defined::getRVA() {
>    llvm_unreachable("unknown symbol kind");
>  }
>
> +// A real symbol object, SymbolBody, is usually stored within a Symbol.
> There's
> +// always one Symbol for each symbol name. The resolver updates the
> SymbolBody
> +// stored in the Body field of this object as it resolves symbols. Symbol
> also
> +// holds computed properties of symbol names.
> +struct Symbol {
> +  // True if this symbol was referenced by a regular (non-bitcode) object.
> +  unsigned IsUsedInRegularObj : 1;
> +
> +  // This field is used to store the Symbol's SymbolBody. This
> instantiation of
> +  // AlignedCharArrayUnion gives us a struct with a char array field that
> is
> +  // large and aligned enough to store any derived class of SymbolBody.
> +  llvm::AlignedCharArrayUnion<DefinedRegular, DefinedCommon,
> DefinedAbsolute,
> +                              DefinedRelative, Lazy, Undefined,
> +                              DefinedImportData, DefinedImportThunk,
> +                              DefinedLocalImport, DefinedBitcode>
> +      Body;
> +
> +  SymbolBody *body() {
> +    return reinterpret_cast<SymbolBody *>(Body.buffer);
> +  }
> +  const SymbolBody *body() const { return const_cast<Symbol
> *>(this)->body(); }
> +};
> +
> +template <typename T, typename... ArgT>
> +void replaceBody(Symbol *S, ArgT &&... Arg) {
> +  static_assert(sizeof(T) <= sizeof(S->Body), "Body too small");
> +  static_assert(alignof(T) <= alignof(decltype(S->Body)),
> +                "Body not aligned enough");
> +  assert(static_cast<SymbolBody *>(static_cast<T *>(nullptr)) == nullptr
> &&
> +         "Not a SymbolBody");
> +  new (S->Body.buffer) T(std::forward<ArgT>(Arg)...);
> +}
> +
> +inline Symbol *SymbolBody::symbol() {
> +  assert(isExternal());
> +  return reinterpret_cast<Symbol *>(reinterpret_cast<char *>(this) -
> +                                    offsetof(Symbol, Body));
> +}
> +
>  std::string toString(SymbolBody &B);
>
>  } // namespace coff
>
> Modified: lld/trunk/COFF/Writer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Writer.cpp?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/COFF/Writer.cpp (original)
> +++ lld/trunk/COFF/Writer.cpp Fri Dec  9 15:55:24 2016
> @@ -388,7 +388,7 @@ void Writer::createMiscChunks() {
>      if (!File->SEHCompat)
>        return;
>      for (SymbolBody *B : File->SEHandlers)
> -      Handlers.insert(cast<Defined>(B->repl()));
> +      Handlers.insert(cast<Defined>(B));
>    }
>
>    SEHTable.reset(new SEHTableChunk(Handlers));
> @@ -428,7 +428,7 @@ void Writer::createImportTables() {
>        Sec->addChunk(C);
>    }
>    if (!DelayIdata.empty()) {
> -    Defined *Helper = cast<Defined>(Config->DelayLoadHelper->repl());
> +    Defined *Helper = cast<Defined>(Config->DelayLoadHelper);
>      DelayIdata.create(Helper);
>      OutputSection *Sec = createSection(".didat");
>      for (Chunk *C : DelayIdata.getChunks())
> @@ -471,6 +471,10 @@ size_t Writer::addEntryToStringTable(Str
>  }
>
>  Optional<coff_symbol16> Writer::createSymbol(Defined *Def) {
> +  // Relative symbols are unrepresentable in a COFF symbol table.
> +  if (isa<DefinedRelative>(Def))
> +    return None;
> +
>    if (auto *D = dyn_cast<DefinedRegular>(Def))
>      if (!D->getChunk()->isLive())
>        return None;
> @@ -497,7 +501,6 @@ Optional<coff_symbol16> Writer::createSy
>
>    switch (Def->kind()) {
>    case SymbolBody::DefinedAbsoluteKind:
> -  case SymbolBody::DefinedRelativeKind:
>      Sym.Value = Def->getRVA();
>      Sym.SectionNumber = IMAGE_SYM_ABSOLUTE;
>      break;
> @@ -530,16 +533,13 @@ void Writer::createSymbolAndStringTable(
>      Sec->setStringTableOff(addEntryToStringTable(Name));
>    }
>
> +  std::set<SymbolBody *> SeenSymbols;
>    for (lld::coff::ObjectFile *File : Symtab->ObjectFiles)
>      for (SymbolBody *B : File->getSymbols())
>        if (auto *D = dyn_cast<Defined>(B))
> -        if (Optional<coff_symbol16> Sym = createSymbol(D))
> -          OutputSymtab.push_back(*Sym);
> -
> -  for (ImportFile *File : Symtab->ImportFiles)
> -    for (SymbolBody *B : File->getSymbols())
> -      if (Optional<coff_symbol16> Sym = createSymbol(cast<Defined>(B)))
> -        OutputSymtab.push_back(*Sym);
> +        if (SeenSymbols.insert(D).second)
> +          if (Optional<coff_symbol16> Sym = createSymbol(D))
> +            OutputSymtab.push_back(*Sym);
>
>    OutputSection *LastSection = OutputSections.back();
>    // We position the symbol table to be adjacent to the end of the last
> section.
> @@ -630,7 +630,7 @@ template <typename PEHeaderTy> void Writ
>    PE->SizeOfImage = SizeOfImage;
>    PE->SizeOfHeaders = SizeOfHeaders;
>    if (!Config->NoEntry) {
> -    Defined *Entry = cast<Defined>(Config->Entry->repl());
> +    Defined *Entry = cast<Defined>(Config->Entry);
>      PE->AddressOfEntryPoint = Entry->getRVA();
>      // Pointer to thumb code must have the LSB set, so adjust it.
>      if (Config->Machine == ARMNT)
> @@ -685,7 +685,7 @@ template <typename PEHeaderTy> void Writ
>      Dir[BASE_RELOCATION_TABLE].Size = Sec->getVirtualSize();
>    }
>    if (Symbol *Sym = Symtab->findUnderscore("_tls_used")) {
> -    if (Defined *B = dyn_cast<Defined>(Sym->Body)) {
> +    if (Defined *B = dyn_cast<Defined>(Sym->body())) {
>        Dir[TLS_TABLE].RelativeVirtualAddress = B->getRVA();
>        Dir[TLS_TABLE].Size = Config->is64()
>                                  ? sizeof(object::coff_tls_directory64)
> @@ -697,7 +697,7 @@ template <typename PEHeaderTy> void Writ
>      Dir[DEBUG_DIRECTORY].Size = DebugDirectory->getSize();
>    }
>    if (Symbol *Sym = Symtab->findUnderscore("_load_config_used")) {
> -    if (auto *B = dyn_cast<DefinedRegular>(Sym->Body)) {
> +    if (auto *B = dyn_cast<DefinedRegular>(Sym->body())) {
>        SectionChunk *SC = B->getChunk();
>        assert(B->getRVA() >= SC->getRVA());
>        uint64_t OffsetInChunk = B->getRVA() - SC->getRVA();
> @@ -754,8 +754,10 @@ void Writer::openFile(StringRef Path) {
>  void Writer::fixSafeSEHSymbols() {
>    if (!SEHTable)
>      return;
> -  Config->SEHTable->setRVA(SEHTable->getRVA());
> -  Config->SEHCount->setVA(SEHTable->getSize() / 4);
> +  if (auto *T = dyn_cast<DefinedRelative>(Config->SEHTable->body()))
> +    T->setRVA(SEHTable->getRVA());
> +  if (auto *C = dyn_cast<DefinedAbsolute>(Config->SEHCount->body()))
> +    C->setVA(SEHTable->getSize() / 4);
>  }
>
>  // Handles /section options to allow users to overwrite
>
> Modified: lld/trunk/test/COFF/include2.test
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/include2.test?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/test/COFF/include2.test (original)
> +++ lld/trunk/test/COFF/include2.test Fri Dec  9 15:55:24 2016
> @@ -9,6 +9,6 @@
>
>  CHECK: include2.test.tmp1.obj
>  CHECK: include2.test.tmp2.lib
> -CHECK: include2.test.tmp3.lib
>  CHECK: include2.test.tmp2.lib(include2.test.tmp2.obj) for foo
> +CHECK: include2.test.tmp3.lib
>  CHECK: include2.test.tmp3.lib(include2.test.tmp3.obj) for bar
>
> Modified: lld/trunk/test/COFF/order.test
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/order.test?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/test/COFF/order.test (original)
> +++ lld/trunk/test/COFF/order.test Fri Dec  9 15:55:24 2016
> @@ -11,5 +11,5 @@
>  CHECK: order.test.tmp1.obj
>  CHECK: order.test.tmp3.obj
>  CHECK: order.test.tmp2.lib
> -CHECK: order.test.tmp3.lib
>  CHECK: order.test.tmp2.lib(order.test.tmp2.obj) for foo
> +CHECK: order.test.tmp3.lib
>
> Modified: lld/trunk/test/COFF/symtab.test
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/symtab.test?rev=289280&r1=289279&r2=289280&view=diff
>
> ==============================================================================
> --- lld/trunk/test/COFF/symtab.test (original)
> +++ lld/trunk/test/COFF/symtab.test Fri Dec  9 15:55:24 2016
> @@ -36,17 +36,17 @@
>  # CHECK-NEXT:     AuxSymbolCount: 0
>  # CHECK-NEXT:

-- 
Mike
Sent from phone
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