[LTO] Switch to the new resolution-based API.

[davide]

Summary

This should be all the logic. Before reviewing the style/code appeareance, I'd like to ensure that this is the right direction, thanks.

Left to be done:

• There are two tests failing, the one which include inline asm (currently investigating).
• The old LTO code wasn't removed yet. I found that it makes the patch less readable, and that can be removed separately.

[ruiu]

I want to see the old code being removed in this patch to see deltas.

[davide]

In D24492#540718, @ruiu wrote:

I want to see the old code being removed in this patch to see deltas.

Fair enough, I'll do that tomorrow.

[davide]

Back to more interesting business, the two asm inline tests that are failing are also failing with the gold plugin, so that might inidcate a bug in lib/LTO. Here's a synthetic testcase.

$ /usr/bin/ld.gold -shared -m elf_x86_64 -o /home/davide/work/llvm/build/test/tools/gold/X86/Output/module_asm.ll.tmp2 -plugin /home/davide/work/llvm/build/./lib/LLVMgold.so /home/davide/work/llvm/build/test/tools/gold/X86/Output/module_asm.ll.tmp.o
ld.gold: ../lib/Linker/IRMover.cpp:1240: llvm::Error (anonymous namespace)::IRLinker::run(): Assertion `!GV->isDeclaration()' failed.

; RUN: llvm-as %s -o %t.o
; RUN: %gold -shared -m elf_x86_64 -o %t2 -plugin %llvmshlibdir/LLVMgold.so %t.o

target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

module asm ".weak patatino"
module asm ".equ patatino, foo"

declare void @patatino()

define void @foo() {
  ret void
}

define void @_start() {
  call void @patatino()
  ret void
}

[davide]

I opened a report for the gold-plugin bug (https://llvm.org/bugs/show_bug.cgi?id=30363). I'll take a closer look tomorrow.

[ruiu]

Davide,

Sure. Go ahead with your patch first.

[davide]

Removed dead code as per Rui's request.
Also, for whoever cares, here's the output of diffstat:

33 files changed, 209 insertions(+), 432 deletions(-)

[ruiu]

This patch contains complex code with almost no comment. Please explain in the code about what you are doing.

ELF/SymbolTable.cpp

116–120 ↗

(On Diff #71405)

Why don't you keep the old interface and replace only the content of LTO.cpp? I think that was a good separation.

[pcc]

ELF/SymbolTable.cpp

213 ↗

(On Diff #71405)

You should replace all uses of IRObjectFile elsewhere with lto::InputFile. Then you won't need to create a new InputFile here, you can just reuse the one in the BitcodeFile.

225 ↗

(On Diff #71405)

You shouldn't need to do this, see r281437.

234 ↗

(On Diff #71405)

This isn't right, this should test whether the SymbolBody is a DefinedBitcode and is defined by this BitcodeFile.

252 ↗

(On Diff #71405)

There's no need to save objects to files, you can just use raw_string_ostream and operate on the object file directly in memory.

[davide]

Addressed comments. I'm working to remove the call to getComdatSymbolTable(). Other than that it should be ready for another look.

[• rafael]

lld/ELF/InputFiles.cpp

627–628

You can use GlobalValue::VisibilityTypes to make the argument type clear.

640–645

static

642

You don't need the llvm:: prefixes.
Do you really want a StringSaver by value?

653

Simplify to just

uint8_t Type = ObjSym.isTLS() ? STT_TLS : STT_NOTYPE;

654

Simplify to

uint8_t Visibility = mapVisibility(ObjSym.getVisibility());

659

You have lost HasUnnamedAddr. Where do you compensate for that?

[davide]

Rafael's comments.

lld/ELF/InputFiles.cpp

659

I think it's not needed anymore becuase lib/LTO will compute it based on GlobalResolution.
I'm garbage collecting it for now.

[ruiu]

lld/ELF/Error.h

36

You are not using Msg.

lld/ELF/LTO.cpp

144

Filenames is not a large vector, so please use std::string for simplicity.

149–150

I'd make getOutputFilename a pure function that returns std::string so that we can do

Filenames[Task] = getOutputFilename(Filename, MaxTasks > 1 ? Task : -1);

[davide]

Rui's comments.

[pcc]

lld/ELF/LTO.cpp

144

Once you make the change below, Filenames will be unused and you can remove it.

154

This could be if (!Buff[I].empty()), then you can make this a for-range loop.

[pcc]

lld/ELF/LTO.cpp

146

Rename to AddStream.

[• rafael]

lld/ELF/InputFiles.cpp

672

You don't need the llvm prefix.

lld/ELF/LTO.cpp

67

Just inline the variable into the single use.

85–88

You don't need the ()

118

Add a comment on why you need the undefined check.

[ruiu]

lld/ELF/Error.h

38

Do you need c_str()?

[pcc]

lld/ELF/LTO.cpp

78

You could just assign without the if statement here and below.

[davide]

lld/ELF/LTO.cpp

154

hmm, I still need I to be passed to saveBuffer, no? Do you want me to use a separate variable incremented at each iteration?

[pcc]

lld/ELF/LTO.cpp

154

No, sorry, what you have is fine.

155

I would remove this comment as it doesn't help readers understand the code.

[davide]

Rebased on top of

commit de07c6a10ee2cbf5877e74fdbbe1d8d3f1d343a4
Author: Etienne Bergeron <[e-mail]>
Date:   Wed Sep 28 18:04:07 2016 +0000

+ removed comment as suggested by Peter.

[ruiu]

lld/ELF/InputFiles.cpp

648–650

Remove ().

lld/ELF/LTO.cpp

85–89

Remove llvm::.

I don't think your code is prepared to see LtoObj being null. Maybe you want to return a new instance regardless of HasError value?

101–103

Why do you want to return here immediately if there was an error before this function?

[davide]

lld/ELF/LTO.cpp

101–103

Ooops, fixed, thanks.

[ruiu]

lld/ELF/LTO.cpp

113

auto -> BasicSymbolRef &

132–133

Stray }?

154

if (Buff[I].empty())
  continue;

[davide]

lld/ELF/LTO.cpp

107–133

hmm, no, just clang-formatted incorrectly. Weird as I have a pre-hook for that that didn't kick in.

[ruiu]

lld/ELF/LTO.cpp

107–133

It seems that it is still formatted weirdly.

[davide]

run clang-format manually and it seems fine on my side.

[pcc]

LGTM with nit. Thanks for working on this!

lld/ELF/InputFiles.cpp

641

Unused argument

[ruiu]

LGTM

lld/ELF/Error.h

 //===- Error.h --------------------------------------------------*- C++ -*-===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLD_ELF_ERROR_H
 #define LLD_ELF_ERROR_H
 
 #include "lld/Core/LLVM.h"
 
+#include "llvm/Support/Error.h"
+
 namespace lld {
 namespace elf {
 
 extern bool HasError;
 extern llvm::raw_ostream *ErrorOS;
 
 void log(const Twine &Msg);
 void warning(const Twine &Msg);
 
 void error(const Twine &Msg);
 void error(std::error_code EC, const Twine &Prefix);
 
 template <typename T> void error(const ErrorOr<T> &V, const Twine &Prefix) {
   error(V.getError(), Prefix);
 }
 
 LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &Msg);
 LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &Msg, const Twine &Prefix);
 
+inline void check(Error E) {
+  handleAllErrors(std::move(E), [&](llvm::ErrorInfoBase &EIB) {
+    error(EIB.message());
+    return Error::success();
+  });
+}
+
 template <class T> T check(ErrorOr<T> E) {
   if (auto EC = E.getError())
     fatal(EC.message());
   return std::move(*E);
 }
 
 template <class T> T check(Expected<T> E) {
   if (!E)

lld/ELF/InputFiles.h

 #include "llvm/IR/Comdat.h"
 #include "llvm/Object/Archive.h"
 #include "llvm/Object/ELF.h"
 #include "llvm/Object/IRObjectFile.h"
 #include "llvm/Support/StringSaver.h"
 
 #include <map>
 
+namespace llvm {
+namespace lto {
+class InputFile;
+}
+}
+
 namespace lld {
 namespace elf {
 
 using llvm::object::Archive;
 
 class InputFile;
 class Lazy;
 class SymbolBody;

 
 class BitcodeFile : public InputFile {
 public:
   explicit BitcodeFile(MemoryBufferRef M);
   static bool classof(const InputFile *F) { return F->kind() == BitcodeKind; }
   template <class ELFT>
   void parse(llvm::DenseSet<StringRef> &ComdatGroups);
   ArrayRef<Symbol *> getSymbols() { return Symbols; }
-  static bool shouldSkip(uint32_t Flags);
-  std::unique_ptr<llvm::object::IRObjectFile> Obj;
+  std::unique_ptr<llvm::lto::InputFile> Obj;
 
 private:
   std::vector<Symbol *> Symbols;
   llvm::BumpPtrAllocator Alloc;
   llvm::StringSaver Saver{Alloc};
-  template <class ELFT>
-  Symbol *createSymbol(const llvm::DenseSet<const llvm::Comdat *> &KeptComdats,
-                       const llvm::object::IRObjectFile &Obj,
-                       const llvm::object::BasicSymbolRef &Sym);
 };
 
 // .so file.
 template <class ELFT> class SharedFile : public ELFFileBase<ELFT> {
   typedef ELFFileBase<ELFT> Base;
   typedef typename ELFT::Shdr Elf_Shdr;
   typedef typename ELFT::Sym Elf_Sym;
   typedef typename ELFT::Word Elf_Word;

lld/ELF/InputFiles.cpp

 //===- InputFiles.cpp -----------------------------------------------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "InputFiles.h"
 #include "Driver.h"
+#include "ELFCreator.h"
 #include "Error.h"
 #include "InputSection.h"
 #include "LinkerScript.h"
-#include "ELFCreator.h"
 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm/CodeGen/Analysis.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
+#include "llvm/LTO/LTO.h"
 #include "llvm/MC/StringTableBuilder.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::object;
 using namespace llvm::sys::fs;
SymbolBody *elf::ObjectFile<ELFT>::createSymbolBody(const Elf_Sym *Sym) {
   }
 
   StringRef Name = check(Sym->getName(this->StringTable));
 
   switch (Sym->st_shndx) {
   case SHN_UNDEF:
     return elf::Symtab<ELFT>::X
         ->addUndefined(Name, Binding, Sym->st_other, Sym->getType(),
-                       /*CanOmitFromDynSym*/ false, /*HasUnnamedAddr*/ false,
-                       this)
+                       /*CanOmitFromDynSym*/ false, this)
         ->body();
   case SHN_COMMON:
     return elf::Symtab<ELFT>::X
         ->addCommon(Name, Sym->st_size, Sym->st_value, Binding, Sym->st_other,
-                    Sym->getType(), /*HasUnnamedAddr*/ false, this)
+                    Sym->getType(), this)
         ->body();
   }
 
   switch (Binding) {
   default:
     fatal(getFilename(this) + ": unexpected binding: " + Twine(Binding));
   case STB_GLOBAL:
   case STB_WEAK:
   case STB_GNU_UNIQUE:
     if (Sec == &InputSection<ELFT>::Discarded)
       return elf::Symtab<ELFT>::X
           ->addUndefined(Name, Binding, Sym->st_other, Sym->getType(),
-                         /*CanOmitFromDynSym*/ false,
-                         /*HasUnnamedAddr*/ false, this)
+                         /*CanOmitFromDynSym*/ false, this)
           ->body();
     return elf::Symtab<ELFT>::X->addRegular(Name, *Sym, Sec)->body();
   }
 }
 
 template <class ELFT> void ArchiveFile::parse() {
   File = check(Archive::create(MB), "failed to parse archive");
 
static uint8_t getBitcodeMachineKind(MemoryBufferRef MB) {
   }
 }
 
 BitcodeFile::BitcodeFile(MemoryBufferRef MB) : InputFile(BitcodeKind, MB) {
   EKind = getBitcodeELFKind(MB);
   EMachine = getBitcodeMachineKind(MB);
 }
 
-static uint8_t getGvVisibility(const GlobalValue *GV) {
-  switch (GV->getVisibility()) {
+static uint8_t mapVisibility(GlobalValue::VisibilityTypes GvVisibility) {
+  switch (GvVisibility) {
   case GlobalValue::DefaultVisibility:
     return STV_DEFAULT;
   case GlobalValue::HiddenVisibility:
     return STV_HIDDEN;
   case GlobalValue::ProtectedVisibility:
     return STV_PROTECTED;
   }
   llvm_unreachable("unknown visibility");
 }
 
 template <class ELFT>
-Symbol *BitcodeFile::createSymbol(const DenseSet<const Comdat *> &KeptComdats,
-                                  const IRObjectFile &Obj,
-                                  const BasicSymbolRef &Sym) {
-  const GlobalValue *GV = Obj.getSymbolGV(Sym.getRawDataRefImpl());
-
-  SmallString<64> Name;
-  raw_svector_ostream OS(Name);
-  Sym.printName(OS);
-  StringRef NameRef = Saver.save(StringRef(Name));
-
-  uint32_t Flags = Sym.getFlags();
+static Symbol *createBitcodeSymbol(const DenseSet<const Comdat *> &KeptComdats,
+                                   const lto::InputFile &Obj,
+                                   const lto::InputFile::Symbol &ObjSym,
+                                   llvm::StringSaver &Saver, BitcodeFile *F) {
+  StringRef NameRef = Saver.save(ObjSym.getName());
+  uint32_t Flags = ObjSym.getFlags();
   uint32_t Binding = (Flags & BasicSymbolRef::SF_Weak) ? STB_WEAK : STB_GLOBAL;
 
-  uint8_t Type = STT_NOTYPE;
-  uint8_t Visibility;
-  bool CanOmitFromDynSym = false;
-  bool HasUnnamedAddr = false;
-
-  // FIXME: Expose a thread-local flag for module asm symbols.
-  if (GV) {
-    if (GV->isThreadLocal())
-      Type = STT_TLS;
-    CanOmitFromDynSym = canBeOmittedFromSymbolTable(GV);
-    Visibility = getGvVisibility(GV);
-    HasUnnamedAddr =
-        GV->getUnnamedAddr() == llvm::GlobalValue::UnnamedAddr::Global;
-  } else {
-    // FIXME: Set SF_Hidden flag correctly for module asm symbols, and expose
-    // protected visibility.
-    Visibility = STV_DEFAULT;
-  }
+  uint8_t Type = (ObjSym.isTLS()) ? STT_TLS : STT_NOTYPE;
+  uint8_t Visibility = mapVisibility(ObjSym.getVisibility());
+  bool CanOmitFromDynSym = ObjSym.canBeOmittedFromSymbolTable();
 
-  if (GV)
-    if (const Comdat *C = GV->getComdat())
-      if (!KeptComdats.count(C))
-        return Symtab<ELFT>::X->addUndefined(NameRef, Binding, Visibility, Type,
-                                             CanOmitFromDynSym, HasUnnamedAddr,
-                                             this);
+  if (const Comdat *C = check(ObjSym.getComdat()))
+                                           CanOmitFromDynSym, F);
 
-  const Module &M = Obj.getModule();
   if (Flags & BasicSymbolRef::SF_Undefined)
     return Symtab<ELFT>::X->addUndefined(NameRef, Binding, Visibility, Type,
-                                         CanOmitFromDynSym, HasUnnamedAddr,
-                                         this);
-  if (Flags & BasicSymbolRef::SF_Common) {
-    // FIXME: Set SF_Common flag correctly for module asm symbols, and expose
-    // size and alignment.
-    assert(GV);
-    const DataLayout &DL = M.getDataLayout();
-    uint64_t Size = DL.getTypeAllocSize(GV->getValueType());
-    return Symtab<ELFT>::X->addCommon(NameRef, Size, GV->getAlignment(),
-                                      Binding, Visibility, STT_OBJECT,
-                                      HasUnnamedAddr, this);
-  }
-  return Symtab<ELFT>::X->addBitcode(NameRef, Binding, Visibility, Type,
-                                     CanOmitFromDynSym, HasUnnamedAddr, this);
-}
+                                         CanOmitFromDynSym, F);
+
+  if (Flags & BasicSymbolRef::SF_Common)
+    return Symtab<ELFT>::X->addCommon(NameRef, ObjSym.getCommonSize(),
+                                      ObjSym.getCommonAlignment(), Binding,
+                                      Visibility, STT_OBJECT, F);
 
-bool BitcodeFile::shouldSkip(uint32_t Flags) {
-  return !(Flags & BasicSymbolRef::SF_Global) ||
-         (Flags & BasicSymbolRef::SF_FormatSpecific);
+  return Symtab<ELFT>::X->addBitcode(NameRef, Binding, Visibility, Type,
+                                     CanOmitFromDynSym, F);
 }
 
 template <class ELFT>
 void BitcodeFile::parse(DenseSet<StringRef> &ComdatGroups) {
-  Obj = check(IRObjectFile::create(MB, Driver->Context));
-  const Module &M = Obj->getModule();
-
+  Obj = check(lto::InputFile::create(MB));
   DenseSet<const Comdat *> KeptComdats;
-  for (const auto &P : M.getComdatSymbolTable()) {
+  for (const auto &P : Obj->getComdatSymbolTable()) {
     StringRef N = Saver.save(P.first());
     if (ComdatGroups.insert(N).second)
       KeptComdats.insert(&P.second);
   }
 
-  for (const BasicSymbolRef &Sym : Obj->symbols())
-    if (!shouldSkip(Sym.getFlags()))
-      Symbols.push_back(createSymbol<ELFT>(KeptComdats, *Obj, Sym));
+  for (auto &ObjSym : Obj->symbols())
+    Symbols.push_back(
+        createBitcodeSymbol<ELFT>(KeptComdats, *Obj, ObjSym, Saver, this));
 }
 
 template <template <class> class T>
 static InputFile *createELFFile(MemoryBufferRef MB) {
   unsigned char Size;
   unsigned char Endian;
   std::tie(Size, Endian) = getElfArchType(MB.getBuffer());
   if (Endian != ELFDATA2LSB && Endian != ELFDATA2MSB)
for (const Elf_Sym &Sym : Syms.slice(FirstNonLocal))
       if (Sym.st_shndx != SHN_UNDEF)
         V.push_back(check(Sym.getName(StringTable)));
     return V;
   }
   return {};
 }
 
 std::vector<StringRef> LazyObjectFile::getBitcodeSymbols() {
-  LLVMContext Context;
-  std::unique_ptr<IRObjectFile> Obj =
-      check(IRObjectFile::create(this->MB, Context));
   std::vector<StringRef> V;
-  for (const BasicSymbolRef &Sym : Obj->symbols()) {
-    uint32_t Flags = Sym.getFlags();
-    if (BitcodeFile::shouldSkip(Flags))
-      continue;
-    if (Flags & BasicSymbolRef::SF_Undefined)
+  std::unique_ptr<lto::InputFile> Obj = check(lto::InputFile::create(this->MB));
+  for (auto &ObjSym : Obj->symbols()) {
+    if (ObjSym.getFlags() & BasicSymbolRef::SF_Undefined)
       continue;
-    SmallString<64> Name;
-    raw_svector_ostream OS(Name);
-    Sym.printName(OS);
-    V.push_back(Saver.save(StringRef(Name)));
+    V.push_back(Saver.save(ObjSym.getName()));
   }
   return V;
 }
 
 // Returns a vector of globally-visible defined symbol names.
 std::vector<StringRef> LazyObjectFile::getSymbols() {
   if (isBitcode(this->MB))
     return getBitcodeSymbols();

lld/ELF/LTO.h

 #define LLD_ELF_LTO_H
 
 #include "lld/Core/LLVM.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Linker/IRMover.h"
 
+namespace llvm {
+namespace lto {
+class LTO;
+}
+}
+
 namespace lld {
 namespace elf {
 
 class BitcodeFile;
 class InputFile;
 
 class BitcodeCompiler {
 public:
   BitcodeCompiler();
+  ~BitcodeCompiler();
   void add(BitcodeFile &F);
   std::vector<InputFile *> compile();
 
-private:
-  std::vector<InputFile *> runSplitCodegen(
-      const std::function<std::unique_ptr<llvm::TargetMachine>()> &TMFactory);
+  std::unique_ptr<llvm::lto::LTO> LtoObj;
 
-  std::unique_ptr<llvm::Module> Combined;
-  std::vector<SmallString<0>> OwningData;
-  llvm::StringSet<> InternalizedSyms;
-  llvm::StringSet<> AsmUndefinedRefs;
+private:
+  std::vector<SmallString<0>> Buff;
 };
 }
 }
 
 #endif

lld/ELF/LTO.cpp

 #include "llvm/Analysis/CGSCCPassManager.h"
 #include "llvm/Analysis/LoopPassManager.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm/CodeGen/CommandFlags.h"
 #include "llvm/CodeGen/ParallelCG.h"
 #include "llvm/IR/AutoUpgrade.h"
+#include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/Verifier.h"
+#include "llvm/LTO/LTO.h"
 #include "llvm/LTO/legacy/UpdateCompilerUsed.h"
 #include "llvm/Linker/IRMover.h"
 #include "llvm/Passes/PassBuilder.h"
 #include "llvm/Support/StringSaver.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/IPO/PassManagerBuilder.h"

 static void saveBuffer(StringRef Buffer, const Twine &Path) {
   std::error_code EC;
   raw_fd_ostream OS(Path.str(), EC, sys::fs::OpenFlags::F_None);
   if (EC)
     error(EC, "cannot create " + Path);
   OS << Buffer;
 }
 
-// This is for use when debugging LTO.
-static void saveBCFile(Module &M, const Twine &Path) {
-  std::error_code EC;
-  raw_fd_ostream OS(Path.str(), EC, sys::fs::OpenFlags::F_None);
-  if (EC)
-    error(EC, "cannot create " + Path);
-  WriteBitcodeToFile(&M, OS, /* ShouldPreserveUseListOrder */ true);
+static void diagnosticHandler(const DiagnosticInfo &DI) {
+  SmallString<128> ErrStorage;
+  raw_svector_ostream OS(ErrStorage);
+  DiagnosticPrinterRawOStream DP(OS);
+  DI.print(DP);
+  warning(ErrStorage);
 }
 
-static void runNewCustomLtoPasses(Module &M, TargetMachine &TM) {
-  PassBuilder PB(&TM);
-
-  AAManager AA;
+static std::unique_ptr<lto::LTO> createLTO() {
+  lto::Config Conf;
+  lto::ThinBackend Backend;
 
-  // Parse a custom AA pipeline if asked to.
-  if (!PB.parseAAPipeline(AA, Config->LtoAAPipeline)) {
-    error("unable to parse AA pipeline description: " + Config->LtoAAPipeline);
-    return;
-  }
-
-  LoopAnalysisManager LAM;
-  FunctionAnalysisManager FAM;
-  CGSCCAnalysisManager CGAM;
-  ModuleAnalysisManager MAM;
-
-  // Register the AA manager first so that our version is the one used.
-  FAM.registerPass([&] { return std::move(AA); });
-
-  // Register all the basic analyses with the managers.
-  PB.registerModuleAnalyses(MAM);
-  PB.registerCGSCCAnalyses(CGAM);
-  PB.registerFunctionAnalyses(FAM);
-  PB.registerLoopAnalyses(LAM);
-  PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
-
-  ModulePassManager MPM;
-  if (!Config->DisableVerify)
-    MPM.addPass(VerifierPass());
-
-  // Now, add all the passes we've been requested to.
-  if (!PB.parsePassPipeline(MPM, Config->LtoNewPmPasses)) {
-    error("unable to parse pass pipeline description: " +
-          Config->LtoNewPmPasses);
-    return;
-  }
-
-  if (!Config->DisableVerify)
-    MPM.addPass(VerifierPass());
-  MPM.run(M, MAM);
-}
-
-static void runOldLtoPasses(Module &M, TargetMachine &TM) {
-  // Note that the gold plugin has a similar piece of code, so
-  // it is probably better to move this code to a common place.
-  legacy::PassManager LtoPasses;
-  LtoPasses.add(createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis()));
-  PassManagerBuilder PMB;
-  PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM.getTargetTriple()));
-  PMB.Inliner = createFunctionInliningPass();
-  PMB.VerifyInput = PMB.VerifyOutput = !Config->DisableVerify;
-  PMB.LoopVectorize = true;
-  PMB.SLPVectorize = true;
-  PMB.OptLevel = Config->LtoO;
-  PMB.populateLTOPassManager(LtoPasses);
-  LtoPasses.run(M);
-}
+  // LLD supports the new relocations.
+  Conf.Options = InitTargetOptionsFromCodeGenFlags();
+  Conf.Options.RelaxELFRelocations = true;
 
-static void runLTOPasses(Module &M, TargetMachine &TM) {
-  if (!Config->LtoNewPmPasses.empty()) {
-    // The user explicitly asked for a set of passes to be run.
-    // This needs the new PM to work as there's no clean way to
-    // pass a set of passes to run in the legacy PM.
-    runNewCustomLtoPasses(M, TM);
-    if (HasError)
-      return;
-  } else {
-    // Run the 'default' set of LTO passes. This code still uses
-    // the legacy PM as the new one is not the default.
-    runOldLtoPasses(M, TM);
-  }
+  Conf.RelocModel = Config->Pic ? Reloc::PIC_ : Reloc::Static;
+  Conf.DisableVerify = Config->DisableVerify;
+  Conf.DiagHandler = diagnosticHandler;
+  Conf.OptLevel = Config->LtoO;
+
+  // Set up a custom pipeline if we've been asked to.
+  Conf.OptPipeline = Config->LtoNewPmPasses;
+  Conf.AAPipeline = Config->LtoAAPipeline;
 
   if (Config->SaveTemps)
-    saveBCFile(M, Config->OutputFile + ".lto.opt.bc");
-}
+    check(Conf.addSaveTemps(std::string(Config->OutputFile) + ".",
+                            /*UseInputModulePath*/ true));
 
-static bool shouldInternalize(const SmallPtrSet<GlobalValue *, 8> &Used,
-                              Symbol *S, GlobalValue *GV) {
-  if (S->IsUsedInRegularObj || Used.count(GV))
-    return false;
-  return !S->includeInDynsym();
+  return HasError
+             ? nullptr
+             : llvm::make_unique<lto::LTO>(std::move(Conf), Backend,
+                                           Config->LtoJobs);
 }
 
-BitcodeCompiler::BitcodeCompiler()
-    : Combined(new Module("ld-temp.o", Driver->Context)) {}
+BitcodeCompiler::BitcodeCompiler() : LtoObj(createLTO()) {}
+
+BitcodeCompiler::~BitcodeCompiler() {}
 
 static void undefine(Symbol *S) {
   replaceBody<Undefined>(S, S->body()->getName(), STV_DEFAULT, S->body()->Type,
                          nullptr);
 }
 
-static void handleUndefinedAsmRefs(const BasicSymbolRef &Sym, GlobalValue *GV,
-                                   StringSet<> &AsmUndefinedRefs) {
-  // GV associated => not an assembly symbol, bail out.
-  if (GV)
-    return;
-
-  // This is an undefined reference to a symbol in asm. We put that in
-  // compiler.used, so that we can preserve it from being dropped from
-  // the output, without necessarily preventing its internalization.
-  SmallString<64> Name;
-  raw_svector_ostream OS(Name);
-  Sym.printName(OS);
-  AsmUndefinedRefs.insert(Name.str());
-}
-
 void BitcodeCompiler::add(BitcodeFile &F) {
-  std::unique_ptr<IRObjectFile> Obj = std::move(F.Obj);
-  std::vector<GlobalValue *> Keep;
-  unsigned BodyIndex = 0;
-  ArrayRef<Symbol *> Syms = F.getSymbols();
+  if (HasError)
+    return;
 
-  Module &M = Obj->getModule();
-  if (M.getDataLayoutStr().empty())
+  lto::InputFile &Obj = *F.Obj;
+  if (Obj.getDataLayoutStr().empty())
     fatal("invalid bitcode file: " + F.getName() + " has no datalayout");
 
-  // Discard non-compatible debug infos if necessary.
-  M.materializeMetadata();
-  UpgradeDebugInfo(M);
-
-  // If a symbol appears in @llvm.used, the linker is required
-  // to treat the symbol as there is a reference to the symbol
-  // that it cannot see. Therefore, we can't internalize.
-  SmallPtrSet<GlobalValue *, 8> Used;
-  collectUsedGlobalVariables(M, Used, /* CompilerUsed */ false);
-
-  for (const BasicSymbolRef &Sym : Obj->symbols()) {
-    uint32_t Flags = Sym.getFlags();
-    GlobalValue *GV = Obj->getSymbolGV(Sym.getRawDataRefImpl());
-    if (GV && GV->hasAppendingLinkage())
-      Keep.push_back(GV);
-    if (BitcodeFile::shouldSkip(Flags))
-      continue;
-    Symbol *S = Syms[BodyIndex++];
-    if (GV)
-      GV->setUnnamedAddr(S->HasUnnamedAddr ? GlobalValue::UnnamedAddr::Global
-                                           : GlobalValue::UnnamedAddr::None);
-    if (Flags & BasicSymbolRef::SF_Undefined) {
-      handleUndefinedAsmRefs(Sym, GV, AsmUndefinedRefs);
-      continue;
+  unsigned SymNum = 0;
+  std::vector<Symbol *> Syms = F.getSymbols();
+  std::vector<lto::SymbolResolution> Resols(Syms.size());
+
+  // Provide a resolution to the LTO API for each symbol.
+  for (auto &ObjSym : Obj.symbols()) {
+    Symbol *Sym = Syms[SymNum];
+    lto::SymbolResolution &R = Resols[SymNum];
+    ++SymNum;
+    SymbolBody *B = Sym->body();
+
+    // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile
+    // reports two symbols for module ASM defined. Without this check, lld
+    // flags an undefined in IR with a definition in ASM as prevailing.
+    // Once IRObjectFile is fixed to report only one symbol this hack can
+    // be removed.
+    R.Prevailing =
+        !(ObjSym.getFlags() & object::BasicSymbolRef::SF_Undefined) &&
+        B->File == &F;
+
+    R.VisibleToRegularObj =
+        Sym->IsUsedInRegularObj || (R.Prevailing && Sym->includeInDynsym());
+    if (R.Prevailing)
+      undefine(Sym);
     }
-    SymbolBody *B = S->body();
-    if (B->File != &F)
-      continue;
-
-    // We collect the set of symbols we want to internalize here
-    // and change the linkage after the IRMover executed, i.e. after
-    // we imported the symbols and satisfied undefined references
-    // to it. We can't just change linkage here because otherwise
-    // the IRMover will just rename the symbol.
-    if (GV && shouldInternalize(Used, S, GV))
-      InternalizedSyms.insert(GV->getName());
-
-    // At this point we know that either the combined LTO object will provide a
-    // definition of a symbol, or we will internalize it. In either case, we
-    // need to undefine the symbol. In the former case, the real definition
-    // needs to be able to replace the original definition without conflicting.
-    // In the latter case, we need to allow the combined LTO object to provide a
-    // definition with the same name, for example when doing parallel codegen.
-    if (auto *C = dyn_cast<DefinedCommon>(B)) {
-      if (auto *GO = dyn_cast<GlobalObject>(GV))
-        GO->setAlignment(C->Alignment);
-    } else {
-      undefine(S);
-    }
-
-    if (!GV)
-      // Module asm symbol.
-      continue;
-
-    switch (GV->getLinkage()) {
-    default:
-      break;
-    case GlobalValue::LinkOnceAnyLinkage:
-      GV->setLinkage(GlobalValue::WeakAnyLinkage);
-      break;
-    case GlobalValue::LinkOnceODRLinkage:
-      GV->setLinkage(GlobalValue::WeakODRLinkage);
-      break;
-    }
-
-    Keep.push_back(GV);
-  }
-
-  IRMover Mover(*Combined);
-  if (Error E = Mover.move(Obj->takeModule(), Keep,
-                           [](GlobalValue &, IRMover::ValueAdder) {})) {
-    handleAllErrors(std::move(E), [&](const ErrorInfoBase &EIB) {
-      fatal("failed to link module " + F.getName() + ": " + EIB.message());
-    });
-  }
-}
-
-static void internalize(GlobalValue &GV) {
-  assert(!GV.hasLocalLinkage() &&
-         "Trying to internalize a symbol with local linkage!");
-  GV.setLinkage(GlobalValue::InternalLinkage);
-}
-
-std::vector<InputFile *> BitcodeCompiler::runSplitCodegen(
-    const std::function<std::unique_ptr<TargetMachine>()> &TMFactory) {
-  unsigned NumThreads = Config->LtoJobs;
-  OwningData.resize(NumThreads);
-
-  std::list<raw_svector_ostream> OSs;
-  std::vector<raw_pwrite_stream *> OSPtrs;
-  for (SmallString<0> &Obj : OwningData) {
-    OSs.emplace_back(Obj);
-    OSPtrs.push_back(&OSs.back());
-  }
-
-  splitCodeGen(std::move(Combined), OSPtrs, {}, TMFactory);
-
-  std::vector<InputFile *> ObjFiles;
-  for (SmallString<0> &Obj : OwningData)
-    ObjFiles.push_back(createObjectFile(
-        MemoryBufferRef(Obj, "LLD-INTERNAL-combined-lto-object")));
-
-  // If -save-temps is given, we need to save temporary objects to files.
-  // This is for debugging.
-  if (Config->SaveTemps) {
-    if (NumThreads == 1) {
-      saveBuffer(OwningData[0], Config->OutputFile + ".lto.o");
-    } else {
-      for (unsigned I = 0; I < NumThreads; ++I)
-        saveBuffer(OwningData[I], Config->OutputFile + Twine(I) + ".lto.o");
-    }
-  }
-
-  return ObjFiles;
+    check(LtoObj->add(std::move(F.Obj), Resols));
 }
 
 // Merge all the bitcode files we have seen, codegen the result
-// and return the resulting ObjectFile.
+// and return the resulting ObjectFile(s).
 std::vector<InputFile *> BitcodeCompiler::compile() {
-  for (const auto &Name : InternalizedSyms) {
-    GlobalValue *GV = Combined->getNamedValue(Name.first());
-    assert(GV);
-    internalize(*GV);
-  }
-
-  std::string TheTriple = Combined->getTargetTriple();
-  std::string Msg;
-  const Target *T = TargetRegistry::lookupTarget(TheTriple, Msg);
-  if (!T)
-    fatal("target not found: " + Msg);
-
-  // LLD supports the new relocations.
-  TargetOptions Options = InitTargetOptionsFromCodeGenFlags();
-  Options.RelaxELFRelocations = true;
-
-  auto CreateTargetMachine = [&]() {
-    return std::unique_ptr<TargetMachine>(T->createTargetMachine(
-        TheTriple, "", "", Options, Config->Pic ? Reloc::PIC_ : Reloc::Static));
+  std::vector<InputFile *> Ret;
+  unsigned MaxTasks = LtoObj->getMaxTasks();
+  Buff.resize(MaxTasks);
+
+  auto AddStream =
+      [&](size_t Task) -> std::unique_ptr<lto::NativeObjectStream> {
+    return llvm::make_unique<lto::NativeObjectStream>(
+        llvm::make_unique<llvm::raw_svector_ostream>(Buff[Task]));
   };
 
-  std::unique_ptr<TargetMachine> TM = CreateTargetMachine();
-
-  // Update llvm.compiler.used so that optimizations won't strip
-  // off AsmUndefinedReferences.
-  updateCompilerUsed(*Combined, *TM, AsmUndefinedRefs);
-
-  if (Config->SaveTemps)
-    saveBCFile(*Combined, Config->OutputFile + ".lto.bc");
-
-  runLTOPasses(*Combined, *TM);
+  check(LtoObj->run(AddStream));
   if (HasError)
-    return {};
+    return Ret;
 
-  return runSplitCodegen(CreateTargetMachine);
+  for (unsigned I = 0; I != MaxTasks; ++I) {
+    if (!Buff[I].empty()) {
+      // Do we want to move this to the LTO API?
+      if (Config->SaveTemps) {
+        if (MaxTasks == 1)
+          saveBuffer(Buff[I], Config->OutputFile + ".lto.o");
+        else
+          saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.o");
+      }
+      MemoryBufferRef CompiledObjRef(Buff[I], "lto.tmp");
+      InputFile *Obj = createObjectFile(CompiledObjRef);
+      Ret.push_back(Obj);
+    }
+  }
+  return Ret;
 }

lld/ELF/SymbolTable.h

public:
 
   DefinedRegular<ELFT> *addAbsolute(StringRef Name,
                                     uint8_t Visibility = llvm::ELF::STV_HIDDEN);
   DefinedRegular<ELFT> *addIgnored(StringRef Name,
                                    uint8_t Visibility = llvm::ELF::STV_HIDDEN);
 
   Symbol *addUndefined(StringRef Name);
   Symbol *addUndefined(StringRef Name, uint8_t Binding, uint8_t StOther,
-                       uint8_t Type, bool CanOmitFromDynSym,
-                       bool HasUnnamedAddr, InputFile *File);
+                       uint8_t Type, bool CanOmitFromDynSym, InputFile *File);
 
   Symbol *addRegular(StringRef Name, const Elf_Sym &Sym,
                      InputSectionBase<ELFT> *Section);
   Symbol *addRegular(StringRef Name, uint8_t Binding, uint8_t StOther);
   Symbol *addSynthetic(StringRef N, OutputSectionBase<ELFT> *Section,
                        uintX_t Value, uint8_t StOther);
   void addShared(SharedFile<ELFT> *F, StringRef Name, const Elf_Sym &Sym,
                  const typename ELFT::Verdef *Verdef);
 
   void addLazyArchive(ArchiveFile *F, const llvm::object::Archive::Symbol S);
   void addLazyObject(StringRef Name, LazyObjectFile &Obj);
   Symbol *addBitcode(StringRef Name, uint8_t Binding, uint8_t StOther,
-                     uint8_t Type, bool CanOmitFromDynSym, bool HasUnnamedAddr,
-                     BitcodeFile *File);
+                     uint8_t Type, bool CanOmitFromDynSym, BitcodeFile *File);
 
   Symbol *addCommon(StringRef N, uint64_t Size, uint64_t Alignment,
                     uint8_t Binding, uint8_t StOther, uint8_t Type,
-                    bool HasUnnamedAddr, InputFile *File);
+                    InputFile *File);
 
   void scanUndefinedFlags();
   void scanShlibUndefined();
   void scanDynamicList();
   void scanVersionScript();
 
   SymbolBody *find(StringRef Name);
 
   void trace(StringRef Name);
   void wrap(StringRef Name);
 
 private:
   std::vector<SymbolBody *> findAll(const llvm::Regex &Re);
   std::pair<Symbol *, bool> insert(StringRef &Name);
   std::pair<Symbol *, bool> insert(StringRef &Name, uint8_t Type,
                                    uint8_t Visibility, bool CanOmitFromDynSym,
-                                   bool HasUnnamedAddr, InputFile *File);
+                                   InputFile *File);
 
   std::string conflictMsg(SymbolBody *Existing, InputFile *NewFile);
   void reportDuplicate(SymbolBody *Existing, InputFile *NewFile);
 
   std::map<std::string, std::vector<SymbolBody *>> getDemangledSyms();
   void handleAnonymousVersion();
 
   struct SymIndex {

lld/ELF/SymbolTable.cpp

std::pair<Symbol *, bool> SymbolTable<ELFT>::insert(StringRef &Name) {
   }
 
   Symbol *Sym;
   if (IsNew) {
     Sym = new (Alloc) Symbol;
     Sym->Binding = STB_WEAK;
     Sym->Visibility = STV_DEFAULT;
     Sym->IsUsedInRegularObj = false;
-    Sym->HasUnnamedAddr = true;
     Sym->ExportDynamic = false;
     Sym->Traced = V.Traced;
     std::tie(Name, Sym->VersionId) = getSymbolVersion(Name);
     SymVector.push_back(Sym);
   } else {
     Sym = SymVector[V.Idx];
   }
   return {Sym, IsNew};
 }
 
 // Find an existing symbol or create and insert a new one, then apply the given
 // attributes.
 template <class ELFT>
 std::pair<Symbol *, bool>
 SymbolTable<ELFT>::insert(StringRef &Name, uint8_t Type, uint8_t Visibility,
-                          bool CanOmitFromDynSym, bool HasUnnamedAddr,
-                          InputFile *File) {
+                          bool CanOmitFromDynSym, InputFile *File) {
   bool IsUsedInRegularObj = !File || File->kind() == InputFile::ObjectKind;
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) = insert(Name);
 
-  // Merge in the new unnamed_addr attribute.
-  S->HasUnnamedAddr &= HasUnnamedAddr;
   // Merge in the new symbol's visibility.
   S->Visibility = getMinVisibility(S->Visibility, Visibility);
   if (!CanOmitFromDynSym && (Config->Shared || Config->ExportDynamic))
     S->ExportDynamic = true;
   if (IsUsedInRegularObj)
     S->IsUsedInRegularObj = true;
   if (!WasInserted && S->body()->Type != SymbolBody::UnknownType &&
       ((Type == STT_TLS) != S->body()->isTls()))
std::string SymbolTable<ELFT>::conflictMsg(SymbolBody *Existing,
   if (Config->Demangle)
     Sym = demangle(Sym);
   return Sym + " in " + getFilename(Existing->File) + " and " +
          getFilename(NewFile);
 }
 
 template <class ELFT> Symbol *SymbolTable<ELFT>::addUndefined(StringRef Name) {
   return addUndefined(Name, STB_GLOBAL, STV_DEFAULT, /*Type*/ 0,
-                      /*CanOmitFromDynSym*/ false, /*HasUnnamedAddr*/ false,
-                      /*File*/ nullptr);
+                      /*CanOmitFromDynSym*/ false, /*File*/ nullptr);
 }
 
 template <class ELFT>
 Symbol *SymbolTable<ELFT>::addUndefined(StringRef Name, uint8_t Binding,
                                         uint8_t StOther, uint8_t Type,
                                         bool CanOmitFromDynSym,
-                                        bool HasUnnamedAddr, InputFile *File) {
+                                        InputFile *File) {
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) =
-      insert(Name, Type, StOther & 3, CanOmitFromDynSym, HasUnnamedAddr, File);
+      insert(Name, Type, StOther & 3, CanOmitFromDynSym, File);
   if (WasInserted) {
     S->Binding = Binding;
     replaceBody<Undefined>(S, Name, StOther, Type, File);
     return S;
   }
   if (Binding != STB_WEAK) {
     if (S->body()->isShared() || S->body()->isLazy())
       S->Binding = Binding;
static int compareDefinedNonCommon(Symbol *S, bool WasInserted,
   }
   return 0;
 }
 
 template <class ELFT>
 Symbol *SymbolTable<ELFT>::addCommon(StringRef N, uint64_t Size,
                                      uint64_t Alignment, uint8_t Binding,
                                      uint8_t StOther, uint8_t Type,
-                                     bool HasUnnamedAddr, InputFile *File) {
+                                     InputFile *File) {
   Symbol *S;
   bool WasInserted;
-  std::tie(S, WasInserted) = insert(
-      N, Type, StOther & 3, /*CanOmitFromDynSym*/ false, HasUnnamedAddr, File);
+  std::tie(S, WasInserted) =
+      insert(N, Type, StOther & 3, /*CanOmitFromDynSym*/ false, File);
   int Cmp = compareDefined(S, WasInserted, Binding);
   if (Cmp > 0) {
     S->Binding = Binding;
     replaceBody<DefinedCommon>(S, N, Size, Alignment, StOther, Type, File);
   } else if (Cmp == 0) {
     auto *C = dyn_cast<DefinedCommon>(S->body());
     if (!C) {
       // Non-common symbols take precedence over common symbols.
else
     error(Msg);
 }
 
 template <typename ELFT>
 Symbol *SymbolTable<ELFT>::addRegular(StringRef Name, const Elf_Sym &Sym,
                                       InputSectionBase<ELFT> *Section) {
   Symbol *S;
   bool WasInserted;
-  std::tie(S, WasInserted) =
-      insert(Name, Sym.getType(), Sym.getVisibility(),
-             /*CanOmitFromDynSym*/ false, /*HasUnnamedAddr*/ false,
+  std::tie(S, WasInserted) = insert(Name, Sym.getType(), Sym.getVisibility(),
+                                    /*CanOmitFromDynSym*/ false,
                                     Section ? Section->getFile() : nullptr);
   int Cmp = compareDefinedNonCommon(S, WasInserted, Sym.getBinding());
   if (Cmp > 0)
     replaceBody<DefinedRegular<ELFT>>(S, Name, Sym, Section);
   else if (Cmp == 0)
     reportDuplicate(S->body(), Section->getFile());
   return S;
 }
 
 template <typename ELFT>
 Symbol *SymbolTable<ELFT>::addRegular(StringRef Name, uint8_t Binding,
                                       uint8_t StOther) {
   Symbol *S;
   bool WasInserted;
-  std::tie(S, WasInserted) =
-      insert(Name, STT_NOTYPE, StOther & 3, /*CanOmitFromDynSym*/ false,
-             /*HasUnnamedAddr*/ false, nullptr);
+  std::tie(S, WasInserted) = insert(Name, STT_NOTYPE, StOther & 3,
+                                    /*CanOmitFromDynSym*/ false, nullptr);
   int Cmp = compareDefinedNonCommon(S, WasInserted, Binding);
   if (Cmp > 0)
     replaceBody<DefinedRegular<ELFT>>(S, Name, StOther);
   else if (Cmp == 0)
     reportDuplicate(S->body(), nullptr);
   return S;
 }
 
 template <typename ELFT>
 Symbol *SymbolTable<ELFT>::addSynthetic(StringRef N,
                                         OutputSectionBase<ELFT> *Section,
                                         uintX_t Value, uint8_t StOther) {
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) = insert(N, STT_NOTYPE, /*Visibility*/ StOther & 0x3,
-                                    /*CanOmitFromDynSym*/ false,
-                                    /*HasUnnamedAddr*/ false, nullptr);
+                                    /*CanOmitFromDynSym*/ false, nullptr);
   int Cmp = compareDefinedNonCommon(S, WasInserted, STB_GLOBAL);
   if (Cmp > 0)
     replaceBody<DefinedSynthetic<ELFT>>(S, N, Value, Section);
   else if (Cmp == 0)
     reportDuplicate(S->body(), nullptr);
   return S;
 }
 
 template <typename ELFT>
 void SymbolTable<ELFT>::addShared(SharedFile<ELFT> *F, StringRef Name,
                                   const Elf_Sym &Sym,
                                   const typename ELFT::Verdef *Verdef) {
   // DSO symbols do not affect visibility in the output, so we pass STV_DEFAULT
   // as the visibility, which will leave the visibility in the symbol table
   // unchanged.
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) =
-      insert(Name, Sym.getType(), STV_DEFAULT, /*CanOmitFromDynSym*/ true,
-             /*HasUnnamedAddr*/ false, F);
+      insert(Name, Sym.getType(), STV_DEFAULT, /*CanOmitFromDynSym*/ true, F);
   // Make sure we preempt DSO symbols with default visibility.
   if (Sym.getVisibility() == STV_DEFAULT)
     S->ExportDynamic = true;
   if (WasInserted || isa<Undefined>(S->body())) {
     replaceBody<SharedSymbol<ELFT>>(S, F, Name, Sym, Verdef);
     if (!S->isWeak())
       F->IsUsed = true;
   }
 }
 
 template <class ELFT>
 Symbol *SymbolTable<ELFT>::addBitcode(StringRef Name, uint8_t Binding,
                                       uint8_t StOther, uint8_t Type,
-                                      bool CanOmitFromDynSym,
-                                      bool HasUnnamedAddr, BitcodeFile *F) {
+                                      bool CanOmitFromDynSym, BitcodeFile *F) {
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) =
-      insert(Name, Type, StOther & 3, CanOmitFromDynSym, HasUnnamedAddr, F);
+      insert(Name, Type, StOther & 3, CanOmitFromDynSym, F);
   int Cmp = compareDefinedNonCommon(S, WasInserted, Binding);
   if (Cmp > 0)
     replaceBody<DefinedRegular<ELFT>>(S, Name, StOther, Type, F);
   else if (Cmp == 0)
     reportDuplicate(S->body(), F);
   return S;
 }
 

lld/ELF/Symbols.h

struct Symbol {
 
   // Version definition index.
   uint16_t VersionId;
 
   // Symbol visibility. This is the computed minimum visibility of all
   // observed non-DSO symbols.
   unsigned Visibility : 2;
 
-  // True if the symbol has unnamed_addr.
-  unsigned HasUnnamedAddr : 1;
-
   // True if the symbol was used for linking and thus need to be added to the
   // output file's symbol table. This is true for all symbols except for
   // unreferenced DSO symbols and bitcode symbols that are unreferenced except
   // by other bitcode objects.
   unsigned IsUsedInRegularObj : 1;
 
   // If this flag is true and the symbol has protected or default visibility, it
   // will appear in .dynsym. This flag is set by interposable DSO symbols in

lld/test/ELF/lto/archive-3.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %S/Inputs/archive-3.ll -o %t1.o
 ; RUN: llvm-as %s -o %t2.o
 
 ; RUN: ld.lld -m elf_x86_64 %t1.o %t2.o  -o %t3 -save-temps
-; RUN: llvm-dis %t3.lto.bc -o - | FileCheck %s
+; RUN: llvm-dis %t3.0.2.internalize.bc -o - | FileCheck %s
 
 ; RUN: rm -f %t.a
 ; RUN: llvm-ar rcs %t.a %t1.o
 ; RUN: ld.lld -m elf_x86_64 %t.a %t1.o %t2.o  -o %t3 -save-temps
-; RUN: llvm-dis %t3.lto.bc -o - | FileCheck %s
+; RUN: llvm-dis %t3.0.2.internalize.bc -o - | FileCheck %s
 
 ; CHECK: define internal void @foo() {
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 define void @_start() {
   ret void
 }

lld/test/ELF/lto/asmundef.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: ld.lld -m elf_x86_64 %t.o -o %t -save-temps
-; RUN: llvm-dis %t.lto.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.0.4.opt.bc -o - | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 module asm ".weak patatino"
 module asm ".equ patatino, foo"
 
 declare void @patatino()

lld/test/ELF/lto/available-externally.ll

 ; RUN: llvm-as %s -o %t1.o
 ; RUN: llvm-as %p/Inputs/available-externally.ll -o %t2.o
 ; RUN: ld.lld %t1.o %t2.o -m elf_x86_64 -o %t.so -shared -save-temps
-; RUN: llvm-dis < %t.so.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t.so.0.2.internalize.bc | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define void @foo() {
   call void @bar()
   call void @zed()
   ret void

lld/test/ELF/lto/common2.ll

 ; RUN: llvm-as %s -o %t1.o
 ; RUN: ld.lld -m elf_x86_64 %t1.o -o %t -shared -save-temps
-; RUN: llvm-dis < %t.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t.0.2.internalize.bc | FileCheck %s
 ; RUN: llvm-readobj -t %t | FileCheck %s --check-prefix=SHARED
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @a = common global i8 0, align 8
 ; CHECK-DAG: @a = common global i8 0, align 8
 

lld/test/ELF/lto/common3.ll

 ; RUN: llvm-as %s -o %t1.o
 ; RUN: llvm-as %S/Inputs/common3.ll -o %t2.o
 ; RUN: ld.lld -m elf_x86_64 %t1.o %t2.o -o %t -shared -save-temps
-; RUN: llvm-dis < %t.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t.0.2.internalize.bc | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 @a = common hidden global i32 0, align 8
 define i32 @f() {
   %t = load i32, i32* @a, align 4
   ret i32 %t
 }
 
 ; CHECK: @a = internal global i64 0, align 8

lld/test/ELF/lto/discard-value-names.ll

 ; RUN: llvm-as %s -o %t.o
 
 ; RUN: ld.lld -m elf_x86_64 -shared -save-temps %t.o -o %t2.o
-; RUN: llvm-dis < %t2.o.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t2.o.0.0.preopt.bc | FileCheck %s
 
 ; CHECK: @GlobalValueName
 ; CHECK: @foo(i32 %in)
 ; CHECK: somelabel:
 ; CHECK:  %GV = load i32, i32* @GlobalValueName
 ; CHECK:  %add = add i32 %in, %GV
 ; CHECK:  ret i32 %add
 

lld/test/ELF/lto/drop-debug-info.ll

 ; REQUIRES: x86
 ;
 ; drop-debug-info.bc was created from "void f(void) {}" with clang 3.5 and
 ; -gline-tables-only, so it contains old debug info.
 ;
 ; RUN: ld.lld -m elf_x86_64 -shared %p/Inputs/drop-debug-info.bc \
 ; RUN: -disable-verify 2>&1 | FileCheck %s
-; CHECK: warning: ignoring debug info with an invalid version (1) in {{.*}}drop-debug-info.bc
+; CHECK: ignoring debug info with an invalid version (1) in {{.*}}drop-debug-info.bc
 

lld/test/ELF/lto/drop-linkage.ll

 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 ; REQUIRES: x86
 ; RUN: llc %s -o %t.o -filetype=obj
 ; RUN: llvm-as %p/Inputs/drop-linkage.ll -o %t2.o
 ; RUN: ld.lld %t.o %t2.o -o %t.so -save-temps -shared
-; RUN: llvm-dis %t.so.lto.opt.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.so.0.4.opt.bc -o - | FileCheck %s
 
 define void @foo() {
   ret void
 }
 
 ; CHECK: declare void @foo()

lld/test/ELF/lto/internalize-basic.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: ld.lld -m elf_x86_64 %t.o -o %t2 -save-temps
-; RUN: llvm-dis < %t2.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t2.0.2.internalize.bc | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @_start() {
   ret void
 }
 

lld/test/ELF/lto/internalize-exportdyn.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: llvm-as %p/Inputs/internalize-exportdyn.ll -o %t2.o
 ; RUN: ld.lld -m elf_x86_64 %t.o %t2.o -o %t2 --export-dynamic -save-temps
-; RUN: llvm-dis < %t2.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t2.0.2.internalize.bc | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @_start() {
   ret void
 }
 

lld/test/ELF/lto/internalize-llvmused.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: ld.lld -m elf_x86_64 %t.o -o %t2 -save-temps
-; RUN: llvm-dis < %t2.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t2.0.2.internalize.bc | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @_start() {
   ret void
 }
 
 define hidden void @f() {
   ret void
 }
 
 @llvm.used = appending global [1 x i8*] [ i8* bitcast (void ()* @f to i8*)]
 
 ; Check that f is not internalized.
 ; CHECK: define hidden void @f()

lld/test/ELF/lto/internalize-undef.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: llvm-as %p/Inputs/internalize-undef.ll -o %t2.o
 ; RUN: ld.lld -m elf_x86_64 %t.o %t2.o -o %t -save-temps
-; RUN: llvm-dis < %t.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t.0.2.internalize.bc | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 declare void @f()
 define void @_start() {
   call void @f()
   ret void
 }
 
 ; CHECK: define internal void @f()

lld/test/ELF/lto/internalize-version-script.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: echo "{ global: foo; local: *; };" > %t.script
 ; RUN: ld.lld -m elf_x86_64 %t.o -o %t2 -shared --version-script %t.script -save-temps
-; RUN: llvm-dis < %t2.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t2.0.2.internalize.bc | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @foo() {
   ret void
 }
 

lld/test/ELF/lto/irmover-error.ll

 ; RUN: llvm-as -o %t1.bc %s
 ; RUN: llvm-as -o %t2.bc %S/Inputs/irmover-error.ll
 ; RUN: not ld.lld -m elf_x86_64 %t1.bc %t2.bc -o %t 2>&1 | FileCheck %s
 
-; CHECK: failed to link module {{.*}}2.bc: linking module flags 'foo': IDs have conflicting values
+; CHECK: linking module flags 'foo': IDs have conflicting values
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 !0 = !{ i32 1, !"foo", i32 1 }
 
 !llvm.module.flags = !{ !0 }

lld/test/ELF/lto/linkonce-odr.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %p/Inputs/linkonce-odr.ll -o %t1.o
 ; RUN: llc -relocation-model=pic %s -o %t2.o -filetype=obj
 ; RUN: ld.lld %t1.o %t2.o -o %t.so -shared -save-temps
-; RUN: llvm-dis %t.so.lto.opt.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.so.0.4.opt.bc -o - | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 declare void @f()
 
 define void @g() {
   call void @f()
   ret void
 }
 
 ; Be sure that 'f' is kept and has weak_odr linkage.
 ; CHECK: define weak_odr void @f()

lld/test/ELF/lto/linkonce.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %p/Inputs/linkonce.ll -o %t1.o
 ; RUN: llc -relocation-model=pic %s -o %t2.o -filetype=obj
 ; RUN: ld.lld %t1.o %t2.o -o %t.so -shared -save-temps
-; RUN: llvm-dis %t.so.lto.opt.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.so.0.4.opt.bc -o - | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 declare void @f()
 
 define void @g() {
   call void @f()
   ret void
 }
 
 ; Be sure that 'f' is kept and has weak linkage.
 ; CHECK: define weak void @f()

lld/test/ELF/lto/ltopasses-basic.ll

 ; REQUIRES: x86
-; RUN: rm -f %t.so.lto.bc %t.so.lto.opt.bc %t.so.lto.o
 ; RUN: llvm-as %s -o %t.o
 ; RUN: ld.lld -m elf_x86_64 %t.o -o %t.so -save-temps -mllvm -debug-pass=Arguments -shared 2>&1 | FileCheck %s --check-prefix=MLLVM
-; RUN: llvm-dis %t.so.lto.opt.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.so.0.4.opt.bc -o - | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @ctor, i8* null }]
 define void @ctor() {
   ret void
 }
 
 ; `@ctor` doesn't do anything and so the optimizer should kill it, leaving no ctors
 ; CHECK: @llvm.global_ctors = appending global [0 x { i32, void ()*, i8* }] zeroinitializer
 
 ; MLLVM: Pass Arguments:

lld/test/ELF/lto/ltopasses-custom.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: ld.lld -m elf_x86_64 %t.o -o %t.so -save-temps --lto-aa-pipeline=basic-aa \
 ; RUN: --lto-newpm-passes=ipsccp -shared
 ; RUN: ld.lld -m elf_x86_64 %t.o -o %t2.so -save-temps --lto-newpm-passes=loweratomic -shared
-; RUN: llvm-dis %t.so.lto.opt.bc -o - | FileCheck %s
-; RUN: llvm-dis %t2.so.lto.opt.bc -o - | FileCheck %s --check-prefix=ATOMIC
+; RUN: llvm-dis %t.so.0.4.opt.bc -o - | FileCheck %s
+; RUN: llvm-dis %t2.so.0.4.opt.bc -o - | FileCheck %s --check-prefix=ATOMIC
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define void @barrier() {
   fence seq_cst
   ret void
 }

lld/test/ELF/lto/save-temps.ll

 ; REQUIRES: x86
 ; RUN: cd %T
 ; RUN: rm -f a.out a.out.lto.bc a.out.lto.o
 ; RUN: llvm-as %s -o %t.o
 ; RUN: llvm-as %p/Inputs/save-temps.ll -o %t2.o
 ; RUN: ld.lld -shared -m elf_x86_64 %t.o %t2.o -save-temps
 ; RUN: llvm-nm a.out | FileCheck %s
-; RUN: llvm-nm a.out.lto.bc | FileCheck %s
+; RUN: llvm-nm a.out.0.0.preopt.bc | FileCheck %s
 ; RUN: llvm-nm a.out.lto.o | FileCheck %s
-; RUN: llvm-dis a.out.lto.bc
+; RUN: llvm-dis a.out.0.0.preopt.bc
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @foo() {
   ret void
 }
 
 ; CHECK: T bar
 ; CHECK: T foo

lld/test/ELF/lto/type-merge.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: llvm-as %p/Inputs/type-merge.ll -o %t2.o
 ; RUN: ld.lld -m elf_x86_64 %t.o %t2.o -o %t -shared -save-temps
-; RUN: llvm-dis < %t.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t.0.0.preopt.bc | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define void @foo()  {
   call void @bar(i8* null)
   ret void
 }

lld/test/ELF/lto/type-merge2.ll

 ; RUN: llvm-as %s -o %t.o
 ; RUN: llvm-as %p/Inputs/type-merge2.ll -o %t2.o
 ; RUN: ld.lld -m elf_x86_64 %t.o %t2.o -o %t.so -shared -save-temps
-; RUN: llvm-dis %t.so.lto.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.so.0.0.preopt.bc -o - | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 %zed = type { i8 }
 define void @foo()  {
   call void @bar(%zed* null)
   ret void

lld/test/ELF/lto/unnamed-addr-comdat.ll

 ; RUN: llvm-as %s -o %t.o
 ; RUN: ld.lld -m elf_x86_64 %t.o %t.o -o %t.so -save-temps -shared
-; RUN: llvm-dis %t.so.lto.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.so.0.2.internalize.bc -o - | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 $foo = comdat any
 @foo = linkonce_odr unnamed_addr constant i32 42, comdat
 
 ; CHECK: @foo = internal unnamed_addr constant i32 42, comdat

lld/test/ELF/lto/unnamed-addr-drop.ll

 ; RUN: llvm-as %s -o %t1.o
 ; RUN: llvm-as %S/Inputs/unnamed-addr-drop.ll -o %t2.o
 ; RUN: ld.lld -m elf_x86_64 %t1.o %t2.o -o %t.so -save-temps -shared
-; RUN: llvm-dis %t.so.lto.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.so.0.2.internalize.bc -o - | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 @foo = weak constant i32 41
 
 ; Check that unnamed_addr is dropped during the merge.
 ; CHECK: @foo = constant i32 42

lld/test/ELF/lto/unnamed-addr-lib.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: llvm-mc %p/Inputs/unnamed-addr-lib.s -o %t2.o -filetype=obj -triple=x86_64-pc-linux
 ; RUN: ld.lld %t2.o -shared -o %t2.so
 ; RUN: ld.lld -m elf_x86_64 %t.o %t2.so -o %t.so -save-temps -shared
-; RUN: llvm-dis %t.so.lto.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.so.0.2.internalize.bc -o - | FileCheck %s
 
 ; This documents a small limitation of lld's internalization logic. We decide
 ; that bar should be in the symbol table because if it is it will preempt the
 ; one in the shared library.
 ; We could add one extra bit for ODR so that we know that preemption is not
 ; necessary, but that is probably not worth it.
 
-; CHECK: @foo = internal constant i8 42
-; CHECK: @bar = weak_odr constant i8 42
+; CHECK: @foo = internal unnamed_addr constant i8 42
+; CHECK: @bar = weak_odr unnamed_addr constant i8 42
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @foo = linkonce_odr unnamed_addr constant i8 42
 @bar = linkonce_odr unnamed_addr constant i8 42

lld/test/ELF/lto/unnamed-addr.ll

 ; RUN: llvm-as %s -o %t.o
 ; RUN: ld.lld -m elf_x86_64 %t.o -o %t.so -save-temps -shared
-; RUN: llvm-dis %t.so.lto.opt.bc -o - | FileCheck %s
+; RUN: llvm-dis %t.so.0.4.opt.bc -o - | FileCheck %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 @a = internal unnamed_addr constant i8 42
 
 define i8* @f() {
   ret i8* @a
 }
 
 ; CHECK: @a = internal unnamed_addr constant i8 42

lld/test/ELF/lto/version-script.ll

 ; REQUIRES: x86
 ; RUN: llvm-as %s -o %t.o
 ; RUN: echo "VERSION_1.0{ global: foo; local: *; }; VERSION_2.0{ global: bar; local: *; };" > %t.script
 ; RUN: ld.lld -m elf_x86_64 %t.o -o %t2 -shared --version-script %t.script -save-temps
-; RUN: llvm-dis < %t2.lto.bc | FileCheck %s
+; RUN: llvm-dis < %t2.0.0.preopt.bc | FileCheck %s
 ; RUN: llvm-readobj -V -dyn-symbols %t2 | FileCheck --check-prefix=DSO %s
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 define void @foo() {
   ret void
 }

llvm/include/llvm/LTO/LTO.h

public:
     GlobalValue::VisibilityTypes getVisibility() const {
       if (GV)
         return GV->getVisibility();
       return GlobalValue::DefaultVisibility;
     }
     bool canBeOmittedFromSymbolTable() const {
       return GV && llvm::canBeOmittedFromSymbolTable(GV);
     }
-    bool isTLS() {
+    bool isTLS() const {
       // FIXME: Expose a thread-local flag for module asm symbols.
       return GV && GV->isThreadLocal();
     }
     Expected<const Comdat *> getComdat() const {
       if (!GV)
         return nullptr;
       const GlobalObject *GO;
       if (auto *GA = dyn_cast<GlobalAlias>(GV)) {
public:
 
   StringRef getSourceFileName() const {
     return Obj->getModule().getSourceFileName();
   }
 
   MemoryBufferRef getMemoryBufferRef() const {
     return Obj->getMemoryBufferRef();
   }
+
+  StringMap<Comdat> &getComdatSymbolTable() {
+    return Obj->getModule().getComdatSymbolTable();
+  }
 };
 
 /// This class wraps an output stream for a native object. Most clients should
 /// just be able to return an instance of this base class from the stream
 /// callback, but if a client needs to perform some action after the stream is
 /// written to, that can be done by deriving from this class and overriding the
 /// destructor.
 class NativeObjectStream {