Object: Extract a ModuleSymbolTable class from IRObjectFile.

[pcc]

Summary

This class represents a symbol table built from in-memory IR. It provides
access to GlobalValues and should only be used if such access is required
(e.g. in the LTO implementation). We will eventually change IRObjectFile
to read from a bitcode symbol table rather than using ModuleSymbolTable,
so it would not be able to expose the module.

Depends on D26928

[pcc]

• Revert an unintentionally added hunk

[mehdi_amini]

llvm/include/llvm/Object/ModuleSymbolTable.h

43

Could it take a MemoryBufferRef and construct a lazy module that it would own? The fact that a Module is created should be an implementation detail.

That seems closer to the goal of having a symbol table in the bitcode file, and will help designing the client APIs appropriately.

[mehdi_amini]

llvm/lib/Object/ModuleSymbolTable.cpp

45

We should assert that every module added have the same triple as the others.

[pcc]

llvm/include/llvm/Object/ModuleSymbolTable.h

43

So the idea here is that this class would be the low-level interface to be used in the case where you know you're dealing with an actual IR module in memory. That's why the class exposes GlobalValues for example.

When symbol tables are introduced, there would be a separate class that would be the low-level interface to the bitcode symbol table. That class would be used by IRObjectFile and lto::InputFile. lib/LTO would also continue to use ModuleSymbolTable in places like LTO::addRegularLTO where it deals with a loaded module.

I'm sorry if I didn't make this clear enough in the discussion on D26951.

[mehdi_amini]

llvm/include/llvm/Object/ModuleSymbolTable.h

43

If this is the low-level interface, what is the high-level one that abstracts away the difference between the low-level ones?
I wouldn't expect the low-level ones to be used in IRObjectFile or lib/LTO, why is that?

[pcc]

llvm/include/llvm/Object/ModuleSymbolTable.h

43

The next higher level interface would be the one that can provide a "bitcode symbol table" for any module, including modules without symbol tables or with old symbol tables, by creating the symbol table on the fly if necessary. Something like:
Expected<std::unique_ptr<MemoryBuffer>> getSymbolTable(MemoryBufferRef Buf);

where the MemoryBuffer would own the symbol table if it needed to be created, or would point inside Buf if not.

That way, no abstraction is needed between in-memory modules and bitcode symbol tables; clients can always just use a bitcode symbol table.

As long as symbol tables don't exist, we're using ModuleSymbolTable in IRObjectFile and lib/LTO. It should be easy enough to switch both of those classes to using getSymbolTable and the bitcode symbol table reader thanks to the work I've done to hide the Module.

[mehdi_amini]

llvm/include/llvm/Object/ModuleSymbolTable.h

43

About Expected<std::unique_ptr<MemoryBuffer>> getSymbolTable(MemoryBufferRef Buf);, assuming the argument Buf is some bitcode without a symbol table, this function would parse the IR to create a module, create a symbol table out of the loaded IR, and then serialize out the symbol table in bitcode format into a new buffer, and return this buffer?

[pcc]

llvm/include/llvm/Object/ModuleSymbolTable.h

43

Correct.

[mehdi_amini]

The class BitcodeSymbolTable I extracted in https://reviews.llvm.org/D23132 had:

std::string Triple;
std::string Datalayout;
std::string ModuleAsm;
std::string SourceFilename;

I think Triple/Datalayout/SourceFilename are likely to be useful as part of the bitcode symbol table (and having them now would allow you to add the assertion I mentioned earlier).

For the ModuleASM, it is not clear to me yet: unless we change the IR I think we won't be able to avoid it either.

[pcc]

Not sure if we'll need accessors. I'd expect that clients which need this information (essentially just the symbol table writer, eventually) would just pull the information out of the module that they presumably have. The assertion seems reasonable though.

I don't think I understand why we'd want all of the module asm. I'd have imagined that we would serialize the AsmSymbols along with the IR symbols. Or is that the IR change you were alluding to?

llvm/lib/Object/ModuleSymbolTable.cpp

45

Sorry, I missed this, will do.

[mehdi_amini]

In D27073#610236, @pcc wrote:

Not sure if we'll need accessors. I'd expect that clients which need this information (essentially just the symbol table writer, eventually) would just pull the information out of the module that they presumably have

The BitcodeModule you mean? Because we're not supposed to have a llvm::Module anymore (the patch I had was removing llvm::Module entirely from LTOModule I believe, and still exposing LTOModule::getTargetTriple.

I don't think I understand why we'd want all of the module asm. I'd have imagined that we would serialize the AsmSymbols along with the IR symbols. Or is that the IR change you were alluding to?

The issue is that we can't make Bitcode serialization dependent on the ASM Parser. So we'd need to change the IR representation for inline ASM. We discussed it here https://llvm.org/bugs/show_bug.cgi?id=28970

[pcc]

In D27073#610238, @mehdi_amini wrote:

In D27073#610236, @pcc wrote:

Not sure if we'll need accessors. I'd expect that clients which need this information (essentially just the symbol table writer, eventually) would just pull the information out of the module that they presumably have

The BitcodeModule you mean? Because we're not supposed to have a llvm::Module anymore (the patch I had was removing llvm::Module entirely from LTOModule I believe, and still exposing LTOModule::getTargetTriple.

Sorry, I meant that we wouldn't need accessors such as getTargetTriple() on ModuleSymbolTable, because as I mentioned that's the class we'll use for going from IR modules to symbol tables, and if you're starting from an IR module then you obviously already have an IR module that you can call accessors on.

In {LTOModule,lto::InputFile,IRObjectFile} we'd eventually be using something like a BitcodeSymtabReader class on which it seems perfectly reasonable to expose these accessors which could read from the bitcode symbol table.

I don't think I understand why we'd want all of the module asm. I'd have imagined that we would serialize the AsmSymbols along with the IR symbols. Or is that the IR change you were alluding to?

The issue is that we can't make Bitcode serialization dependent on the ASM Parser. So we'd need to change the IR representation for inline ASM. We discussed it here https://llvm.org/bugs/show_bug.cgi?id=28970

Thanks for the pointer, I'll take a look. It looks like this happened while I was on vacation and I must have missed it.

[mehdi_amini]

Sorry, I meant that we wouldn't need accessors such as getTargetTriple() on ModuleSymbolTable, because as I mentioned that's the class we'll use for going from IR modules to symbol tables, and if you're starting from an IR module then you obviously already have an IR module that you can call accessors on.

Right, I forgot you plan on another class for the BitcodeSymbolTable.

[pcc]

• Assert that each module added to the symbol table has the same target triple

[mehdi_amini]

LGTM.

llvm/include/llvm/Object/IRObjectFile.h

 // This file declares the IRObjectFile template class.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_OBJECT_IROBJECTFILE_H
 #define LLVM_OBJECT_IROBJECTFILE_H
 
 #include "llvm/ADT/PointerUnion.h"
+#include "llvm/Object/ModuleSymbolTable.h"
 #include "llvm/Object/SymbolicFile.h"
 
 namespace llvm {
 class Mangler;
 class Module;
 class GlobalValue;
 class Triple;
 
 namespace object {
 class ObjectFile;
 
 class IRObjectFile : public SymbolicFile {
   std::unique_ptr<Module> M;
-  std::unique_ptr<Mangler> Mang;
-  typedef std::pair<std::string, uint32_t> AsmSymbol;
-  SpecificBumpPtrAllocator<AsmSymbol> AsmSymbols;
-
-  typedef PointerUnion<GlobalValue *, AsmSymbol *> Sym;
-  std::vector<Sym> SymTab;
-  static Sym getSym(DataRefImpl &Symb) {
-    return *reinterpret_cast<Sym *>(Symb.p);
-  }
+  ModuleSymbolTable SymTab;
 
 public:
   IRObjectFile(MemoryBufferRef Object, std::unique_ptr<Module> M);
   ~IRObjectFile() override;
   void moveSymbolNext(DataRefImpl &Symb) const override;
   std::error_code printSymbolName(raw_ostream &OS,
                                   DataRefImpl Symb) const override;
   uint32_t getSymbolFlags(DataRefImpl Symb) const override;
public:
   static inline bool classof(const Binary *v) {
     return v->isIR();
   }
 
   /// \brief Finds and returns bitcode embedded in the given object file, or an
   /// error code if not found.
   static ErrorOr<MemoryBufferRef> findBitcodeInObject(const ObjectFile &Obj);
 
-  /// Parse inline ASM and collect the symbols that are not defined in
-  /// the current module.
-  ///
-  /// For each found symbol, call \p AsmUndefinedRefs with the name of the
-  /// symbol found and the associated flags.
-  static void CollectAsmUndefinedRefs(
-      const Triple &TheTriple, StringRef InlineAsm,
-      function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmUndefinedRefs);
-
   /// \brief Finds and returns bitcode in the given memory buffer (which may
   /// be either a bitcode file or a native object file with embedded bitcode),
   /// or an error code if not found.
   static ErrorOr<MemoryBufferRef>
   findBitcodeInMemBuffer(MemoryBufferRef Object);
 
   static Expected<std::unique_ptr<IRObjectFile>> create(MemoryBufferRef Object,
                                                         LLVMContext &Context);
 };
 }
 }
 
 #endif

llvm/include/llvm/Object/ModuleSymbolTable.h

+//===- ModuleSymbolTable.h - symbol table for in-memory IR ----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This class represents a symbol table built from in-memory IR. It provides
+// access to GlobalValues and should only be used if such access is required
+// (e.g. in the LTO implementation).
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_OBJECT_MODULESYMBOLTABLE_H
+#define LLVM_OBJECT_MODULESYMBOLTABLE_H
+
+#include "llvm/ADT/PointerUnion.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/IR/Mangler.h"
+#include "llvm/Object/SymbolicFile.h"
+#include <string>
+#include <utility>
+
+namespace llvm {
+
+class GlobalValue;
+
+class ModuleSymbolTable {
+public:
+  typedef std::pair<std::string, uint32_t> AsmSymbol;
+  typedef PointerUnion<GlobalValue *, AsmSymbol *> Symbol;
+
+private:
+  Module *FirstMod = nullptr;
+
+  SpecificBumpPtrAllocator<AsmSymbol> AsmSymbols;
+  std::vector<Symbol> SymTab;
+  Mangler Mang;
+
+public:
+  ArrayRef<Symbol> symbols() const { return SymTab; }
+  void addModule(Module *M);
+
+  void printSymbolName(raw_ostream &OS, Symbol S) const;
+  uint32_t getSymbolFlags(Symbol S) const;
+
+  /// Parse inline ASM and collect the symbols that are defined or referenced in
+  /// the current module.
+  ///
+  /// For each found symbol, call \p AsmSymbol with the name of the symbol found
+  /// and the associated flags.
+  static void CollectAsmSymbols(
+      const Triple &TheTriple, StringRef InlineAsm,
+      function_ref<void(StringRef, object::BasicSymbolRef::Flags)> AsmSymbol);
+};
+
+}
+
+#endif

llvm/lib/Analysis/ModuleSummaryAnalysis.cpp

if (!M.getModuleInlineAsm().empty()) {
     // summaries for these symbols so that they can be marked as NoRename,
     // to prevent export of any use of them in regular IR that would require
     // renaming within the module level asm. Note we don't need to create a
     // summary for weak or global defs, as they don't need to be flagged as
     // NoRename, and defs in module level asm can't be imported anyway.
     // Also, any values used but not defined within module level asm should
     // be listed on the llvm.used or llvm.compiler.used global and marked as
     // referenced from there.
-    // FIXME: Rename CollectAsmUndefinedRefs to something more general, as we
-    // are also using it to find the file-scope locals defined in module asm.
-    object::IRObjectFile::CollectAsmUndefinedRefs(
+    ModuleSymbolTable::CollectAsmSymbols(
         Triple(M.getTargetTriple()), M.getModuleInlineAsm(),
         [&M, &Index](StringRef Name, object::BasicSymbolRef::Flags Flags) {
           // Symbols not marked as Weak or Global are local definitions.
           if (Flags & (object::BasicSymbolRef::SF_Weak ||
                        object::BasicSymbolRef::SF_Global))
             return;
           GlobalValue *GV = M.getNamedValue(Name);
           if (!GV)

llvm/lib/LTO/LTOBackend.cpp

 }
 
 }
 
 static void handleAsmUndefinedRefs(Module &Mod, TargetMachine &TM) {
   // Collect the list of undefined symbols used in asm and update
   // llvm.compiler.used to prevent optimization to drop these from the output.
   StringSet<> AsmUndefinedRefs;
-  object::IRObjectFile::CollectAsmUndefinedRefs(
+  ModuleSymbolTable::CollectAsmSymbols(
       Triple(Mod.getTargetTriple()), Mod.getModuleInlineAsm(),
       [&AsmUndefinedRefs](StringRef Name, object::BasicSymbolRef::Flags Flags) {
         if (Flags & object::BasicSymbolRef::SF_Undefined)
           AsmUndefinedRefs.insert(Name);
       });
   updateCompilerUsed(Mod, TM, AsmUndefinedRefs);
 }
 

llvm/lib/Object/CMakeLists.txt

 add_llvm_library(LLVMObject
   Archive.cpp
   ArchiveWriter.cpp
   Binary.cpp
   COFFObjectFile.cpp
   ELF.cpp
   ELFObjectFile.cpp
   Error.cpp
   IRObjectFile.cpp
   MachOObjectFile.cpp
   MachOUniversal.cpp
   ModuleSummaryIndexObjectFile.cpp
+  ModuleSymbolTable.cpp
   Object.cpp
   ObjectFile.cpp
   RecordStreamer.cpp
   SymbolicFile.cpp
   SymbolSize.cpp
   WasmObjectFile.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Object
 
   DEPENDS
   intrinsics_gen
   )

llvm/lib/Object/IRObjectFile.cpp

 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 using namespace object;
 
 IRObjectFile::IRObjectFile(MemoryBufferRef Object, std::unique_ptr<Module> Mod)
     : SymbolicFile(Binary::ID_IR, Object), M(std::move(Mod)) {
-  Mang.reset(new Mangler());
-
-  for (Function &F : *M)
-    SymTab.push_back(&F);
-  for (GlobalVariable &GV : M->globals())
-    SymTab.push_back(&GV);
-  for (GlobalAlias &GA : M->aliases())
-    SymTab.push_back(&GA);
-
-  CollectAsmUndefinedRefs(Triple(M->getTargetTriple()), M->getModuleInlineAsm(),
-                          [this](StringRef Name, BasicSymbolRef::Flags Flags) {
-                            SymTab.push_back(new (AsmSymbols.Allocate())
-                                                 AsmSymbol(Name, Flags));
-                          });
-}
-
-// Parse inline ASM and collect the list of symbols that are not defined in
-// the current module. This is inspired from IRObjectFile.
-void IRObjectFile::CollectAsmUndefinedRefs(
-    const Triple &TT, StringRef InlineAsm,
-    function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmUndefinedRefs) {
-  if (InlineAsm.empty())
-    return;
-
-  std::string Err;
-  const Target *T = TargetRegistry::lookupTarget(TT.str(), Err);
-  assert(T && T->hasMCAsmParser());
-
-  std::unique_ptr<MCRegisterInfo> MRI(T->createMCRegInfo(TT.str()));
-  if (!MRI)
-    return;
-
-  std::unique_ptr<MCAsmInfo> MAI(T->createMCAsmInfo(*MRI, TT.str()));
-  if (!MAI)
-    return;
-
-  std::unique_ptr<MCSubtargetInfo> STI(
-      T->createMCSubtargetInfo(TT.str(), "", ""));
-  if (!STI)
-    return;
-
-  std::unique_ptr<MCInstrInfo> MCII(T->createMCInstrInfo());
-  if (!MCII)
-    return;
-
-  MCObjectFileInfo MOFI;
-  MCContext MCCtx(MAI.get(), MRI.get(), &MOFI);
-  MOFI.InitMCObjectFileInfo(TT, /*PIC*/ false, CodeModel::Default, MCCtx);
-  RecordStreamer Streamer(MCCtx);
-  T->createNullTargetStreamer(Streamer);
-
-  std::unique_ptr<MemoryBuffer> Buffer(MemoryBuffer::getMemBuffer(InlineAsm));
-  SourceMgr SrcMgr;
-  SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());
-  std::unique_ptr<MCAsmParser> Parser(
-      createMCAsmParser(SrcMgr, MCCtx, Streamer, *MAI));
-
-  MCTargetOptions MCOptions;
-  std::unique_ptr<MCTargetAsmParser> TAP(
-      T->createMCAsmParser(*STI, *Parser, *MCII, MCOptions));
-  if (!TAP)
-    return;
-
-  Parser->setTargetParser(*TAP);
-  if (Parser->Run(false))
-    return;
-
-  for (auto &KV : Streamer) {
-    StringRef Key = KV.first();
-    RecordStreamer::State Value = KV.second;
-    uint32_t Res = BasicSymbolRef::SF_None;
-    switch (Value) {
-    case RecordStreamer::NeverSeen:
-      llvm_unreachable("NeverSeen should have been replaced earlier");
-    case RecordStreamer::DefinedGlobal:
-      Res |= BasicSymbolRef::SF_Global;
-      break;
-    case RecordStreamer::Defined:
-      break;
-    case RecordStreamer::Global:
-    case RecordStreamer::Used:
-      Res |= BasicSymbolRef::SF_Undefined;
-      Res |= BasicSymbolRef::SF_Global;
-      break;
-    case RecordStreamer::DefinedWeak:
-      Res |= BasicSymbolRef::SF_Weak;
-      Res |= BasicSymbolRef::SF_Global;
-      break;
-    case RecordStreamer::UndefinedWeak:
-      Res |= BasicSymbolRef::SF_Weak;
-      Res |= BasicSymbolRef::SF_Undefined;
-    }
-    AsmUndefinedRefs(Key, BasicSymbolRef::Flags(Res));
-  }
+  SymTab.addModule(M.get());
 }
 
 IRObjectFile::~IRObjectFile() {}
 
+static ModuleSymbolTable::Symbol getSym(DataRefImpl &Symb) {
+  return *reinterpret_cast<ModuleSymbolTable::Symbol *>(Symb.p);
+}
+
 void IRObjectFile::moveSymbolNext(DataRefImpl &Symb) const {
-  Symb.p += sizeof(Sym);
+  Symb.p += sizeof(ModuleSymbolTable::Symbol);
 }
 
 std::error_code IRObjectFile::printSymbolName(raw_ostream &OS,
                                               DataRefImpl Symb) const {
-  Sym S = getSym(Symb);
-  if (S.is<AsmSymbol *>()) {
-    OS << S.get<AsmSymbol *>()->first;
-    return std::error_code();
-  }
-
-  auto *GV = S.get<GlobalValue *>();
-  if (GV->hasDLLImportStorageClass())
-    OS << "__imp_";
-
-  if (Mang)
-    Mang->getNameWithPrefix(OS, GV, false);
-  else
-    OS << GV->getName();
-
+  SymTab.printSymbolName(OS, getSym(Symb));
   return std::error_code();
 }
 
 uint32_t IRObjectFile::getSymbolFlags(DataRefImpl Symb) const {
-  Sym S = getSym(Symb);
-  if (S.is<AsmSymbol *>())
-    return S.get<AsmSymbol *>()->second;
-
-  auto *GV = S.get<GlobalValue *>();
-
-  uint32_t Res = BasicSymbolRef::SF_None;
-  if (GV->isDeclarationForLinker())
-    Res |= BasicSymbolRef::SF_Undefined;
-  else if (GV->hasHiddenVisibility() && !GV->hasLocalLinkage())
-    Res |= BasicSymbolRef::SF_Hidden;
-  if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
-    if (GVar->isConstant())
-      Res |= BasicSymbolRef::SF_Const;
-  }
-  if (GV->hasPrivateLinkage())
-    Res |= BasicSymbolRef::SF_FormatSpecific;
-  if (!GV->hasLocalLinkage())
-    Res |= BasicSymbolRef::SF_Global;
-  if (GV->hasCommonLinkage())
-    Res |= BasicSymbolRef::SF_Common;
-  if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
-      GV->hasExternalWeakLinkage())
-    Res |= BasicSymbolRef::SF_Weak;
-
-  if (GV->getName().startswith("llvm."))
-    Res |= BasicSymbolRef::SF_FormatSpecific;
-  else if (auto *Var = dyn_cast<GlobalVariable>(GV)) {
-    if (Var->getSection() == "llvm.metadata")
-      Res |= BasicSymbolRef::SF_FormatSpecific;
-  }
-
-  return Res;
+  return SymTab.getSymbolFlags(getSym(Symb));
 }
 
 GlobalValue *IRObjectFile::getSymbolGV(DataRefImpl Symb) {
   return getSym(Symb).dyn_cast<GlobalValue *>();
 }
 
 std::unique_ptr<Module> IRObjectFile::takeModule() { return std::move(M); }
 
 basic_symbol_iterator IRObjectFile::symbol_begin() const {
   DataRefImpl Ret;
-  Ret.p = reinterpret_cast<uintptr_t>(SymTab.data());
+  Ret.p = reinterpret_cast<uintptr_t>(SymTab.symbols().data());
   return basic_symbol_iterator(BasicSymbolRef(Ret, this));
 }
 
 basic_symbol_iterator IRObjectFile::symbol_end() const {
   DataRefImpl Ret;
-  Ret.p = reinterpret_cast<uintptr_t>(SymTab.data() + SymTab.size());
+  Ret.p = reinterpret_cast<uintptr_t>(SymTab.symbols().data() +
+                                      SymTab.symbols().size());
   return basic_symbol_iterator(BasicSymbolRef(Ret, this));
 }
 
 StringRef IRObjectFile::getTargetTriple() const { return M->getTargetTriple(); }
 
 ErrorOr<MemoryBufferRef> IRObjectFile::findBitcodeInObject(const ObjectFile &Obj) {
   for (const SectionRef &Sec : Obj.sections()) {
     if (Sec.isBitcode()) {

llvm/lib/Object/ModuleSymbolTable.cpp

-//===- IRObjectFile.cpp - IR object file implementation ---------*- C++ -*-===//
+//===- ModuleSymbolTable.cpp - symbol table for in-memory IR ----*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
-// Part of the IRObjectFile class implementation.
+// This class represents a symbol table built from in-memory IR. It provides
+// access to GlobalValues and should only be used if such access is required
+// (e.g. in the LTO implementation).
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Object/IRObjectFile.h"
 #include "RecordStreamer.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/IR/GVMaterializer.h"

 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 using namespace object;
 
-IRObjectFile::IRObjectFile(MemoryBufferRef Object, std::unique_ptr<Module> Mod)
-    : SymbolicFile(Binary::ID_IR, Object), M(std::move(Mod)) {
-  Mang.reset(new Mangler());
+void ModuleSymbolTable::addModule(Module *M) {
+  if (FirstMod)
+    assert(FirstMod->getTargetTriple() == M->getTargetTriple());
+  else
+    FirstMod = M;
 
   for (Function &F : *M)
     SymTab.push_back(&F);
   for (GlobalVariable &GV : M->globals())
     SymTab.push_back(&GV);
   for (GlobalAlias &GA : M->aliases())
     SymTab.push_back(&GA);
 
-  CollectAsmUndefinedRefs(Triple(M->getTargetTriple()), M->getModuleInlineAsm(),
-                          [this](StringRef Name, BasicSymbolRef::Flags Flags) {
-                            SymTab.push_back(new (AsmSymbols.Allocate())
-                                                 AsmSymbol(Name, Flags));
-                          });
+  CollectAsmSymbols(Triple(M->getTargetTriple()), M->getModuleInlineAsm(),
 }
 
-// Parse inline ASM and collect the list of symbols that are not defined in
-// the current module. This is inspired from IRObjectFile.
-void IRObjectFile::CollectAsmUndefinedRefs(
+void ModuleSymbolTable::CollectAsmSymbols(
     const Triple &TT, StringRef InlineAsm,
-    function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmUndefinedRefs) {
+    function_ref<void(StringRef, BasicSymbolRef::Flags)> AsmSymbol) {
   if (InlineAsm.empty())
     return;
 
   std::string Err;
   const Target *T = TargetRegistry::lookupTarget(TT.str(), Err);
   assert(T && T->hasMCAsmParser());
 
   std::unique_ptr<MCRegisterInfo> MRI(T->createMCRegInfo(TT.str()));
for (auto &KV : Streamer) {
     case RecordStreamer::DefinedWeak:
       Res |= BasicSymbolRef::SF_Weak;
       Res |= BasicSymbolRef::SF_Global;
       break;
     case RecordStreamer::UndefinedWeak:
       Res |= BasicSymbolRef::SF_Weak;
       Res |= BasicSymbolRef::SF_Undefined;
     }
-    AsmUndefinedRefs(Key, BasicSymbolRef::Flags(Res));
-  }
+    AsmSymbol(Key, BasicSymbolRef::Flags(Res));
   }
-
-IRObjectFile::~IRObjectFile() {}
-
-void IRObjectFile::moveSymbolNext(DataRefImpl &Symb) const {
-  Symb.p += sizeof(Sym);
 }
 
-std::error_code IRObjectFile::printSymbolName(raw_ostream &OS,
-                                              DataRefImpl Symb) const {
-  Sym S = getSym(Symb);
+void ModuleSymbolTable::printSymbolName(raw_ostream &OS, Symbol S) const {
   if (S.is<AsmSymbol *>()) {
     OS << S.get<AsmSymbol *>()->first;
-    return std::error_code();
+    return;
   }
 
   auto *GV = S.get<GlobalValue *>();
   if (GV->hasDLLImportStorageClass())
     OS << "__imp_";
 
-  if (Mang)
-    Mang->getNameWithPrefix(OS, GV, false);
-  else
-    OS << GV->getName();
-
-  return std::error_code();
+  Mang.getNameWithPrefix(OS, GV, false);
 }
 
-uint32_t IRObjectFile::getSymbolFlags(DataRefImpl Symb) const {
-  Sym S = getSym(Symb);
+uint32_t ModuleSymbolTable::getSymbolFlags(Symbol S) const {
   if (S.is<AsmSymbol *>())
     return S.get<AsmSymbol *>()->second;
 
   auto *GV = S.get<GlobalValue *>();
 
   uint32_t Res = BasicSymbolRef::SF_None;
   if (GV->isDeclarationForLinker())
     Res |= BasicSymbolRef::SF_Undefined;
if (GV->getName().startswith("llvm."))
     Res |= BasicSymbolRef::SF_FormatSpecific;
   else if (auto *Var = dyn_cast<GlobalVariable>(GV)) {
     if (Var->getSection() == "llvm.metadata")
       Res |= BasicSymbolRef::SF_FormatSpecific;
   }
 
   return Res;
 }
-
-GlobalValue *IRObjectFile::getSymbolGV(DataRefImpl Symb) {
-  return getSym(Symb).dyn_cast<GlobalValue *>();
-}
-
-std::unique_ptr<Module> IRObjectFile::takeModule() { return std::move(M); }
-
-basic_symbol_iterator IRObjectFile::symbol_begin() const {
-  DataRefImpl Ret;
-  Ret.p = reinterpret_cast<uintptr_t>(SymTab.data());
-  return basic_symbol_iterator(BasicSymbolRef(Ret, this));
-}
-
-basic_symbol_iterator IRObjectFile::symbol_end() const {
-  DataRefImpl Ret;
-  Ret.p = reinterpret_cast<uintptr_t>(SymTab.data() + SymTab.size());
-  return basic_symbol_iterator(BasicSymbolRef(Ret, this));
-}
-
-StringRef IRObjectFile::getTargetTriple() const { return M->getTargetTriple(); }
-
-ErrorOr<MemoryBufferRef> IRObjectFile::findBitcodeInObject(const ObjectFile &Obj) {
-  for (const SectionRef &Sec : Obj.sections()) {
-    if (Sec.isBitcode()) {
-      StringRef SecContents;
-      if (std::error_code EC = Sec.getContents(SecContents))
-        return EC;
-      return MemoryBufferRef(SecContents, Obj.getFileName());
-    }
-  }
-
-  return object_error::bitcode_section_not_found;
-}
-
-ErrorOr<MemoryBufferRef> IRObjectFile::findBitcodeInMemBuffer(MemoryBufferRef Object) {
-  sys::fs::file_magic Type = sys::fs::identify_magic(Object.getBuffer());
-  switch (Type) {
-  case sys::fs::file_magic::bitcode:
-    return Object;
-  case sys::fs::file_magic::elf_relocatable:
-  case sys::fs::file_magic::macho_object:
-  case sys::fs::file_magic::coff_object: {
-    Expected<std::unique_ptr<ObjectFile>> ObjFile =
-        ObjectFile::createObjectFile(Object, Type);
-    if (!ObjFile)
-      return errorToErrorCode(ObjFile.takeError());
-    return findBitcodeInObject(*ObjFile->get());
-  }
-  default:
-    return object_error::invalid_file_type;
-  }
-}
-
-Expected<std::unique_ptr<IRObjectFile>>
-llvm::object::IRObjectFile::create(MemoryBufferRef Object,
-                                   LLVMContext &Context) {
-  ErrorOr<MemoryBufferRef> BCOrErr = findBitcodeInMemBuffer(Object);
-  if (!BCOrErr)
-    return errorCodeToError(BCOrErr.getError());
-
-  Expected<std::unique_ptr<Module>> MOrErr =
-      getLazyBitcodeModule(*BCOrErr, Context,
-                           /*ShouldLazyLoadMetadata*/ true);
-  if (!MOrErr)
-    return MOrErr.takeError();
-
-  std::unique_ptr<Module> &M = MOrErr.get();
-  return llvm::make_unique<IRObjectFile>(BCOrErr.get(), std::move(M));
-}

llvm/lib/Transforms/IPO/FunctionImport.cpp

 }
 
 /// Run internalization on \p TheModule based on symmary analysis.
 void llvm::thinLTOInternalizeModule(Module &TheModule,
                                     const GVSummaryMapTy &DefinedGlobals) {
   // Parse inline ASM and collect the list of symbols that are not defined in
   // the current module.
   StringSet<> AsmUndefinedRefs;
-  object::IRObjectFile::CollectAsmUndefinedRefs(
+  ModuleSymbolTable::CollectAsmSymbols(
       Triple(TheModule.getTargetTriple()), TheModule.getModuleInlineAsm(),
       [&AsmUndefinedRefs](StringRef Name, object::BasicSymbolRef::Flags Flags) {
         if (Flags & object::BasicSymbolRef::SF_Undefined)
           AsmUndefinedRefs.insert(Name);
       });
 
   // Declare a callback for the internalize pass that will ask for every
   // candidate GlobalValue if it can be internalized or not.