llvm-project/llvm/lib/Object/ModuleSymbolTable.cpp

//===- 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.
//
//===----------------------------------------------------------------------===//
//
// 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/IR/LLVMContext.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCParser/MCAsmParser.h"
#include "llvm/MC/MCParser/MCTargetAsmParser.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSubtargetInfo.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;

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);

  CollectAsmSymbols(Triple(M->getTargetTriple()), M->getModuleInlineAsm(),
                    [this](StringRef Name, BasicSymbolRef::Flags Flags) {
                      SymTab.push_back(new (AsmSymbols.Allocate())
                                           AsmSymbol(Name, Flags));
                    });
}

void ModuleSymbolTable::CollectAsmSymbols(
    const Triple &TT, StringRef InlineAsm,
    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()));
  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;
    // FIXME: For now we just assume that all asm symbols are executable.
    uint32_t Res = BasicSymbolRef::SF_Executable;
    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;
    }
    AsmSymbol(Key, BasicSymbolRef::Flags(Res));
  }
}

void ModuleSymbolTable::printSymbolName(raw_ostream &OS, Symbol S) const {
  if (S.is<AsmSymbol *>()) {
    OS << S.get<AsmSymbol *>()->first;
    return;
  }

  auto *GV = S.get<GlobalValue *>();
  if (GV->hasDLLImportStorageClass())
    OS << "__imp_";

  Mang.getNameWithPrefix(OS, GV, false);
}

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;
  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 (dyn_cast_or_null<Function>(GV->getBaseObject()))
    Res |= BasicSymbolRef::SF_Executable;
  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;
}