C++ GlobalValue::hasLinkOnceODRLinkage方法代码示例

//.........这里部分代码省略.........
    if (shouldSkip(ObjSym.getFlags()))
      continue;
    ld_plugin_symbol &Sym = F.syms[SymNum];
    ++SymNum;

    ld_plugin_symbol_resolution Resolution =
        (ld_plugin_symbol_resolution)Sym.resolution;

    if (options::generate_api_file)
      *ApiFile << Sym.name << ' ' << getResolutionName(Resolution) << '\n';

    GlobalValue *GV = Obj.getSymbolGV(ObjSym.getRawDataRefImpl());
    if (!GV) {
      freeSymName(Sym);
      continue; // Asm symbol.
    }

    if (Resolution != LDPR_PREVAILING_DEF_IRONLY && GV->hasCommonLinkage()) {
      // Common linkage is special. There is no single symbol that wins the
      // resolution. Instead we have to collect the maximum alignment and size.
      // The IR linker does that for us if we just pass it every common GV.
      // We still have to keep track of LDPR_PREVAILING_DEF_IRONLY so we
      // internalize once the IR linker has done its job.
      freeSymName(Sym);
      continue;
    }

    switch (Resolution) {
    case LDPR_UNKNOWN:
      llvm_unreachable("Unexpected resolution");

    case LDPR_RESOLVED_IR:
    case LDPR_RESOLVED_EXEC:
    case LDPR_RESOLVED_DYN:
      assert(GV->isDeclarationForLinker());
      break;

    case LDPR_UNDEF:
      if (!GV->isDeclarationForLinker()) {
        assert(GV->hasComdat());
        Drop.insert(GV);
      }
      break;

    case LDPR_PREVAILING_DEF_IRONLY: {
      keepGlobalValue(*GV, KeptAliases);
      if (!Used.count(GV)) {
        // Since we use the regular lib/Linker, we cannot just internalize GV
        // now or it will not be copied to the merged module. Instead we force
        // it to be copied and then internalize it.
        Internalize.insert(GV->getName());
      }
      break;
    }

    case LDPR_PREVAILING_DEF:
      keepGlobalValue(*GV, KeptAliases);
      break;

    case LDPR_PREEMPTED_IR:
      // Gold might have selected a linkonce_odr and preempted a weak_odr.
      // In that case we have to make sure we don't end up internalizing it.
      if (!GV->isDiscardableIfUnused())
        Maybe.erase(GV->getName());

      // fall-through
    case LDPR_PREEMPTED_REG:
      Drop.insert(GV);
      break;

    case LDPR_PREVAILING_DEF_IRONLY_EXP: {
      // We can only check for address uses after we merge the modules. The
      // reason is that this GV might have a copy in another module
      // and in that module the address might be significant, but that
      // copy will be LDPR_PREEMPTED_IR.
      if (GV->hasLinkOnceODRLinkage())
        Maybe.insert(GV->getName());
      keepGlobalValue(*GV, KeptAliases);
      break;
    }
    }

    freeSymName(Sym);
  }

  ValueToValueMapTy VM;
  LocalValueMaterializer Materializer(Drop);
  for (GlobalAlias *GA : KeptAliases) {
    // Gold told us to keep GA. It is possible that a GV usied in the aliasee
    // expression is being dropped. If that is the case, that GV must be copied.
    Constant *Aliasee = GA->getAliasee();
    Constant *Replacement = mapConstantToLocalCopy(Aliasee, VM, &Materializer);
    GA->setAliasee(Replacement);
  }

  for (auto *GV : Drop)
    drop(*GV);

  return Obj.takeModule();
}

static std::unique_ptr<Module>
getModuleForFile(LLVMContext &Context, claimed_file &F, raw_fd_ostream *ApiFile,
                 StringSet<> &Internalize, StringSet<> &Maybe) {
  ld_plugin_input_file File;
  if (get_input_file(F.handle, &File) != LDPS_OK)
    message(LDPL_FATAL, "Failed to get file information");

  if (get_symbols(F.handle, F.syms.size(), &F.syms[0]) != LDPS_OK)
    message(LDPL_FATAL, "Failed to get symbol information");

  const void *View;
  if (get_view(F.handle, &View) != LDPS_OK)
    message(LDPL_FATAL, "Failed to get a view of file");

  std::unique_ptr<MemoryBuffer> Buffer = MemoryBuffer::getMemBuffer(
      StringRef((char *)View, File.filesize), "", false);

  if (release_input_file(F.handle) != LDPS_OK)
    message(LDPL_FATAL, "Failed to release file information");

  ErrorOr<Module *> MOrErr = getLazyBitcodeModule(std::move(Buffer), Context);

  if (std::error_code EC = MOrErr.getError())
    message(LDPL_FATAL, "Could not read bitcode from file : %s",
            EC.message().c_str());

  std::unique_ptr<Module> M(MOrErr.get());

  SmallPtrSet<GlobalValue *, 8> Used;
  collectUsedGlobalVariables(*M, Used, /*CompilerUsed*/ false);

  DenseSet<GlobalValue *> Drop;
  std::vector<GlobalAlias *> KeptAliases;
  for (ld_plugin_symbol &Sym : F.syms) {
    ld_plugin_symbol_resolution Resolution =
        (ld_plugin_symbol_resolution)Sym.resolution;

    if (options::generate_api_file)
      *ApiFile << Sym.name << ' ' << getResolutionName(Resolution) << '\n';

    GlobalValue *GV = M->getNamedValue(Sym.name);
    if (!GV)
      continue; // Asm symbol.

    if (GV->hasCommonLinkage()) {
      // Common linkage is special. There is no single symbol that wins the
      // resolution. Instead we have to collect the maximum alignment and size.
      // The IR linker does that for us if we just pass it every common GV.
      continue;
    }

    switch (Resolution) {
    case LDPR_UNKNOWN:
      llvm_unreachable("Unexpected resolution");

    case LDPR_RESOLVED_IR:
    case LDPR_RESOLVED_EXEC:
    case LDPR_RESOLVED_DYN:
    case LDPR_UNDEF:
      assert(isDeclaration(*GV));
      break;

    case LDPR_PREVAILING_DEF_IRONLY: {
      keepGlobalValue(*GV, KeptAliases);
      if (!Used.count(GV)) {
        // Since we use the regular lib/Linker, we cannot just internalize GV
        // now or it will not be copied to the merged module. Instead we force
        // it to be copied and then internalize it.
        Internalize.insert(Sym.name);
      }
      break;
    }

    case LDPR_PREVAILING_DEF:
      keepGlobalValue(*GV, KeptAliases);
      break;

    case LDPR_PREEMPTED_REG:
    case LDPR_PREEMPTED_IR:
      Drop.insert(GV);
      break;

    case LDPR_PREVAILING_DEF_IRONLY_EXP: {
      // We can only check for address uses after we merge the modules. The
      // reason is that this GV might have a copy in another module
      // and in that module the address might be significant, but that
      // copy will be LDPR_PREEMPTED_IR.
      if (GV->hasLinkOnceODRLinkage())
        Maybe.insert(Sym.name);
      keepGlobalValue(*GV, KeptAliases);
      break;
    }
    }

    free(Sym.name);
    free(Sym.comdat_key);
    Sym.name = nullptr;
    Sym.comdat_key = nullptr;
  }

//.........这里部分代码省略.........