C++ list::front方法代码示例

/// Bundle the files. Return true if an error was found.
static bool BundleFiles() {
  std::error_code EC;

  // Create output file.
  raw_fd_ostream OutputFile(OutputFileNames.front(), EC, sys::fs::F_None);

  if (EC) {
    errs() << "error: Can't open file " << OutputFileNames.front() << ".\n";
    return true;
  }

  // Open input files.
  std::vector<std::unique_ptr<MemoryBuffer>> InputBuffers(
      InputFileNames.size());

  unsigned Idx = 0;
  for (auto &I : InputFileNames) {
    ErrorOr<std::unique_ptr<MemoryBuffer>> CodeOrErr =
        MemoryBuffer::getFileOrSTDIN(I);
    if (std::error_code EC = CodeOrErr.getError()) {
      errs() << "error: Can't open file " << I << ": " << EC.message() << "\n";
      return true;
    }
    InputBuffers[Idx++] = std::move(CodeOrErr.get());
  }

  // Get the file handler. We use the host buffer as reference.
  assert(HostInputIndex != ~0u && "Host input index undefined??");
  std::unique_ptr<FileHandler> FH;
  FH.reset(CreateFileHandler(*InputBuffers[HostInputIndex].get()));

  // Quit if we don't have a handler.
  if (!FH.get())
    return true;

  // Write header.
  FH.get()->WriteHeader(OutputFile, InputBuffers);

  // Write all bundles along with the start/end markers. If an error was found
  // writing the end of the bundle component, abort the bundle writing.
  auto Input = InputBuffers.begin();
  for (auto &Triple : TargetNames) {
    FH.get()->WriteBundleStart(OutputFile, Triple);
    FH.get()->WriteBundle(OutputFile, *Input->get());
    if (FH.get()->WriteBundleEnd(OutputFile, Triple))
      return true;
    ++Input;
  }
  return false;
}

// main - Entry point for the llc compiler.
//
int main(int argc, char **argv) {
  sys::PrintStackTraceOnErrorSignal();
  PrettyStackTraceProgram X(argc, argv);

  // Enable debug stream buffering.
  EnableDebugBuffering = true;

  LLVMContext &Context = getGlobalContext();
  llvm_shutdown_obj Y;  // Call llvm_shutdown() on exit.

  // Initialize targets first, so that --version shows registered targets.
  InitializeAllTargets();
  InitializeAllTargetMCs();
  InitializeAllAsmPrinters();
  InitializeAllAsmParsers();

  // Initialize codegen and IR passes used by llc so that the -print-after,
  // -print-before, and -stop-after options work.
  PassRegistry *Registry = PassRegistry::getPassRegistry();
  initializeCore(*Registry);
  initializeCodeGen(*Registry);
  initializeLoopStrengthReducePass(*Registry);
  initializeLowerIntrinsicsPass(*Registry);
  initializeUnreachableBlockElimPass(*Registry);

  // Register the target printer for --version.
  cl::AddExtraVersionPrinter(TargetRegistry::printRegisteredTargetsForVersion);

  cl::ParseCommandLineOptions(argc, argv, "llvm system compiler\n");

  // Load the module to be compiled...
  SMDiagnostic Err;
  std::auto_ptr<Module> M;
  Module *mod = 0;
  Triple TheTriple;

  bool SkipModule = MCPU == "help" ||
                    (!MAttrs.empty() && MAttrs.front() == "help");

  // If user just wants to list available options, skip module loading
  if (!SkipModule) {
    M.reset(ParseIRFile(InputFilename, Err, Context));
    mod = M.get();
    if (mod == 0) {
      Err.print(argv[0], errs());
      return 1;
    }

    // If we are supposed to override the target triple, do so now.
    if (!TargetTriple.empty())
      mod->setTargetTriple(Triple::normalize(TargetTriple));
    TheTriple = Triple(mod->getTargetTriple());
  } else {
    TheTriple = Triple(Triple::normalize(TargetTriple));
  }

  if (TheTriple.getTriple().empty())
    TheTriple.setTriple(sys::getDefaultTargetTriple());

  // Get the target specific parser.
  std::string Error;
  const Target *TheTarget = TargetRegistry::lookupTarget(MArch, TheTriple,
                                                         Error);
  if (!TheTarget) {
    errs() << argv[0] << ": " << Error;
    return 1;
  }

  // Package up features to be passed to target/subtarget
  std::string FeaturesStr;
  if (MAttrs.size()) {
    SubtargetFeatures Features;
    for (unsigned i = 0; i != MAttrs.size(); ++i)
      Features.AddFeature(MAttrs[i]);
    FeaturesStr = Features.getString();
  }

  CodeGenOpt::Level OLvl = CodeGenOpt::Default;
  switch (OptLevel) {
  default:
    errs() << argv[0] << ": invalid optimization level.\n";
    return 1;
  case ' ': break;
  case '0': OLvl = CodeGenOpt::None; break;
  case '1': OLvl = CodeGenOpt::Less; break;
  case '2': OLvl = CodeGenOpt::Default; break;
  case '3': OLvl = CodeGenOpt::Aggressive; break;
  }

  TargetOptions Options;
  Options.LessPreciseFPMADOption = EnableFPMAD;
  Options.NoFramePointerElim = DisableFPElim;
  Options.NoFramePointerElimNonLeaf = DisableFPElimNonLeaf;
  Options.AllowFPOpFusion = FuseFPOps;
  Options.UnsafeFPMath = EnableUnsafeFPMath;
  Options.NoInfsFPMath = EnableNoInfsFPMath;
  Options.NoNaNsFPMath = EnableNoNaNsFPMath;
  Options.HonorSignDependentRoundingFPMathOption =
//.........这里部分代码省略.........

// Unbundle the files. Return true if an error was found.
static bool UnbundleFiles() {
  // Open Input file.
  ErrorOr<std::unique_ptr<MemoryBuffer>> CodeOrErr =
      MemoryBuffer::getFileOrSTDIN(InputFileNames.front());
  if (std::error_code EC = CodeOrErr.getError()) {
    errs() << "error: Can't open file " << InputFileNames.front() << ": "
           << EC.message() << "\n";
    return true;
  }

  MemoryBuffer &Input = *CodeOrErr.get();

  // Select the right files handler.
  std::unique_ptr<FileHandler> FH;
  FH.reset(CreateFileHandler(Input));

  // Quit if we don't have a handler.
  if (!FH.get())
    return true;

  // Read the header of the bundled file.
  FH.get()->ReadHeader(Input);

  // Create a work list that consist of the map triple/output file.
  StringMap<StringRef> Worklist;
  auto Output = OutputFileNames.begin();
  for (auto &Triple : TargetNames) {
    Worklist[Triple] = *Output;
    ++Output;
  }

  // Read all the bundles that are in the work list. If we find no bundles we
  // assume the file is meant for the host target.
  bool FoundHostBundle = false;
  while (!Worklist.empty()) {
    StringRef CurTriple = FH.get()->ReadBundleStart(Input);

    // We don't have more bundles.
    if (CurTriple.empty())
      break;

    auto Output = Worklist.find(CurTriple);
    // The file may have more bundles for other targets, that we don't care
    // about. Therefore, move on to the next triple
    if (Output == Worklist.end()) {
      continue;
    }

    // Check if the output file can be opened and copy the bundle to it.
    std::error_code EC;
    raw_fd_ostream OutputFile(Output->second, EC, sys::fs::F_None);
    if (EC) {
      errs() << "error: Can't open file " << Output->second << ": "
             << EC.message() << "\n";
      return true;
    }
    FH.get()->ReadBundle(OutputFile, Input);
    FH.get()->ReadBundleEnd(Input);
    Worklist.erase(Output);

    // Record if we found the host bundle.
    if (hasHostKind(CurTriple))
      FoundHostBundle = true;
  }

  // If no bundles were found, assume the input file is the host bundle and
  // create empty files for the remaining targets.
  if (Worklist.size() == TargetNames.size()) {
    for (auto &E : Worklist) {
      std::error_code EC;
      raw_fd_ostream OutputFile(E.second, EC, sys::fs::F_None);
      if (EC) {
        errs() << "error: Can't open file " << E.second << ": " << EC.message()
               << "\n";
        return true;
      }

      // If this entry has a host kind, copy the input file to the output file.
      if (hasHostKind(E.first()))
        OutputFile.write(Input.getBufferStart(), Input.getBufferSize());
    }
    return false;
  }

  // If we found elements, we emit an error if none of those were for the host.
  if (!FoundHostBundle) {
    errs() << "error: Can't find bundle for the host target\n";
    return true;
  }

  // If we still have any elements in the worklist, create empty files for them.
  for (auto &E : Worklist) {
    std::error_code EC;
    raw_fd_ostream OutputFile(E.second, EC, sys::fs::F_None);
    if (EC) {
      errs() << "error: Can't open file " << E.second << ": "  << EC.message()
             << "\n";
      return true;
    }
//.........这里部分代码省略.........

  bool WriteBundleEnd(raw_fd_ostream &OS, StringRef TargetTriple) final {
    assert(NumberOfProcessedInputs <= NumberOfInputs &&
           "Processing more inputs that actually exist!");
    assert(HostInputIndex != ~0u && "Host input index not defined.");

    // If this is not the last output, we don't have to do anything.
    if (NumberOfProcessedInputs != NumberOfInputs)
      return false;

    // Create the bitcode file name to write the resulting code to. Keep it if
    // save-temps is active.
    SmallString<128> BitcodeFileName;
    if (sys::fs::createTemporaryFile("clang-offload-bundler", "bc",
                                     BitcodeFileName)) {
      errs() << "error: unable to create temporary file.\n";
      return true;
    }

    // Dump the contents of the temporary file if that was requested.
    if (DumpTemporaryFiles) {
      errs() << ";\n; Object file bundler IR file.\n;\n";
      AuxModule.get()->print(errs(), nullptr,
                             /*ShouldPreserveUseListOrder=*/false,
                             /*IsForDebug=*/true);
      errs() << '\n';
    }

    // Find clang in order to create the bundle binary.
    StringRef Dir = sys::path::parent_path(BundlerExecutable);

    auto ClangBinary = sys::findProgramByName("clang", Dir);
    if (ClangBinary.getError()) {
      // Remove bitcode file.
      sys::fs::remove(BitcodeFileName);

      errs() << "error: unable to find 'clang' in path.\n";
      return true;
    }

    // Do the incremental linking. We write to the output file directly. So, we
    // close it and use the name to pass down to clang.
    OS.close();
    SmallString<128> TargetName = getTriple(TargetNames[HostInputIndex]);
    std::vector<StringRef> ClangArgs = {"clang",
                                        "-r",
                                        "-target",
                                        TargetName.c_str(),
                                        "-o",
                                        OutputFileNames.front().c_str(),
                                        InputFileNames[HostInputIndex].c_str(),
                                        BitcodeFileName.c_str(),
                                        "-nostdlib"};

    // If the user asked for the commands to be printed out, we do that instead
    // of executing it.
    if (PrintExternalCommands) {
      errs() << "\"" << ClangBinary.get() << "\"";
      for (StringRef Arg : ClangArgs)
        errs() << " \"" << Arg << "\"";
      errs() << "\n";
    } else {
      // Write the bitcode contents to the temporary file.
      {
        std::error_code EC;
        raw_fd_ostream BitcodeFile(BitcodeFileName, EC, sys::fs::F_None);
        if (EC) {
          errs() << "error: unable to open temporary file.\n";
          return true;
        }
        WriteBitcodeToFile(*AuxModule, BitcodeFile);
      }

      bool Failed = sys::ExecuteAndWait(ClangBinary.get(), ClangArgs);

      // Remove bitcode file.
      sys::fs::remove(BitcodeFileName);

      if (Failed) {
        errs() << "error: incremental linking by external tool failed.\n";
        return true;
      }
    }

    return false;
  }