clang/lib/Driver/Driver.cpp

//===--- Driver.cpp - Clang GCC Compatible Driver -------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "clang/Driver/Driver.h"
#include "InputInfo.h"
#include "ToolChains.h"
#include "clang/Basic/Version.h"
#include "clang/Config/config.h"
#include "clang/Driver/Action.h"
#include "clang/Driver/Compilation.h"
#include "clang/Driver/DriverDiagnostic.h"
#include "clang/Driver/Job.h"
#include "clang/Driver/Options.h"
#include "clang/Driver/SanitizerArgs.h"
#include "clang/Driver/Tool.h"
#include "clang/Driver/ToolChain.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Option/Arg.h"
#include "llvm/Option/ArgList.h"
#include "llvm/Option/OptSpecifier.h"
#include "llvm/Option/OptTable.h"
#include "llvm/Option/Option.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/PrettyStackTrace.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/raw_ostream.h"
#include <map>
#include <memory>

using namespace clang::driver;
using namespace clang;
using namespace llvm::opt;

Driver::Driver(StringRef ClangExecutable, StringRef DefaultTargetTriple,
               DiagnosticsEngine &Diags)
    : Opts(createDriverOptTable()), Diags(Diags), Mode(GCCMode),
      SaveTemps(SaveTempsNone), ClangExecutable(ClangExecutable),
      SysRoot(DEFAULT_SYSROOT), UseStdLib(true),
      DefaultTargetTriple(DefaultTargetTriple),
      DriverTitle("clang LLVM compiler"), CCPrintOptionsFilename(nullptr),
      CCPrintHeadersFilename(nullptr), CCLogDiagnosticsFilename(nullptr),
      CCCPrintBindings(false), CCPrintHeaders(false), CCLogDiagnostics(false),
      CCGenDiagnostics(false), CCCGenericGCCName(""), CheckInputsExist(true),
      CCCUsePCH(true), SuppressMissingInputWarning(false) {

  Name = llvm::sys::path::filename(ClangExecutable);
  Dir  = llvm::sys::path::parent_path(ClangExecutable);

  // Compute the path to the resource directory.
  StringRef ClangResourceDir(CLANG_RESOURCE_DIR);
  SmallString<128> P(Dir);
  if (ClangResourceDir != "") {
    llvm::sys::path::append(P, ClangResourceDir);
  } else {
    StringRef ClangLibdirSuffix(CLANG_LIBDIR_SUFFIX);
    llvm::sys::path::append(P, "..", Twine("lib") + ClangLibdirSuffix, "clang",
                            CLANG_VERSION_STRING);
  }
  ResourceDir = P.str();
}

Driver::~Driver() {
  delete Opts;

  llvm::DeleteContainerSeconds(ToolChains);
}

void Driver::ParseDriverMode(ArrayRef<const char *> Args) {
  const std::string OptName =
    getOpts().getOption(options::OPT_driver_mode).getPrefixedName();

  for (size_t I = 0, E = Args.size(); I != E; ++I) {
    // Ingore nullptrs, they are response file's EOL markers
    if (Args[I] == nullptr)
      continue;
    const StringRef Arg = Args[I];
    if (!Arg.startswith(OptName))
      continue;

    const StringRef Value = Arg.drop_front(OptName.size());
    const unsigned M = llvm::StringSwitch<unsigned>(Value)
        .Case("gcc", GCCMode)
        .Case("g++", GXXMode)
        .Case("cpp", CPPMode)
        .Case("cl",  CLMode)
        .Default(~0U);

    if (M != ~0U)
      Mode = static_cast<DriverMode>(M);
    else
      Diag(diag::err_drv_unsupported_option_argument) << OptName << Value;
  }
}

InputArgList *Driver::ParseArgStrings(ArrayRef<const char *> ArgStrings) {
  llvm::PrettyStackTraceString CrashInfo("Command line argument parsing");

  unsigned IncludedFlagsBitmask;
  unsigned ExcludedFlagsBitmask;
  std::tie(IncludedFlagsBitmask, ExcludedFlagsBitmask) =
    getIncludeExcludeOptionFlagMasks();

  unsigned MissingArgIndex, MissingArgCount;
  InputArgList *Args =
      getOpts().ParseArgs(ArgStrings, MissingArgIndex, MissingArgCount,
                          IncludedFlagsBitmask, ExcludedFlagsBitmask);

  // Check for missing argument error.
  if (MissingArgCount)
    Diag(clang::diag::err_drv_missing_argument)
      << Args->getArgString(MissingArgIndex) << MissingArgCount;

  // Check for unsupported options.
  for (const Arg *A : *Args) {
    if (A->getOption().hasFlag(options::Unsupported)) {
      Diag(clang::diag::err_drv_unsupported_opt) << A->getAsString(*Args);
      continue;
    }

    // Warn about -mcpu= without an argument.
    if (A->getOption().matches(options::OPT_mcpu_EQ) &&
        A->containsValue("")) {
      Diag(clang::diag::warn_drv_empty_joined_argument) <<
        A->getAsString(*Args);
    }
  }

  for (const Arg *A : Args->filtered(options::OPT_UNKNOWN))
    Diags.Report(diag::err_drv_unknown_argument) << A->getAsString(*Args);

  return Args;
}

// Determine which compilation mode we are in. We look for options which
// affect the phase, starting with the earliest phases, and record which
// option we used to determine the final phase.
phases::ID Driver::getFinalPhase(const DerivedArgList &DAL, Arg **FinalPhaseArg)
const {
  Arg *PhaseArg = nullptr;
  phases::ID FinalPhase;

  // -{E,EP,P,M,MM} only run the preprocessor.
  if (CCCIsCPP() ||
      (PhaseArg = DAL.getLastArg(options::OPT_E)) ||
      (PhaseArg = DAL.getLastArg(options::OPT__SLASH_EP)) ||
      (PhaseArg = DAL.getLastArg(options::OPT_M, options::OPT_MM)) ||
      (PhaseArg = DAL.getLastArg(options::OPT__SLASH_P))) {
    FinalPhase = phases::Preprocess;

    // -{fsyntax-only,-analyze,emit-ast} only run up to the compiler.
  } else if ((PhaseArg = DAL.getLastArg(options::OPT_fsyntax_only)) ||
             (PhaseArg = DAL.getLastArg(options::OPT_module_file_info)) ||
             (PhaseArg = DAL.getLastArg(options::OPT_verify_pch)) ||
             (PhaseArg = DAL.getLastArg(options::OPT_rewrite_objc)) ||
             (PhaseArg = DAL.getLastArg(options::OPT_rewrite_legacy_objc)) ||
             (PhaseArg = DAL.getLastArg(options::OPT__migrate)) ||
             (PhaseArg = DAL.getLastArg(options::OPT__analyze,
                                        options::OPT__analyze_auto)) ||
             (PhaseArg = DAL.getLastArg(options::OPT_emit_ast))) {
    FinalPhase = phases::Compile;

    // -S only runs up to the backend.
  } else if ((PhaseArg = DAL.getLastArg(options::OPT_S))) {
    FinalPhase = phases::Backend;

    // -c only runs up to the assembler.
  } else if ((PhaseArg = DAL.getLastArg(options::OPT_c))) {
    FinalPhase = phases::Assemble;

    // Otherwise do everything.
  } else
    FinalPhase = phases::Link;

  if (FinalPhaseArg)
    *FinalPhaseArg = PhaseArg;

  return FinalPhase;
}

static Arg* MakeInputArg(DerivedArgList &Args, OptTable *Opts,
                         StringRef Value) {
  Arg *A = new Arg(Opts->getOption(options::OPT_INPUT), Value,
                   Args.getBaseArgs().MakeIndex(Value), Value.data());
  Args.AddSynthesizedArg(A);
  A->claim();
  return A;
}

DerivedArgList *Driver::TranslateInputArgs(const InputArgList &Args) const {
  DerivedArgList *DAL = new DerivedArgList(Args);

  bool HasNostdlib = Args.hasArg(options::OPT_nostdlib);
  for (Arg *A : Args) {
    // Unfortunately, we have to parse some forwarding options (-Xassembler,
    // -Xlinker, -Xpreprocessor) because we either integrate their functionality
    // (assembler and preprocessor), or bypass a previous driver ('collect2').

    // Rewrite linker options, to replace --no-demangle with a custom internal
    // option.
    if ((A->getOption().matches(options::OPT_Wl_COMMA) ||
         A->getOption().matches(options::OPT_Xlinker)) &&
        A->containsValue("--no-demangle")) {
      // Add the rewritten no-demangle argument.
      DAL->AddFlagArg(A, Opts->getOption(options::OPT_Z_Xlinker__no_demangle));

      // Add the remaining values as Xlinker arguments.
      for (unsigned i = 0, e = A->getNumValues(); i != e; ++i)
        if (StringRef(A->getValue(i)) != "--no-demangle")
          DAL->AddSeparateArg(A, Opts->getOption(options::OPT_Xlinker),
                              A->getValue(i));

      continue;
    }

    // Rewrite preprocessor options, to replace -Wp,-MD,FOO which is used by
    // some build systems. We don't try to be complete here because we don't
    // care to encourage this usage model.
    if (A->getOption().matches(options::OPT_Wp_COMMA) &&
        (A->getValue(0) == StringRef("-MD") ||
         A->getValue(0) == StringRef("-MMD"))) {
      // Rewrite to -MD/-MMD along with -MF.
      if (A->getValue(0) == StringRef("-MD"))
        DAL->AddFlagArg(A, Opts->getOption(options::OPT_MD));
      else
        DAL->AddFlagArg(A, Opts->getOption(options::OPT_MMD));
      if (A->getNumValues() == 2)
        DAL->AddSeparateArg(A, Opts->getOption(options::OPT_MF),
                            A->getValue(1));
      continue;
    }

    // Rewrite reserved library names.
    if (A->getOption().matches(options::OPT_l)) {
      StringRef Value = A->getValue();

      // Rewrite unless -nostdlib is present.
      if (!HasNostdlib && Value == "stdc++") {
        DAL->AddFlagArg(A, Opts->getOption(
                              options::OPT_Z_reserved_lib_stdcxx));
        continue;
      }

      // Rewrite unconditionally.
      if (Value == "cc_kext") {
        DAL->AddFlagArg(A, Opts->getOption(
                              options::OPT_Z_reserved_lib_cckext));
        continue;
      }
    }

    // Pick up inputs via the -- option.
    if (A->getOption().matches(options::OPT__DASH_DASH)) {
      A->claim();
      for (unsigned i = 0, e = A->getNumValues(); i != e; ++i)
        DAL->append(MakeInputArg(*DAL, Opts, A->getValue(i)));
      continue;
    }

    DAL->append(A);
  }

  // Add a default value of -mlinker-version=, if one was given and the user
  // didn't specify one.
#if defined(HOST_LINK_VERSION)
  if (!Args.hasArg(options::OPT_mlinker_version_EQ) &&
      strlen(HOST_LINK_VERSION) > 0) {
    DAL->AddJoinedArg(0, Opts->getOption(options::OPT_mlinker_version_EQ),
                      HOST_LINK_VERSION);
    DAL->getLastArg(options::OPT_mlinker_version_EQ)->claim();
  }
#endif

  return DAL;
}

Compilation *Driver::BuildCompilation(ArrayRef<const char *> ArgList) {
  llvm::PrettyStackTraceString CrashInfo("Compilation construction");

  // FIXME: Handle environment options which affect driver behavior, somewhere
  // (client?). GCC_EXEC_PREFIX, LPATH, CC_PRINT_OPTIONS.

  if (char *env = ::getenv("COMPILER_PATH")) {
    StringRef CompilerPath = env;
    while (!CompilerPath.empty()) {
      std::pair<StringRef, StringRef> Split
        = CompilerPath.split(llvm::sys::EnvPathSeparator);
      PrefixDirs.push_back(Split.first);
      CompilerPath = Split.second;
    }
  }

  // We look for the driver mode option early, because the mode can affect
  // how other options are parsed.
  ParseDriverMode(ArgList.slice(1));

  // FIXME: What are we going to do with -V and -b?

  // FIXME: This stuff needs to go into the Compilation, not the driver.
  bool CCCPrintActions;

  InputArgList *Args = ParseArgStrings(ArgList.slice(1));

  // -no-canonical-prefixes is used very early in main.
  Args->ClaimAllArgs(options::OPT_no_canonical_prefixes);

  // Ignore -pipe.
  Args->ClaimAllArgs(options::OPT_pipe);

  // Extract -ccc args.
  //
  // FIXME: We need to figure out where this behavior should live. Most of it
  // should be outside in the client; the parts that aren't should have proper
  // options, either by introducing new ones or by overloading gcc ones like -V
  // or -b.
  CCCPrintActions = Args->hasArg(options::OPT_ccc_print_phases);
  CCCPrintBindings = Args->hasArg(options::OPT_ccc_print_bindings);
  if (const Arg *A = Args->getLastArg(options::OPT_ccc_gcc_name))
    CCCGenericGCCName = A->getValue();
  CCCUsePCH = Args->hasFlag(options::OPT_ccc_pch_is_pch,
                            options::OPT_ccc_pch_is_pth);
  // FIXME: DefaultTargetTriple is used by the target-prefixed calls to as/ld
  // and getToolChain is const.
  if (IsCLMode()) {
    // clang-cl targets MSVC-style Win32.
    llvm::Triple T(DefaultTargetTriple);
    T.setOS(llvm::Triple::Win32);
    T.setEnvironment(llvm::Triple::MSVC);
    DefaultTargetTriple = T.str();
  }
  if (const Arg *A = Args->getLastArg(options::OPT_target))
    DefaultTargetTriple = A->getValue();
  if (const Arg *A = Args->getLastArg(options::OPT_ccc_install_dir))
    Dir = InstalledDir = A->getValue();
  for (const Arg *A : Args->filtered(options::OPT_B)) {
    A->claim();
    PrefixDirs.push_back(A->getValue(0));
  }
  if (const Arg *A = Args->getLastArg(options::OPT__sysroot_EQ))
    SysRoot = A->getValue();
  if (const Arg *A = Args->getLastArg(options::OPT__dyld_prefix_EQ))
    DyldPrefix = A->getValue();
  if (Args->hasArg(options::OPT_nostdlib))
    UseStdLib = false;

  if (const Arg *A = Args->getLastArg(options::OPT_resource_dir))
    ResourceDir = A->getValue();

  if (const Arg *A = Args->getLastArg(options::OPT_save_temps_EQ)) {
    SaveTemps = llvm::StringSwitch<SaveTempsMode>(A->getValue())
                    .Case("cwd", SaveTempsCwd)
                    .Case("obj", SaveTempsObj)
                    .Default(SaveTempsCwd);
  }

  // Perform the default argument translations.
  DerivedArgList *TranslatedArgs = TranslateInputArgs(*Args);

  // Owned by the host.
  const ToolChain &TC = getToolChain(*Args);

  // The compilation takes ownership of Args.
  Compilation *C = new Compilation(*this, TC, Args, TranslatedArgs);

  if (!HandleImmediateArgs(*C))
    return C;

  // Construct the list of inputs.
  InputList Inputs;
  BuildInputs(C->getDefaultToolChain(), *TranslatedArgs, Inputs);

  // Construct the list of abstract actions to perform for this compilation. On
  // MachO targets this uses the driver-driver and universal actions.
  if (TC.getTriple().isOSBinFormatMachO())
    BuildUniversalActions(C->getDefaultToolChain(), C->getArgs(),
                          Inputs, C->getActions());
  else
    BuildActions(C->getDefaultToolChain(), C->getArgs(), Inputs,
                 C->getActions());

  if (CCCPrintActions) {
    PrintActions(*C);
    return C;
  }

  BuildJobs(*C);

  return C;
}

// When clang crashes, produce diagnostic information including the fully
// preprocessed source file(s).  Request that the developer attach the
// diagnostic information to a bug report.
void Driver::generateCompilationDiagnostics(Compilation &C,
                                            const Command &FailingCommand) {
  if (C.getArgs().hasArg(options::OPT_fno_crash_diagnostics))
    return;

  // Don't try to generate diagnostics for link or dsymutil jobs.
  if (FailingCommand.getCreator().isLinkJob() ||
      FailingCommand.getCreator().isDsymutilJob())
    return;

  // Print the version of the compiler.
  PrintVersion(C, llvm::errs());

  Diag(clang::diag::note_drv_command_failed_diag_msg)
    << "PLEASE submit a bug report to " BUG_REPORT_URL " and include the "
    "crash backtrace, preprocessed source, and associated run script.";

  // Suppress driver output and emit preprocessor output to temp file.
  Mode = CPPMode;
  CCGenDiagnostics = true;

  // Save the original job command(s).
  Command Cmd = FailingCommand;

  // Keep track of whether we produce any errors while trying to produce
  // preprocessed sources.
  DiagnosticErrorTrap Trap(Diags);

  // Suppress tool output.
  C.initCompilationForDiagnostics();

  // Construct the list of inputs.
  InputList Inputs;
  BuildInputs(C.getDefaultToolChain(), C.getArgs(), Inputs);

  for (InputList::iterator it = Inputs.begin(), ie = Inputs.end(); it != ie;) {
    bool IgnoreInput = false;

    // Ignore input from stdin or any inputs that cannot be preprocessed.
    // Check type first as not all linker inputs have a value.
   if (types::getPreprocessedType(it->first) == types::TY_INVALID) {
      IgnoreInput = true;
    } else if (!strcmp(it->second->getValue(), "-")) {
      Diag(clang::diag::note_drv_command_failed_diag_msg)
        << "Error generating preprocessed source(s) - ignoring input from stdin"
        ".";
      IgnoreInput = true;
    }

    if (IgnoreInput) {
      it = Inputs.erase(it);
      ie = Inputs.end();
    } else {
      ++it;
    }
  }

  if (Inputs.empty()) {
    Diag(clang::diag::note_drv_command_failed_diag_msg)
      << "Error generating preprocessed source(s) - no preprocessable inputs.";
    return;
  }

  // Don't attempt to generate preprocessed files if multiple -arch options are
  // used, unless they're all duplicates.
  llvm::StringSet<> ArchNames;
  for (const Arg *A : C.getArgs()) {
    if (A->getOption().matches(options::OPT_arch)) {
      StringRef ArchName = A->getValue();
      ArchNames.insert(ArchName);
    }
  }
  if (ArchNames.size() > 1) {
    Diag(clang::diag::note_drv_command_failed_diag_msg)
      << "Error generating preprocessed source(s) - cannot generate "
      "preprocessed source with multiple -arch options.";
    return;
  }

  // Construct the list of abstract actions to perform for this compilation. On
  // Darwin OSes this uses the driver-driver and builds universal actions.
  const ToolChain &TC = C.getDefaultToolChain();
  if (TC.getTriple().isOSBinFormatMachO())
    BuildUniversalActions(TC, C.getArgs(), Inputs, C.getActions());
  else
    BuildActions(TC, C.getArgs(), Inputs, C.getActions());

  BuildJobs(C);

  // If there were errors building the compilation, quit now.
  if (Trap.hasErrorOccurred()) {
    Diag(clang::diag::note_drv_command_failed_diag_msg)
      << "Error generating preprocessed source(s).";
    return;
  }

  // Generate preprocessed output.
  SmallVector<std::pair<int, const Command *>, 4> FailingCommands;
  C.ExecuteJob(C.getJobs(), FailingCommands);

  // If any of the preprocessing commands failed, clean up and exit.
  if (!FailingCommands.empty()) {
    if (!isSaveTempsEnabled())
      C.CleanupFileList(C.getTempFiles(), true);

    Diag(clang::diag::note_drv_command_failed_diag_msg)
      << "Error generating preprocessed source(s).";
    return;
  }

  const ArgStringList &TempFiles = C.getTempFiles();
  if (TempFiles.empty()) {
    Diag(clang::diag::note_drv_command_failed_diag_msg)
      << "Error generating preprocessed source(s).";
    return;
  }

  Diag(clang::diag::note_drv_command_failed_diag_msg)
      << "\n********************\n\n"
         "PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:\n"
         "Preprocessed source(s) and associated run script(s) are located at:";

  SmallString<128> VFS;
  for (const char *TempFile : TempFiles) {
    Diag(clang::diag::note_drv_command_failed_diag_msg) << TempFile;
    if (StringRef(TempFile).endswith(".cache")) {
      // In some cases (modules) we'll dump extra data to help with reproducing
      // the crash into a directory next to the output.
      VFS = llvm::sys::path::filename(TempFile);
      llvm::sys::path::append(VFS, "vfs", "vfs.yaml");
    }
  }

  // Assume associated files are based off of the first temporary file.
  CrashReportInfo CrashInfo(TempFiles[0], VFS);

  std::string Script = CrashInfo.Filename.rsplit('.').first.str() + ".sh";
  std::error_code EC;
  llvm::raw_fd_ostream ScriptOS(Script, EC, llvm::sys::fs::F_Excl);
  if (EC) {
    Diag(clang::diag::note_drv_command_failed_diag_msg)
        << "Error generating run script: " + Script + " " + EC.message();
  } else {
    ScriptOS << "# Crash reproducer for " << getClangFullVersion() << "\n"
             << "# Original command: ";
    Cmd.Print(ScriptOS, "\n", /*Quote=*/true);
    Cmd.Print(ScriptOS, "\n", /*Quote=*/true, &CrashInfo);
    Diag(clang::diag::note_drv_command_failed_diag_msg) << Script;
  }

  for (const auto &A : C.getArgs().filtered(options::OPT_frewrite_map_file,
                                            options::OPT_frewrite_map_file_EQ))
    Diag(clang::diag::note_drv_command_failed_diag_msg) << A->getValue();

  Diag(clang::diag::note_drv_command_failed_diag_msg)
      << "\n\n********************";
}

void Driver::setUpResponseFiles(Compilation &C, Job &J) {
  if (JobList *Jobs = dyn_cast<JobList>(&J)) {
    for (auto &Job : *Jobs)
      setUpResponseFiles(C, Job);
    return;
  }

  Command *CurCommand = dyn_cast<Command>(&J);
  if (!CurCommand)
    return;

  // Since argumentsFitWithinSystemLimits() may underestimate system's capacity
  // if the tool does not support response files, there is a chance/ that things
  // will just work without a response file, so we silently just skip it.
  if (CurCommand->getCreator().getResponseFilesSupport() == Tool::RF_None ||
      llvm::sys::argumentsFitWithinSystemLimits(CurCommand->getArguments()))
    return;

  std::string TmpName = GetTemporaryPath("response", "txt");
  CurCommand->setResponseFile(C.addTempFile(C.getArgs().MakeArgString(
      TmpName.c_str())));
}

int Driver::ExecuteCompilation(Compilation &C,
    SmallVectorImpl< std::pair<int, const Command *> > &FailingCommands) {
  // Just print if -### was present.
  if (C.getArgs().hasArg(options::OPT__HASH_HASH_HASH)) {
    C.getJobs().Print(llvm::errs(), "\n", true);
    return 0;
  }

  // If there were errors building the compilation, quit now.
  if (Diags.hasErrorOccurred())
    return 1;

  // Set up response file names for each command, if necessary
  setUpResponseFiles(C, C.getJobs());

  C.ExecuteJob(C.getJobs(), FailingCommands);

  // Remove temp files.
  C.CleanupFileList(C.getTempFiles());

  // If the command succeeded, we are done.
  if (FailingCommands.empty())
    return 0;

  // Otherwise, remove result files and print extra information about abnormal
  // failures.
  for (SmallVectorImpl< std::pair<int, const Command *> >::iterator it =
         FailingCommands.begin(), ie = FailingCommands.end(); it != ie; ++it) {
    int Res = it->first;
    const Command *FailingCommand = it->second;

    // Remove result files if we're not saving temps.
    if (!isSaveTempsEnabled()) {
      const JobAction *JA = cast<JobAction>(&FailingCommand->getSource());
      C.CleanupFileMap(C.getResultFiles(), JA, true);

      // Failure result files are valid unless we crashed.
      if (Res < 0)
        C.CleanupFileMap(C.getFailureResultFiles(), JA, true);
    }

    // Print extra information about abnormal failures, if possible.
    //
    // This is ad-hoc, but we don't want to be excessively noisy. If the result
    // status was 1, assume the command failed normally. In particular, if it
    // was the compiler then assume it gave a reasonable error code. Failures
    // in other tools are less common, and they generally have worse
    // diagnostics, so always print the diagnostic there.
    const Tool &FailingTool = FailingCommand->getCreator();

    if (!FailingCommand->getCreator().hasGoodDiagnostics() || Res != 1) {
      // FIXME: See FIXME above regarding result code interpretation.
      if (Res < 0)
        Diag(clang::diag::err_drv_command_signalled)
          << FailingTool.getShortName();
      else
        Diag(clang::diag::err_drv_command_failed)
          << FailingTool.getShortName() << Res;
    }
  }
  return 0;
}

void Driver::PrintHelp(bool ShowHidden) const {
  unsigned IncludedFlagsBitmask;
  unsigned ExcludedFlagsBitmask;
  std::tie(IncludedFlagsBitmask, ExcludedFlagsBitmask) =
    getIncludeExcludeOptionFlagMasks();

  ExcludedFlagsBitmask |= options::NoDriverOption;
  if (!ShowHidden)
    ExcludedFlagsBitmask |= HelpHidden;

  getOpts().PrintHelp(llvm::outs(), Name.c_str(), DriverTitle.c_str(),
                      IncludedFlagsBitmask, ExcludedFlagsBitmask);
}

void Driver::PrintVersion(const Compilation &C, raw_ostream &OS) const {
  // FIXME: The following handlers should use a callback mechanism, we don't
  // know what the client would like to do.
  OS << getClangFullVersion() << '\n';
  const ToolChain &TC = C.getDefaultToolChain();
  OS << "Target: " << TC.getTripleString() << '\n';

  // Print the threading model.
  if (Arg *A = C.getArgs().getLastArg(options::OPT_mthread_model)) {
    // Don't print if the ToolChain would have barfed on it already
    if (TC.isThreadModelSupported(A->getValue()))
      OS << "Thread model: " << A->getValue();
  } else
    OS << "Thread model: " << TC.getThreadModel();
  OS << '\n';
}

/// PrintDiagnosticCategories - Implement the --print-diagnostic-categories
/// option.
static void PrintDiagnosticCategories(raw_ostream &OS) {
  // Skip the empty category.
  for (unsigned i = 1, max = DiagnosticIDs::getNumberOfCategories();
       i != max; ++i)
    OS << i << ',' << DiagnosticIDs::getCategoryNameFromID(i) << '\n';
}

bool Driver::HandleImmediateArgs(const Compilation &C) {
  // The order these options are handled in gcc is all over the place, but we
  // don't expect inconsistencies w.r.t. that to matter in practice.

  if (C.getArgs().hasArg(options::OPT_dumpmachine)) {
    llvm::outs() << C.getDefaultToolChain().getTripleString() << '\n';
    return false;
  }

  if (C.getArgs().hasArg(options::OPT_dumpversion)) {
    // Since -dumpversion is only implemented for pedantic GCC compatibility, we
    // return an answer which matches our definition of __VERSION__.
    //
    // If we want to return a more correct answer some day, then we should
    // introduce a non-pedantically GCC compatible mode to Clang in which we
    // provide sensible definitions for -dumpversion, __VERSION__, etc.
    llvm::outs() << "4.2.1\n";
    return false;
  }

  if (C.getArgs().hasArg(options::OPT__print_diagnostic_categories)) {
    PrintDiagnosticCategories(llvm::outs());
    return false;
  }

  if (C.getArgs().hasArg(options::OPT_help) ||
      C.getArgs().hasArg(options::OPT__help_hidden)) {
    PrintHelp(C.getArgs().hasArg(options::OPT__help_hidden));
    return false;
  }

  if (C.getArgs().hasArg(options::OPT__version)) {
    // Follow gcc behavior and use stdout for --version and stderr for -v.
    PrintVersion(C, llvm::outs());
    return false;
  }

  if (C.getArgs().hasArg(options::OPT_v) ||
      C.getArgs().hasArg(options::OPT__HASH_HASH_HASH)) {
    PrintVersion(C, llvm::errs());
    SuppressMissingInputWarning = true;
  }

  const ToolChain &TC = C.getDefaultToolChain();

  if (C.getArgs().hasArg(options::OPT_v))
    TC.printVerboseInfo(llvm::errs());

  if (C.getArgs().hasArg(options::OPT_print_search_dirs)) {
    llvm::outs() << "programs: =";
    for (ToolChain::path_list::const_iterator it = TC.getProgramPaths().begin(),
           ie = TC.getProgramPaths().end(); it != ie; ++it) {
      if (it != TC.getProgramPaths().begin())
        llvm::outs() << ':';
      llvm::outs() << *it;
    }
    llvm::outs() << "\n";
    llvm::outs() << "libraries: =" << ResourceDir;

    StringRef sysroot = C.getSysRoot();

    for (ToolChain::path_list::const_iterator it = TC.getFilePaths().begin(),
           ie = TC.getFilePaths().end(); it != ie; ++it) {
      llvm::outs() << ':';
      const char *path = it->c_str();
      if (path[0] == '=')
        llvm::outs() << sysroot << path + 1;
      else
        llvm::outs() << path;
    }
    llvm::outs() << "\n";
    return false;
  }

  // FIXME: The following handlers should use a callback mechanism, we don't
  // know what the client would like to do.
  if (Arg *A = C.getArgs().getLastArg(options::OPT_print_file_name_EQ)) {
    llvm::outs() << GetFilePath(A->getValue(), TC) << "\n";
    return false;
  }

  if (Arg *A = C.getArgs().getLastArg(options::OPT_print_prog_name_EQ)) {
    llvm::outs() << GetProgramPath(A->getValue(), TC) << "\n";
    return false;
  }

  if (C.getArgs().hasArg(options::OPT_print_libgcc_file_name)) {
    llvm::outs() << GetFilePath("libgcc.a", TC) << "\n";
    return false;
  }

  if (C.getArgs().hasArg(options::OPT_print_multi_lib)) {
    const MultilibSet &Multilibs = TC.getMultilibs();

    for (MultilibSet::const_iterator I = Multilibs.begin(), E = Multilibs.end();
         I != E; ++I) {
      llvm::outs() << *I << "\n";
    }
    return false;
  }

  if (C.getArgs().hasArg(options::OPT_print_multi_directory)) {
    const MultilibSet &Multilibs = TC.getMultilibs();
    for (MultilibSet::const_iterator I = Multilibs.begin(), E = Multilibs.end();
         I != E; ++I) {
      if (I->gccSuffix().empty())
        llvm::outs() << ".\n";
      else {
        StringRef Suffix(I->gccSuffix());
        assert(Suffix.front() == '/');
        llvm::outs() << Suffix.substr(1) << "\n";
      }
    }
    return false;
  }

  if (C.getArgs().hasArg(options::OPT_print_multi_os_directory)) {
    // FIXME: This should print out "lib/../lib", "lib/../lib64", or
    // "lib/../lib32" as appropriate for the toolchain. For now, print
    // nothing because it's not supported yet.
    return false;
  }

  return true;
}

// Display an action graph human-readably.  Action A is the "sink" node
// and latest-occuring action. Traversal is in pre-order, visiting the
// inputs to each action before printing the action itself.
static unsigned PrintActions1(const Compilation &C, Action *A,
                              std::map<Action*, unsigned> &Ids) {
  if (Ids.count(A)) // A was already visited.
    return Ids[A];

  std::string str;
  llvm::raw_string_ostream os(str);

  os << Action::getClassName(A->getKind()) << ", ";
  if (InputAction *IA = dyn_cast<InputAction>(A)) {
    os << "\"" << IA->getInputArg().getValue() << "\"";
  } else if (BindArchAction *BIA = dyn_cast<BindArchAction>(A)) {
    os << '"' << BIA->getArchName() << '"'
       << ", {" << PrintActions1(C, *BIA->begin(), Ids) << "}";
  } else {
    os << "{";
    for (Action::iterator it = A->begin(), ie = A->end(); it != ie;) {
      os << PrintActions1(C, *it, Ids);
      ++it;
      if (it != ie)
        os << ", ";
    }
    os << "}";
  }

  unsigned Id = Ids.size();
  Ids[A] = Id;
  llvm::errs() << Id << ": " << os.str() << ", "
               << types::getTypeName(A->getType()) << "\n";

  return Id;
}

// Print the action graphs in a compilation C.
// For example "clang -c file1.c file2.c" is composed of two subgraphs.
void Driver::PrintActions(const Compilation &C) const {
  std::map<Action*, unsigned> Ids;
  for (ActionList::const_iterator it = C.getActions().begin(),
         ie = C.getActions().end(); it != ie; ++it)
    PrintActions1(C, *it, Ids);
}

/// \brief Check whether the given input tree contains any compilation or
/// assembly actions.
static bool ContainsCompileOrAssembleAction(const Action *A) {
  if (isa<CompileJobAction>(A) ||
      isa<BackendJobAction>(A) ||
      isa<AssembleJobAction>(A))
    return true;

  for (Action::const_iterator it = A->begin(), ie = A->end(); it != ie; ++it)
    if (ContainsCompileOrAssembleAction(*it))
      return true;

  return false;
}

void Driver::BuildUniversalActions(const ToolChain &TC,
                                   DerivedArgList &Args,
                                   const InputList &BAInputs,
                                   ActionList &Actions) const {
  llvm::PrettyStackTraceString CrashInfo("Building universal build actions");
  // Collect the list of architectures. Duplicates are allowed, but should only
  // be handled once (in the order seen).
  llvm::StringSet<> ArchNames;
  SmallVector<const char *, 4> Archs;
  for (Arg *A : Args) {
    if (A->getOption().matches(options::OPT_arch)) {
      // Validate the option here; we don't save the type here because its
      // particular spelling may participate in other driver choices.
      llvm::Triple::ArchType Arch =
        tools::darwin::getArchTypeForMachOArchName(A->getValue());
      if (Arch == llvm::Triple::UnknownArch) {
        Diag(clang::diag::err_drv_invalid_arch_name)
          << A->getAsString(Args);
        continue;
      }

      A->claim();
      if (ArchNames.insert(A->getValue()).second)
        Archs.push_back(A->getValue());
    }
  }

  // When there is no explicit arch for this platform, make sure we still bind
  // the architecture (to the default) so that -Xarch_ is handled correctly.
  if (!Archs.size())
    Archs.push_back(Args.MakeArgString(TC.getDefaultUniversalArchName()));

  ActionList SingleActions;
  BuildActions(TC, Args, BAInputs, SingleActions);

  // Add in arch bindings for every top level action, as well as lipo and
  // dsymutil steps if needed.
  for (unsigned i = 0, e = SingleActions.size(); i != e; ++i) {
    Action *Act = SingleActions[i];

    // Make sure we can lipo this kind of output. If not (and it is an actual
    // output) then we disallow, since we can't create an output file with the
    // right name without overwriting it. We could remove this oddity by just
    // changing the output names to include the arch, which would also fix
    // -save-temps. Compatibility wins for now.

    if (Archs.size() > 1 && !types::canLipoType(Act->getType()))
      Diag(clang::diag::err_drv_invalid_output_with_multiple_archs)
        << types::getTypeName(Act->getType());

    ActionList Inputs;
    for (unsigned i = 0, e = Archs.size(); i != e; ++i) {
      Inputs.push_back(
          new BindArchAction(std::unique_ptr<Action>(Act), Archs[i]));
      if (i != 0)
        Inputs.back()->setOwnsInputs(false);
    }

    // Lipo if necessary, we do it this way because we need to set the arch flag
    // so that -Xarch_ gets overwritten.
    if (Inputs.size() == 1 || Act->getType() == types::TY_Nothing)
      Actions.append(Inputs.begin(), Inputs.end());
    else
      Actions.push_back(new LipoJobAction(Inputs, Act->getType()));

    // Handle debug info queries.
    Arg *A = Args.getLastArg(options::OPT_g_Group);
    if (A && !A->getOption().matches(options::OPT_g0) &&
        !A->getOption().matches(options::OPT_gstabs) &&
        ContainsCompileOrAssembleAction(Actions.back())) {

      // Add a 'dsymutil' step if necessary, when debug info is enabled and we
      // have a compile input. We need to run 'dsymutil' ourselves in such cases
      // because the debug info will refer to a temporary object file which
      // will be removed at the end of the compilation process.
      if (Act->getType() == types::TY_Image) {
        ActionList Inputs;
        Inputs.push_back(Actions.back());
        Actions.pop_back();
        Actions.push_back(new DsymutilJobAction(Inputs, types::TY_dSYM));
      }

      // Verify the debug info output.
      if (Args.hasArg(options::OPT_verify_debug_info)) {
        std::unique_ptr<Action> VerifyInput(Actions.back());
        Actions.pop_back();
        Actions.push_back(new VerifyDebugInfoJobAction(std::move(VerifyInput),
                                                       types::TY_Nothing));
      }
    }
  }
}

/// \brief Check that the file referenced by Value exists. If it doesn't,
/// issue a diagnostic and return false.
static bool DiagnoseInputExistence(const Driver &D, const DerivedArgList &Args,
                                   StringRef Value) {
  if (!D.getCheckInputsExist())
    return true;

  // stdin always exists.
  if (Value == "-")
    return true;

  SmallString<64> Path(Value);
  if (Arg *WorkDir = Args.getLastArg(options::OPT_working_directory)) {
    if (!llvm::sys::path::is_absolute(Path)) {
      SmallString<64> Directory(WorkDir->getValue());
      llvm::sys::path::append(Directory, Value);
      Path.assign(Directory);
    }
  }

  if (llvm::sys::fs::exists(Twine(Path)))
    return true;

  if (D.IsCLMode() && !llvm::sys::path::is_absolute(Twine(Path)) &&
      llvm::sys::Process::FindInEnvPath("LIB", Value))
    return true;

  D.Diag(clang::diag::err_drv_no_such_file) << Path;
  return false;
}

// Construct a the list of inputs and their types.
void Driver::BuildInputs(const ToolChain &TC, DerivedArgList &Args,
                         InputList &Inputs) const {
  // Track the current user specified (-x) input. We also explicitly track the
  // argument used to set the type; we only want to claim the type when we
  // actually use it, so we warn about unused -x arguments.
  types::ID InputType = types::TY_Nothing;
  Arg *InputTypeArg = nullptr;

  // The last /TC or /TP option sets the input type to C or C++ globally.
  if (Arg *TCTP = Args.getLastArgNoClaim(options::OPT__SLASH_TC,
                                         options::OPT__SLASH_TP)) {
    InputTypeArg = TCTP;
    InputType = TCTP->getOption().matches(options::OPT__SLASH_TC)
        ? types::TY_C : types::TY_CXX;

    arg_iterator it = Args.filtered_begin(options::OPT__SLASH_TC,
                                          options::OPT__SLASH_TP);
    const arg_iterator ie = Args.filtered_end();
    Arg *Previous = *it++;
    bool ShowNote = false;
    while (it != ie) {
      Diag(clang::diag::warn_drv_overriding_flag_option)
          << Previous->getSpelling() << (*it)->getSpelling();
      Previous = *it++;
      ShowNote = true;
    }
    if (ShowNote)
      Diag(clang::diag::note_drv_t_option_is_global);

    // No driver mode exposes -x and /TC or /TP; we don't support mixing them.
    assert(!Args.hasArg(options::OPT_x) && "-x and /TC or /TP is not allowed");
  }

  for (Arg *A : Args) {
    if (A->getOption().getKind() == Option::InputClass) {
      const char *Value = A->getValue();
      types::ID Ty = types::TY_INVALID;

      // Infer the input type if necessary.
      if (InputType == types::TY_Nothing) {
        // If there was an explicit arg for this, claim it.
        if (InputTypeArg)
          InputTypeArg->claim();

        // stdin must be handled specially.
        if (memcmp(Value, "-", 2) == 0) {
          // If running with -E, treat as a C input (this changes the builtin
          // macros, for example). This may be overridden by -ObjC below.
          //
          // Otherwise emit an error but still use a valid type to avoid
          // spurious errors (e.g., no inputs).
          if (!Args.hasArgNoClaim(options::OPT_E) && !CCCIsCPP())
            Diag(IsCLMode() ? clang::diag::err_drv_unknown_stdin_type_clang_cl
                            : clang::diag::err_drv_unknown_stdin_type);
          Ty = types::TY_C;
        } else {
          // Otherwise lookup by extension.
          // Fallback is C if invoked as C preprocessor or Object otherwise.
          // We use a host hook here because Darwin at least has its own
          // idea of what .s is.
          if (const char *Ext = strrchr(Value, '.'))
            Ty = TC.LookupTypeForExtension(Ext + 1);

          if (Ty == types::TY_INVALID) {
            if (CCCIsCPP())
              Ty = types::TY_C;
            else
              Ty = types::TY_Object;
          }

          // If the driver is invoked as C++ compiler (like clang++ or c++) it
          // should autodetect some input files as C++ for g++ compatibility.
          if (CCCIsCXX()) {
            types::ID OldTy = Ty;
            Ty = types::lookupCXXTypeForCType(Ty);

            if (Ty != OldTy)
              Diag(clang::diag::warn_drv_treating_input_as_cxx)
                << getTypeName(OldTy) << getTypeName(Ty);
          }
        }

        // -ObjC and -ObjC++ override the default language, but only for "source
        // files". We just treat everything that isn't a linker input as a
        // source file.
        //
        // FIXME: Clean this up if we move the phase sequence into the type.
        if (Ty != types::TY_Object) {
          if (Args.hasArg(options::OPT_ObjC))
            Ty = types::TY_ObjC;
          else if (Args.hasArg(options::OPT_ObjCXX))
            Ty = types::TY_ObjCXX;
        }
      } else {
        assert(InputTypeArg && "InputType set w/o InputTypeArg");
        if (!InputTypeArg->getOption().matches(options::OPT_x)) {
          // If emulating cl.exe, make sure that /TC and /TP don't affect input
          // object files.
          const char *Ext = strrchr(Value, '.');
          if (Ext && TC.LookupTypeForExtension(Ext + 1) == types::TY_Object)
            Ty = types::TY_Object;
        }
        if (Ty == types::TY_INVALID) {
          Ty = InputType;
          InputTypeArg->claim();
        }
      }

      if (DiagnoseInputExistence(*this, Args, Value))
        Inputs.push_back(std::make_pair(Ty, A));

    } else if (A->getOption().matches(options::OPT__SLASH_Tc)) {
      StringRef Value = A->getValue();
      if (DiagnoseInputExistence(*this, Args, Value)) {
        Arg *InputArg = MakeInputArg(Args, Opts, A->getValue());
        Inputs.push_back(std::make_pair(types::TY_C, InputArg));
      }
      A->claim();
    } else if (A->getOption().matches(options::OPT__SLASH_Tp)) {
      StringRef Value = A->getValue();
      if (DiagnoseInputExistence(*this, Args, Value)) {
        Arg *InputArg = MakeInputArg(Args, Opts, A->getValue());
        Inputs.push_back(std::make_pair(types::TY_CXX, InputArg));
      }
      A->claim();
    } else if (A->getOption().hasFlag(options::LinkerInput)) {
      // Just treat as object type, we could make a special type for this if
      // necessary.
      Inputs.push_back(std::make_pair(types::TY_Object, A));

    } else if (A->getOption().matches(options::OPT_x)) {
      InputTypeArg = A;
      InputType = types::lookupTypeForTypeSpecifier(A->getValue());
      A->claim();

      // Follow gcc behavior and treat as linker input for invalid -x
      // options. Its not clear why we shouldn't just revert to unknown; but
      // this isn't very important, we might as well be bug compatible.
      if (!InputType) {
        Diag(clang::diag::err_drv_unknown_language) << A->getValue();
        InputType = types::TY_Object;
      }
    }
  }
  if (CCCIsCPP() && Inputs.empty()) {
    // If called as standalone preprocessor, stdin is processed
    // if no other input is present.
    Arg *A = MakeInputArg(Args, Opts, "-");
    Inputs.push_back(std::make_pair(types::TY_C, A));
  }
}

void Driver::BuildActions(const ToolChain &TC, DerivedArgList &Args,
                          const InputList &Inputs, ActionList &Actions) const {
  llvm::PrettyStackTraceString CrashInfo("Building compilation actions");

  if (!SuppressMissingInputWarning && Inputs.empty()) {
    Diag(clang::diag::err_drv_no_input_files);
    return;
  }

  Arg *FinalPhaseArg;
  phases::ID FinalPhase = getFinalPhase(Args, &FinalPhaseArg);

  if (FinalPhase == phases::Link && Args.hasArg(options::OPT_emit_llvm)) {
    Diag(clang::diag::err_drv_emit_llvm_link);
  }

  // Reject -Z* at the top level, these options should never have been exposed
  // by gcc.
  if (Arg *A = Args.getLastArg(options::OPT_Z_Joined))
    Diag(clang::diag::err_drv_use_of_Z_option) << A->getAsString(Args);

  // Diagnose misuse of /Fo.
  if (Arg *A = Args.getLastArg(options::OPT__SLASH_Fo)) {
    StringRef V = A->getValue();
    if (Inputs.size() > 1 && !V.empty() &&
        !llvm::sys::path::is_separator(V.back())) {
      // Check whether /Fo tries to name an output file for multiple inputs.
      Diag(clang::diag::err_drv_out_file_argument_with_multiple_sources)
        << A->getSpelling() << V;
      Args.eraseArg(options::OPT__SLASH_Fo);
    }
  }

  // Diagnose misuse of /Fa.
  if (Arg *A = Args.getLastArg(options::OPT__SLASH_Fa)) {
    StringRef V = A->getValue();
    if (Inputs.size() > 1 && !V.empty() &&
        !llvm::sys::path::is_separator(V.back())) {
      // Check whether /Fa tries to name an asm file for multiple inputs.
      Diag(clang::diag::err_drv_out_file_argument_with_multiple_sources)
        << A->getSpelling() << V;
      Args.eraseArg(options::OPT__SLASH_Fa);
    }
  }

  // Diagnose misuse of /o.
  if (Arg *A = Args.getLastArg(options::OPT__SLASH_o)) {
    if (A->getValue()[0] == '\0') {
      // It has to have a value.
      Diag(clang::diag::err_drv_missing_argument) << A->getSpelling() << 1;
      Args.eraseArg(options::OPT__SLASH_o);
    }
  }

  // Construct the actions to perform.
  ActionList LinkerInputs;

  llvm::SmallVector<phases::ID, phases::MaxNumberOfPhases> PL;
  for (unsigned i = 0, e = Inputs.size(); i != e; ++i) {
    types::ID InputType = Inputs[i].first;
    const Arg *InputArg = Inputs[i].second;

    PL.clear();
    types::getCompilationPhases(InputType, PL);

    // If the first step comes after the final phase we are doing as part of
    // this compilation, warn the user about it.
    phases::ID InitialPhase = PL[0];
    if (InitialPhase > FinalPhase) {
      // Claim here to avoid the more general unused warning.
      InputArg->claim();

      // Suppress all unused style warnings with -Qunused-arguments
      if (Args.hasArg(options::OPT_Qunused_arguments))
        continue;

      // Special case when final phase determined by binary name, rather than
      // by a command-line argument with a corresponding Arg.
      if (CCCIsCPP())
        Diag(clang::diag::warn_drv_input_file_unused_by_cpp)
          << InputArg->getAsString(Args)
          << getPhaseName(InitialPhase);
      // Special case '-E' warning on a previously preprocessed file to make
      // more sense.
      else if (InitialPhase == phases::Compile &&
               FinalPhase == phases::Preprocess &&
               getPreprocessedType(InputType) == types::TY_INVALID)
        Diag(clang::diag::warn_drv_preprocessed_input_file_unused)
          << InputArg->getAsString(Args)
          << !!FinalPhaseArg
          << (FinalPhaseArg ? FinalPhaseArg->getOption().getName() : "");
      else
        Diag(clang::diag::warn_drv_input_file_unused)
          << InputArg->getAsString(Args)
          << getPhaseName(InitialPhase)
          << !!FinalPhaseArg
          << (FinalPhaseArg ? FinalPhaseArg->getOption().getName() : "");
      continue;
    }

    // Build the pipeline for this file.
    std::unique_ptr<Action> Current(new InputAction(*InputArg, InputType));
    for (SmallVectorImpl<phases::ID>::iterator
           i = PL.begin(), e = PL.end(); i != e; ++i) {
      phases::ID Phase = *i;

      // We are done if this step is past what the user requested.
      if (Phase > FinalPhase)
        break;

      // Queue linker inputs.
      if (Phase == phases::Link) {
        assert((i + 1) == e && "linking must be final compilation step.");
        LinkerInputs.push_back(Current.release());
        break;
      }

      // Some types skip the assembler phase (e.g., llvm-bc), but we can't
      // encode this in the steps because the intermediate type depends on
      // arguments. Just special case here.
      if (Phase == phases::Assemble && Current->getType() != types::TY_PP_Asm)
        continue;

      // Otherwise construct the appropriate action.
      Current = ConstructPhaseAction(TC, Args, Phase, std::move(Current));
      if (Current->getType() == types::TY_Nothing)
        break;
    }

    // If we ended with something, add to the output list.
    if (Current)
      Actions.push_back(Current.release());
  }

  // Add a link action if necessary.
  if (!LinkerInputs.empty())
    Actions.push_back(new LinkJobAction(LinkerInputs, types::TY_Image));

  // If we are linking, claim any options which are obviously only used for
  // compilation.
  if (FinalPhase == phases::Link && PL.size() == 1) {
    Args.ClaimAllArgs(options::OPT_CompileOnly_Group);
    Args.ClaimAllArgs(options::OPT_cl_compile_Group);
  }

  // Claim ignored clang-cl options.
  Args.ClaimAllArgs(options::OPT_cl_ignored_Group);
}

std::unique_ptr<Action>
Driver::ConstructPhaseAction(const ToolChain &TC, const ArgList &Args,
                             phases::ID Phase,
                             std::unique_ptr<Action> Input) const {
  llvm::PrettyStackTraceString CrashInfo("Constructing phase actions");
  // Build the appropriate action.
  switch (Phase) {
  case phases::Link: llvm_unreachable("link action invalid here.");
  case phases::Preprocess: {
    types::ID OutputTy;
    // -{M, MM} alter the output type.
    if (Args.hasArg(options::OPT_M, options::OPT_MM)) {
      OutputTy = types::TY_Dependencies;
    } else {
      OutputTy = Input->getType();
      if (!Args.hasFlag(options::OPT_frewrite_includes,
                        options::OPT_fno_rewrite_includes, false) &&
          !CCGenDiagnostics)
        OutputTy = types::getPreprocessedType(OutputTy);
      assert(OutputTy != types::TY_INVALID &&
             "Cannot preprocess this input type!");
    }
    return llvm::make_unique<PreprocessJobAction>(std::move(Input), OutputTy);
  }
  case phases::Precompile: {
    types::ID OutputTy = types::TY_PCH;
    if (Args.hasArg(options::OPT_fsyntax_only)) {
      // Syntax checks should not emit a PCH file
      OutputTy = types::TY_Nothing;
    }
    return llvm::make_unique<PrecompileJobAction>(std::move(Input), OutputTy);
  }
  case phases::Compile: {
    if (Args.hasArg(options::OPT_fsyntax_only))
      return llvm::make_unique<CompileJobAction>(std::move(Input),
                                                 types::TY_Nothing);
    if (Args.hasArg(options::OPT_rewrite_objc))
      return llvm::make_unique<CompileJobAction>(std::move(Input),
                                                 types::TY_RewrittenObjC);
    if (Args.hasArg(options::OPT_rewrite_legacy_objc))
      return llvm::make_unique<CompileJobAction>(std::move(Input),
                                                 types::TY_RewrittenLegacyObjC);
    if (Args.hasArg(options::OPT__analyze, options::OPT__analyze_auto))
      return llvm::make_unique<AnalyzeJobAction>(std::move(Input),
                                                 types::TY_Plist);
    if (Args.hasArg(options::OPT__migrate))
      return llvm::make_unique<MigrateJobAction>(std::move(Input),
                                                 types::TY_Remap);
    if (Args.hasArg(options::OPT_emit_ast))
      return llvm::make_unique<CompileJobAction>(std::move(Input),
                                                 types::TY_AST);
    if (Args.hasArg(options::OPT_module_file_info))
      return llvm::make_unique<CompileJobAction>(std::move(Input),
                                                 types::TY_ModuleFile);
    if (Args.hasArg(options::OPT_verify_pch))
      return llvm::make_unique<VerifyPCHJobAction>(std::move(Input),
                                                   types::TY_Nothing);
    return llvm::make_unique<CompileJobAction>(std::move(Input),
                                               types::TY_LLVM_BC);
  }
  case phases::Backend: {
    if (IsUsingLTO(Args)) {
      types::ID Output =
        Args.hasArg(options::OPT_S) ? types::TY_LTO_IR : types::TY_LTO_BC;
      return llvm::make_unique<BackendJobAction>(std::move(Input), Output);
    }
    if (Args.hasArg(options::OPT_emit_llvm)) {
      types::ID Output =
        Args.hasArg(options::OPT_S) ? types::TY_LLVM_IR : types::TY_LLVM_BC;
      return llvm::make_unique<BackendJobAction>(std::move(Input), Output);
    }
    return llvm::make_unique<BackendJobAction>(std::move(Input),
                                               types::TY_PP_Asm);
  }
  case phases::Assemble:
    return llvm::make_unique<AssembleJobAction>(std::move(Input),
                                                types::TY_Object);
  }

  llvm_unreachable("invalid phase in ConstructPhaseAction");
}

bool Driver::IsUsingLTO(const ArgList &Args) const {
  return Args.hasFlag(options::OPT_flto, options::OPT_fno_lto, false);
}

void Driver::BuildJobs(Compilation &C) const {
  llvm::PrettyStackTraceString CrashInfo("Building compilation jobs");

  Arg *FinalOutput = C.getArgs().getLastArg(options::OPT_o);

  // It is an error to provide a -o option if we are making multiple output
  // files.
  if (FinalOutput) {
    unsigned NumOutputs = 0;
    for (const Action *A : C.getActions())
      if (A->getType() != types::TY_Nothing)
        ++NumOutputs;

    if (NumOutputs > 1) {
      Diag(clang::diag::err_drv_output_argument_with_multiple_files);
      FinalOutput = nullptr;
    }
  }

  // Collect the list of architectures.
  llvm::StringSet<> ArchNames;
  if (C.getDefaultToolChain().getTriple().isOSBinFormatMachO())
    for (const Arg *A : C.getArgs())
      if (A->getOption().matches(options::OPT_arch))
        ArchNames.insert(A->getValue());

  for (Action *A : C.getActions()) {
    // If we are linking an image for multiple archs then the linker wants
    // -arch_multiple and -final_output <final image name>. Unfortunately, this
    // doesn't fit in cleanly because we have to pass this information down.
    //
    // FIXME: This is a hack; find a cleaner way to integrate this into the
    // process.
    const char *LinkingOutput = nullptr;
    if (isa<LipoJobAction>(A)) {
      if (FinalOutput)
        LinkingOutput = FinalOutput->getValue();
      else
        LinkingOutput = getDefaultImageName();
    }

    InputInfo II;
    BuildJobsForAction(C, A, &C.getDefaultToolChain(),
                       /*BoundArch*/nullptr,
                       /*AtTopLevel*/ true,
                       /*MultipleArchs*/ ArchNames.size() > 1,
                       /*LinkingOutput*/ LinkingOutput,
                       II);
  }

  // If the user passed -Qunused-arguments or there were errors, don't warn
  // about any unused arguments.
  if (Diags.hasErrorOccurred() ||
      C.getArgs().hasArg(options::OPT_Qunused_arguments))
    return;

  // Claim -### here.
  (void) C.getArgs().hasArg(options::OPT__HASH_HASH_HASH);

  // Claim --driver-mode, it was handled earlier.
  (void) C.getArgs().hasArg(options::OPT_driver_mode);

  for (Arg *A : C.getArgs()) {
    // FIXME: It would be nice to be able to send the argument to the
    // DiagnosticsEngine, so that extra values, position, and so on could be
    // printed.
    if (!A->isClaimed()) {
      if (A->getOption().hasFlag(options::NoArgumentUnused))
        continue;

      // Suppress the warning automatically if this is just a flag, and it is an
      // instance of an argument we already claimed.
      const Option &Opt = A->getOption();
      if (Opt.getKind() == Option::FlagClass) {
        bool DuplicateClaimed = false;

        for (const Arg *AA : C.getArgs().filtered(&Opt)) {
          if (AA->isClaimed()) {
            DuplicateClaimed = true;
            break;
          }
        }

        if (DuplicateClaimed)
          continue;
      }

      Diag(clang::diag::warn_drv_unused_argument)
        << A->getAsString(C.getArgs());
    }
  }
}

static const Tool *SelectToolForJob(Compilation &C, bool SaveTemps,
                                    const ToolChain *TC, const JobAction *JA,
                                    const ActionList *&Inputs) {
  const Tool *ToolForJob = nullptr;

  // See if we should look for a compiler with an integrated assembler. We match
  // bottom up, so what we are actually looking for is an assembler job with a
  // compiler input.

  if (TC->useIntegratedAs() &&
      !SaveTemps &&
      !C.getArgs().hasArg(options::OPT_via_file_asm) &&
      !C.getArgs().hasArg(options::OPT__SLASH_FA) &&
      !C.getArgs().hasArg(options::OPT__SLASH_Fa) &&
      isa<AssembleJobAction>(JA) &&
      Inputs->size() == 1 && isa<BackendJobAction>(*Inputs->begin())) {
    // A BackendJob is always preceded by a CompileJob, and without
    // -save-temps they will always get combined together, so instead of
    // checking the backend tool, check if the tool for the CompileJob
    // has an integrated assembler.
    const ActionList *BackendInputs = &(*Inputs)[0]->getInputs();
    JobAction *CompileJA = cast<CompileJobAction>(*BackendInputs->begin());
    const Tool *Compiler = TC->SelectTool(*CompileJA);
    if (!Compiler)
      return nullptr;
    if (Compiler->hasIntegratedAssembler()) {
      Inputs = &(*BackendInputs)[0]->getInputs();
      ToolForJob = Compiler;
    }
  }

  // A backend job should always be combined with the preceding compile job
  // unless OPT_save_temps is enabled and the compiler is capable of emitting
  // LLVM IR as an intermediate output.
  if (isa<BackendJobAction>(JA)) {
    // Check if the compiler supports emitting LLVM IR.
    assert(Inputs->size() == 1);
    JobAction *CompileJA = cast<CompileJobAction>(*Inputs->begin());
    const Tool *Compiler = TC->SelectTool(*CompileJA);
    if (!Compiler)
      return nullptr;
    if (!Compiler->canEmitIR() || !SaveTemps) {
      Inputs = &(*Inputs)[0]->getInputs();
      ToolForJob = Compiler;
    }
  }

  // Otherwise use the tool for the current job.
  if (!ToolForJob)
    ToolForJob = TC->SelectTool(*JA);

  // See if we should use an integrated preprocessor. We do so when we have
  // exactly one input, since this is the only use case we care about
  // (irrelevant since we don't support combine yet).
  if (Inputs->size() == 1 && isa<PreprocessJobAction>(*Inputs->begin()) &&
      !C.getArgs().hasArg(options::OPT_no_integrated_cpp) &&
      !C.getArgs().hasArg(options::OPT_traditional_cpp) &&
      !SaveTemps &&
      !C.getArgs().hasArg(options::OPT_rewrite_objc) &&
      ToolForJob->hasIntegratedCPP())
    Inputs = &(*Inputs)[0]->getInputs();

  return ToolForJob;
}

void Driver::BuildJobsForAction(Compilation &C,
                                const Action *A,
                                const ToolChain *TC,
                                const char *BoundArch,
                                bool AtTopLevel,
                                bool MultipleArchs,
                                const char *LinkingOutput,
                                InputInfo &Result) const {
  llvm::PrettyStackTraceString CrashInfo("Building compilation jobs");

  if (const InputAction *IA = dyn_cast<InputAction>(A)) {
    // FIXME: It would be nice to not claim this here; maybe the old scheme of
    // just using Args was better?
    const Arg &Input = IA->getInputArg();
    Input.claim();
    if (Input.getOption().matches(options::OPT_INPUT)) {
      const char *Name = Input.getValue();
      Result = InputInfo(Name, A->getType(), Name);
    } else {
      Result = InputInfo(&Input, A->getType(), "");
    }
    return;
  }

  if (const BindArchAction *BAA = dyn_cast<BindArchAction>(A)) {
    const ToolChain *TC;
    const char *ArchName = BAA->getArchName();

    if (ArchName)
      TC = &getToolChain(C.getArgs(), ArchName);
    else
      TC = &C.getDefaultToolChain();

    BuildJobsForAction(C, *BAA->begin(), TC, BAA->getArchName(),
                       AtTopLevel, MultipleArchs, LinkingOutput, Result);
    return;
  }

  const ActionList *Inputs = &A->getInputs();

  const JobAction *JA = cast<JobAction>(A);
  const Tool *T = SelectToolForJob(C, isSaveTempsEnabled(), TC, JA, Inputs);
  if (!T)
    return;

  // Only use pipes when there is exactly one input.
  InputInfoList InputInfos;
  for (const Action *Input : *Inputs) {
    // Treat dsymutil and verify sub-jobs as being at the top-level too, they
    // shouldn't get temporary output names.
    // FIXME: Clean this up.
    bool SubJobAtTopLevel = false;
    if (AtTopLevel && (isa<DsymutilJobAction>(A) || isa<VerifyJobAction>(A)))
      SubJobAtTopLevel = true;

    InputInfo II;
    BuildJobsForAction(C, Input, TC, BoundArch, SubJobAtTopLevel, MultipleArchs,
                       LinkingOutput, II);
    InputInfos.push_back(II);
  }

  // Always use the first input as the base input.
  const char *BaseInput = InputInfos[0].getBaseInput();

  // ... except dsymutil actions, which use their actual input as the base
  // input.
  if (JA->getType() == types::TY_dSYM)
    BaseInput = InputInfos[0].getFilename();

  // Determine the place to write output to, if any.
  if (JA->getType() == types::TY_Nothing)
    Result = InputInfo(A->getType(), BaseInput);
  else
    Result = InputInfo(GetNamedOutputPath(C, *JA, BaseInput, BoundArch,
                                          AtTopLevel, MultipleArchs),
                       A->getType(), BaseInput);

  if (CCCPrintBindings && !CCGenDiagnostics) {
    llvm::errs() << "# \"" << T->getToolChain().getTripleString() << '"'
                 << " - \"" << T->getName() << "\", inputs: [";
    for (unsigned i = 0, e = InputInfos.size(); i != e; ++i) {
      llvm::errs() << InputInfos[i].getAsString();
      if (i + 1 != e)
        llvm::errs() << ", ";
    }
    llvm::errs() << "], output: " << Result.getAsString() << "\n";
  } else {
    T->ConstructJob(C, *JA, Result, InputInfos,
                    C.getArgsForToolChain(TC, BoundArch), LinkingOutput);
  }
}

const char *Driver::getDefaultImageName() const {
  llvm::Triple Target(llvm::Triple::normalize(DefaultTargetTriple));
  return Target.isOSWindows() ? "a.exe" : "a.out";
}

/// \brief Create output filename based on ArgValue, which could either be a
/// full filename, filename without extension, or a directory. If ArgValue
/// does not provide a filename, then use BaseName, and use the extension
/// suitable for FileType.
static const char *MakeCLOutputFilename(const ArgList &Args, StringRef ArgValue,
                                        StringRef BaseName, types::ID FileType) {
  SmallString<128> Filename = ArgValue;

  if (ArgValue.empty()) {
    // If the argument is empty, output to BaseName in the current dir.
    Filename = BaseName;
  } else if (llvm::sys::path::is_separator(Filename.back())) {
    // If the argument is a directory, output to BaseName in that dir.
    llvm::sys::path::append(Filename, BaseName);
  }

  if (!llvm::sys::path::has_extension(ArgValue)) {
    // If the argument didn't provide an extension, then set it.
    const char *Extension = types::getTypeTempSuffix(FileType, true);

    if (FileType == types::TY_Image &&
        Args.hasArg(options::OPT__SLASH_LD, options::OPT__SLASH_LDd)) {
      // The output file is a dll.
      Extension = "dll";
    }

    llvm::sys::path::replace_extension(Filename, Extension);
  }

  return Args.MakeArgString(Filename.c_str());
}

const char *Driver::GetNamedOutputPath(Compilation &C,
                                       const JobAction &JA,
                                       const char *BaseInput,
                                       const char *BoundArch,
                                       bool AtTopLevel,
                                       bool MultipleArchs) const {
  llvm::PrettyStackTraceString CrashInfo("Computing output path");
  // Output to a user requested destination?
  if (AtTopLevel && !isa<DsymutilJobAction>(JA) &&
      !isa<VerifyJobAction>(JA)) {
    if (Arg *FinalOutput = C.getArgs().getLastArg(options::OPT_o))
      return C.addResultFile(FinalOutput->getValue(), &JA);
  }

  // For /P, preprocess to file named after BaseInput.
  if (C.getArgs().hasArg(options::OPT__SLASH_P)) {
    assert(AtTopLevel && isa<PreprocessJobAction>(JA));
    StringRef BaseName = llvm::sys::path::filename(BaseInput);
    StringRef NameArg;
    if (Arg *A = C.getArgs().getLastArg(options::OPT__SLASH_Fi))
      NameArg = A->getValue();
    return C.addResultFile(MakeCLOutputFilename(C.getArgs(), NameArg, BaseName,
                                                types::TY_PP_C), &JA);
  }

  // Default to writing to stdout?
  if (AtTopLevel && !CCGenDiagnostics &&
      (isa<PreprocessJobAction>(JA) || JA.getType() == types::TY_ModuleFile))
    return "-";

  // Is this the assembly listing for /FA?
  if (JA.getType() == types::TY_PP_Asm &&
      (C.getArgs().hasArg(options::OPT__SLASH_FA) ||
       C.getArgs().hasArg(options::OPT__SLASH_Fa))) {
    // Use /Fa and the input filename to determine the asm file name.
    StringRef BaseName = llvm::sys::path::filename(BaseInput);
    StringRef FaValue = C.getArgs().getLastArgValue(options::OPT__SLASH_Fa);
    return C.addResultFile(MakeCLOutputFilename(C.getArgs(), FaValue, BaseName,
                                                JA.getType()), &JA);
  }

  // Output to a temporary file?
  if ((!AtTopLevel && !isSaveTempsEnabled() &&
        !C.getArgs().hasArg(options::OPT__SLASH_Fo)) ||
      CCGenDiagnostics) {
    StringRef Name = llvm::sys::path::filename(BaseInput);
    std::pair<StringRef, StringRef> Split = Name.split('.');
    std::string TmpName =
      GetTemporaryPath(Split.first,
          types::getTypeTempSuffix(JA.getType(), IsCLMode()));
    return C.addTempFile(C.getArgs().MakeArgString(TmpName.c_str()));
  }

  SmallString<128> BasePath(BaseInput);
  StringRef BaseName;

  // Dsymutil actions should use the full path.
  if (isa<DsymutilJobAction>(JA) || isa<VerifyJobAction>(JA))
    BaseName = BasePath;
  else
    BaseName = llvm::sys::path::filename(BasePath);

  // Determine what the derived output name should be.
  const char *NamedOutput;

  if (JA.getType() == types::TY_Object &&
      C.getArgs().hasArg(options::OPT__SLASH_Fo, options::OPT__SLASH_o)) {
    // The /Fo or /o flag decides the object filename.
    StringRef Val = C.getArgs().getLastArg(options::OPT__SLASH_Fo,
                                           options::OPT__SLASH_o)->getValue();
    NamedOutput = MakeCLOutputFilename(C.getArgs(), Val, BaseName,
                                       types::TY_Object);
  } else if (JA.getType() == types::TY_Image &&
             C.getArgs().hasArg(options::OPT__SLASH_Fe, options::OPT__SLASH_o)) {
    // The /Fe or /o flag names the linked file.
    StringRef Val = C.getArgs().getLastArg(options::OPT__SLASH_Fe,
                                           options::OPT__SLASH_o)->getValue();
    NamedOutput = MakeCLOutputFilename(C.getArgs(), Val, BaseName,
                                       types::TY_Image);
  } else if (JA.getType() == types::TY_Image) {
    if (IsCLMode()) {
      // clang-cl uses BaseName for the executable name.
      NamedOutput = MakeCLOutputFilename(C.getArgs(), "", BaseName,
                                         types::TY_Image);
    } else if (MultipleArchs && BoundArch) {
      SmallString<128> Output(getDefaultImageName());
      Output += "-";
      Output.append(BoundArch);
      NamedOutput = C.getArgs().MakeArgString(Output.c_str());
    } else
      NamedOutput = getDefaultImageName();
  } else {
    const char *Suffix = types::getTypeTempSuffix(JA.getType(), IsCLMode());
    assert(Suffix && "All types used for output should have a suffix.");

    std::string::size_type End = std::string::npos;
    if (!types::appendSuffixForType(JA.getType()))
      End = BaseName.rfind('.');
    SmallString<128> Suffixed(BaseName.substr(0, End));
    if (MultipleArchs && BoundArch) {
      Suffixed += "-";
      Suffixed.append(BoundArch);
    }
    // When using both -save-temps and -emit-llvm, use a ".tmp.bc" suffix for
    // the unoptimized bitcode so that it does not get overwritten by the ".bc"
    // optimized bitcode output.
    if (!AtTopLevel && C.getArgs().hasArg(options::OPT_emit_llvm) &&
        JA.getType() == types::TY_LLVM_BC)
      Suffixed += ".tmp";
    Suffixed += '.';
    Suffixed += Suffix;
    NamedOutput = C.getArgs().MakeArgString(Suffixed.c_str());
  }

  // Prepend object file path if -save-temps=obj
  if (!AtTopLevel && isSaveTempsObj() && C.getArgs().hasArg(options::OPT_o) &&
      JA.getType() != types::TY_PCH) {
    Arg *FinalOutput = C.getArgs().getLastArg(options::OPT_o);
    SmallString<128> TempPath(FinalOutput->getValue());
    llvm::sys::path::remove_filename(TempPath);
    StringRef OutputFileName = llvm::sys::path::filename(NamedOutput);
    llvm::sys::path::append(TempPath, OutputFileName);
    NamedOutput = C.getArgs().MakeArgString(TempPath.c_str());
  }

  // If we're saving temps and the temp file conflicts with the input file,
  // then avoid overwriting input file.
  if (!AtTopLevel && isSaveTempsEnabled() && NamedOutput == BaseName) {
    bool SameFile = false;
    SmallString<256> Result;
    llvm::sys::fs::current_path(Result);
    llvm::sys::path::append(Result, BaseName);
    llvm::sys::fs::equivalent(BaseInput, Result.c_str(), SameFile);
    // Must share the same path to conflict.
    if (SameFile) {
      StringRef Name = llvm::sys::path::filename(BaseInput);
      std::pair<StringRef, StringRef> Split = Name.split('.');
      std::string TmpName =
        GetTemporaryPath(Split.first,
            types::getTypeTempSuffix(JA.getType(), IsCLMode()));
      return C.addTempFile(C.getArgs().MakeArgString(TmpName.c_str()));
    }
  }

  // As an annoying special case, PCH generation doesn't strip the pathname.
  if (JA.getType() == types::TY_PCH) {
    llvm::sys::path::remove_filename(BasePath);
    if (BasePath.empty())
      BasePath = NamedOutput;
    else
      llvm::sys::path::append(BasePath, NamedOutput);
    return C.addResultFile(C.getArgs().MakeArgString(BasePath.c_str()), &JA);
  } else {
    return C.addResultFile(NamedOutput, &JA);
  }
}

std::string Driver::GetFilePath(const char *Name, const ToolChain &TC) const {
  // Respect a limited subset of the '-Bprefix' functionality in GCC by
  // attempting to use this prefix when looking for file paths.
  for (Driver::prefix_list::const_iterator it = PrefixDirs.begin(),
       ie = PrefixDirs.end(); it != ie; ++it) {
    std::string Dir(*it);
    if (Dir.empty())
      continue;
    if (Dir[0] == '=')
      Dir = SysRoot + Dir.substr(1);
    SmallString<128> P(Dir);
    llvm::sys::path::append(P, Name);
    if (llvm::sys::fs::exists(Twine(P)))
      return P.str();
  }

  SmallString<128> P(ResourceDir);
  llvm::sys::path::append(P, Name);
  if (llvm::sys::fs::exists(Twine(P)))
    return P.str();

  const ToolChain::path_list &List = TC.getFilePaths();
  for (ToolChain::path_list::const_iterator
         it = List.begin(), ie = List.end(); it != ie; ++it) {
    std::string Dir(*it);
    if (Dir.empty())
      continue;
    if (Dir[0] == '=')
      Dir = SysRoot + Dir.substr(1);
    SmallString<128> P(Dir);
    llvm::sys::path::append(P, Name);
    if (llvm::sys::fs::exists(Twine(P)))
      return P.str();
  }

  return Name;
}

void
Driver::generatePrefixedToolNames(const char *Tool, const ToolChain &TC,
                                  SmallVectorImpl<std::string> &Names) const {
  // FIXME: Needs a better variable than DefaultTargetTriple
  Names.emplace_back(DefaultTargetTriple + "-" + Tool);
  Names.emplace_back(Tool);
}

static bool ScanDirForExecutable(SmallString<128> &Dir,
                                 ArrayRef<std::string> Names) {
  for (const auto &Name : Names) {
    llvm::sys::path::append(Dir, Name);
    if (llvm::sys::fs::can_execute(Twine(Dir)))
      return true;
    llvm::sys::path::remove_filename(Dir);
  }
  return false;
}

std::string Driver::GetProgramPath(const char *Name,
                                   const ToolChain &TC) const {
  SmallVector<std::string, 2> TargetSpecificExecutables;
  generatePrefixedToolNames(Name, TC, TargetSpecificExecutables);

  // Respect a limited subset of the '-Bprefix' functionality in GCC by
  // attempting to use this prefix when looking for program paths.
  for (const auto &PrefixDir : PrefixDirs) {
    if (llvm::sys::fs::is_directory(PrefixDir)) {
      SmallString<128> P(PrefixDir);
      if (ScanDirForExecutable(P, TargetSpecificExecutables))
        return P.str();
    } else {
      SmallString<128> P(PrefixDir + Name);
      if (llvm::sys::fs::can_execute(Twine(P)))
        return P.str();
    }
  }

  const ToolChain::path_list &List = TC.getProgramPaths();
  for (const auto &Path : List) {
    SmallString<128> P(Path);
    if (ScanDirForExecutable(P, TargetSpecificExecutables))
      return P.str();
  }

  // If all else failed, search the path.
  for (const auto &TargetSpecificExecutable : TargetSpecificExecutables)
    if (llvm::ErrorOr<std::string> P =
            llvm::sys::findProgramByName(TargetSpecificExecutable))
      return *P;

  return Name;
}

std::string Driver::GetTemporaryPath(StringRef Prefix, const char *Suffix)
  const {
  SmallString<128> Path;
  std::error_code EC = llvm::sys::fs::createTemporaryFile(Prefix, Suffix, Path);
  if (EC) {
    Diag(clang::diag::err_unable_to_make_temp) << EC.message();
    return "";
  }

  return Path.str();
}

/// \brief Compute target triple from args.
///
/// This routine provides the logic to compute a target triple from various
/// args passed to the driver and the default triple string.
static llvm::Triple computeTargetTriple(StringRef DefaultTargetTriple,
                                        const ArgList &Args,
                                        StringRef DarwinArchName) {
  // FIXME: Already done in Compilation *Driver::BuildCompilation
  if (const Arg *A = Args.getLastArg(options::OPT_target))
    DefaultTargetTriple = A->getValue();

  llvm::Triple Target(llvm::Triple::normalize(DefaultTargetTriple));

  // Handle Apple-specific options available here.
  if (Target.isOSBinFormatMachO()) {
    // If an explict Darwin arch name is given, that trumps all.
    if (!DarwinArchName.empty()) {
      tools::darwin::setTripleTypeForMachOArchName(Target, DarwinArchName);
      return Target;
    }

    // Handle the Darwin '-arch' flag.
    if (Arg *A = Args.getLastArg(options::OPT_arch)) {
      StringRef ArchName = A->getValue();
      tools::darwin::setTripleTypeForMachOArchName(Target, ArchName);
    }
  }

  // Handle pseudo-target flags '-mlittle-endian'/'-EL' and
  // '-mbig-endian'/'-EB'.
  if (Arg *A = Args.getLastArg(options::OPT_mlittle_endian,
                               options::OPT_mbig_endian)) {
    if (A->getOption().matches(options::OPT_mlittle_endian)) {
      if (Target.getArch() == llvm::Triple::mips)
        Target.setArch(llvm::Triple::mipsel);
      else if (Target.getArch() == llvm::Triple::mips64)
        Target.setArch(llvm::Triple::mips64el);
      else if (Target.getArch() == llvm::Triple::aarch64_be)
        Target.setArch(llvm::Triple::aarch64);
    } else {
      if (Target.getArch() == llvm::Triple::mipsel)
        Target.setArch(llvm::Triple::mips);
      else if (Target.getArch() == llvm::Triple::mips64el)
        Target.setArch(llvm::Triple::mips64);
      else if (Target.getArch() == llvm::Triple::aarch64)
        Target.setArch(llvm::Triple::aarch64_be);
    }
  }

  // Skip further flag support on OSes which don't support '-m32' or '-m64'.
  if (Target.getArchName() == "tce" || Target.getOS() == llvm::Triple::Minix)
    return Target;

  // Handle pseudo-target flags '-m64', '-mx32', '-m32' and '-m16'.
  if (Arg *A = Args.getLastArg(options::OPT_m64, options::OPT_mx32,
                               options::OPT_m32, options::OPT_m16)) {
    llvm::Triple::ArchType AT = llvm::Triple::UnknownArch;

    if (A->getOption().matches(options::OPT_m64)) {
      AT = Target.get64BitArchVariant().getArch();
      if (Target.getEnvironment() == llvm::Triple::GNUX32)
        Target.setEnvironment(llvm::Triple::GNU);
    } else if (A->getOption().matches(options::OPT_mx32) &&
             Target.get64BitArchVariant().getArch() == llvm::Triple::x86_64) {
      AT = llvm::Triple::x86_64;
      Target.setEnvironment(llvm::Triple::GNUX32);
    } else if (A->getOption().matches(options::OPT_m32)) {
      AT = Target.get32BitArchVariant().getArch();
      if (Target.getEnvironment() == llvm::Triple::GNUX32)
        Target.setEnvironment(llvm::Triple::GNU);
    } else if (A->getOption().matches(options::OPT_m16) &&
             Target.get32BitArchVariant().getArch() == llvm::Triple::x86) {
      AT = llvm::Triple::x86;
      Target.setEnvironment(llvm::Triple::CODE16);
    }

    if (AT != llvm::Triple::UnknownArch && AT != Target.getArch())
      Target.setArch(AT);
  }

  return Target;
}

const ToolChain &Driver::getToolChain(const ArgList &Args,
                                      StringRef DarwinArchName) const {
  llvm::Triple Target =
      computeTargetTriple(DefaultTargetTriple, Args, DarwinArchName);

  ToolChain *&TC = ToolChains[Target.str()];
  if (!TC) {
    switch (Target.getOS()) {
    case llvm::Triple::CloudABI:
      TC = new toolchains::CloudABI(*this, Target, Args);
      break;
    case llvm::Triple::Darwin:
    case llvm::Triple::MacOSX:
    case llvm::Triple::IOS:
      TC = new toolchains::DarwinClang(*this, Target, Args);
      break;
    case llvm::Triple::DragonFly:
      TC = new toolchains::DragonFly(*this, Target, Args);
      break;
    case llvm::Triple::OpenBSD:
      TC = new toolchains::OpenBSD(*this, Target, Args);
      break;
    case llvm::Triple::Bitrig:
      TC = new toolchains::Bitrig(*this, Target, Args);
      break;
    case llvm::Triple::NetBSD:
      TC = new toolchains::NetBSD(*this, Target, Args);
      break;
    case llvm::Triple::FreeBSD:
      TC = new toolchains::FreeBSD(*this, Target, Args);
      break;
    case llvm::Triple::Minix:
      TC = new toolchains::Minix(*this, Target, Args);
      break;
    case llvm::Triple::Linux:
      if (Target.getArch() == llvm::Triple::hexagon)
        TC = new toolchains::Hexagon_TC(*this, Target, Args);
      else
        TC = new toolchains::Linux(*this, Target, Args);
      break;
    case llvm::Triple::NaCl:
      TC = new toolchains::NaCl_TC(*this, Target, Args);
      break;
    case llvm::Triple::Solaris:
      TC = new toolchains::Solaris(*this, Target, Args);
      break;
    case llvm::Triple::Win32:
      switch (Target.getEnvironment()) {
      default:
        if (Target.isOSBinFormatELF())
          TC = new toolchains::Generic_ELF(*this, Target, Args);
        else if (Target.isOSBinFormatMachO())
          TC = new toolchains::MachO(*this, Target, Args);
        else
          TC = new toolchains::Generic_GCC(*this, Target, Args);
        break;
      case llvm::Triple::GNU:
        // FIXME: We need a MinGW toolchain.  Use the default Generic_GCC
        // toolchain for now as the default case would below otherwise.
        if (Target.isOSBinFormatELF())
          TC = new toolchains::Generic_ELF(*this, Target, Args);
        else
          TC = new toolchains::Generic_GCC(*this, Target, Args);
        break;
      case llvm::Triple::Itanium:
        TC = new toolchains::CrossWindowsToolChain(*this, Target, Args);
        break;
      case llvm::Triple::MSVC:
      case llvm::Triple::UnknownEnvironment:
        TC = new toolchains::MSVCToolChain(*this, Target, Args);
        break;
      }
      break;
    default:
      // Of these targets, Hexagon is the only one that might have
      // an OS of Linux, in which case it got handled above already.
      if (Target.getArchName() == "tce")
        TC = new toolchains::TCEToolChain(*this, Target, Args);
      else if (Target.getArch() == llvm::Triple::hexagon)
        TC = new toolchains::Hexagon_TC(*this, Target, Args);
      else if (Target.getArch() == llvm::Triple::xcore)
        TC = new toolchains::XCore(*this, Target, Args);
      else if (Target.getArch() == llvm::Triple::shave)
        TC = new toolchains::SHAVEToolChain(*this, Target, Args);
      else if (Target.isOSBinFormatELF())
        TC = new toolchains::Generic_ELF(*this, Target, Args);
      else if (Target.isOSBinFormatMachO())
        TC = new toolchains::MachO(*this, Target, Args);
      else
        TC = new toolchains::Generic_GCC(*this, Target, Args);
      break;
    }
  }
  return *TC;
}

bool Driver::ShouldUseClangCompiler(const JobAction &JA) const {
  // Say "no" if there is not exactly one input of a type clang understands.
  if (JA.size() != 1 ||
      !types::isAcceptedByClang((*JA.begin())->getType()))
    return false;

  // And say "no" if this is not a kind of action clang understands.
  if (!isa<PreprocessJobAction>(JA) && !isa<PrecompileJobAction>(JA) &&
      !isa<CompileJobAction>(JA) && !isa<BackendJobAction>(JA))
    return false;

  return true;
}

/// GetReleaseVersion - Parse (([0-9]+)(.([0-9]+)(.([0-9]+)?))?)? and return the
/// grouped values as integers. Numbers which are not provided are set to 0.
///
/// \return True if the entire string was parsed (9.2), or all groups were
/// parsed (10.3.5extrastuff).
bool Driver::GetReleaseVersion(const char *Str, unsigned &Major,
                               unsigned &Minor, unsigned &Micro,
                               bool &HadExtra) {
  HadExtra = false;

  Major = Minor = Micro = 0;
  if (*Str == '\0')
    return false;

  char *End;
  Major = (unsigned) strtol(Str, &End, 10);
  if (*Str != '\0' && *End == '\0')
    return true;
  if (*End != '.')
    return false;

  Str = End+1;
  Minor = (unsigned) strtol(Str, &End, 10);
  if (*Str != '\0' && *End == '\0')
    return true;
  if (*End != '.')
    return false;

  Str = End+1;
  Micro = (unsigned) strtol(Str, &End, 10);
  if (*Str != '\0' && *End == '\0')
    return true;
  if (Str == End)
    return false;
  HadExtra = true;
  return true;
}

std::pair<unsigned, unsigned> Driver::getIncludeExcludeOptionFlagMasks() const {
  unsigned IncludedFlagsBitmask = 0;
  unsigned ExcludedFlagsBitmask = options::NoDriverOption;

  if (Mode == CLMode) {
    // Include CL and Core options.
    IncludedFlagsBitmask |= options::CLOption;
    IncludedFlagsBitmask |= options::CoreOption;
  } else {
    ExcludedFlagsBitmask |= options::CLOption;
  }

  return std::make_pair(IncludedFlagsBitmask, ExcludedFlagsBitmask);
}

bool clang::driver::isOptimizationLevelFast(const ArgList &Args) {
  return Args.hasFlag(options::OPT_Ofast, options::OPT_O_Group, false);
}