llvm-project/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 "clang/Driver/Action.h"
#include "clang/Driver/Arg.h"
#include "clang/Driver/ArgList.h"
#include "clang/Driver/Compilation.h"
#include "clang/Driver/DriverDiagnostic.h"
#include "clang/Driver/HostInfo.h"
#include "clang/Driver/Job.h"
#include "clang/Driver/OptTable.h"
#include "clang/Driver/Option.h"
#include "clang/Driver/Options.h"
#include "clang/Driver/Tool.h"
#include "clang/Driver/ToolChain.h"
#include "clang/Driver/Types.h"

#include "clang/Basic/Version.h"

#include "llvm/ADT/StringSet.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/Support/PrettyStackTrace.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/System/Path.h"
#include "llvm/System/Program.h"

#include "InputInfo.h"

#include <map>

using namespace clang::driver;
using namespace clang;

// Used to set values for "production" clang, for releases.
// #define USE_PRODUCTION_CLANG

Driver::Driver(llvm::StringRef _Name, llvm::StringRef _Dir,
               llvm::StringRef _DefaultHostTriple,
               llvm::StringRef _DefaultImageName,
               bool IsProduction, bool CXXIsProduction,
               Diagnostic &_Diags)
  : Opts(createDriverOptTable()), Diags(_Diags),
    Name(_Name), Dir(_Dir), DefaultHostTriple(_DefaultHostTriple),
    DefaultImageName(_DefaultImageName),
    DriverTitle("clang \"gcc-compatible\" driver"),
    Host(0),
    CCCGenericGCCName("gcc"), CCPrintOptionsFilename(0), CCCIsCXX(false),
    CCCEcho(false), CCCPrintBindings(false), CCPrintOptions(false),
    CheckInputsExist(true), CCCUseClang(true), CCCUseClangCXX(true),
    CCCUseClangCPP(true), CCCUsePCH(true), SuppressMissingInputWarning(false) {
  if (IsProduction) {
    // In a "production" build, only use clang on architectures we expect to
    // work, and don't use clang C++.
    //
    // During development its more convenient to always have the driver use
    // clang, but we don't want users to be confused when things don't work, or
    // to file bugs for things we don't support.
    CCCClangArchs.insert(llvm::Triple::x86);
    CCCClangArchs.insert(llvm::Triple::x86_64);
    CCCClangArchs.insert(llvm::Triple::arm);

    if (!CXXIsProduction)
      CCCUseClangCXX = false;
  }

  // Compute the path to the resource directory.
  llvm::sys::Path P(Dir);
  P.eraseComponent(); // Remove /bin from foo/bin
  P.appendComponent("lib");
  P.appendComponent("clang");
  P.appendComponent(CLANG_VERSION_STRING);
  ResourceDir = P.str();
}

Driver::~Driver() {
  delete Opts;
  delete Host;
}

InputArgList *Driver::ParseArgStrings(const char **ArgBegin,
                                      const char **ArgEnd) {
  llvm::PrettyStackTraceString CrashInfo("Command line argument parsing");
  unsigned MissingArgIndex, MissingArgCount;
  InputArgList *Args = getOpts().ParseArgs(ArgBegin, ArgEnd,
                                           MissingArgIndex, MissingArgCount);

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

  // Check for unsupported options.
  for (ArgList::const_iterator it = Args->begin(), ie = Args->end();
       it != ie; ++it) {
    Arg *A = *it;
    if (A->getOption().isUnsupported()) {
      Diag(clang::diag::err_drv_unsupported_opt) << A->getAsString(*Args);
      continue;
    }
  }

  return Args;
}

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

  for (ArgList::const_iterator it = Args.begin(),
         ie = Args.end(); it != ie; ++it) {
    const Arg *A = *it;

    // 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 (llvm::StringRef(A->getValue(Args, i)) != "--no-demangle")
          DAL->AddSeparateArg(A, Opts->getOption(options::OPT_Xlinker),
                              A->getValue(Args, 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->getNumValues() == 2 &&
        (A->getValue(Args, 0) == llvm::StringRef("-MD") ||
         A->getValue(Args, 0) == llvm::StringRef("-MMD"))) {
      // Rewrite to -MD/-MMD along with -MF.
      if (A->getValue(Args, 0) == llvm::StringRef("-MD"))
        DAL->AddFlagArg(A, Opts->getOption(options::OPT_MD));
      else
        DAL->AddFlagArg(A, Opts->getOption(options::OPT_MMD));
      DAL->AddSeparateArg(A, Opts->getOption(options::OPT_MF),
                          A->getValue(Args, 1));
      continue;
    }

    DAL->append(*it);
  }

  return DAL;
}

Compilation *Driver::BuildCompilation(int argc, const char **argv) {
  llvm::PrettyStackTraceString CrashInfo("Compilation construction");

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

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

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

  const char **Start = argv + 1, **End = argv + argc;
  const char *HostTriple = DefaultHostTriple.c_str();

  InputArgList *Args = ParseArgStrings(Start, End);

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

  // 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.
  CCCPrintOptions = Args->hasArg(options::OPT_ccc_print_options);
  CCCPrintActions = Args->hasArg(options::OPT_ccc_print_phases);
  CCCPrintBindings = Args->hasArg(options::OPT_ccc_print_bindings);
  CCCIsCXX = Args->hasArg(options::OPT_ccc_cxx) || CCCIsCXX;
  CCCEcho = Args->hasArg(options::OPT_ccc_echo);
  if (const Arg *A = Args->getLastArg(options::OPT_ccc_gcc_name))
    CCCGenericGCCName = A->getValue(*Args);
  CCCUseClangCXX = Args->hasFlag(options::OPT_ccc_clang_cxx,
                                 options::OPT_ccc_no_clang_cxx,
                                 CCCUseClangCXX);
  CCCUsePCH = Args->hasFlag(options::OPT_ccc_pch_is_pch,
                            options::OPT_ccc_pch_is_pth);
  CCCUseClang = !Args->hasArg(options::OPT_ccc_no_clang);
  CCCUseClangCPP = !Args->hasArg(options::OPT_ccc_no_clang_cpp);
  if (const Arg *A = Args->getLastArg(options::OPT_ccc_clang_archs)) {
    llvm::StringRef Cur = A->getValue(*Args);

    CCCClangArchs.clear();
    while (!Cur.empty()) {
      std::pair<llvm::StringRef, llvm::StringRef> Split = Cur.split(',');

      if (!Split.first.empty()) {
        llvm::Triple::ArchType Arch =
          llvm::Triple(Split.first, "", "").getArch();

        if (Arch == llvm::Triple::UnknownArch)
          Diag(clang::diag::err_drv_invalid_arch_name) << Split.first;

        CCCClangArchs.insert(Arch);
      }

      Cur = Split.second;
    }
  }
  if (const Arg *A = Args->getLastArg(options::OPT_ccc_host_triple))
    HostTriple = A->getValue(*Args);
  if (const Arg *A = Args->getLastArg(options::OPT_ccc_install_dir))
    Dir = A->getValue(*Args);
  if (const Arg *A = Args->getLastArg(options::OPT_B))
    PrefixDir = A->getValue(*Args);

  Host = GetHostInfo(HostTriple);

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

  // The compilation takes ownership of Args.
  Compilation *C = new Compilation(*this, *Host->CreateToolChain(*Args), Args,
                                   TranslatedArgs);

  // FIXME: This behavior shouldn't be here.
  if (CCCPrintOptions) {
    PrintOptions(C->getInputArgs());
    return C;
  }

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

  // Construct the list of abstract actions to perform for this compilation. We
  // avoid passing a Compilation here simply to enforce the abstraction that
  // pipelining is not host or toolchain dependent (other than the driver driver
  // test).
  if (Host->useDriverDriver())
    BuildUniversalActions(C->getArgs(), C->getActions());
  else
    BuildActions(C->getArgs(), C->getActions());

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

  BuildJobs(*C);

  return C;
}

int Driver::ExecuteCompilation(const Compilation &C) const {
  // Just print if -### was present.
  if (C.getArgs().hasArg(options::OPT__HASH_HASH_HASH)) {
    C.PrintJob(llvm::errs(), C.getJobs(), "\n", true);
    return 0;
  }

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

  const Command *FailingCommand = 0;
  int Res = C.ExecuteJob(C.getJobs(), FailingCommand);

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

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

  // Otherwise, remove result files as well.
  if (!C.getArgs().hasArg(options::OPT_save_temps))
    C.CleanupFileList(C.getResultFiles(), 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() << -Res;
    else
      Diag(clang::diag::err_drv_command_failed)
        << FailingTool.getShortName() << Res;
  }

  return Res;
}

void Driver::PrintOptions(const ArgList &Args) const {
  unsigned i = 0;
  for (ArgList::const_iterator it = Args.begin(), ie = Args.end();
       it != ie; ++it, ++i) {
    Arg *A = *it;
    llvm::errs() << "Option " << i << " - "
                 << "Name: \"" << A->getOption().getName() << "\", "
                 << "Values: {";
    for (unsigned j = 0; j < A->getNumValues(); ++j) {
      if (j)
        llvm::errs() << ", ";
      llvm::errs() << '"' << A->getValue(Args, j) << '"';
    }
    llvm::errs() << "}\n";
  }
}

void Driver::PrintHelp(bool ShowHidden) const {
  getOpts().PrintHelp(llvm::outs(), Name.c_str(), DriverTitle.c_str(),
                      ShowHidden);
}

void Driver::PrintVersion(const Compilation &C, llvm::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.
  //
  // FIXME: Implement correctly.
  OS << "Thread model: " << "posix" << '\n';
}

/// PrintDiagnosticCategories - Implement the --print-diagnostic-categories
/// option.
static void PrintDiagnosticCategories(llvm::raw_ostream &OS) {
  for (unsigned i = 1; // Skip the empty category.
       const char *CategoryName = Diagnostic::getCategoryNameFromID(i); ++i)
    OS << i << ',' << CategoryName << '\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_dumpversion)) {
    llvm::outs() << CLANG_VERSION_STRING "\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_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: =";
    for (ToolChain::path_list::const_iterator it = TC.getFilePaths().begin(),
           ie = TC.getFilePaths().end(); it != ie; ++it) {
      if (it != TC.getFilePaths().begin())
        llvm::outs() << ':';
      llvm::outs() << *it;
    }
    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(C.getArgs()), TC) << "\n";
    return false;
  }

  if (Arg *A = C.getArgs().getLastArg(options::OPT_print_prog_name_EQ)) {
    llvm::outs() << GetProgramPath(A->getValue(C.getArgs()), 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)) {
    // FIXME: We need tool chain support for this.
    llvm::outs() << ".;\n";

    switch (C.getDefaultToolChain().getTriple().getArch()) {
    default:
      break;

    case llvm::Triple::x86_64:
      llvm::outs() << "x86_64;@m64" << "\n";
      break;

    case llvm::Triple::ppc64:
      llvm::outs() << "ppc64;@m64" << "\n";
      break;
    }
    return false;
  }

  // FIXME: What is the difference between print-multi-directory and
  // print-multi-os-directory?
  if (C.getArgs().hasArg(options::OPT_print_multi_directory) ||
      C.getArgs().hasArg(options::OPT_print_multi_os_directory)) {
    switch (C.getDefaultToolChain().getTriple().getArch()) {
    default:
    case llvm::Triple::x86:
    case llvm::Triple::ppc:
      llvm::outs() << "." << "\n";
      break;

    case llvm::Triple::x86_64:
      llvm::outs() << "x86_64" << "\n";
      break;

    case llvm::Triple::ppc64:
      llvm::outs() << "ppc64" << "\n";
      break;
    }
    return false;
  }

  return true;
}

static unsigned PrintActions1(const Compilation &C, Action *A,
                              std::map<Action*, unsigned> &Ids) {
  if (Ids.count(A))
    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(C.getArgs()) << "\"";
  } else if (BindArchAction *BIA = dyn_cast<BindArchAction>(A)) {
    os << '"' << (BIA->getArchName() ? BIA->getArchName() :
                  C.getDefaultToolChain().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;
}

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);
}

void Driver::BuildUniversalActions(const ArgList &Args,
                                   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;
  llvm::SmallVector<const char *, 4> Archs;
  for (ArgList::const_iterator it = Args.begin(), ie = Args.end();
       it != ie; ++it) {
    Arg *A = *it;

    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 =
        llvm::Triple::getArchTypeForDarwinArchName(A->getValue(Args));
      if (Arch == llvm::Triple::UnknownArch) {
        Diag(clang::diag::err_drv_invalid_arch_name)
          << A->getAsString(Args);
        continue;
      }

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

  // 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(0);

  // FIXME: We killed off some others but these aren't yet detected in a
  // functional manner. If we added information to jobs about which "auxiliary"
  // files they wrote then we could detect the conflict these cause downstream.
  if (Archs.size() > 1) {
    // No recovery needed, the point of this is just to prevent
    // overwriting the same files.
    if (const Arg *A = Args.getLastArg(options::OPT_save_temps))
      Diag(clang::diag::err_drv_invalid_opt_with_multiple_archs)
        << A->getAsString(Args);
  }

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

    // Add a 'dsymutil' step if necessary.
    if (Act->getType() == types::TY_Image) {
      Arg *A = Args.getLastArg(options::OPT_g_Group);
      if (A && !A->getOption().matches(options::OPT_g0) &&
          !A->getOption().matches(options::OPT_gstabs)) {
        ActionList Inputs;
        Inputs.push_back(Actions.back());
        Actions.pop_back();

        Actions.push_back(new DsymutilJobAction(Inputs, types::TY_dSYM));
      }
    }
  }
}

void Driver::BuildActions(const ArgList &Args, ActionList &Actions) const {
  llvm::PrettyStackTraceString CrashInfo("Building compilation actions");
  // Start by constructing the list of inputs and their types.

  // 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 = 0;

  llvm::SmallVector<std::pair<types::ID, const Arg*>, 16> Inputs;
  for (ArgList::const_iterator it = Args.begin(), ie = Args.end();
       it != ie; ++it) {
    Arg *A = *it;

    if (isa<InputOption>(A->getOption())) {
      const char *Value = A->getValue(Args);
      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))
            Diag(clang::diag::err_drv_unknown_stdin_type);
          Ty = types::TY_C;
        } else {
          // Otherwise lookup by extension, and fallback to ObjectType if not
          // found. 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 = Host->lookupTypeForExtension(Ext + 1);

          if (Ty == types::TY_INVALID)
            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");
        InputTypeArg->claim();
        Ty = InputType;
      }

      // Check that the file exists, if enabled.
      if (CheckInputsExist && memcmp(Value, "-", 2) != 0 &&
          !llvm::sys::Path(Value).exists())
        Diag(clang::diag::err_drv_no_such_file) << A->getValue(Args);
      else
        Inputs.push_back(std::make_pair(Ty, A));

    } else if (A->getOption().isLinkerInput()) {
      // 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(Args));

      // 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 comatible.
      if (!InputType) {
        Diag(clang::diag::err_drv_unknown_language) << A->getValue(Args);
        InputType = types::TY_Object;
      }
    }
  }

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

  // 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.
  Arg *FinalPhaseArg = 0;
  phases::ID FinalPhase;

  // -{E,M,MM} only run the preprocessor.
  if ((FinalPhaseArg = Args.getLastArg(options::OPT_E)) ||
      (FinalPhaseArg = Args.getLastArg(options::OPT_M)) ||
      (FinalPhaseArg = Args.getLastArg(options::OPT_MM))) {
    FinalPhase = phases::Preprocess;

    // -{fsyntax-only,-analyze,emit-ast,S} only run up to the compiler.
  } else if ((FinalPhaseArg = Args.getLastArg(options::OPT_fsyntax_only)) ||
             (FinalPhaseArg = Args.getLastArg(options::OPT_rewrite_objc)) ||
             (FinalPhaseArg = Args.getLastArg(options::OPT__analyze,
                                              options::OPT__analyze_auto)) ||
             (FinalPhaseArg = Args.getLastArg(options::OPT_emit_ast)) ||
             (FinalPhaseArg = Args.getLastArg(options::OPT_S))) {
    FinalPhase = phases::Compile;

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

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

  // Construct the actions to perform.
  ActionList LinkerInputs;
  for (unsigned i = 0, e = Inputs.size(); i != e; ++i) {
    types::ID InputType = Inputs[i].first;
    const Arg *InputArg = Inputs[i].second;

    unsigned NumSteps = types::getNumCompilationPhases(InputType);
    assert(NumSteps && "Invalid number of steps!");

    // 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 = types::getCompilationPhase(InputType, 0);
    if (InitialPhase > FinalPhase) {
      // Claim here to avoid the more general unused warning.
      InputArg->claim();

      // Special case '-E' warning on a previously preprocessed file to make
      // more sense.
      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->getOption().getName();
      else
        Diag(clang::diag::warn_drv_input_file_unused)
          << InputArg->getAsString(Args)
          << getPhaseName(InitialPhase)
          << FinalPhaseArg->getOption().getName();
      continue;
    }

    // Build the pipeline for this file.
    llvm::OwningPtr<Action> Current(new InputAction(*InputArg, InputType));
    for (unsigned i = 0; i != NumSteps; ++i) {
      phases::ID Phase = types::getCompilationPhase(InputType, 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 == NumSteps && "linking must be final compilation step.");
        LinkerInputs.push_back(Current.take());
        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.reset(ConstructPhaseAction(Args, Phase, Current.take()));
      if (Current->getType() == types::TY_Nothing)
        break;
    }

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

  // 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)
    Args.ClaimAllArgs(options::OPT_CompileOnly_Group);
}

Action *Driver::ConstructPhaseAction(const ArgList &Args, phases::ID Phase,
                                     Action *Input) const {
  llvm::PrettyStackTraceString CrashInfo("Constructing phase actions");
  // Build the appropriate action.
  switch (Phase) {
  case phases::Link: assert(0 && "link action invalid here.");
  case phases::Preprocess: {
    types::ID OutputTy;
    // -{M, MM} alter the output type.
    if (Args.hasArg(options::OPT_M) || Args.hasArg(options::OPT_MM)) {
      OutputTy = types::TY_Dependencies;
    } else {
      OutputTy = types::getPreprocessedType(Input->getType());
      assert(OutputTy != types::TY_INVALID &&
             "Cannot preprocess this input type!");
    }
    return new PreprocessJobAction(Input, OutputTy);
  }
  case phases::Precompile:
    return new PrecompileJobAction(Input, types::TY_PCH);
  case phases::Compile: {
    bool HasO4 = false;
    if (const Arg *A = Args.getLastArg(options::OPT_O_Group))
      HasO4 = A->getOption().matches(options::OPT_O4);

    if (Args.hasArg(options::OPT_fsyntax_only)) {
      return new CompileJobAction(Input, types::TY_Nothing);
    } else if (Args.hasArg(options::OPT_rewrite_objc)) {
      return new CompileJobAction(Input, types::TY_RewrittenObjC);
    } else if (Args.hasArg(options::OPT__analyze, options::OPT__analyze_auto)) {
      return new AnalyzeJobAction(Input, types::TY_Plist);
    } else if (Args.hasArg(options::OPT_emit_ast)) {
      return new CompileJobAction(Input, types::TY_AST);
    } else if (Args.hasArg(options::OPT_emit_llvm) ||
               Args.hasArg(options::OPT_flto) || HasO4) {
      types::ID Output =
        Args.hasArg(options::OPT_S) ? types::TY_LTO_IR : types::TY_LTO_BC;
      return new CompileJobAction(Input, Output);
    } else {
      return new CompileJobAction(Input, types::TY_PP_Asm);
    }
  }
  case phases::Assemble:
    return new AssembleJobAction(Input, types::TY_Object);
  }

  assert(0 && "invalid phase in ConstructPhaseAction");
  return 0;
}

void Driver::BuildJobs(Compilation &C) const {
  llvm::PrettyStackTraceString CrashInfo("Building compilation jobs");
  bool SaveTemps = C.getArgs().hasArg(options::OPT_save_temps);
  bool UsePipes = C.getArgs().hasArg(options::OPT_pipe);

  // FIXME: Pipes are forcibly disabled until we support executing them.
  if (!CCCPrintBindings)
    UsePipes = false;

  // -save-temps inhibits pipes.
  if (SaveTemps && UsePipes)
    Diag(clang::diag::warn_drv_pipe_ignored_with_save_temps);

  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 (ActionList::const_iterator it = C.getActions().begin(),
           ie = C.getActions().end(); it != ie; ++it)
      if ((*it)->getType() != types::TY_Nothing)
        ++NumOutputs;

    if (NumOutputs > 1) {
      Diag(clang::diag::err_drv_output_argument_with_multiple_files);
      FinalOutput = 0;
    }
  }

  for (ActionList::const_iterator it = C.getActions().begin(),
         ie = C.getActions().end(); it != ie; ++it) {
    Action *A = *it;

    // 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 = 0;
    if (isa<LipoJobAction>(A)) {
      if (FinalOutput)
        LinkingOutput = FinalOutput->getValue(C.getArgs());
      else
        LinkingOutput = DefaultImageName.c_str();
    }

    InputInfo II;
    BuildJobsForAction(C, A, &C.getDefaultToolChain(),
                       /*BoundArch*/0,
                       /*CanAcceptPipe*/ true,
                       /*AtTopLevel*/ true,
                       /*LinkingOutput*/ LinkingOutput,
                       II);
  }

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

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

  for (ArgList::const_iterator it = C.getArgs().begin(), ie = C.getArgs().end();
       it != ie; ++it) {
    Arg *A = *it;

    // FIXME: It would be nice to be able to send the argument to the
    // Diagnostic, so that extra values, position, and so on could be printed.
    if (!A->isClaimed()) {
      if (A->getOption().hasNoArgumentUnused())
        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 (isa<FlagOption>(Opt)) {
        bool DuplicateClaimed = false;

        for (arg_iterator it = C.getArgs().filtered_begin(&Opt),
               ie = C.getArgs().filtered_end(); it != ie; ++it) {
          if ((*it)->isClaimed()) {
            DuplicateClaimed = true;
            break;
          }
        }

        if (DuplicateClaimed)
          continue;
      }

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

static const Tool &SelectToolForJob(Compilation &C, const ToolChain *TC,
                                    const JobAction *JA,
                                    const ActionList *&Inputs) {
  const Tool *ToolForJob = 0;

  // 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.

  // FIXME: This doesn't belong here, but ideally we will support static soon
  // anyway.
  bool HasStatic = (C.getArgs().hasArg(options::OPT_mkernel) ||
                    C.getArgs().hasArg(options::OPT_static) ||
                    C.getArgs().hasArg(options::OPT_fapple_kext));
  bool IsIADefault = (TC->IsIntegratedAssemblerDefault() && !HasStatic);
  if (C.getArgs().hasFlag(options::OPT_integrated_as,
                         options::OPT_no_integrated_as,
                         IsIADefault) &&
      !C.getArgs().hasArg(options::OPT_save_temps) &&
      isa<AssembleJobAction>(JA) &&
      Inputs->size() == 1 && isa<CompileJobAction>(*Inputs->begin())) {
    const Tool &Compiler = TC->SelectTool(C,cast<JobAction>(**Inputs->begin()));
    if (Compiler.hasIntegratedAssembler()) {
      Inputs = &(*Inputs)[0]->getInputs();
      ToolForJob = &Compiler;
    }
  }

  // Otherwise use the tool for the current job.
  if (!ToolForJob)
    ToolForJob = &TC->SelectTool(C, *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) &&
      !C.getArgs().hasArg(options::OPT_save_temps) &&
      ToolForJob->hasIntegratedCPP())
    Inputs = &(*Inputs)[0]->getInputs();

  return *ToolForJob;
}

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

  bool UsePipes = C.getArgs().hasArg(options::OPT_pipe);
  // FIXME: Pipes are forcibly disabled until we support executing them.
  if (!CCCPrintBindings)
    UsePipes = false;

  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(C.getArgs());
      Result = InputInfo(Name, A->getType(), Name);
    } else
      Result = InputInfo(&Input, A->getType(), "");
    return;
  }

  if (const BindArchAction *BAA = dyn_cast<BindArchAction>(A)) {
    const ToolChain *TC = &C.getDefaultToolChain();

    std::string Arch;
    if (BAA->getArchName())
      TC = Host->CreateToolChain(C.getArgs(), BAA->getArchName());

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

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

  const JobAction *JA = cast<JobAction>(A);
  const Tool &T = SelectToolForJob(C, TC, JA, Inputs);

  // Only use pipes when there is exactly one input.
  bool TryToUsePipeInput = Inputs->size() == 1 && T.acceptsPipedInput();
  InputInfoList InputInfos;
  for (ActionList::const_iterator it = Inputs->begin(), ie = Inputs->end();
       it != ie; ++it) {
    // Treat dsymutil 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))
      SubJobAtTopLevel = true;

    InputInfo II;
    BuildJobsForAction(C, *it, TC, BoundArch, TryToUsePipeInput,
                       SubJobAtTopLevel, LinkingOutput, II);
    InputInfos.push_back(II);
  }

  // Determine if we should output to a pipe.
  bool OutputToPipe = false;
  if (CanAcceptPipe && T.canPipeOutput()) {
    // Some actions default to writing to a pipe if they are the top level phase
    // and there was no user override.
    //
    // FIXME: Is there a better way to handle this?
    if (AtTopLevel) {
      if (isa<PreprocessJobAction>(A) && !C.getArgs().hasArg(options::OPT_o))
        OutputToPipe = true;
    } else if (UsePipes)
      OutputToPipe = true;
  }

  // Figure out where to put the job (pipes).
  Job *Dest = &C.getJobs();
  if (InputInfos[0].isPipe()) {
    assert(TryToUsePipeInput && "Unrequested pipe!");
    assert(InputInfos.size() == 1 && "Unexpected pipe with multiple inputs.");
    Dest = &InputInfos[0].getPipe();
  }

  // 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 (nothing, pipe, or filename) and
  // where to put the new job.
  if (JA->getType() == types::TY_Nothing) {
    Result = InputInfo(A->getType(), BaseInput);
  } else if (OutputToPipe) {
    // Append to current piped job or create a new one as appropriate.
    PipedJob *PJ = dyn_cast<PipedJob>(Dest);
    if (!PJ) {
      PJ = new PipedJob();
      // FIXME: Temporary hack so that -ccc-print-bindings work until we have
      // pipe support. Please remove later.
      if (!CCCPrintBindings)
        cast<JobList>(Dest)->addJob(PJ);
      Dest = PJ;
    }
    Result = InputInfo(PJ, A->getType(), BaseInput);
  } else {
    Result = InputInfo(GetNamedOutputPath(C, *JA, BaseInput, AtTopLevel),
                       A->getType(), BaseInput);
  }

  if (CCCPrintBindings) {
    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, *Dest, Result, InputInfos,
                   C.getArgsForToolChain(TC, BoundArch), LinkingOutput);
  }
}

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

  // Output to a temporary file?
  if (!AtTopLevel && !C.getArgs().hasArg(options::OPT_save_temps)) {
    std::string TmpName =
      GetTemporaryPath(types::getTypeTempSuffix(JA.getType()));
    return C.addTempFile(C.getArgs().MakeArgString(TmpName.c_str()));
  }

  llvm::sys::Path BasePath(BaseInput);
  std::string BaseName(BasePath.getLast());

  // Determine what the derived output name should be.
  const char *NamedOutput;
  if (JA.getType() == types::TY_Image) {
    NamedOutput = DefaultImageName.c_str();
  } else {
    const char *Suffix = types::getTypeTempSuffix(JA.getType());
    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('.');
    std::string Suffixed(BaseName.substr(0, End));
    Suffixed += '.';
    Suffixed += Suffix;
    NamedOutput = C.getArgs().MakeArgString(Suffixed.c_str());
  }

  // As an annoying special case, PCH generation doesn't strip the pathname.
  if (JA.getType() == types::TY_PCH) {
    BasePath.eraseComponent();
    if (BasePath.isEmpty())
      BasePath = NamedOutput;
    else
      BasePath.appendComponent(NamedOutput);
    return C.addResultFile(C.getArgs().MakeArgString(BasePath.c_str()));
  } else {
    return C.addResultFile(NamedOutput);
  }
}

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 lokup up program paths.
  if (!PrefixDir.empty()) {
    llvm::sys::Path P(PrefixDir);
    P.appendComponent(Name);
    if (P.exists())
      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) {
    llvm::sys::Path P(*it);
    P.appendComponent(Name);
    if (P.exists())
      return P.str();
  }

  return Name;
}

std::string Driver::GetProgramPath(const char *Name, const ToolChain &TC,
                                   bool WantFile) const {
  // Respect a limited subset of the '-Bprefix' functionality in GCC by
  // attempting to use this prefix when lokup up program paths.
  if (!PrefixDir.empty()) {
    llvm::sys::Path P(PrefixDir);
    P.appendComponent(Name);
    if (WantFile ? P.exists() : P.canExecute())
      return P.str();
  }

  const ToolChain::path_list &List = TC.getProgramPaths();
  for (ToolChain::path_list::const_iterator
         it = List.begin(), ie = List.end(); it != ie; ++it) {
    llvm::sys::Path P(*it);
    P.appendComponent(Name);
    if (WantFile ? P.exists() : P.canExecute())
      return P.str();
  }

  // If all else failed, search the path.
  llvm::sys::Path P(llvm::sys::Program::FindProgramByName(Name));
  if (!P.empty())
    return P.str();

  return Name;
}

std::string Driver::GetTemporaryPath(const char *Suffix) const {
  // FIXME: This is lame; sys::Path should provide this function (in particular,
  // it should know how to find the temporary files dir).
  std::string Error;
  const char *TmpDir = ::getenv("TMPDIR");
  if (!TmpDir)
    TmpDir = ::getenv("TEMP");
  if (!TmpDir)
    TmpDir = ::getenv("TMP");
  if (!TmpDir)
    TmpDir = "/tmp";
  llvm::sys::Path P(TmpDir);
  P.appendComponent("cc");
  if (P.makeUnique(false, &Error)) {
    Diag(clang::diag::err_drv_unable_to_make_temp) << Error;
    return "";
  }

  // FIXME: Grumble, makeUnique sometimes leaves the file around!?  PR3837.
  P.eraseFromDisk(false, 0);

  P.appendSuffix(Suffix);
  return P.str();
}

const HostInfo *Driver::GetHostInfo(const char *TripleStr) const {
  llvm::PrettyStackTraceString CrashInfo("Constructing host");
  llvm::Triple Triple(TripleStr);

  // TCE is an osless target
  if (Triple.getArchName() == "tce")
    return createTCEHostInfo(*this, Triple);

  switch (Triple.getOS()) {
  case llvm::Triple::AuroraUX:
    return createAuroraUXHostInfo(*this, Triple);
  case llvm::Triple::Darwin:
    return createDarwinHostInfo(*this, Triple);
  case llvm::Triple::DragonFly:
    return createDragonFlyHostInfo(*this, Triple);
  case llvm::Triple::OpenBSD:
    return createOpenBSDHostInfo(*this, Triple);
  case llvm::Triple::FreeBSD:
    return createFreeBSDHostInfo(*this, Triple);
  case llvm::Triple::Linux:
    return createLinuxHostInfo(*this, Triple);
  default:
    return createUnknownHostInfo(*this, Triple);
  }
}

bool Driver::ShouldUseClangCompiler(const Compilation &C, const JobAction &JA,
                                    const llvm::Triple &Triple) const {
  // Check if user requested no clang, or clang doesn't understand this type (we
  // only handle single inputs for now).
  if (!CCCUseClang || JA.size() != 1 ||
      !types::isAcceptedByClang((*JA.begin())->getType()))
    return false;

  // Otherwise make sure this is an action clang understands.
  if (isa<PreprocessJobAction>(JA)) {
    if (!CCCUseClangCPP) {
      Diag(clang::diag::warn_drv_not_using_clang_cpp);
      return false;
    }
  } else if (!isa<PrecompileJobAction>(JA) && !isa<CompileJobAction>(JA))
    return false;

  // Use clang for C++?
  if (!CCCUseClangCXX && types::isCXX((*JA.begin())->getType())) {
    Diag(clang::diag::warn_drv_not_using_clang_cxx);
    return false;
  }

  // Always use clang for precompiling, AST generation, and rewriting,
  // regardless of archs.
  if (isa<PrecompileJobAction>(JA) ||
      types::isOnlyAcceptedByClang(JA.getType()))
    return true;

  // Finally, don't use clang if this isn't one of the user specified archs to
  // build.
  if (!CCCClangArchs.empty() && !CCCClangArchs.count(Triple.getArch())) {
    Diag(clang::diag::warn_drv_not_using_clang_arch) << Triple.getArchName();
    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 true;

  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;
}