std::string
MSVCToolChain::ComputeEffectiveClangTriple(const ArgList &Args,
        types::ID InputType) const {
    std::string TripleStr =
        ToolChain::ComputeEffectiveClangTriple(Args, InputType);
    llvm::Triple Triple(TripleStr);
    VersionTuple MSVT =
        tools::visualstudio::getMSVCVersion(/*D=*/nullptr, *this, Triple, Args,
                /*IsWindowsMSVC=*/true);
    if (MSVT.empty())
        return TripleStr;

    MSVT = VersionTuple(MSVT.getMajor(), MSVT.getMinor().getValueOr(0),
                        MSVT.getSubminor().getValueOr(0));

    if (Triple.getEnvironment() == llvm::Triple::MSVC) {
        StringRef ObjFmt = Triple.getEnvironmentName().split('-').second;
        if (ObjFmt.empty())
            Triple.setEnvironmentName((Twine("msvc") + MSVT.getAsString()).str());
        else
            Triple.setEnvironmentName(
                (Twine("msvc") + MSVT.getAsString() + Twine('-') + ObjFmt).str());
    }
    return Triple.getTriple();
}

VersionTuple
ToolChain::computeMSVCVersion(const Driver *D,
                              const llvm::opt::ArgList &Args) const {
  const Arg *MSCVersion = Args.getLastArg(options::OPT_fmsc_version);
  const Arg *MSCompatibilityVersion =
      Args.getLastArg(options::OPT_fms_compatibility_version);

  if (MSCVersion && MSCompatibilityVersion) {
    if (D)
      D->Diag(diag::err_drv_argument_not_allowed_with)
          << MSCVersion->getAsString(Args)
          << MSCompatibilityVersion->getAsString(Args);
    return VersionTuple();
  }

  if (MSCompatibilityVersion) {
    VersionTuple MSVT;
    if (MSVT.tryParse(MSCompatibilityVersion->getValue())) {
      if (D)
        D->Diag(diag::err_drv_invalid_value)
            << MSCompatibilityVersion->getAsString(Args)
            << MSCompatibilityVersion->getValue();
    } else {
      return MSVT;
    }
  }

  if (MSCVersion) {
    unsigned Version = 0;
    if (StringRef(MSCVersion->getValue()).getAsInteger(10, Version)) {
      if (D)
        D->Diag(diag::err_drv_invalid_value)
            << MSCVersion->getAsString(Args) << MSCVersion->getValue();
    } else {
      return separateMSVCFullVersion(Version);
    }
  }

  return VersionTuple();
}

static void InitializePredefinedMacros(const TargetInfo &TI,
                                       const LangOptions &LangOpts,
                                       const FrontendOptions &FEOpts,
                                       MacroBuilder &Builder) {
  // Compiler version introspection macros.
  Builder.defineMacro("__llvm__");  // LLVM Backend
  Builder.defineMacro("__clang__"); // Clang Frontend
#define TOSTR2(X) #X
#define TOSTR(X) TOSTR2(X)
  Builder.defineMacro("__clang_major__", TOSTR(CLANG_VERSION_MAJOR));
  Builder.defineMacro("__clang_minor__", TOSTR(CLANG_VERSION_MINOR));
#ifdef CLANG_VERSION_PATCHLEVEL
  Builder.defineMacro("__clang_patchlevel__", TOSTR(CLANG_VERSION_PATCHLEVEL));
#else
  Builder.defineMacro("__clang_patchlevel__", "0");
#endif
  Builder.defineMacro("__clang_version__", 
                      "\"" CLANG_VERSION_STRING " "
                      + getClangFullRepositoryVersion() + "\"");
#undef TOSTR
#undef TOSTR2
  if (!LangOpts.MSVCCompat) {
    // Currently claim to be compatible with GCC 4.2.1-5621, but only if we're
    // not compiling for MSVC compatibility
    Builder.defineMacro("__GNUC_MINOR__", "2");
    Builder.defineMacro("__GNUC_PATCHLEVEL__", "1");
    Builder.defineMacro("__GNUC__", "4");
    Builder.defineMacro("__GXX_ABI_VERSION", "1002");
  }

  // Define macros for the C11 / C++11 memory orderings
  Builder.defineMacro("__ATOMIC_RELAXED", "0");
  Builder.defineMacro("__ATOMIC_CONSUME", "1");
  Builder.defineMacro("__ATOMIC_ACQUIRE", "2");
  Builder.defineMacro("__ATOMIC_RELEASE", "3");
  Builder.defineMacro("__ATOMIC_ACQ_REL", "4");
  Builder.defineMacro("__ATOMIC_SEQ_CST", "5");

  // Support for #pragma redefine_extname (Sun compatibility)
  Builder.defineMacro("__PRAGMA_REDEFINE_EXTNAME", "1");

  // As sad as it is, enough software depends on the __VERSION__ for version
  // checks that it is necessary to report 4.2.1 (the base GCC version we claim
  // compatibility with) first.
  Builder.defineMacro("__VERSION__", "\"4.2.1 Compatible " + 
                      Twine(getClangFullCPPVersion()) + "\"");

  // Initialize language-specific preprocessor defines.

  // Standard conforming mode?
  if (!LangOpts.GNUMode && !LangOpts.MSVCCompat)
    Builder.defineMacro("__STRICT_ANSI__");

  if (!LangOpts.MSVCCompat && LangOpts.CPlusPlus11)
    Builder.defineMacro("__GXX_EXPERIMENTAL_CXX0X__");

  if (LangOpts.ObjC1) {
    if (LangOpts.ObjCRuntime.isNonFragile()) {
      Builder.defineMacro("__OBJC2__");
      
      if (LangOpts.ObjCExceptions)
        Builder.defineMacro("OBJC_ZEROCOST_EXCEPTIONS");
    }

    if (LangOpts.getGC() != LangOptions::NonGC)
      Builder.defineMacro("__OBJC_GC__");

    if (LangOpts.ObjCRuntime.isNeXTFamily())
      Builder.defineMacro("__NEXT_RUNTIME__");

    if (LangOpts.ObjCRuntime.getKind() == ObjCRuntime::ObjFW) {
      VersionTuple tuple = LangOpts.ObjCRuntime.getVersion();

      unsigned minor = 0;
      if (tuple.getMinor().hasValue())
        minor = tuple.getMinor().getValue();

      unsigned subminor = 0;
      if (tuple.getSubminor().hasValue())
        subminor = tuple.getSubminor().getValue();

      Builder.defineMacro("__OBJFW_RUNTIME_ABI__",
                          Twine(tuple.getMajor() * 10000 + minor * 100 +
                                subminor));
    }

    Builder.defineMacro("IBOutlet", "__attribute__((iboutlet))");
    Builder.defineMacro("IBOutletCollection(ClassName)",
                        "__attribute__((iboutletcollection(ClassName)))");
    Builder.defineMacro("IBAction", "void)__attribute__((ibaction)");
    Builder.defineMacro("IBInspectable", "");
    Builder.defineMacro("IB_DESIGNABLE", "");
  }

  if (LangOpts.CPlusPlus)
    InitializeCPlusPlusFeatureTestMacros(LangOpts, Builder);

  // darwin_constant_cfstrings controls this. This is also dependent
  // on other things like the runtime I believe.  This is set even for C code.
  if (!LangOpts.NoConstantCFStrings)
//.........这里部分代码省略.........

//.........这里部分代码省略.........
  }

  if (Parts.Exceptions.size() != 0) {
    Result << "<Exceptions>";
    for (unsigned i = 0, e = Parts.Exceptions.size(); i != e; ++i)
      visit(Parts.Exceptions[i]);
    Result << "</Exceptions>";
  }

  if (Parts.Returns.size() != 0) {
    Result << "<ResultDiscussion>";
    for (unsigned i = 0, e = Parts.Returns.size(); i != e; ++i)
      visit(Parts.Returns[i]);
    Result << "</ResultDiscussion>";
  }

  if (DI->CommentDecl->hasAttrs()) {
    const AttrVec &Attrs = DI->CommentDecl->getAttrs();
    for (unsigned i = 0, e = Attrs.size(); i != e; i++) {
      const AvailabilityAttr *AA = dyn_cast<AvailabilityAttr>(Attrs[i]);
      if (!AA) {
        if (const DeprecatedAttr *DA = dyn_cast<DeprecatedAttr>(Attrs[i])) {
          if (DA->getMessage().empty())
            Result << "<Deprecated/>";
          else {
            Result << "<Deprecated>";
            appendToResultWithXMLEscaping(DA->getMessage());
            Result << "</Deprecated>";
          }
        }
        else if (const UnavailableAttr *UA = dyn_cast<UnavailableAttr>(Attrs[i])) {
          if (UA->getMessage().empty())
            Result << "<Unavailable/>";
          else {
            Result << "<Unavailable>";
            appendToResultWithXMLEscaping(UA->getMessage());
            Result << "</Unavailable>";
          }
        }
        continue;
      }

      // 'availability' attribute.
      Result << "<Availability";
      StringRef Distribution;
      if (AA->getPlatform()) {
        Distribution = AvailabilityAttr::getPrettyPlatformName(
                                        AA->getPlatform()->getName());
        if (Distribution.empty())
          Distribution = AA->getPlatform()->getName();
      }
      Result << " distribution=\"" << Distribution << "\">";
      VersionTuple IntroducedInVersion = AA->getIntroduced();
      if (!IntroducedInVersion.empty()) {
        Result << "<IntroducedInVersion>"
               << IntroducedInVersion.getAsString()
               << "</IntroducedInVersion>";
      }
      VersionTuple DeprecatedInVersion = AA->getDeprecated();
      if (!DeprecatedInVersion.empty()) {
        Result << "<DeprecatedInVersion>"
               << DeprecatedInVersion.getAsString()
               << "</DeprecatedInVersion>";
      }
      VersionTuple RemovedAfterVersion = AA->getObsoleted();
      if (!RemovedAfterVersion.empty()) {
        Result << "<RemovedAfterVersion>"
               << RemovedAfterVersion.getAsString()
               << "</RemovedAfterVersion>";
      }
      StringRef DeprecationSummary = AA->getMessage();
      if (!DeprecationSummary.empty()) {
        Result << "<DeprecationSummary>";
        appendToResultWithXMLEscaping(DeprecationSummary);
        Result << "</DeprecationSummary>";
      }
      if (AA->getUnavailable())
        Result << "<Unavailable/>";
      Result << "</Availability>";
    }
  }

  {
    bool StartTagEmitted = false;
    for (unsigned i = 0, e = Parts.MiscBlocks.size(); i != e; ++i) {
      const Comment *C = Parts.MiscBlocks[i];
      if (FirstParagraphIsBrief && C == Parts.FirstParagraph)
        continue;
      if (!StartTagEmitted) {
        Result << "<Discussion>";
        StartTagEmitted = true;
      }
      visit(C);
    }
    if (StartTagEmitted)
      Result << "</Discussion>";
  }

  Result << RootEndTag;
}

/// \brief Determine the availability of the given declaration based on
/// the target platform.
///
/// When it returns an availability result other than \c AR_Available,
/// if the \p Message parameter is non-NULL, it will be set to a
/// string describing why the entity is unavailable.
///
/// FIXME: Make these strings localizable, since they end up in
/// diagnostics.
static AvailabilityResult CheckAvailability(ASTContext &Context,
                                            const AvailabilityAttr *A,
                                            std::string *Message) {
  StringRef TargetPlatform = Context.getTargetInfo().getPlatformName();
  StringRef PrettyPlatformName
    = AvailabilityAttr::getPrettyPlatformName(TargetPlatform);
  if (PrettyPlatformName.empty())
    PrettyPlatformName = TargetPlatform;

  VersionTuple TargetMinVersion = Context.getTargetInfo().getPlatformMinVersion();
  if (TargetMinVersion.empty())
    return AR_Available;

  // Match the platform name.
  if (A->getPlatform()->getName() != TargetPlatform)
    return AR_Available;
  
  std::string HintMessage;
  if (!A->getMessage().empty()) {
    HintMessage = " - ";
    HintMessage += A->getMessage();
  }
  
  // Make sure that this declaration has not been marked 'unavailable'.
  if (A->getUnavailable()) {
    if (Message) {
      Message->clear();
      llvm::raw_string_ostream Out(*Message);
      Out << "not available on " << PrettyPlatformName 
          << HintMessage;
    }

    return AR_Unavailable;
  }

  // Make sure that this declaration has already been introduced.
  if (!A->getIntroduced().empty() && 
      TargetMinVersion < A->getIntroduced()) {
    if (Message) {
      Message->clear();
      llvm::raw_string_ostream Out(*Message);
      Out << "introduced in " << PrettyPlatformName << ' ' 
          << A->getIntroduced() << HintMessage;
    }

    return AR_NotYetIntroduced;
  }

  // Make sure that this declaration hasn't been obsoleted.
  if (!A->getObsoleted().empty() && TargetMinVersion >= A->getObsoleted()) {
    if (Message) {
      Message->clear();
      llvm::raw_string_ostream Out(*Message);
      Out << "obsoleted in " << PrettyPlatformName << ' ' 
          << A->getObsoleted() << HintMessage;
    }
    
    return AR_Unavailable;
  }

  // Make sure that this declaration hasn't been deprecated.
  if (!A->getDeprecated().empty() && TargetMinVersion >= A->getDeprecated()) {
    if (Message) {
      Message->clear();
      llvm::raw_string_ostream Out(*Message);
      Out << "first deprecated in " << PrettyPlatformName << ' '
          << A->getDeprecated() << HintMessage;
    }
    
    return AR_Deprecated;
  }

  return AR_Available;
}