text: //===-- ASTReader.cpp - AST File Reader ----------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  //  This file defines the ASTReader class, which reads AST files.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Serialization/ASTReader.h"
  #include "ASTCommon.h"
  #include "ASTReaderInternals.h"
  #include "clang/AST/ASTConsumer.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/DeclTemplate.h"
  #include "clang/AST/Expr.h"
  #include "clang/AST/ExprCXX.h"
  #include "clang/Frontend/PCHContainerOperations.h"
  #include "clang/AST/ASTMutationListener.h"
  #include "clang/AST/NestedNameSpecifier.h"
  #include "clang/AST/Type.h"
  #include "clang/AST/TypeLocVisitor.h"
  #include "clang/Basic/DiagnosticOptions.h"
  #include "clang/Basic/FileManager.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Basic/SourceManagerInternals.h"
  #include "clang/Basic/TargetInfo.h"
  #include "clang/Basic/TargetOptions.h"
  #include "clang/Basic/Version.h"
  #include "clang/Basic/VersionTuple.h"
  #include "clang/Frontend/Utils.h"
  #include "clang/Lex/HeaderSearch.h"
  #include "clang/Lex/HeaderSearchOptions.h"
  #include "clang/Lex/MacroInfo.h"
  #include "clang/Lex/PreprocessingRecord.h"
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Lex/PreprocessorOptions.h"
  #include "clang/Sema/Scope.h"
  #include "clang/Sema/Sema.h"
  #include "clang/Serialization/ASTDeserializationListener.h"
  #include "clang/Serialization/GlobalModuleIndex.h"
  #include "clang/Serialization/ModuleManager.h"
  #include "clang/Serialization/SerializationDiagnostic.h"
  #include "llvm/ADT/Hashing.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/Bitcode/BitstreamReader.h"
  #include "llvm/Support/Compression.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/FileSystem.h"
  #include "llvm/Support/MemoryBuffer.h"
  #include "llvm/Support/Path.h"
  #include "llvm/Support/SaveAndRestore.h"
  #include "llvm/Support/raw_ostream.h"
  #include <algorithm>
  #include <cstdio>
  #include <iterator>
  #include <system_error>
  
  using namespace clang;
  using namespace clang::serialization;
  using namespace clang::serialization::reader;
  using llvm::BitstreamCursor;
  
  
  //===----------------------------------------------------------------------===//
  // ChainedASTReaderListener implementation
  //===----------------------------------------------------------------------===//
  
  bool
  ChainedASTReaderListener::ReadFullVersionInformation(StringRef FullVersion) {
    return First->ReadFullVersionInformation(FullVersion) ||
           Second->ReadFullVersionInformation(FullVersion);
  }
  void ChainedASTReaderListener::ReadModuleName(StringRef ModuleName) {
    First->ReadModuleName(ModuleName);
    Second->ReadModuleName(ModuleName);
  }
  void ChainedASTReaderListener::ReadModuleMapFile(StringRef ModuleMapPath) {
    First->ReadModuleMapFile(ModuleMapPath);
    Second->ReadModuleMapFile(ModuleMapPath);
  }
  bool
  ChainedASTReaderListener::ReadLanguageOptions(const LangOptions &LangOpts,
                                                bool Complain,
                                                bool AllowCompatibleDifferences) {
    return First->ReadLanguageOptions(LangOpts, Complain,
                                      AllowCompatibleDifferences) ||
           Second->ReadLanguageOptions(LangOpts, Complain,
                                       AllowCompatibleDifferences);
  }
  bool ChainedASTReaderListener::ReadTargetOptions(
      const TargetOptions &TargetOpts, bool Complain,
      bool AllowCompatibleDifferences) {
    return First->ReadTargetOptions(TargetOpts, Complain,
                                    AllowCompatibleDifferences) ||
           Second->ReadTargetOptions(TargetOpts, Complain,
                                     AllowCompatibleDifferences);
  }
  bool ChainedASTReaderListener::ReadDiagnosticOptions(
      IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts, bool Complain) {
    return First->ReadDiagnosticOptions(DiagOpts, Complain) ||
           Second->ReadDiagnosticOptions(DiagOpts, Complain);
  }
  bool
  ChainedASTReaderListener::ReadFileSystemOptions(const FileSystemOptions &FSOpts,
                                                  bool Complain) {
    return First->ReadFileSystemOptions(FSOpts, Complain) ||
           Second->ReadFileSystemOptions(FSOpts, Complain);
  }
  
  bool ChainedASTReaderListener::ReadHeaderSearchOptions(
      const HeaderSearchOptions &HSOpts, StringRef SpecificModuleCachePath,
      bool Complain) {
    return First->ReadHeaderSearchOptions(HSOpts, SpecificModuleCachePath,
                                          Complain) ||
           Second->ReadHeaderSearchOptions(HSOpts, SpecificModuleCachePath,
                                           Complain);
  }
  bool ChainedASTReaderListener::ReadPreprocessorOptions(
      const PreprocessorOptions &PPOpts, bool Complain,
      std::string &SuggestedPredefines) {
    return First->ReadPreprocessorOptions(PPOpts, Complain,
                                          SuggestedPredefines) ||
           Second->ReadPreprocessorOptions(PPOpts, Complain, SuggestedPredefines);
  }
  void ChainedASTReaderListener::ReadCounter(const serialization::ModuleFile &M,
                                             unsigned Value) {
    First->ReadCounter(M, Value);
    Second->ReadCounter(M, Value);
  }
  bool ChainedASTReaderListener::needsInputFileVisitation() {
    return First->needsInputFileVisitation() ||
           Second->needsInputFileVisitation();
  }
  bool ChainedASTReaderListener::needsSystemInputFileVisitation() {
    return First->needsSystemInputFileVisitation() ||
    Second->needsSystemInputFileVisitation();
  }
  void ChainedASTReaderListener::visitModuleFile(StringRef Filename,
                                                 ModuleKind Kind) {
    First->visitModuleFile(Filename, Kind);
    Second->visitModuleFile(Filename, Kind);
  }
  bool ChainedASTReaderListener::visitInputFile(StringRef Filename,
                                                bool isSystem,
                                                bool isOverridden,
                                                bool isExplicitModule) {
    bool Continue = false;
    if (First->needsInputFileVisitation() &&
        (!isSystem || First->needsSystemInputFileVisitation()))
      Continue |= First->visitInputFile(Filename, isSystem, isOverridden,
                                        isExplicitModule);
    if (Second->needsInputFileVisitation() &&
        (!isSystem || Second->needsSystemInputFileVisitation()))
      Continue |= Second->visitInputFile(Filename, isSystem, isOverridden,
                                         isExplicitModule);
    return Continue;
  }
  
  void ChainedASTReaderListener::readModuleFileExtension(
         const ModuleFileExtensionMetadata &Metadata) {
    First->readModuleFileExtension(Metadata);
    Second->readModuleFileExtension(Metadata);
  }
  
  //===----------------------------------------------------------------------===//
  // PCH validator implementation
  //===----------------------------------------------------------------------===//
  
  ASTReaderListener::~ASTReaderListener() {}
  
  /// \brief Compare the given set of language options against an existing set of
  /// language options.
  ///
  /// \param Diags If non-NULL, diagnostics will be emitted via this engine.
  /// \param AllowCompatibleDifferences If true, differences between compatible
  ///        language options will be permitted.
  ///
  /// \returns true if the languagae options mis-match, false otherwise.
  static bool checkLanguageOptions(const LangOptions &LangOpts,
                                   const LangOptions &ExistingLangOpts,
                                   DiagnosticsEngine *Diags,
                                   bool AllowCompatibleDifferences = true) {
  #define LANGOPT(Name, Bits, Default, Description)                 \
    if (ExistingLangOpts.Name != LangOpts.Name) {                   \
      if (Diags)                                                    \
        Diags->Report(diag::err_pch_langopt_mismatch)               \
          << Description << LangOpts.Name << ExistingLangOpts.Name; \
      return true;                                                  \
    }
  
  #define VALUE_LANGOPT(Name, Bits, Default, Description)   \
    if (ExistingLangOpts.Name != LangOpts.Name) {           \
      if (Diags)                                            \
        Diags->Report(diag::err_pch_langopt_value_mismatch) \
          << Description;                                   \
      return true;                                          \
    }
  
  #define ENUM_LANGOPT(Name, Type, Bits, Default, Description)   \
    if (ExistingLangOpts.get##Name() != LangOpts.get##Name()) {  \
      if (Diags)                                                 \
        Diags->Report(diag::err_pch_langopt_value_mismatch)      \
          << Description;                                        \
      return true;                                               \
    }
  
  #define COMPATIBLE_LANGOPT(Name, Bits, Default, Description)  \
    if (!AllowCompatibleDifferences)                            \
      LANGOPT(Name, Bits, Default, Description)
  
  #define COMPATIBLE_ENUM_LANGOPT(Name, Bits, Default, Description)  \
    if (!AllowCompatibleDifferences)                                 \
      ENUM_LANGOPT(Name, Bits, Default, Description)
  
  #define COMPATIBLE_VALUE_LANGOPT(Name, Bits, Default, Description) \
    if (!AllowCompatibleDifferences)                                 \
      VALUE_LANGOPT(Name, Bits, Default, Description)
  
  #define BENIGN_LANGOPT(Name, Bits, Default, Description)
  #define BENIGN_ENUM_LANGOPT(Name, Type, Bits, Default, Description)
  #define BENIGN_VALUE_LANGOPT(Name, Type, Bits, Default, Description)
  #include "clang/Basic/LangOptions.def"
  
    if (ExistingLangOpts.ModuleFeatures != LangOpts.ModuleFeatures) {
      if (Diags)
        Diags->Report(diag::err_pch_langopt_value_mismatch) << "module features";
      return true;
    }
  
    if (ExistingLangOpts.ObjCRuntime != LangOpts.ObjCRuntime) {
      if (Diags)
        Diags->Report(diag::err_pch_langopt_value_mismatch)
        << "target Objective-C runtime";
      return true;
    }
  
    if (ExistingLangOpts.CommentOpts.BlockCommandNames !=
        LangOpts.CommentOpts.BlockCommandNames) {
      if (Diags)
        Diags->Report(diag::err_pch_langopt_value_mismatch)
          << "block command names";
      return true;
    }
  
    return false;
  }
  
  /// \brief Compare the given set of target options against an existing set of
  /// target options.
  ///
  /// \param Diags If non-NULL, diagnostics will be emitted via this engine.
  ///
  /// \returns true if the target options mis-match, false otherwise.
  static bool checkTargetOptions(const TargetOptions &TargetOpts,
                                 const TargetOptions &ExistingTargetOpts,
                                 DiagnosticsEngine *Diags,
                                 bool AllowCompatibleDifferences = true) {
  #define CHECK_TARGET_OPT(Field, Name)                             \
    if (TargetOpts.Field != ExistingTargetOpts.Field) {             \
      if (Diags)                                                    \
        Diags->Report(diag::err_pch_targetopt_mismatch)             \
          << Name << TargetOpts.Field << ExistingTargetOpts.Field;  \
      return true;                                                  \
    }
  
    // The triple and ABI must match exactly.
    CHECK_TARGET_OPT(Triple, "target");
    CHECK_TARGET_OPT(ABI, "target ABI");
  
    // We can tolerate different CPUs in many cases, notably when one CPU
    // supports a strict superset of another. When allowing compatible
    // differences skip this check.
    if (!AllowCompatibleDifferences)
      CHECK_TARGET_OPT(CPU, "target CPU");
  
  #undef CHECK_TARGET_OPT
  
    // Compare feature sets.
    SmallVector<StringRef, 4> ExistingFeatures(
                                               ExistingTargetOpts.FeaturesAsWritten.begin(),
                                               ExistingTargetOpts.FeaturesAsWritten.end());
    SmallVector<StringRef, 4> ReadFeatures(TargetOpts.FeaturesAsWritten.begin(),
                                           TargetOpts.FeaturesAsWritten.end());
    std::sort(ExistingFeatures.begin(), ExistingFeatures.end());
    std::sort(ReadFeatures.begin(), ReadFeatures.end());
  
    // We compute the set difference in both directions explicitly so that we can
    // diagnose the differences differently.
    SmallVector<StringRef, 4> UnmatchedExistingFeatures, UnmatchedReadFeatures;
    std::set_difference(
        ExistingFeatures.begin(), ExistingFeatures.end(), ReadFeatures.begin(),
        ReadFeatures.end(), std::back_inserter(UnmatchedExistingFeatures));
    std::set_difference(ReadFeatures.begin(), ReadFeatures.end(),
                        ExistingFeatures.begin(), ExistingFeatures.end(),
                        std::back_inserter(UnmatchedReadFeatures));
  
    // If we are allowing compatible differences and the read feature set is
    // a strict subset of the existing feature set, there is nothing to diagnose.
    if (AllowCompatibleDifferences && UnmatchedReadFeatures.empty())
      return false;
  
    if (Diags) {
      for (StringRef Feature : UnmatchedReadFeatures)
        Diags->Report(diag::err_pch_targetopt_feature_mismatch)
            << /* is-existing-feature */ false << Feature;
      for (StringRef Feature : UnmatchedExistingFeatures)
        Diags->Report(diag::err_pch_targetopt_feature_mismatch)
            << /* is-existing-feature */ true << Feature;
    }
  
    return !UnmatchedReadFeatures.empty() || !UnmatchedExistingFeatures.empty();
  }
  
  bool
  PCHValidator::ReadLanguageOptions(const LangOptions &LangOpts,
                                    bool Complain,
                                    bool AllowCompatibleDifferences) {
    const LangOptions &ExistingLangOpts = PP.getLangOpts();
    return checkLanguageOptions(LangOpts, ExistingLangOpts,
                                Complain ? &Reader.Diags : nullptr,
                                AllowCompatibleDifferences);
  }
  
  bool PCHValidator::ReadTargetOptions(const TargetOptions &TargetOpts,
                                       bool Complain,
                                       bool AllowCompatibleDifferences) {
    const TargetOptions &ExistingTargetOpts = PP.getTargetInfo().getTargetOpts();
    return checkTargetOptions(TargetOpts, ExistingTargetOpts,
                              Complain ? &Reader.Diags : nullptr,
                              AllowCompatibleDifferences);
  }
  
  namespace {
    typedef llvm::StringMap<std::pair<StringRef, bool /*IsUndef*/> >
      MacroDefinitionsMap;
    typedef llvm::DenseMap<DeclarationName, SmallVector<NamedDecl *, 8> >
      DeclsMap;
  }
  
  static bool checkDiagnosticGroupMappings(DiagnosticsEngine &StoredDiags,
                                           DiagnosticsEngine &Diags,
                                           bool Complain) {
    typedef DiagnosticsEngine::Level Level;
  
    // Check current mappings for new -Werror mappings, and the stored mappings
    // for cases that were explicitly mapped to *not* be errors that are now
    // errors because of options like -Werror.
    DiagnosticsEngine *MappingSources[] = { &Diags, &StoredDiags };
  
    for (DiagnosticsEngine *MappingSource : MappingSources) {
      for (auto DiagIDMappingPair : MappingSource->getDiagnosticMappings()) {
        diag::kind DiagID = DiagIDMappingPair.first;
        Level CurLevel = Diags.getDiagnosticLevel(DiagID, SourceLocation());
        if (CurLevel < DiagnosticsEngine::Error)
          continue; // not significant
        Level StoredLevel =
            StoredDiags.getDiagnosticLevel(DiagID, SourceLocation());
        if (StoredLevel < DiagnosticsEngine::Error) {
          if (Complain)
            Diags.Report(diag::err_pch_diagopt_mismatch) << "-Werror=" +
                Diags.getDiagnosticIDs()->getWarningOptionForDiag(DiagID).str();
          return true;
        }
      }
    }
  
    return false;
  }
  
  static bool isExtHandlingFromDiagsError(DiagnosticsEngine &Diags) {
    diag::Severity Ext = Diags.getExtensionHandlingBehavior();
    if (Ext == diag::Severity::Warning && Diags.getWarningsAsErrors())
      return true;
    return Ext >= diag::Severity::Error;
  }
  
  static bool checkDiagnosticMappings(DiagnosticsEngine &StoredDiags,
                                      DiagnosticsEngine &Diags,
                                      bool IsSystem, bool Complain) {
    // Top-level options
    if (IsSystem) {
      if (Diags.getSuppressSystemWarnings())
        return false;
      // If -Wsystem-headers was not enabled before, be conservative
      if (StoredDiags.getSuppressSystemWarnings()) {
        if (Complain)
          Diags.Report(diag::err_pch_diagopt_mismatch) << "-Wsystem-headers";
        return true;
      }
    }
  
    if (Diags.getWarningsAsErrors() && !StoredDiags.getWarningsAsErrors()) {
      if (Complain)
        Diags.Report(diag::err_pch_diagopt_mismatch) << "-Werror";
      return true;
    }
  
    if (Diags.getWarningsAsErrors() && Diags.getEnableAllWarnings() &&
        !StoredDiags.getEnableAllWarnings()) {
      if (Complain)
        Diags.Report(diag::err_pch_diagopt_mismatch) << "-Weverything -Werror";
      return true;
    }
  
    if (isExtHandlingFromDiagsError(Diags) &&
        !isExtHandlingFromDiagsError(StoredDiags)) {
      if (Complain)
        Diags.Report(diag::err_pch_diagopt_mismatch) << "-pedantic-errors";
      return true;
    }
  
    return checkDiagnosticGroupMappings(StoredDiags, Diags, Complain);
  }
  
  bool PCHValidator::ReadDiagnosticOptions(
      IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts, bool Complain) {
    DiagnosticsEngine &ExistingDiags = PP.getDiagnostics();
    IntrusiveRefCntPtr<DiagnosticIDs> DiagIDs(ExistingDiags.getDiagnosticIDs());
    IntrusiveRefCntPtr<DiagnosticsEngine> Diags(
        new DiagnosticsEngine(DiagIDs, DiagOpts.get()));
    // This should never fail, because we would have processed these options
    // before writing them to an ASTFile.
    ProcessWarningOptions(*Diags, *DiagOpts, /*Report*/false);
  
    ModuleManager &ModuleMgr = Reader.getModuleManager();
    assert(ModuleMgr.size() >= 1 && "what ASTFile is this then");
  
    // If the original import came from a file explicitly generated by the user,
    // don't check the diagnostic mappings.
    // FIXME: currently this is approximated by checking whether this is not a
    // module import of an implicitly-loaded module file.
    // Note: ModuleMgr.rbegin() may not be the current module, but it must be in
    // the transitive closure of its imports, since unrelated modules cannot be
    // imported until after this module finishes validation.
    ModuleFile *TopImport = *ModuleMgr.rbegin();
    while (!TopImport->ImportedBy.empty())
      TopImport = TopImport->ImportedBy[0];
    if (TopImport->Kind != MK_ImplicitModule)
      return false;
  
    StringRef ModuleName = TopImport->ModuleName;
    assert(!ModuleName.empty() && "diagnostic options read before module name");
  
    Module *M = PP.getHeaderSearchInfo().lookupModule(ModuleName);
    assert(M && "missing module");
  
    // FIXME: if the diagnostics are incompatible, save a DiagnosticOptions that
    // contains the union of their flags.
    return checkDiagnosticMappings(*Diags, ExistingDiags, M->IsSystem, Complain);
  }
  
  /// \brief Collect the macro definitions provided by the given preprocessor
  /// options.
  static void
  collectMacroDefinitions(const PreprocessorOptions &PPOpts,
                          MacroDefinitionsMap &Macros,
                          SmallVectorImpl<StringRef> *MacroNames = nullptr) {
    for (unsigned I = 0, N = PPOpts.Macros.size(); I != N; ++I) {
      StringRef Macro = PPOpts.Macros[I].first;
      bool IsUndef = PPOpts.Macros[I].second;
  
      std::pair<StringRef, StringRef> MacroPair = Macro.split('=');
      StringRef MacroName = MacroPair.first;
      StringRef MacroBody = MacroPair.second;
  
      // For an #undef'd macro, we only care about the name.
      if (IsUndef) {
        if (MacroNames && !Macros.count(MacroName))
          MacroNames->push_back(MacroName);
  
        Macros[MacroName] = std::make_pair("", true);
        continue;
      }
  
      // For a #define'd macro, figure out the actual definition.
      if (MacroName.size() == Macro.size())
        MacroBody = "1";
      else {
        // Note: GCC drops anything following an end-of-line character.
        StringRef::size_type End = MacroBody.find_first_of("\n\r");
        MacroBody = MacroBody.substr(0, End);
      }
  
      if (MacroNames && !Macros.count(MacroName))
        MacroNames->push_back(MacroName);
      Macros[MacroName] = std::make_pair(MacroBody, false);
    }
  }
  
  /// \brief Check the preprocessor options deserialized from the control block
  /// against the preprocessor options in an existing preprocessor.
  ///
  /// \param Diags If non-null, produce diagnostics for any mismatches incurred.
  static bool checkPreprocessorOptions(const PreprocessorOptions &PPOpts,
                                       const PreprocessorOptions &ExistingPPOpts,
                                       DiagnosticsEngine *Diags,
                                       FileManager &FileMgr,
                                       std::string &SuggestedPredefines,
                                       const LangOptions &LangOpts) {
    // Check macro definitions.
    MacroDefinitionsMap ASTFileMacros;
    collectMacroDefinitions(PPOpts, ASTFileMacros);
    MacroDefinitionsMap ExistingMacros;
    SmallVector<StringRef, 4> ExistingMacroNames;
    collectMacroDefinitions(ExistingPPOpts, ExistingMacros, &ExistingMacroNames);
  
    for (unsigned I = 0, N = ExistingMacroNames.size(); I != N; ++I) {
      // Dig out the macro definition in the existing preprocessor options.
      StringRef MacroName = ExistingMacroNames[I];
      std::pair<StringRef, bool> Existing = ExistingMacros[MacroName];
  
      // Check whether we know anything about this macro name or not.
      llvm::StringMap<std::pair<StringRef, bool /*IsUndef*/> >::iterator Known
        = ASTFileMacros.find(MacroName);
      if (Known == ASTFileMacros.end()) {
        // FIXME: Check whether this identifier was referenced anywhere in the
        // AST file. If so, we should reject the AST file. Unfortunately, this
        // information isn't in the control block. What shall we do about it?
  
        if (Existing.second) {
          SuggestedPredefines += "#undef ";
          SuggestedPredefines += MacroName.str();
          SuggestedPredefines += '\n';
        } else {
          SuggestedPredefines += "#define ";
          SuggestedPredefines += MacroName.str();
          SuggestedPredefines += ' ';
          SuggestedPredefines += Existing.first.str();
          SuggestedPredefines += '\n';
        }
        continue;
      }
  
      // If the macro was defined in one but undef'd in the other, we have a
      // conflict.
      if (Existing.second != Known->second.second) {
        if (Diags) {
          Diags->Report(diag::err_pch_macro_def_undef)
            << MacroName << Known->second.second;
        }
        return true;
      }
  
      // If the macro was #undef'd in both, or if the macro bodies are identical,
      // it's fine.
      if (Existing.second || Existing.first == Known->second.first)
        continue;
  
      // The macro bodies differ; complain.
      if (Diags) {
        Diags->Report(diag::err_pch_macro_def_conflict)
          << MacroName << Known->second.first << Existing.first;
      }
      return true;
    }
  
    // Check whether we're using predefines.
    if (PPOpts.UsePredefines != ExistingPPOpts.UsePredefines) {
      if (Diags) {
        Diags->Report(diag::err_pch_undef) << ExistingPPOpts.UsePredefines;
      }
      return true;
    }
  
    // Detailed record is important since it is used for the module cache hash.
    if (LangOpts.Modules &&
        PPOpts.DetailedRecord != ExistingPPOpts.DetailedRecord) {
      if (Diags) {
        Diags->Report(diag::err_pch_pp_detailed_record) << PPOpts.DetailedRecord;
      }
      return true;
    }
  
    // Compute the #include and #include_macros lines we need.
    for (unsigned I = 0, N = ExistingPPOpts.Includes.size(); I != N; ++I) {
      StringRef File = ExistingPPOpts.Includes[I];
      if (File == ExistingPPOpts.ImplicitPCHInclude)
        continue;
  
      if (std::find(PPOpts.Includes.begin(), PPOpts.Includes.end(), File)
            != PPOpts.Includes.end())
        continue;
  
      SuggestedPredefines += "#include \"";
      SuggestedPredefines += File;
      SuggestedPredefines += "\"\n";
    }
  
    for (unsigned I = 0, N = ExistingPPOpts.MacroIncludes.size(); I != N; ++I) {
      StringRef File = ExistingPPOpts.MacroIncludes[I];
      if (std::find(PPOpts.MacroIncludes.begin(), PPOpts.MacroIncludes.end(),
                    File)
          != PPOpts.MacroIncludes.end())
        continue;
  
      SuggestedPredefines += "#__include_macros \"";
      SuggestedPredefines += File;
      SuggestedPredefines += "\"\n##\n";
    }
  
    return false;
  }
  
  bool PCHValidator::ReadPreprocessorOptions(const PreprocessorOptions &PPOpts,
                                             bool Complain,
                                             std::string &SuggestedPredefines) {
    const PreprocessorOptions &ExistingPPOpts = PP.getPreprocessorOpts();
  
    return checkPreprocessorOptions(PPOpts, ExistingPPOpts,
                                    Complain? &Reader.Diags : nullptr,
                                    PP.getFileManager(),
                                    SuggestedPredefines,
                                    PP.getLangOpts());
  }
  
  /// Check the header search options deserialized from the control block
  /// against the header search options in an existing preprocessor.
  ///
  /// \param Diags If non-null, produce diagnostics for any mismatches incurred.
  static bool checkHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
                                       StringRef SpecificModuleCachePath,
                                       StringRef ExistingModuleCachePath,
                                       DiagnosticsEngine *Diags,
                                       const LangOptions &LangOpts) {
    if (LangOpts.Modules) {
      if (SpecificModuleCachePath != ExistingModuleCachePath) {
        if (Diags)
          Diags->Report(diag::err_pch_modulecache_mismatch)
            << SpecificModuleCachePath << ExistingModuleCachePath;
        return true;
      }
    }
  
    return false;
  }
  
  bool PCHValidator::ReadHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
                                             StringRef SpecificModuleCachePath,
                                             bool Complain) {
    return checkHeaderSearchOptions(HSOpts, SpecificModuleCachePath,
                                    PP.getHeaderSearchInfo().getModuleCachePath(),
                                    Complain ? &Reader.Diags : nullptr,
                                    PP.getLangOpts());
  }
  
  void PCHValidator::ReadCounter(const ModuleFile &M, unsigned Value) {
    PP.setCounterValue(Value);
  }
  
  //===----------------------------------------------------------------------===//
  // AST reader implementation
  //===----------------------------------------------------------------------===//
  
  void ASTReader::setDeserializationListener(ASTDeserializationListener *Listener,
                                             bool TakeOwnership) {
    DeserializationListener = Listener;
    OwnsDeserializationListener = TakeOwnership;
  }
  
  
  
  unsigned ASTSelectorLookupTrait::ComputeHash(Selector Sel) {
    return serialization::ComputeHash(Sel);
  }
  
  
  std::pair<unsigned, unsigned>
  ASTSelectorLookupTrait::ReadKeyDataLength(const unsigned char*& d) {
    using namespace llvm::support;
    unsigned KeyLen = endian::readNext<uint16_t, little, unaligned>(d);
    unsigned DataLen = endian::readNext<uint16_t, little, unaligned>(d);
    return std::make_pair(KeyLen, DataLen);
  }
  
  ASTSelectorLookupTrait::internal_key_type 
  ASTSelectorLookupTrait::ReadKey(const unsigned char* d, unsigned) {
    using namespace llvm::support;
    SelectorTable &SelTable = Reader.getContext().Selectors;
    unsigned N = endian::readNext<uint16_t, little, unaligned>(d);
    IdentifierInfo *FirstII = Reader.getLocalIdentifier(
        F, endian::readNext<uint32_t, little, unaligned>(d));
    if (N == 0)
      return SelTable.getNullarySelector(FirstII);
    else if (N == 1)
      return SelTable.getUnarySelector(FirstII);
  
    SmallVector<IdentifierInfo *, 16> Args;
    Args.push_back(FirstII);
    for (unsigned I = 1; I != N; ++I)
      Args.push_back(Reader.getLocalIdentifier(
          F, endian::readNext<uint32_t, little, unaligned>(d)));
  
    return SelTable.getSelector(N, Args.data());
  }
  
  ASTSelectorLookupTrait::data_type 
  ASTSelectorLookupTrait::ReadData(Selector, const unsigned char* d, 
                                   unsigned DataLen) {
    using namespace llvm::support;
  
    data_type Result;
  
    Result.ID = Reader.getGlobalSelectorID(
        F, endian::readNext<uint32_t, little, unaligned>(d));
    unsigned FullInstanceBits = endian::readNext<uint16_t, little, unaligned>(d);
    unsigned FullFactoryBits = endian::readNext<uint16_t, little, unaligned>(d);
    Result.InstanceBits = FullInstanceBits & 0x3;
    Result.InstanceHasMoreThanOneDecl = (FullInstanceBits >> 2) & 0x1;
    Result.FactoryBits = FullFactoryBits & 0x3;
    Result.FactoryHasMoreThanOneDecl = (FullFactoryBits >> 2) & 0x1;
    unsigned NumInstanceMethods = FullInstanceBits >> 3;
    unsigned NumFactoryMethods = FullFactoryBits >> 3;
  
    // Load instance methods
    for (unsigned I = 0; I != NumInstanceMethods; ++I) {
      if (ObjCMethodDecl *Method = Reader.GetLocalDeclAs<ObjCMethodDecl>(
              F, endian::readNext<uint32_t, little, unaligned>(d)))
        Result.Instance.push_back(Method);
    }
  
    // Load factory methods
    for (unsigned I = 0; I != NumFactoryMethods; ++I) {
      if (ObjCMethodDecl *Method = Reader.GetLocalDeclAs<ObjCMethodDecl>(
              F, endian::readNext<uint32_t, little, unaligned>(d)))
        Result.Factory.push_back(Method);
    }
  
    return Result;
  }
  
  unsigned ASTIdentifierLookupTraitBase::ComputeHash(const internal_key_type& a) {
    return llvm::HashString(a);
  }
  
  std::pair<unsigned, unsigned>
  ASTIdentifierLookupTraitBase::ReadKeyDataLength(const unsigned char*& d) {
    using namespace llvm::support;
    unsigned DataLen = endian::readNext<uint16_t, little, unaligned>(d);
    unsigned KeyLen = endian::readNext<uint16_t, little, unaligned>(d);
    return std::make_pair(KeyLen, DataLen);
  }
  
  ASTIdentifierLookupTraitBase::internal_key_type
  ASTIdentifierLookupTraitBase::ReadKey(const unsigned char* d, unsigned n) {
    assert(n >= 2 && d[n-1] == '\0');
    return StringRef((const char*) d, n-1);
  }
  
  /// \brief Whether the given identifier is "interesting".
  static bool isInterestingIdentifier(ASTReader &Reader, IdentifierInfo &II,
                                      bool IsModule) {
    return II.hadMacroDefinition() ||
           II.isPoisoned() ||
           (IsModule ? II.hasRevertedBuiltin() : II.getObjCOrBuiltinID()) ||
           II.hasRevertedTokenIDToIdentifier() ||
           (!(IsModule && Reader.getContext().getLangOpts().CPlusPlus) &&
            II.getFETokenInfo<void>());
  }
  
  static bool readBit(unsigned &Bits) {
    bool Value = Bits & 0x1;
    Bits >>= 1;
    return Value;
  }
  
  IdentID ASTIdentifierLookupTrait::ReadIdentifierID(const unsigned char *d) {
    using namespace llvm::support;
    unsigned RawID = endian::readNext<uint32_t, little, unaligned>(d);
    return Reader.getGlobalIdentifierID(F, RawID >> 1);
  }
  
  static void markIdentifierFromAST(ASTReader &Reader, IdentifierInfo &II) {
    if (!II.isFromAST()) {
      II.setIsFromAST();
      bool IsModule = Reader.getPreprocessor().getCurrentModule() != nullptr;
      if (isInterestingIdentifier(Reader, II, IsModule))
        II.setChangedSinceDeserialization();
    }
  }
  
  IdentifierInfo *ASTIdentifierLookupTrait::ReadData(const internal_key_type& k,
                                                     const unsigned char* d,
                                                     unsigned DataLen) {
    using namespace llvm::support;
    unsigned RawID = endian::readNext<uint32_t, little, unaligned>(d);
    bool IsInteresting = RawID & 0x01;
  
    // Wipe out the "is interesting" bit.
    RawID = RawID >> 1;
  
    // Build the IdentifierInfo and link the identifier ID with it.
    IdentifierInfo *II = KnownII;
    if (!II) {
      II = &Reader.getIdentifierTable().getOwn(k);
      KnownII = II;
    }
    markIdentifierFromAST(Reader, *II);
    Reader.markIdentifierUpToDate(II);
  
    IdentID ID = Reader.getGlobalIdentifierID(F, RawID);
    if (!IsInteresting) {
      // For uninteresting identifiers, there's nothing else to do. Just notify
      // the reader that we've finished loading this identifier.
      Reader.SetIdentifierInfo(ID, II);
      return II;
    }
  
    unsigned ObjCOrBuiltinID = endian::readNext<uint16_t, little, unaligned>(d);
    unsigned Bits = endian::readNext<uint16_t, little, unaligned>(d);
    bool CPlusPlusOperatorKeyword = readBit(Bits);
    bool HasRevertedTokenIDToIdentifier = readBit(Bits);
    bool HasRevertedBuiltin = readBit(Bits);
    bool Poisoned = readBit(Bits);
    bool ExtensionToken = readBit(Bits);
    bool HadMacroDefinition = readBit(Bits);
  
    assert(Bits == 0 && "Extra bits in the identifier?");
    DataLen -= 8;
  
    // Set or check the various bits in the IdentifierInfo structure.
    // Token IDs are read-only.
    if (HasRevertedTokenIDToIdentifier && II->getTokenID() != tok::identifier)
      II->revertTokenIDToIdentifier();
    if (!F.isModule())
      II->setObjCOrBuiltinID(ObjCOrBuiltinID);
    else if (HasRevertedBuiltin && II->getBuiltinID()) {
      II->revertBuiltin();
      assert((II->hasRevertedBuiltin() ||
              II->getObjCOrBuiltinID() == ObjCOrBuiltinID) &&
             "Incorrect ObjC keyword or builtin ID");
    }
    assert(II->isExtensionToken() == ExtensionToken &&
           "Incorrect extension token flag");
    (void)ExtensionToken;
    if (Poisoned)
      II->setIsPoisoned(true);
    assert(II->isCPlusPlusOperatorKeyword() == CPlusPlusOperatorKeyword &&
           "Incorrect C++ operator keyword flag");
    (void)CPlusPlusOperatorKeyword;
  
    // If this identifier is a macro, deserialize the macro
    // definition.
    if (HadMacroDefinition) {
      uint32_t MacroDirectivesOffset =
          endian::readNext<uint32_t, little, unaligned>(d);
      DataLen -= 4;
  
      Reader.addPendingMacro(II, &F, MacroDirectivesOffset);
    }
  
    Reader.SetIdentifierInfo(ID, II);
  
    // Read all of the declarations visible at global scope with this
    // name.
    if (DataLen > 0) {
      SmallVector<uint32_t, 4> DeclIDs;
      for (; DataLen > 0; DataLen -= 4)
        DeclIDs.push_back(Reader.getGlobalDeclID(
            F, endian::readNext<uint32_t, little, unaligned>(d)));
      Reader.SetGloballyVisibleDecls(II, DeclIDs);
    }
  
    return II;
  }
  
  DeclarationNameKey::DeclarationNameKey(DeclarationName Name)
      : Kind(Name.getNameKind()) {
    switch (Kind) {
    case DeclarationName::Identifier:
      Data = (uint64_t)Name.getAsIdentifierInfo();
      break;
    case DeclarationName::ObjCZeroArgSelector:
    case DeclarationName::ObjCOneArgSelector:
    case DeclarationName::ObjCMultiArgSelector:
      Data = (uint64_t)Name.getObjCSelector().getAsOpaquePtr();
      break;
    case DeclarationName::CXXOperatorName:
      Data = Name.getCXXOverloadedOperator();
      break;
    case DeclarationName::CXXLiteralOperatorName:
      Data = (uint64_t)Name.getCXXLiteralIdentifier();
      break;
    case DeclarationName::CXXConstructorName:
    case DeclarationName::CXXDestructorName:
    case DeclarationName::CXXConversionFunctionName:
    case DeclarationName::CXXUsingDirective:
      Data = 0;
      break;
    }
  }
  
  unsigned DeclarationNameKey::getHash() const {
    llvm::FoldingSetNodeID ID;
    ID.AddInteger(Kind);
  
    switch (Kind) {
    case DeclarationName::Identifier:
    case DeclarationName::CXXLiteralOperatorName:
      ID.AddString(((IdentifierInfo*)Data)->getName());
      break;
    case DeclarationName::ObjCZeroArgSelector:
    case DeclarationName::ObjCOneArgSelector:
    case DeclarationName::ObjCMultiArgSelector:
      ID.AddInteger(serialization::ComputeHash(Selector(Data)));
      break;
    case DeclarationName::CXXOperatorName:
      ID.AddInteger((OverloadedOperatorKind)Data);
      break;
    case DeclarationName::CXXConstructorName:
    case DeclarationName::CXXDestructorName:
    case DeclarationName::CXXConversionFunctionName:
    case DeclarationName::CXXUsingDirective:
      break;
    }
  
    return ID.ComputeHash();
  }
  
  ModuleFile *
  ASTDeclContextNameLookupTrait::ReadFileRef(const unsigned char *&d) {
    using namespace llvm::support;
    uint32_t ModuleFileID = endian::readNext<uint32_t, little, unaligned>(d);
    return Reader.getLocalModuleFile(F, ModuleFileID);
  }
  
  std::pair<unsigned, unsigned>
  ASTDeclContextNameLookupTrait::ReadKeyDataLength(const unsigned char *&d) {
    using namespace llvm::support;
    unsigned KeyLen = endian::readNext<uint16_t, little, unaligned>(d);
    unsigned DataLen = endian::readNext<uint16_t, little, unaligned>(d);
    return std::make_pair(KeyLen, DataLen);
  }
  
  ASTDeclContextNameLookupTrait::internal_key_type
  ASTDeclContextNameLookupTrait::ReadKey(const unsigned char *d, unsigned) {
    using namespace llvm::support;
  
    auto Kind = (DeclarationName::NameKind)*d++;
    uint64_t Data;
    switch (Kind) {
    case DeclarationName::Identifier:
      Data = (uint64_t)Reader.getLocalIdentifier(
          F, endian::readNext<uint32_t, little, unaligned>(d));
      break;
    case DeclarationName::ObjCZeroArgSelector:
    case DeclarationName::ObjCOneArgSelector:
    case DeclarationName::ObjCMultiArgSelector:
      Data =
          (uint64_t)Reader.getLocalSelector(
                               F, endian::readNext<uint32_t, little, unaligned>(
                                      d)).getAsOpaquePtr();
      break;
    case DeclarationName::CXXOperatorName:
      Data = *d++; // OverloadedOperatorKind
      break;
    case DeclarationName::CXXLiteralOperatorName:
      Data = (uint64_t)Reader.getLocalIdentifier(
          F, endian::readNext<uint32_t, little, unaligned>(d));
      break;
    case DeclarationName::CXXConstructorName:
    case DeclarationName::CXXDestructorName:
    case DeclarationName::CXXConversionFunctionName:
    case DeclarationName::CXXUsingDirective:
      Data = 0;
      break;
    }
  
    return DeclarationNameKey(Kind, Data);
  }
  
  void ASTDeclContextNameLookupTrait::ReadDataInto(internal_key_type,
                                                   const unsigned char *d,
                                                   unsigned DataLen,
                                                   data_type_builder &Val) {
    using namespace llvm::support;
    for (unsigned NumDecls = DataLen / 4; NumDecls; --NumDecls) {
      uint32_t LocalID = endian::readNext<uint32_t, little, unaligned>(d);
      Val.insert(Reader.getGlobalDeclID(F, LocalID));
    }
  }
  
  bool ASTReader::ReadLexicalDeclContextStorage(ModuleFile &M,
                                                BitstreamCursor &Cursor,
                                                uint64_t Offset,
                                                DeclContext *DC) {
    assert(Offset != 0);
  
    SavedStreamPosition SavedPosition(Cursor);
    Cursor.JumpToBit(Offset);
  
    RecordData Record;
    StringRef Blob;
    unsigned Code = Cursor.ReadCode();
    unsigned RecCode = Cursor.readRecord(Code, Record, &Blob);
    if (RecCode != DECL_CONTEXT_LEXICAL) {
      Error("Expected lexical block");
      return true;
    }
  
    assert(!isa<TranslationUnitDecl>(DC) &&
           "expected a TU_UPDATE_LEXICAL record for TU");
    // If we are handling a C++ class template instantiation, we can see multiple
    // lexical updates for the same record. It's important that we select only one
    // of them, so that field numbering works properly. Just pick the first one we
    // see.
    auto &Lex = LexicalDecls[DC];
    if (!Lex.first) {
      Lex = std::make_pair(
          &M, llvm::makeArrayRef(
                  reinterpret_cast<const llvm::support::unaligned_uint32_t *>(
                      Blob.data()),
                  Blob.size() / 4));
    }
    DC->setHasExternalLexicalStorage(true);
    return false;
  }
  
  bool ASTReader::ReadVisibleDeclContextStorage(ModuleFile &M,
                                                BitstreamCursor &Cursor,
                                                uint64_t Offset,
                                                DeclID ID) {
    assert(Offset != 0);
  
    SavedStreamPosition SavedPosition(Cursor);
    Cursor.JumpToBit(Offset);
  
    RecordData Record;
    StringRef Blob;
    unsigned Code = Cursor.ReadCode();
    unsigned RecCode = Cursor.readRecord(Code, Record, &Blob);
    if (RecCode != DECL_CONTEXT_VISIBLE) {
      Error("Expected visible lookup table block");
      return true;
    }
  
    // We can't safely determine the primary context yet, so delay attaching the
    // lookup table until we're done with recursive deserialization.
    auto *Data = (const unsigned char*)Blob.data();
    PendingVisibleUpdates[ID].push_back(PendingVisibleUpdate{&M, Data});
    return false;
  }
  
  void ASTReader::Error(StringRef Msg) {
    Error(diag::err_fe_pch_malformed, Msg);
    if (Context.getLangOpts().Modules && !Diags.isDiagnosticInFlight() &&
        !PP.getHeaderSearchInfo().getModuleCachePath().empty()) {
      Diag(diag::note_module_cache_path)
        << PP.getHeaderSearchInfo().getModuleCachePath();
    }
  }
  
  void ASTReader::Error(unsigned DiagID,
                        StringRef Arg1, StringRef Arg2) {
    if (Diags.isDiagnosticInFlight())
      Diags.SetDelayedDiagnostic(DiagID, Arg1, Arg2);
    else
      Diag(DiagID) << Arg1 << Arg2;
  }
  
  //===----------------------------------------------------------------------===//
  // Source Manager Deserialization
  //===----------------------------------------------------------------------===//
  
  /// \brief Read the line table in the source manager block.
  /// \returns true if there was an error.
  bool ASTReader::ParseLineTable(ModuleFile &F,
                                 const RecordData &Record) {
    unsigned Idx = 0;
    LineTableInfo &LineTable = SourceMgr.getLineTable();
  
    // Parse the file names
    std::map<int, int> FileIDs;
    for (unsigned I = 0; Record[Idx]; ++I) {
      // Extract the file name
      auto Filename = ReadPath(F, Record, Idx);
      FileIDs[I] = LineTable.getLineTableFilenameID(Filename);
    }
    ++Idx;
  
    // Parse the line entries
    std::vector<LineEntry> Entries;
    while (Idx < Record.size()) {
      int FID = Record[Idx++];
      assert(FID >= 0 && "Serialized line entries for non-local file.");
      // Remap FileID from 1-based old view.
      FID += F.SLocEntryBaseID - 1;
  
      // Extract the line entries
      unsigned NumEntries = Record[Idx++];
      assert(NumEntries && "no line entries for file ID");
      Entries.clear();
      Entries.reserve(NumEntries);
      for (unsigned I = 0; I != NumEntries; ++I) {
        unsigned FileOffset = Record[Idx++];
        unsigned LineNo = Record[Idx++];
        int FilenameID = FileIDs[Record[Idx++]];
        SrcMgr::CharacteristicKind FileKind
          = (SrcMgr::CharacteristicKind)Record[Idx++];
        unsigned IncludeOffset = Record[Idx++];
        Entries.push_back(LineEntry::get(FileOffset, LineNo, FilenameID,
                                         FileKind, IncludeOffset));
      }
      LineTable.AddEntry(FileID::get(FID), Entries);
    }
  
    return false;
  }
  
  /// \brief Read a source manager block
  bool ASTReader::ReadSourceManagerBlock(ModuleFile &F) {
    using namespace SrcMgr;
  
    BitstreamCursor &SLocEntryCursor = F.SLocEntryCursor;
  
    // Set the source-location entry cursor to the current position in
    // the stream. This cursor will be used to read the contents of the
    // source manager block initially, and then lazily read
    // source-location entries as needed.
    SLocEntryCursor = F.Stream;
  
    // The stream itself is going to skip over the source manager block.
    if (F.Stream.SkipBlock()) {
      Error("malformed block record in AST file");
      return true;
    }
  
    // Enter the source manager block.
    if (SLocEntryCursor.EnterSubBlock(SOURCE_MANAGER_BLOCK_ID)) {
      Error("malformed source manager block record in AST file");
      return true;
    }
  
    RecordData Record;
    while (true) {
      llvm::BitstreamEntry E = SLocEntryCursor.advanceSkippingSubblocks();
      
      switch (E.Kind) {
      case llvm::BitstreamEntry::SubBlock: // Handled for us already.
      case llvm::BitstreamEntry::Error:
        Error("malformed block record in AST file");
        return true;
      case llvm::BitstreamEntry::EndBlock:
        return false;
      case llvm::BitstreamEntry::Record:
        // The interesting case.
        break;
      }
      
      // Read a record.
      Record.clear();
      StringRef Blob;
      switch (SLocEntryCursor.readRecord(E.ID, Record, &Blob)) {
      default:  // Default behavior: ignore.
        break;
  
      case SM_SLOC_FILE_ENTRY:
      case SM_SLOC_BUFFER_ENTRY:
      case SM_SLOC_EXPANSION_ENTRY:
        // Once we hit one of the source location entries, we're done.
        return false;
      }
    }
  }
  
  /// \brief If a header file is not found at the path that we expect it to be
  /// and the PCH file was moved from its original location, try to resolve the
  /// file by assuming that header+PCH were moved together and the header is in
  /// the same place relative to the PCH.
  static std::string
  resolveFileRelativeToOriginalDir(const std::string &Filename,
                                   const std::string &OriginalDir,
                                   const std::string &CurrDir) {
    assert(OriginalDir != CurrDir &&
           "No point trying to resolve the file if the PCH dir didn't change");
    using namespace llvm::sys;
    SmallString<128> filePath(Filename);
    fs::make_absolute(filePath);
    assert(path::is_absolute(OriginalDir));
    SmallString<128> currPCHPath(CurrDir);
  
    path::const_iterator fileDirI = path::begin(path::parent_path(filePath)),
                         fileDirE = path::end(path::parent_path(filePath));
    path::const_iterator origDirI = path::begin(OriginalDir),
                         origDirE = path::end(OriginalDir);
    // Skip the common path components from filePath and OriginalDir.
    while (fileDirI != fileDirE && origDirI != origDirE &&
           *fileDirI == *origDirI) {
      ++fileDirI;
      ++origDirI;
    }
    for (; origDirI != origDirE; ++origDirI)
      path::append(currPCHPath, "..");
    path::append(currPCHPath, fileDirI, fileDirE);
    path::append(currPCHPath, path::filename(Filename));
    return currPCHPath.str();
  }
  
  bool ASTReader::ReadSLocEntry(int ID) {
    if (ID == 0)
      return false;
  
    if (unsigned(-ID) - 2 >= getTotalNumSLocs() || ID > 0) {
      Error("source location entry ID out-of-range for AST file");
      return true;
    }
  
    // Local helper to read the (possibly-compressed) buffer data following the
    // entry record.
    auto ReadBuffer = [this](
        BitstreamCursor &SLocEntryCursor,
        StringRef Name) -> std::unique_ptr<llvm::MemoryBuffer> {
      RecordData Record;
      StringRef Blob;
      unsigned Code = SLocEntryCursor.ReadCode();
      unsigned RecCode = SLocEntryCursor.readRecord(Code, Record, &Blob);
  
      if (RecCode == SM_SLOC_BUFFER_BLOB_COMPRESSED) {
        SmallString<0> Uncompressed;
        if (llvm::zlib::uncompress(Blob, Uncompressed, Record[0]) !=
            llvm::zlib::StatusOK) {
          Error("could not decompress embedded file contents");
          return nullptr;
        }
        return llvm::MemoryBuffer::getMemBufferCopy(Uncompressed, Name);
      } else if (RecCode == SM_SLOC_BUFFER_BLOB) {
        return llvm::MemoryBuffer::getMemBuffer(Blob.drop_back(1), Name, true);
      } else {
        Error("AST record has invalid code");
        return nullptr;
      }
    };
  
    ModuleFile *F = GlobalSLocEntryMap.find(-ID)->second;
    F->SLocEntryCursor.JumpToBit(F->SLocEntryOffsets[ID - F->SLocEntryBaseID]);
    BitstreamCursor &SLocEntryCursor = F->SLocEntryCursor;
    unsigned BaseOffset = F->SLocEntryBaseOffset;
  
    ++NumSLocEntriesRead;
    llvm::BitstreamEntry Entry = SLocEntryCursor.advance();
    if (Entry.Kind != llvm::BitstreamEntry::Record) {
      Error("incorrectly-formatted source location entry in AST file");
      return true;
    }
    
    RecordData Record;
    StringRef Blob;
    switch (SLocEntryCursor.readRecord(Entry.ID, Record, &Blob)) {
    default:
      Error("incorrectly-formatted source location entry in AST file");
      return true;
  
    case SM_SLOC_FILE_ENTRY: {
      // We will detect whether a file changed and return 'Failure' for it, but
      // we will also try to fail gracefully by setting up the SLocEntry.
      unsigned InputID = Record[4];
      InputFile IF = getInputFile(*F, InputID);
      const FileEntry *File = IF.getFile();
      bool OverriddenBuffer = IF.isOverridden();
  
      // Note that we only check if a File was returned. If it was out-of-date
      // we have complained but we will continue creating a FileID to recover
      // gracefully.
      if (!File)
        return true;
  
      SourceLocation IncludeLoc = ReadSourceLocation(*F, Record[1]);
      if (IncludeLoc.isInvalid() && F->Kind != MK_MainFile) {
        // This is the module's main file.
        IncludeLoc = getImportLocation(F);
      }
      SrcMgr::CharacteristicKind
        FileCharacter = (SrcMgr::CharacteristicKind)Record[2];
      FileID FID = SourceMgr.createFileID(File, IncludeLoc, FileCharacter,
                                          ID, BaseOffset + Record[0]);
      SrcMgr::FileInfo &FileInfo =
            const_cast<SrcMgr::FileInfo&>(SourceMgr.getSLocEntry(FID).getFile());
      FileInfo.NumCreatedFIDs = Record[5];
      if (Record[3])
        FileInfo.setHasLineDirectives();
  
      const DeclID *FirstDecl = F->FileSortedDecls + Record[6];
      unsigned NumFileDecls = Record[7];
      if (NumFileDecls) {
        assert(F->FileSortedDecls && "FILE_SORTED_DECLS not encountered yet ?");
        FileDeclIDs[FID] = FileDeclsInfo(F, llvm::makeArrayRef(FirstDecl,
                                                               NumFileDecls));
      }
  
      const SrcMgr::ContentCache *ContentCache
        = SourceMgr.getOrCreateContentCache(File,
                                /*isSystemFile=*/FileCharacter != SrcMgr::C_User);
      if (OverriddenBuffer && !ContentCache->BufferOverridden &&
          ContentCache->ContentsEntry == ContentCache->OrigEntry &&
          !ContentCache->getRawBuffer()) {
        auto Buffer = ReadBuffer(SLocEntryCursor, File->getName());
        if (!Buffer)
          return true;
        SourceMgr.overrideFileContents(File, std::move(Buffer));
      }
  
      break;
    }
  
    case SM_SLOC_BUFFER_ENTRY: {
      const char *Name = Blob.data();
      unsigned Offset = Record[0];
      SrcMgr::CharacteristicKind
        FileCharacter = (SrcMgr::CharacteristicKind)Record[2];
      SourceLocation IncludeLoc = ReadSourceLocation(*F, Record[1]);
      if (IncludeLoc.isInvalid() &&
          (F->Kind == MK_ImplicitModule || F->Kind == MK_ExplicitModule)) {
        IncludeLoc = getImportLocation(F);
      }
  
      auto Buffer = ReadBuffer(SLocEntryCursor, Name);
      if (!Buffer)
        return true;
      SourceMgr.createFileID(std::move(Buffer), FileCharacter, ID,
                             BaseOffset + Offset, IncludeLoc);
      break;
    }
  
    case SM_SLOC_EXPANSION_ENTRY: {
      SourceLocation SpellingLoc = ReadSourceLocation(*F, Record[1]);
      SourceMgr.createExpansionLoc(SpellingLoc,
                                       ReadSourceLocation(*F, Record[2]),
                                       ReadSourceLocation(*F, Record[3]),
                                       Record[4],
                                       ID,
                                       BaseOffset + Record[0]);
      break;
    }
    }
  
    return false;
  }
  
  std::pair<SourceLocation, StringRef> ASTReader::getModuleImportLoc(int ID) {
    if (ID == 0)
      return std::make_pair(SourceLocation(), "");
  
    if (unsigned(-ID) - 2 >= getTotalNumSLocs() || ID > 0) {
      Error("source location entry ID out-of-range for AST file");
      return std::make_pair(SourceLocation(), "");
    }
  
    // Find which module file this entry lands in.
    ModuleFile *M = GlobalSLocEntryMap.find(-ID)->second;
    if (M->Kind != MK_ImplicitModule && M->Kind != MK_ExplicitModule)
      return std::make_pair(SourceLocation(), "");
  
    // FIXME: Can we map this down to a particular submodule? That would be
    // ideal.
    return std::make_pair(M->ImportLoc, StringRef(M->ModuleName));
  }
  
  /// \brief Find the location where the module F is imported.
  SourceLocation ASTReader::getImportLocation(ModuleFile *F) {
    if (F->ImportLoc.isValid())
      return F->ImportLoc;
    
    // Otherwise we have a PCH. It's considered to be "imported" at the first
    // location of its includer.
    if (F->ImportedBy.empty() || !F->ImportedBy[0]) {
      // Main file is the importer.
      assert(SourceMgr.getMainFileID().isValid() && "missing main file");
      return SourceMgr.getLocForStartOfFile(SourceMgr.getMainFileID());
    }
    return F->ImportedBy[0]->FirstLoc;
  }
  
  /// ReadBlockAbbrevs - Enter a subblock of the specified BlockID with the
  /// specified cursor.  Read the abbreviations that are at the top of the block
  /// and then leave the cursor pointing into the block.
  bool ASTReader::ReadBlockAbbrevs(BitstreamCursor &Cursor, unsigned BlockID) {
    if (Cursor.EnterSubBlock(BlockID))
      return true;
  
    while (true) {
      uint64_t Offset = Cursor.GetCurrentBitNo();
      unsigned Code = Cursor.ReadCode();
  
      // We expect all abbrevs to be at the start of the block.
      if (Code != llvm::bitc::DEFINE_ABBREV) {
        Cursor.JumpToBit(Offset);
        return false;
      }
      Cursor.ReadAbbrevRecord();
    }
  }
  
  Token ASTReader::ReadToken(ModuleFile &F, const RecordDataImpl &Record,
                             unsigned &Idx) {
    Token Tok;
    Tok.startToken();
    Tok.setLocation(ReadSourceLocation(F, Record, Idx));
    Tok.setLength(Record[Idx++]);
    if (IdentifierInfo *II = getLocalIdentifier(F, Record[Idx++]))
      Tok.setIdentifierInfo(II);
    Tok.setKind((tok::TokenKind)Record[Idx++]);
    Tok.setFlag((Token::TokenFlags)Record[Idx++]);
    return Tok;
  }
  
  MacroInfo *ASTReader::ReadMacroRecord(ModuleFile &F, uint64_t Offset) {
    BitstreamCursor &Stream = F.MacroCursor;
  
    // Keep track of where we are in the stream, then jump back there
    // after reading this macro.
    SavedStreamPosition SavedPosition(Stream);
  
    Stream.JumpToBit(Offset);
    RecordData Record;
    SmallVector<IdentifierInfo*, 16> MacroArgs;
    MacroInfo *Macro = nullptr;
  
    while (true) {
      // Advance to the next record, but if we get to the end of the block, don't
      // pop it (removing all the abbreviations from the cursor) since we want to
      // be able to reseek within the block and read entries.
      unsigned Flags = BitstreamCursor::AF_DontPopBlockAtEnd;
      llvm::BitstreamEntry Entry = Stream.advanceSkippingSubblocks(Flags);
      
      switch (Entry.Kind) {
      case llvm::BitstreamEntry::SubBlock: // Handled for us already.
      case llvm::BitstreamEntry::Error:
        Error("malformed block record in AST file");
        return Macro;
      case llvm::BitstreamEntry::EndBlock:
        return Macro;
      case llvm::BitstreamEntry::Record:
        // The interesting case.
        break;
      }
  
      // Read a record.
      Record.clear();
      PreprocessorRecordTypes RecType =
        (PreprocessorRecordTypes)Stream.readRecord(Entry.ID, Record);
      switch (RecType) {
      case PP_MODULE_MACRO:
      case PP_MACRO_DIRECTIVE_HISTORY:
        return Macro;
  
      case PP_MACRO_OBJECT_LIKE:
      case PP_MACRO_FUNCTION_LIKE: {
        // If we already have a macro, that means that we've hit the end
        // of the definition of the macro we were looking for. We're
        // done.
        if (Macro)
          return Macro;
  
        unsigned NextIndex = 1; // Skip identifier ID.
        SubmoduleID SubModID = getGlobalSubmoduleID(F, Record[NextIndex++]);
        SourceLocation Loc = ReadSourceLocation(F, Record, NextIndex);
        MacroInfo *MI = PP.AllocateDeserializedMacroInfo(Loc, SubModID);
        MI->setDefinitionEndLoc(ReadSourceLocation(F, Record, NextIndex));
        MI->setIsUsed(Record[NextIndex++]);
        MI->setUsedForHeaderGuard(Record[NextIndex++]);
  
        if (RecType == PP_MACRO_FUNCTION_LIKE) {
          // Decode function-like macro info.
          bool isC99VarArgs = Record[NextIndex++];
          bool isGNUVarArgs = Record[NextIndex++];
          bool hasCommaPasting = Record[NextIndex++];
          MacroArgs.clear();
          unsigned NumArgs = Record[NextIndex++];
          for (unsigned i = 0; i != NumArgs; ++i)
            MacroArgs.push_back(getLocalIdentifier(F, Record[NextIndex++]));
  
          // Install function-like macro info.
          MI->setIsFunctionLike();
          if (isC99VarArgs) MI->setIsC99Varargs();
          if (isGNUVarArgs) MI->setIsGNUVarargs();
          if (hasCommaPasting) MI->setHasCommaPasting();
          MI->setArgumentList(MacroArgs, PP.getPreprocessorAllocator());
        }
  
        // Remember that we saw this macro last so that we add the tokens that
        // form its body to it.
        Macro = MI;
  
        if (NextIndex + 1 == Record.size() && PP.getPreprocessingRecord() &&
            Record[NextIndex]) {
          // We have a macro definition. Register the association
          PreprocessedEntityID
              GlobalID = getGlobalPreprocessedEntityID(F, Record[NextIndex]);
          PreprocessingRecord &PPRec = *PP.getPreprocessingRecord();
          PreprocessingRecord::PPEntityID PPID =
              PPRec.getPPEntityID(GlobalID - 1, /*isLoaded=*/true);
          MacroDefinitionRecord *PPDef = cast_or_null<MacroDefinitionRecord>(
              PPRec.getPreprocessedEntity(PPID));
          if (PPDef)
            PPRec.RegisterMacroDefinition(Macro, PPDef);
        }
  
        ++NumMacrosRead;
        break;
      }
  
      case PP_TOKEN: {
        // If we see a TOKEN before a PP_MACRO_*, then the file is
        // erroneous, just pretend we didn't see this.
        if (!Macro) break;
  
        unsigned Idx = 0;
        Token Tok = ReadToken(F, Record, Idx);
        Macro->AddTokenToBody(Tok);
        break;
      }
      }
    }
  }
  
  PreprocessedEntityID 
  ASTReader::getGlobalPreprocessedEntityID(ModuleFile &M, unsigned LocalID) const {
    ContinuousRangeMap<uint32_t, int, 2>::const_iterator 
      I = M.PreprocessedEntityRemap.find(LocalID - NUM_PREDEF_PP_ENTITY_IDS);
    assert(I != M.PreprocessedEntityRemap.end() 
           && "Invalid index into preprocessed entity index remap");
    
    return LocalID + I->second;
  }
  
  unsigned HeaderFileInfoTrait::ComputeHash(internal_key_ref ikey) {
    return llvm::hash_combine(ikey.Size, ikey.ModTime);
  }
  
  HeaderFileInfoTrait::internal_key_type 
  HeaderFileInfoTrait::GetInternalKey(const FileEntry *FE) {
    internal_key_type ikey = {FE->getSize(),
                              M.HasTimestamps ? FE->getModificationTime() : 0,
                              FE->getName(), /*Imported*/ false};
    return ikey;
  }
      
  bool HeaderFileInfoTrait::EqualKey(internal_key_ref a, internal_key_ref b) {
    if (a.Size != b.Size || (a.ModTime && b.ModTime && a.ModTime != b.ModTime))
      return false;
  
    if (llvm::sys::path::is_absolute(a.Filename) &&
        strcmp(a.Filename, b.Filename) == 0)
      return true;
    
    // Determine whether the actual files are equivalent.
    FileManager &FileMgr = Reader.getFileManager();
    auto GetFile = [&](const internal_key_type &Key) -> const FileEntry* {
      if (!Key.Imported)
        return FileMgr.getFile(Key.Filename);
  
      std::string Resolved = Key.Filename;
      Reader.ResolveImportedPath(M, Resolved);
      return FileMgr.getFile(Resolved);
    };
  
    const FileEntry *FEA = GetFile(a);
    const FileEntry *FEB = GetFile(b);
    return FEA && FEA == FEB;
  }
      
  std::pair<unsigned, unsigned>
  HeaderFileInfoTrait::ReadKeyDataLength(const unsigned char*& d) {
    using namespace llvm::support;
    unsigned KeyLen = (unsigned) endian::readNext<uint16_t, little, unaligned>(d);
    unsigned DataLen = (unsigned) *d++;
    return std::make_pair(KeyLen, DataLen);
  }
  
  HeaderFileInfoTrait::internal_key_type
  HeaderFileInfoTrait::ReadKey(const unsigned char *d, unsigned) {
    using namespace llvm::support;
    internal_key_type ikey;
    ikey.Size = off_t(endian::readNext<uint64_t, little, unaligned>(d));
    ikey.ModTime = time_t(endian::readNext<uint64_t, little, unaligned>(d));
    ikey.Filename = (const char *)d;
    ikey.Imported = true;
    return ikey;
  }
  
  HeaderFileInfoTrait::data_type 
  HeaderFileInfoTrait::ReadData(internal_key_ref key, const unsigned char *d,
                                unsigned DataLen) {
    const unsigned char *End = d + DataLen;
    using namespace llvm::support;
    HeaderFileInfo HFI;
    unsigned Flags = *d++;
    // FIXME: Refactor with mergeHeaderFileInfo in HeaderSearch.cpp.
    HFI.isImport |= (Flags >> 4) & 0x01;
    HFI.isPragmaOnce |= (Flags >> 3) & 0x01;
    HFI.DirInfo = (Flags >> 1) & 0x03;
    HFI.IndexHeaderMapHeader = Flags & 0x01;
    // FIXME: Find a better way to handle this. Maybe just store a
    // "has been included" flag?
    HFI.NumIncludes = std::max(endian::readNext<uint16_t, little, unaligned>(d),
                               HFI.NumIncludes);
    HFI.ControllingMacroID = Reader.getGlobalIdentifierID(
        M, endian::readNext<uint32_t, little, unaligned>(d));
    if (unsigned FrameworkOffset =
            endian::readNext<uint32_t, little, unaligned>(d)) {
      // The framework offset is 1 greater than the actual offset, 
      // since 0 is used as an indicator for "no framework name".
      StringRef FrameworkName(FrameworkStrings + FrameworkOffset - 1);
      HFI.Framework = HS->getUniqueFrameworkName(FrameworkName);
    }
  
    assert((End - d) % 4 == 0 &&
           "Wrong data length in HeaderFileInfo deserialization");
    while (d != End) {
      uint32_t LocalSMID = endian::readNext<uint32_t, little, unaligned>(d);
      auto HeaderRole = static_cast<ModuleMap::ModuleHeaderRole>(LocalSMID & 3);
      LocalSMID >>= 2;
  
      // This header is part of a module. Associate it with the module to enable
      // implicit module import.
      SubmoduleID GlobalSMID = Reader.getGlobalSubmoduleID(M, LocalSMID);
      Module *Mod = Reader.getSubmodule(GlobalSMID);
      FileManager &FileMgr = Reader.getFileManager();
      ModuleMap &ModMap =
          Reader.getPreprocessor().getHeaderSearchInfo().getModuleMap();
  
      std::string Filename = key.Filename;
      if (key.Imported)
        Reader.ResolveImportedPath(M, Filename);
      // FIXME: This is not always the right filename-as-written, but we're not
      // going to use this information to rebuild the module, so it doesn't make
      // a lot of difference.
      Module::Header H = { key.Filename, FileMgr.getFile(Filename) };
      ModMap.addHeader(Mod, H, HeaderRole, /*Imported*/true);
      HFI.isModuleHeader |= !(HeaderRole & ModuleMap::TextualHeader);
    }
  
    // This HeaderFileInfo was externally loaded.
    HFI.External = true;
    HFI.IsValid = true;
    return HFI;
  }
  
  void ASTReader::addPendingMacro(IdentifierInfo *II,
                                  ModuleFile *M,
                                  uint64_t MacroDirectivesOffset) {
    assert(NumCurrentElementsDeserializing > 0 &&"Missing deserialization guard");
    PendingMacroIDs[II].push_back(PendingMacroInfo(M, MacroDirectivesOffset));
  }
  
  void ASTReader::ReadDefinedMacros() {
    // Note that we are loading defined macros.
    Deserializing Macros(this);
  
    for (auto &I : llvm::reverse(ModuleMgr)) {
      BitstreamCursor &MacroCursor = I->MacroCursor;
  
      // If there was no preprocessor block, skip this file.
      if (!MacroCursor.getBitStreamReader())
        continue;
  
      BitstreamCursor Cursor = MacroCursor;
      Cursor.JumpToBit(I->MacroStartOffset);
  
      RecordData Record;
      while (true) {
        llvm::BitstreamEntry E = Cursor.advanceSkippingSubblocks();
        
        switch (E.Kind) {
        case llvm::BitstreamEntry::SubBlock: // Handled for us already.
        case llvm::BitstreamEntry::Error:
          Error("malformed block record in AST file");
          return;
        case llvm::BitstreamEntry::EndBlock:
          goto NextCursor;
          
        case llvm::BitstreamEntry::Record:
          Record.clear();
          switch (Cursor.readRecord(E.ID, Record)) {
          default:  // Default behavior: ignore.
            break;
            
          case PP_MACRO_OBJECT_LIKE:
          case PP_MACRO_FUNCTION_LIKE: {
            IdentifierInfo *II = getLocalIdentifier(*I, Record[0]);
            if (II->isOutOfDate())
              updateOutOfDateIdentifier(*II);
            break;
          }
            
          case PP_TOKEN:
            // Ignore tokens.
            break;
          }
          break;
        }
      }
      NextCursor:  ;
    }
  }
  
  namespace {
    /// \brief Visitor class used to look up identifirs in an AST file.
    class IdentifierLookupVisitor {
      StringRef Name;
      unsigned NameHash;
      unsigned PriorGeneration;
      unsigned &NumIdentifierLookups;
      unsigned &NumIdentifierLookupHits;
      IdentifierInfo *Found;
  
    public:
      IdentifierLookupVisitor(StringRef Name, unsigned PriorGeneration,
                              unsigned &NumIdentifierLookups,
                              unsigned &NumIdentifierLookupHits)
        : Name(Name), NameHash(ASTIdentifierLookupTrait::ComputeHash(Name)),
          PriorGeneration(PriorGeneration),
          NumIdentifierLookups(NumIdentifierLookups),
          NumIdentifierLookupHits(NumIdentifierLookupHits),
          Found()
      {
      }
  
      bool operator()(ModuleFile &M) {
        // If we've already searched this module file, skip it now.
        if (M.Generation <= PriorGeneration)
          return true;
  
        ASTIdentifierLookupTable *IdTable
          = (ASTIdentifierLookupTable *)M.IdentifierLookupTable;
        if (!IdTable)
          return false;
  
        ASTIdentifierLookupTrait Trait(IdTable->getInfoObj().getReader(), M,
                                       Found);
        ++NumIdentifierLookups;
        ASTIdentifierLookupTable::iterator Pos =
            IdTable->find_hashed(Name, NameHash, &Trait);
        if (Pos == IdTable->end())
          return false;
        
        // Dereferencing the iterator has the effect of building the
        // IdentifierInfo node and populating it with the various
        // declarations it needs.
        ++NumIdentifierLookupHits;
        Found = *Pos;
        return true;
      }
      
      // \brief Retrieve the identifier info found within the module
      // files.
      IdentifierInfo *getIdentifierInfo() const { return Found; }
    };
  }
  
  void ASTReader::updateOutOfDateIdentifier(IdentifierInfo &II) {
    // Note that we are loading an identifier.
    Deserializing AnIdentifier(this);
  
    unsigned PriorGeneration = 0;
    if (getContext().getLangOpts().Modules)
      PriorGeneration = IdentifierGeneration[&II];
  
    // If there is a global index, look there first to determine which modules
    // provably do not have any results for this identifier.
    GlobalModuleIndex::HitSet Hits;
    GlobalModuleIndex::HitSet *HitsPtr = nullptr;
    if (!loadGlobalIndex()) {
      if (GlobalIndex->lookupIdentifier(II.getName(), Hits)) {
        HitsPtr = &Hits;
      }
    }
  
    IdentifierLookupVisitor Visitor(II.getName(), PriorGeneration,
                                    NumIdentifierLookups,
                                    NumIdentifierLookupHits);
    ModuleMgr.visit(Visitor, HitsPtr);
    markIdentifierUpToDate(&II);
  }
  
  void ASTReader::markIdentifierUpToDate(IdentifierInfo *II) {
    if (!II)
      return;
    
    II->setOutOfDate(false);
  
    // Update the generation for this identifier.
    if (getContext().getLangOpts().Modules)
      IdentifierGeneration[II] = getGeneration();
  }
  
  void ASTReader::resolvePendingMacro(IdentifierInfo *II,
                                      const PendingMacroInfo &PMInfo) {
    ModuleFile &M = *PMInfo.M;
  
    BitstreamCursor &Cursor = M.MacroCursor;
    SavedStreamPosition SavedPosition(Cursor);
    Cursor.JumpToBit(PMInfo.MacroDirectivesOffset);
  
    struct ModuleMacroRecord {
      SubmoduleID SubModID;
      MacroInfo *MI;
      SmallVector<SubmoduleID, 8> Overrides;
    };
    llvm::SmallVector<ModuleMacroRecord, 8> ModuleMacros;
  
    // We expect to see a sequence of PP_MODULE_MACRO records listing exported
    // macros, followed by a PP_MACRO_DIRECTIVE_HISTORY record with the complete
    // macro histroy.
    RecordData Record;
    while (true) {
      llvm::BitstreamEntry Entry =
          Cursor.advance(BitstreamCursor::AF_DontPopBlockAtEnd);
      if (Entry.Kind != llvm::BitstreamEntry::Record) {
        Error("malformed block record in AST file");
        return;
      }
  
      Record.clear();
      switch ((PreprocessorRecordTypes)Cursor.readRecord(Entry.ID, Record)) {
      case PP_MACRO_DIRECTIVE_HISTORY:
        break;
  
      case PP_MODULE_MACRO: {
        ModuleMacros.push_back(ModuleMacroRecord());
        auto &Info = ModuleMacros.back();
        Info.SubModID = getGlobalSubmoduleID(M, Record[0]);
        Info.MI = getMacro(getGlobalMacroID(M, Record[1]));
        for (int I = 2, N = Record.size(); I != N; ++I)
          Info.Overrides.push_back(getGlobalSubmoduleID(M, Record[I]));
        continue;
      }
  
      default:
        Error("malformed block record in AST file");
        return;
      }
  
      // We found the macro directive history; that's the last record
      // for this macro.
      break;
    }
  
    // Module macros are listed in reverse dependency order.
    {
      std::reverse(ModuleMacros.begin(), ModuleMacros.end());
      llvm::SmallVector<ModuleMacro*, 8> Overrides;
      for (auto &MMR : ModuleMacros) {
        Overrides.clear();
        for (unsigned ModID : MMR.Overrides) {
          Module *Mod = getSubmodule(ModID);
          auto *Macro = PP.getModuleMacro(Mod, II);
          assert(Macro && "missing definition for overridden macro");
          Overrides.push_back(Macro);
        }
  
        bool Inserted = false;
        Module *Owner = getSubmodule(MMR.SubModID);
        PP.addModuleMacro(Owner, II, MMR.MI, Overrides, Inserted);
      }
    }
  
    // Don't read the directive history for a module; we don't have anywhere
    // to put it.
    if (M.Kind == MK_ImplicitModule || M.Kind == MK_ExplicitModule)
      return;
  
    // Deserialize the macro directives history in reverse source-order.
    MacroDirective *Latest = nullptr, *Earliest = nullptr;
    unsigned Idx = 0, N = Record.size();
    while (Idx < N) {
      MacroDirective *MD = nullptr;
      SourceLocation Loc = ReadSourceLocation(M, Record, Idx);
      MacroDirective::Kind K = (MacroDirective::Kind)Record[Idx++];
      switch (K) {
      case MacroDirective::MD_Define: {
        MacroInfo *MI = getMacro(getGlobalMacroID(M, Record[Idx++]));
        MD = PP.AllocateDefMacroDirective(MI, Loc);
        break;
      }
      case MacroDirective::MD_Undefine: {
        MD = PP.AllocateUndefMacroDirective(Loc);
        break;
      }
      case MacroDirective::MD_Visibility:
        bool isPublic = Record[Idx++];
        MD = PP.AllocateVisibilityMacroDirective(Loc, isPublic);
        break;
      }
  
      if (!Latest)
        Latest = MD;
      if (Earliest)
        Earliest->setPrevious(MD);
      Earliest = MD;
    }
  
    if (Latest)
      PP.setLoadedMacroDirective(II, Latest);
  }
  
  ASTReader::InputFileInfo
  ASTReader::readInputFileInfo(ModuleFile &F, unsigned ID) {
    // Go find this input file.
    BitstreamCursor &Cursor = F.InputFilesCursor;
    SavedStreamPosition SavedPosition(Cursor);
    Cursor.JumpToBit(F.InputFileOffsets[ID-1]);
  
    unsigned Code = Cursor.ReadCode();
    RecordData Record;
    StringRef Blob;
  
    unsigned Result = Cursor.readRecord(Code, Record, &Blob);
    assert(static_cast<InputFileRecordTypes>(Result) == INPUT_FILE &&
           "invalid record type for input file");
    (void)Result;
  
    assert(Record[0] == ID && "Bogus stored ID or offset");
    InputFileInfo R;
    R.StoredSize = static_cast<off_t>(Record[1]);
    R.StoredTime = static_cast<time_t>(Record[2]);
    R.Overridden = static_cast<bool>(Record[3]);
    R.Transient = static_cast<bool>(Record[4]);
    R.Filename = Blob;
    ResolveImportedPath(F, R.Filename);
    return R;
  }
  
  InputFile ASTReader::getInputFile(ModuleFile &F, unsigned ID, bool Complain) {
    // If this ID is bogus, just return an empty input file.
    if (ID == 0 || ID > F.InputFilesLoaded.size())
      return InputFile();
  
    // If we've already loaded this input file, return it.
    if (F.InputFilesLoaded[ID-1].getFile())
      return F.InputFilesLoaded[ID-1];
  
    if (F.InputFilesLoaded[ID-1].isNotFound())
      return InputFile();
  
    // Go find this input file.
    BitstreamCursor &Cursor = F.InputFilesCursor;
    SavedStreamPosition SavedPosition(Cursor);
    Cursor.JumpToBit(F.InputFileOffsets[ID-1]);
    
    InputFileInfo FI = readInputFileInfo(F, ID);
    off_t StoredSize = FI.StoredSize;
    time_t StoredTime = FI.StoredTime;
    bool Overridden = FI.Overridden;
    bool Transient = FI.Transient;
    StringRef Filename = FI.Filename;
  
    const FileEntry *File = FileMgr.getFile(Filename, /*OpenFile=*/false);
  
    // If we didn't find the file, resolve it relative to the
    // original directory from which this AST file was created.
    if (File == nullptr && !F.OriginalDir.empty() && !CurrentDir.empty() &&
        F.OriginalDir != CurrentDir) {
      std::string Resolved = resolveFileRelativeToOriginalDir(Filename,
                                                              F.OriginalDir,
                                                              CurrentDir);
      if (!Resolved.empty())
        File = FileMgr.getFile(Resolved);
    }
  
    // For an overridden file, create a virtual file with the stored
    // size/timestamp.
    if ((Overridden || Transient) && File == nullptr)
      File = FileMgr.getVirtualFile(Filename, StoredSize, StoredTime);
  
    if (File == nullptr) {
      if (Complain) {
        std::string ErrorStr = "could not find file '";
        ErrorStr += Filename;
        ErrorStr += "' referenced by AST file '";
        ErrorStr += F.FileName;
        ErrorStr += "'";
        Error(ErrorStr.c_str());
      }
      // Record that we didn't find the file.
      F.InputFilesLoaded[ID-1] = InputFile::getNotFound();
      return InputFile();
    }
  
    // Check if there was a request to override the contents of the file
    // that was part of the precompiled header. Overridding such a file
    // can lead to problems when lexing using the source locations from the
    // PCH.
    SourceManager &SM = getSourceManager();
    // FIXME: Reject if the overrides are different.
    if ((!Overridden && !Transient) && SM.isFileOverridden(File)) {
      if (Complain)
        Error(diag::err_fe_pch_file_overridden, Filename);
      // After emitting the diagnostic, recover by disabling the override so
      // that the original file will be used.
      //
      // FIXME: This recovery is just as broken as the original state; there may
      // be another precompiled module that's using the overridden contents, or
      // we might be half way through parsing it. Instead, we should treat the
      // overridden contents as belonging to a separate FileEntry.
      SM.disableFileContentsOverride(File);
      // The FileEntry is a virtual file entry with the size of the contents
      // that would override the original contents. Set it to the original's
      // size/time.
      FileMgr.modifyFileEntry(const_cast<FileEntry*>(File),
                              StoredSize, StoredTime);
    }
  
    bool IsOutOfDate = false;
  
    // For an overridden file, there is nothing to validate.
    if (!Overridden && //
        (StoredSize != File->getSize() ||
         (StoredTime && StoredTime != File->getModificationTime() &&
          !DisableValidation)
         )) {
      if (Complain) {
        // Build a list of the PCH imports that got us here (in reverse).
        SmallVector<ModuleFile *, 4> ImportStack(1, &F);
        while (ImportStack.back()->ImportedBy.size() > 0)
          ImportStack.push_back(ImportStack.back()->ImportedBy[0]);
  
        // The top-level PCH is stale.
        StringRef TopLevelPCHName(ImportStack.back()->FileName);
        Error(diag::err_fe_pch_file_modified, Filename, TopLevelPCHName);
  
        // Print the import stack.
        if (ImportStack.size() > 1 && !Diags.isDiagnosticInFlight()) {
          Diag(diag::note_pch_required_by)
            << Filename << ImportStack[0]->FileName;
          for (unsigned I = 1; I < ImportStack.size(); ++I)
            Diag(diag::note_pch_required_by)
              << ImportStack[I-1]->FileName << ImportStack[I]->FileName;
        }
  
        if (!Diags.isDiagnosticInFlight())
          Diag(diag::note_pch_rebuild_required) << TopLevelPCHName;
      }
  
      IsOutOfDate = true;
    }
    // FIXME: If the file is overridden and we've already opened it,
    // issue an error (or split it into a separate FileEntry).
  
    InputFile IF = InputFile(File, Overridden || Transient, IsOutOfDate);
  
    // Note that we've loaded this input file.
    F.InputFilesLoaded[ID-1] = IF;
    return IF;
  }
  
  /// \brief If we are loading a relocatable PCH or module file, and the filename
  /// is not an absolute path, add the system or module root to the beginning of
  /// the file name.
  void ASTReader::ResolveImportedPath(ModuleFile &M, std::string &Filename) {
    // Resolve relative to the base directory, if we have one.
    if (!M.BaseDirectory.empty())
      return ResolveImportedPath(Filename, M.BaseDirectory);
  }
  
  void ASTReader::ResolveImportedPath(std::string &Filename, StringRef Prefix) {
    if (Filename.empty() || llvm::sys::path::is_absolute(Filename))
      return;
  
    SmallString<128> Buffer;
    llvm::sys::path::append(Buffer, Prefix, Filename);
    Filename.assign(Buffer.begin(), Buffer.end());
  }
  
  static bool isDiagnosedResult(ASTReader::ASTReadResult ARR, unsigned Caps) {
    switch (ARR) {
    case ASTReader::Failure: return true;
    case ASTReader::Missing: return !(Caps & ASTReader::ARR_Missing);
    case ASTReader::OutOfDate: return !(Caps & ASTReader::ARR_OutOfDate);
    case ASTReader::VersionMismatch: return !(Caps & ASTReader::ARR_VersionMismatch);
    case ASTReader::ConfigurationMismatch:
      return !(Caps & ASTReader::ARR_ConfigurationMismatch);
    case ASTReader::HadErrors: return true;
    case ASTReader::Success: return false;
    }
  
    llvm_unreachable("unknown ASTReadResult");
  }
  
  ASTReader::ASTReadResult ASTReader::ReadOptionsBlock(
      BitstreamCursor &Stream, unsigned ClientLoadCapabilities,
      bool AllowCompatibleConfigurationMismatch, ASTReaderListener &Listener,
      std::string &SuggestedPredefines) {
    if (Stream.EnterSubBlock(OPTIONS_BLOCK_ID))
      return Failure;
  
    // Read all of the records in the options block.
    RecordData Record;
    ASTReadResult Result = Success;
    while (1) {
      llvm::BitstreamEntry Entry = Stream.advance();
      
      switch (Entry.Kind) {
      case llvm::BitstreamEntry::Error:
      case llvm::BitstreamEntry::SubBlock:
        return Failure;
  
      case llvm::BitstreamEntry::EndBlock:
        return Result;
  
      case llvm::BitstreamEntry::Record:
        // The interesting case.
        break;
      }
  
      // Read and process a record.
      Record.clear();
      switch ((OptionsRecordTypes)Stream.readRecord(Entry.ID, Record)) {
      case LANGUAGE_OPTIONS: {
        bool Complain = (ClientLoadCapabilities & ARR_ConfigurationMismatch) == 0;
        if (ParseLanguageOptions(Record, Complain, Listener,
                                 AllowCompatibleConfigurationMismatch))
          Result = ConfigurationMismatch;
        break;
      }
  
      case TARGET_OPTIONS: {
        bool Complain = (ClientLoadCapabilities & ARR_ConfigurationMismatch) == 0;
        if (ParseTargetOptions(Record, Complain, Listener,
                               AllowCompatibleConfigurationMismatch))
          Result = ConfigurationMismatch;
        break;
      }
  
      case DIAGNOSTIC_OPTIONS: {
        bool Complain = (ClientLoadCapabilities & ARR_OutOfDate) == 0;
        if (!AllowCompatibleConfigurationMismatch &&
            ParseDiagnosticOptions(Record, Complain, Listener))
          return OutOfDate;
        break;
      }
  
      case FILE_SYSTEM_OPTIONS: {
        bool Complain = (ClientLoadCapabilities & ARR_ConfigurationMismatch) == 0;
        if (!AllowCompatibleConfigurationMismatch &&
            ParseFileSystemOptions(Record, Complain, Listener))
          Result = ConfigurationMismatch;
        break;
      }
  
      case HEADER_SEARCH_OPTIONS: {
        bool Complain = (ClientLoadCapabilities & ARR_ConfigurationMismatch) == 0;
        if (!AllowCompatibleConfigurationMismatch &&
            ParseHeaderSearchOptions(Record, Complain, Listener))
          Result = ConfigurationMismatch;
        break;
      }
  
      case PREPROCESSOR_OPTIONS:
        bool Complain = (ClientLoadCapabilities & ARR_ConfigurationMismatch) == 0;
        if (!AllowCompatibleConfigurationMismatch &&
            ParsePreprocessorOptions(Record, Complain, Listener,
                                     SuggestedPredefines))
          Result = ConfigurationMismatch;
        break;
      }
    }
  }
  
  ASTReader::ASTReadResult
  ASTReader::ReadControlBlock(ModuleFile &F,
                              SmallVectorImpl<ImportedModule> &Loaded,
                              const ModuleFile *ImportedBy,
                              unsigned ClientLoadCapabilities) {
    BitstreamCursor &Stream = F.Stream;
    ASTReadResult Result = Success;
  
    if (Stream.EnterSubBlock(CONTROL_BLOCK_ID)) {
      Error("malformed block record in AST file");
      return Failure;
    }
  
    // Read all of the records and blocks in the control block.
    RecordData Record;
    unsigned NumInputs = 0;
    unsigned NumUserInputs = 0;
    while (1) {
      llvm::BitstreamEntry Entry = Stream.advance();
      
      switch (Entry.Kind) {
      case llvm::BitstreamEntry::Error:
        Error("malformed block record in AST file");
        return Failure;
      case llvm::BitstreamEntry::EndBlock: {
        // Validate input files.
        const HeaderSearchOptions &HSOpts =
            PP.getHeaderSearchInfo().getHeaderSearchOpts();
  
        // All user input files reside at the index range [0, NumUserInputs), and
        // system input files reside at [NumUserInputs, NumInputs). For explicitly
        // loaded module files, ignore missing inputs.
        if (!DisableValidation && F.Kind != MK_ExplicitModule) {
          bool Complain = (ClientLoadCapabilities & ARR_OutOfDate) == 0;
  
          // If we are reading a module, we will create a verification timestamp,
          // so we verify all input files.  Otherwise, verify only user input
          // files.
  
          unsigned N = NumUserInputs;
          if (ValidateSystemInputs ||
              (HSOpts.ModulesValidateOncePerBuildSession &&
               F.InputFilesValidationTimestamp <= HSOpts.BuildSessionTimestamp &&
               F.Kind == MK_ImplicitModule))
            N = NumInputs;
  
          for (unsigned I = 0; I < N; ++I) {
            InputFile IF = getInputFile(F, I+1, Complain);
            if (!IF.getFile() || IF.isOutOfDate())
              return OutOfDate;
          }
        }
  
        if (Listener)
          Listener->visitModuleFile(F.FileName, F.Kind);
  
        if (Listener && Listener->needsInputFileVisitation()) {
          unsigned N = Listener->needsSystemInputFileVisitation() ? NumInputs
                                                                  : NumUserInputs;
          for (unsigned I = 0; I < N; ++I) {
            bool IsSystem = I >= NumUserInputs;
            InputFileInfo FI = readInputFileInfo(F, I+1);
            Listener->visitInputFile(FI.Filename, IsSystem, FI.Overridden,
                                     F.Kind == MK_ExplicitModule);
          }
        }
  
        return Result;
      }
  
      case llvm::BitstreamEntry::SubBlock:
        switch (Entry.ID) {
        case INPUT_FILES_BLOCK_ID:
          F.InputFilesCursor = Stream;
          if (Stream.SkipBlock() || // Skip with the main cursor
              // Read the abbreviations
              ReadBlockAbbrevs(F.InputFilesCursor, INPUT_FILES_BLOCK_ID)) {
            Error("malformed block record in AST file");
            return Failure;
          }
          continue;
  
        case OPTIONS_BLOCK_ID:
          // If we're reading the first module for this group, check its options
          // are compatible with ours. For modules it imports, no further checking
          // is required, because we checked them when we built it.
          if (Listener && !ImportedBy) {
            // Should we allow the configuration of the module file to differ from
            // the configuration of the current translation unit in a compatible
            // way?
            //
            // FIXME: Allow this for files explicitly specified with -include-pch.
            bool AllowCompatibleConfigurationMismatch =
                F.Kind == MK_ExplicitModule;
  
            Result = ReadOptionsBlock(Stream, ClientLoadCapabilities,
                                      AllowCompatibleConfigurationMismatch,
                                      *Listener, SuggestedPredefines);
            if (Result == Failure) {
              Error("malformed block record in AST file");
              return Result;
            }
  
            if (DisableValidation ||
                (AllowConfigurationMismatch && Result == ConfigurationMismatch))
              Result = Success;
  
            // If we can't load the module, exit early since we likely
            // will rebuild the module anyway. The stream may be in the
            // middle of a block.
            if (Result != Success)
              return Result;
          } else if (Stream.SkipBlock()) {
            Error("malformed block record in AST file");
            return Failure;
          }
          continue;
            
        default:
          if (Stream.SkipBlock()) {
            Error("malformed block record in AST file");
            return Failure;
          }
          continue;
        }
        
      case llvm::BitstreamEntry::Record:
        // The interesting case.
        break;
      }
  
      // Read and process a record.
      Record.clear();
      StringRef Blob;
      switch ((ControlRecordTypes)Stream.readRecord(Entry.ID, Record, &Blob)) {
      case METADATA: {
        if (Record[0] != VERSION_MAJOR && !DisableValidation) {
          if ((ClientLoadCapabilities & ARR_VersionMismatch) == 0)
            Diag(Record[0] < VERSION_MAJOR? diag::err_pch_version_too_old
                                          : diag::err_pch_version_too_new);
          return VersionMismatch;
        }
  
        bool hasErrors = Record[6];
        if (hasErrors && !DisableValidation && !AllowASTWithCompilerErrors) {
          Diag(diag::err_pch_with_compiler_errors);
          return HadErrors;
        }
        if (hasErrors) {
          Diags.ErrorOccurred = true;
          Diags.UncompilableErrorOccurred = true;
          Diags.UnrecoverableErrorOccurred = true;
        }
  
        F.RelocatablePCH = Record[4];
        // Relative paths in a relocatable PCH are relative to our sysroot.
        if (F.RelocatablePCH)
          F.BaseDirectory = isysroot.empty() ? "/" : isysroot;
  
        F.HasTimestamps = Record[5];
  
        const std::string &CurBranch = getClangFullRepositoryVersion();
        StringRef ASTBranch = Blob;
        if (StringRef(CurBranch) != ASTBranch && !DisableValidation) {
          if ((ClientLoadCapabilities & ARR_VersionMismatch) == 0)
            Diag(diag::err_pch_different_branch) << ASTBranch << CurBranch;
          return VersionMismatch;
        }
        break;
      }
  
      case SIGNATURE:
        assert((!F.Signature || F.Signature == Record[0]) && "signature changed");
        F.Signature = Record[0];
        break;
  
      case IMPORTS: {
        // Load each of the imported PCH files. 
        unsigned Idx = 0, N = Record.size();
        while (Idx < N) {
          // Read information about the AST file.
          ModuleKind ImportedKind = (ModuleKind)Record[Idx++];
          // The import location will be the local one for now; we will adjust
          // all import locations of module imports after the global source
          // location info are setup, in ReadAST.
          SourceLocation ImportLoc =
              ReadUntranslatedSourceLocation(Record[Idx++]);
          off_t StoredSize = (off_t)Record[Idx++];
          time_t StoredModTime = (time_t)Record[Idx++];
          ASTFileSignature StoredSignature = Record[Idx++];
          auto ImportedFile = ReadPath(F, Record, Idx);
  
          // If our client can't cope with us being out of date, we can't cope with
          // our dependency being missing.
          unsigned Capabilities = ClientLoadCapabilities;
          if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
            Capabilities &= ~ARR_Missing;
  
          // Load the AST file.
          auto Result = ReadASTCore(ImportedFile, ImportedKind, ImportLoc, &F,
                                    Loaded, StoredSize, StoredModTime,
                                    StoredSignature, Capabilities);
  
          // If we diagnosed a problem, produce a backtrace.
          if (isDiagnosedResult(Result, Capabilities))
            Diag(diag::note_module_file_imported_by)
                << F.FileName << !F.ModuleName.empty() << F.ModuleName;
  
          switch (Result) {
          case Failure: return Failure;
            // If we have to ignore the dependency, we'll have to ignore this too.
          case Missing:
          case OutOfDate: return OutOfDate;
          case VersionMismatch: return VersionMismatch;
          case ConfigurationMismatch: return ConfigurationMismatch;
          case HadErrors: return HadErrors;
          case Success: break;
          }
        }
        break;
      }
  
      case ORIGINAL_FILE:
        F.OriginalSourceFileID = FileID::get(Record[0]);
        F.ActualOriginalSourceFileName = Blob;
        F.OriginalSourceFileName = F.ActualOriginalSourceFileName;
        ResolveImportedPath(F, F.OriginalSourceFileName);
        break;
  
      case ORIGINAL_FILE_ID:
        F.OriginalSourceFileID = FileID::get(Record[0]);
        break;
  
      case ORIGINAL_PCH_DIR:
        F.OriginalDir = Blob;
        break;
  
      case MODULE_NAME:
        F.ModuleName = Blob;
        if (Listener)
          Listener->ReadModuleName(F.ModuleName);
        break;
  
      case MODULE_DIRECTORY: {
        assert(!F.ModuleName.empty() &&
               "MODULE_DIRECTORY found before MODULE_NAME");
        // If we've already loaded a module map file covering this module, we may
        // have a better path for it (relative to the current build).
        Module *M = PP.getHeaderSearchInfo().lookupModule(F.ModuleName);
        if (M && M->Directory) {
          // If we're implicitly loading a module, the base directory can't
          // change between the build and use.
          if (F.Kind != MK_ExplicitModule) {
            const DirectoryEntry *BuildDir =
                PP.getFileManager().getDirectory(Blob);
            if (!BuildDir || BuildDir != M->Directory) {
              if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
                Diag(diag::err_imported_module_relocated)
                    << F.ModuleName << Blob << M->Directory->getName();
              return OutOfDate;
            }
          }
          F.BaseDirectory = M->Directory->getName();
        } else {
          F.BaseDirectory = Blob;
        }
        break;
      }
  
      case MODULE_MAP_FILE:
        if (ASTReadResult Result =
                ReadModuleMapFileBlock(Record, F, ImportedBy, ClientLoadCapabilities))
          return Result;
        break;
  
      case INPUT_FILE_OFFSETS:
        NumInputs = Record[0];
        NumUserInputs = Record[1];
        F.InputFileOffsets =
            (const llvm::support::unaligned_uint64_t *)Blob.data();
        F.InputFilesLoaded.resize(NumInputs);
        break;
      }
    }
  }
  
  ASTReader::ASTReadResult
  ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
    BitstreamCursor &Stream = F.Stream;
  
    if (Stream.EnterSubBlock(AST_BLOCK_ID)) {
      Error("malformed block record in AST file");
      return Failure;
    }
  
    // Read all of the records and blocks for the AST file.
    RecordData Record;
    while (1) {
      llvm::BitstreamEntry Entry = Stream.advance();
      
      switch (Entry.Kind) {
      case llvm::BitstreamEntry::Error:
        Error("error at end of module block in AST file");
        return Failure;
      case llvm::BitstreamEntry::EndBlock: {
        // Outside of C++, we do not store a lookup map for the translation unit.
        // Instead, mark it as needing a lookup map to be built if this module
        // contains any declarations lexically within it (which it always does!).
        // This usually has no cost, since we very rarely need the lookup map for
        // the translation unit outside C++.
        DeclContext *DC = Context.getTranslationUnitDecl();
        if (DC->hasExternalLexicalStorage() &&
            !getContext().getLangOpts().CPlusPlus)
          DC->setMustBuildLookupTable();
        
        return Success;
      }
      case llvm::BitstreamEntry::SubBlock:
        switch (Entry.ID) {
        case DECLTYPES_BLOCK_ID:
          // We lazily load the decls block, but we want to set up the
          // DeclsCursor cursor to point into it.  Clone our current bitcode
          // cursor to it, enter the block and read the abbrevs in that block.
          // With the main cursor, we just skip over it.
          F.DeclsCursor = Stream;
          if (Stream.SkipBlock() ||  // Skip with the main cursor.
              // Read the abbrevs.
              ReadBlockAbbrevs(F.DeclsCursor, DECLTYPES_BLOCK_ID)) {
            Error("malformed block record in AST file");
            return Failure;
          }
          break;
  
        case PREPROCESSOR_BLOCK_ID:
          F.MacroCursor = Stream;
          if (!PP.getExternalSource())
            PP.setExternalSource(this);
          
          if (Stream.SkipBlock() ||
              ReadBlockAbbrevs(F.MacroCursor, PREPROCESSOR_BLOCK_ID)) {
            Error("malformed block record in AST file");
            return Failure;
          }
          F.MacroStartOffset = F.MacroCursor.GetCurrentBitNo();
          break;
          
        case PREPROCESSOR_DETAIL_BLOCK_ID:
          F.PreprocessorDetailCursor = Stream;
          if (Stream.SkipBlock() ||
              ReadBlockAbbrevs(F.PreprocessorDetailCursor,
                               PREPROCESSOR_DETAIL_BLOCK_ID)) {
                Error("malformed preprocessor detail record in AST file");
                return Failure;
              }
          F.PreprocessorDetailStartOffset
          = F.PreprocessorDetailCursor.GetCurrentBitNo();
          
          if (!PP.getPreprocessingRecord())
            PP.createPreprocessingRecord();
          if (!PP.getPreprocessingRecord()->getExternalSource())
            PP.getPreprocessingRecord()->SetExternalSource(*this);
          break;
          
        case SOURCE_MANAGER_BLOCK_ID:
          if (ReadSourceManagerBlock(F))
            return Failure;
          break;
          
        case SUBMODULE_BLOCK_ID:
          if (ASTReadResult Result = ReadSubmoduleBlock(F, ClientLoadCapabilities))
            return Result;
          break;
          
        case COMMENTS_BLOCK_ID: {
          BitstreamCursor C = Stream;
          if (Stream.SkipBlock() ||
              ReadBlockAbbrevs(C, COMMENTS_BLOCK_ID)) {
            Error("malformed comments block in AST file");
            return Failure;
          }
          CommentsCursors.push_back(std::make_pair(C, &F));
          break;
        }
          
        default:
          if (Stream.SkipBlock()) {
            Error("malformed block record in AST file");
            return Failure;
          }
          break;
        }
        continue;
      
      case llvm::BitstreamEntry::Record:
        // The interesting case.
        break;
      }
  
      // Read and process a record.
      Record.clear();
      StringRef Blob;
      switch ((ASTRecordTypes)Stream.readRecord(Entry.ID, Record, &Blob)) {
      default:  // Default behavior: ignore.
        break;
  
      case TYPE_OFFSET: {
        if (F.LocalNumTypes != 0) {
          Error("duplicate TYPE_OFFSET record in AST file");
          return Failure;
        }
        F.TypeOffsets = (const uint32_t *)Blob.data();
        F.LocalNumTypes = Record[0];
        unsigned LocalBaseTypeIndex = Record[1];
        F.BaseTypeIndex = getTotalNumTypes();
          
        if (F.LocalNumTypes > 0) {
          // Introduce the global -> local mapping for types within this module.
          GlobalTypeMap.insert(std::make_pair(getTotalNumTypes(), &F));
          
          // Introduce the local -> global mapping for types within this module.
          F.TypeRemap.insertOrReplace(
            std::make_pair(LocalBaseTypeIndex, 
                           F.BaseTypeIndex - LocalBaseTypeIndex));
  
          TypesLoaded.resize(TypesLoaded.size() + F.LocalNumTypes);
        }
        break;
      }
          
      case DECL_OFFSET: {
        if (F.LocalNumDecls != 0) {
          Error("duplicate DECL_OFFSET record in AST file");
          return Failure;
        }
        F.DeclOffsets = (const DeclOffset *)Blob.data();
        F.LocalNumDecls = Record[0];
        unsigned LocalBaseDeclID = Record[1];
        F.BaseDeclID = getTotalNumDecls();
          
        if (F.LocalNumDecls > 0) {
          // Introduce the global -> local mapping for declarations within this 
          // module.
          GlobalDeclMap.insert(
            std::make_pair(getTotalNumDecls() + NUM_PREDEF_DECL_IDS, &F));
          
          // Introduce the local -> global mapping for declarations within this
          // module.
          F.DeclRemap.insertOrReplace(
            std::make_pair(LocalBaseDeclID, F.BaseDeclID - LocalBaseDeclID));
          
          // Introduce the global -> local mapping for declarations within this
          // module.
          F.GlobalToLocalDeclIDs[&F] = LocalBaseDeclID;
  
          DeclsLoaded.resize(DeclsLoaded.size() + F.LocalNumDecls);
        }
        break;
      }
          
      case TU_UPDATE_LEXICAL: {
        DeclContext *TU = Context.getTranslationUnitDecl();
        LexicalContents Contents(
            reinterpret_cast<const llvm::support::unaligned_uint32_t *>(
                Blob.data()),
            static_cast<unsigned int>(Blob.size() / 4));
        TULexicalDecls.push_back(std::make_pair(&F, Contents));
        TU->setHasExternalLexicalStorage(true);
        break;
      }
  
      case UPDATE_VISIBLE: {
        unsigned Idx = 0;
        serialization::DeclID ID = ReadDeclID(F, Record, Idx);
        auto *Data = (const unsigned char*)Blob.data();
        PendingVisibleUpdates[ID].push_back(PendingVisibleUpdate{&F, Data});
        // If we've already loaded the decl, perform the updates when we finish
        // loading this block.
        if (Decl *D = GetExistingDecl(ID))
          PendingUpdateRecords.push_back(std::make_pair(ID, D));
        break;
      }
  
      case IDENTIFIER_TABLE:
        F.IdentifierTableData = Blob.data();
        if (Record[0]) {
          F.IdentifierLookupTable = ASTIdentifierLookupTable::Create(
              (const unsigned char *)F.IdentifierTableData + Record[0],
              (const unsigned char *)F.IdentifierTableData + sizeof(uint32_t),
              (const unsigned char *)F.IdentifierTableData,
              ASTIdentifierLookupTrait(*this, F));
          
          PP.getIdentifierTable().setExternalIdentifierLookup(this);
        }
        break;
  
      case IDENTIFIER_OFFSET: {
        if (F.LocalNumIdentifiers != 0) {
          Error("duplicate IDENTIFIER_OFFSET record in AST file");
          return Failure;
        }
        F.IdentifierOffsets = (const uint32_t *)Blob.data();
        F.LocalNumIdentifiers = Record[0];
        unsigned LocalBaseIdentifierID = Record[1];
        F.BaseIdentifierID = getTotalNumIdentifiers();
          
        if (F.LocalNumIdentifiers > 0) {
          // Introduce the global -> local mapping for identifiers within this
          // module.
          GlobalIdentifierMap.insert(std::make_pair(getTotalNumIdentifiers() + 1, 
                                                    &F));
          
          // Introduce the local -> global mapping for identifiers within this
          // module.
          F.IdentifierRemap.insertOrReplace(
            std::make_pair(LocalBaseIdentifierID,
                           F.BaseIdentifierID - LocalBaseIdentifierID));
  
          IdentifiersLoaded.resize(IdentifiersLoaded.size()
                                   + F.LocalNumIdentifiers);
        }
        break;
      }
  
      case INTERESTING_IDENTIFIERS:
        F.PreloadIdentifierOffsets.assign(Record.begin(), Record.end());
        break;
  
      case EAGERLY_DESERIALIZED_DECLS:
        // FIXME: Skip reading this record if our ASTConsumer doesn't care
        // about "interesting" decls (for instance, if we're building a module).
        // FIXME: Store this somewhere per-module and defer until
        // markModuleReferenced is called.
        for (unsigned I = 0, N = Record.size(); I != N; ++I)
          EagerlyDeserializedDecls.push_back(getGlobalDeclID(F, Record[I]));
        break;
  
      case SPECIAL_TYPES:
        if (SpecialTypes.empty()) {
          for (unsigned I = 0, N = Record.size(); I != N; ++I)
            SpecialTypes.push_back(getGlobalTypeID(F, Record[I]));
          break;
        }
  
        if (SpecialTypes.size() != Record.size()) {
          Error("invalid special-types record");
          return Failure;
        }
  
        for (unsigned I = 0, N = Record.size(); I != N; ++I) {
          serialization::TypeID ID = getGlobalTypeID(F, Record[I]);
          if (!SpecialTypes[I])
            SpecialTypes[I] = ID;
          // FIXME: If ID && SpecialTypes[I] != ID, do we need a separate
          // merge step?
        }
        break;
  
      case STATISTICS:
        TotalNumStatements += Record[0];
        TotalNumMacros += Record[1];
        TotalLexicalDeclContexts += Record[2];
        TotalVisibleDeclContexts += Record[3];
        break;
  
      case UNUSED_FILESCOPED_DECLS:
        for (unsigned I = 0, N = Record.size(); I != N; ++I)
          UnusedFileScopedDecls.push_back(getGlobalDeclID(F, Record[I]));
        break;
  
      case DELEGATING_CTORS:
        for (unsigned I = 0, N = Record.size(); I != N; ++I)
          DelegatingCtorDecls.push_back(getGlobalDeclID(F, Record[I]));
        break;
  
      case WEAK_UNDECLARED_IDENTIFIERS:
        if (Record.size() % 4 != 0) {
          Error("invalid weak identifiers record");
          return Failure;
        }
          
        // FIXME: Ignore weak undeclared identifiers from non-original PCH 
        // files. This isn't the way to do it :)
        WeakUndeclaredIdentifiers.clear();
          
        // Translate the weak, undeclared identifiers into global IDs.
        for (unsigned I = 0, N = Record.size(); I < N; /* in loop */) {
          WeakUndeclaredIdentifiers.push_back(
            getGlobalIdentifierID(F, Record[I++]));
          WeakUndeclaredIdentifiers.push_back(
            getGlobalIdentifierID(F, Record[I++]));
          WeakUndeclaredIdentifiers.push_back(
            ReadSourceLocation(F, Record, I).getRawEncoding());
          WeakUndeclaredIdentifiers.push_back(Record[I++]);
        }
        break;
  
      case SELECTOR_OFFSETS: {
        F.SelectorOffsets = (const uint32_t *)Blob.data();
        F.LocalNumSelectors = Record[0];
        unsigned LocalBaseSelectorID = Record[1];
        F.BaseSelectorID = getTotalNumSelectors();
          
        if (F.LocalNumSelectors > 0) {
          // Introduce the global -> local mapping for selectors within this 
          // module.
          GlobalSelectorMap.insert(std::make_pair(getTotalNumSelectors()+1, &F));
          
          // Introduce the local -> global mapping for selectors within this 
          // module.
          F.SelectorRemap.insertOrReplace(
            std::make_pair(LocalBaseSelectorID,
                           F.BaseSelectorID - LocalBaseSelectorID));
  
          SelectorsLoaded.resize(SelectorsLoaded.size() + F.LocalNumSelectors);
        }
        break;
      }
          
      case METHOD_POOL:
        F.SelectorLookupTableData = (const unsigned char *)Blob.data();
        if (Record[0])
          F.SelectorLookupTable
            = ASTSelectorLookupTable::Create(
                          F.SelectorLookupTableData + Record[0],
                          F.SelectorLookupTableData,
                          ASTSelectorLookupTrait(*this, F));
        TotalNumMethodPoolEntries += Record[1];
        break;
  
      case REFERENCED_SELECTOR_POOL:
        if (!Record.empty()) {
          for (unsigned Idx = 0, N = Record.size() - 1; Idx < N; /* in loop */) {
            ReferencedSelectorsData.push_back(getGlobalSelectorID(F, 
                                                                  Record[Idx++]));
            ReferencedSelectorsData.push_back(ReadSourceLocation(F, Record, Idx).
                                                getRawEncoding());
          }
        }
        break;
  
      case PP_COUNTER_VALUE:
        if (!Record.empty() && Listener)
          Listener->ReadCounter(F, Record[0]);
        break;
        
      case FILE_SORTED_DECLS:
        F.FileSortedDecls = (const DeclID *)Blob.data();
        F.NumFileSortedDecls = Record[0];
        break;
  
      case SOURCE_LOCATION_OFFSETS: {
        F.SLocEntryOffsets = (const uint32_t *)Blob.data();
        F.LocalNumSLocEntries = Record[0];
        unsigned SLocSpaceSize = Record[1];
        std::tie(F.SLocEntryBaseID, F.SLocEntryBaseOffset) =
            SourceMgr.AllocateLoadedSLocEntries(F.LocalNumSLocEntries,
                                                SLocSpaceSize);
        if (!F.SLocEntryBaseID) {
          Error("ran out of source locations");
          break;
        }
        // Make our entry in the range map. BaseID is negative and growing, so
        // we invert it. Because we invert it, though, we need the other end of
        // the range.
        unsigned RangeStart =
            unsigned(-F.SLocEntryBaseID) - F.LocalNumSLocEntries + 1;
        GlobalSLocEntryMap.insert(std::make_pair(RangeStart, &F));
        F.FirstLoc = SourceLocation::getFromRawEncoding(F.SLocEntryBaseOffset);
  
        // SLocEntryBaseOffset is lower than MaxLoadedOffset and decreasing.
        assert((F.SLocEntryBaseOffset & (1U << 31U)) == 0);
        GlobalSLocOffsetMap.insert(
            std::make_pair(SourceManager::MaxLoadedOffset - F.SLocEntryBaseOffset
                             - SLocSpaceSize,&F));
  
        // Initialize the remapping table.
        // Invalid stays invalid.
        F.SLocRemap.insertOrReplace(std::make_pair(0U, 0));
        // This module. Base was 2 when being compiled.
        F.SLocRemap.insertOrReplace(std::make_pair(2U,
                                    static_cast<int>(F.SLocEntryBaseOffset - 2)));
        
        TotalNumSLocEntries += F.LocalNumSLocEntries;
        break;
      }
  
      case MODULE_OFFSET_MAP: {
        // Additional remapping information.
        const unsigned char *Data = (const unsigned char*)Blob.data();
        const unsigned char *DataEnd = Data + Blob.size();
  
        // If we see this entry before SOURCE_LOCATION_OFFSETS, add placeholders.
        if (F.SLocRemap.find(0) == F.SLocRemap.end()) {
          F.SLocRemap.insert(std::make_pair(0U, 0));
          F.SLocRemap.insert(std::make_pair(2U, 1));
        }
  
        // Continuous range maps we may be updating in our module.
        typedef ContinuousRangeMap<uint32_t, int, 2>::Builder
            RemapBuilder;
        RemapBuilder SLocRemap(F.SLocRemap);
        RemapBuilder IdentifierRemap(F.IdentifierRemap);
        RemapBuilder MacroRemap(F.MacroRemap);
        RemapBuilder PreprocessedEntityRemap(F.PreprocessedEntityRemap);
        RemapBuilder SubmoduleRemap(F.SubmoduleRemap);
        RemapBuilder SelectorRemap(F.SelectorRemap);
        RemapBuilder DeclRemap(F.DeclRemap);
        RemapBuilder TypeRemap(F.TypeRemap);
  
        while (Data < DataEnd) {
          using namespace llvm::support;
          uint16_t Len = endian::readNext<uint16_t, little, unaligned>(Data);
          StringRef Name = StringRef((const char*)Data, Len);
          Data += Len;
          ModuleFile *OM = ModuleMgr.lookup(Name);
          if (!OM) {
            Error("SourceLocation remap refers to unknown module");
            return Failure;
          }
  
          uint32_t SLocOffset =
              endian::readNext<uint32_t, little, unaligned>(Data);
          uint32_t IdentifierIDOffset =
              endian::readNext<uint32_t, little, unaligned>(Data);
          uint32_t MacroIDOffset =
              endian::readNext<uint32_t, little, unaligned>(Data);
          uint32_t PreprocessedEntityIDOffset =
              endian::readNext<uint32_t, little, unaligned>(Data);
          uint32_t SubmoduleIDOffset =
              endian::readNext<uint32_t, little, unaligned>(Data);
          uint32_t SelectorIDOffset =
              endian::readNext<uint32_t, little, unaligned>(Data);
          uint32_t DeclIDOffset =
              endian::readNext<uint32_t, little, unaligned>(Data);
          uint32_t TypeIndexOffset =
              endian::readNext<uint32_t, little, unaligned>(Data);
  
          uint32_t None = std::numeric_limits<uint32_t>::max();
  
          auto mapOffset = [&](uint32_t Offset, uint32_t BaseOffset,
                               RemapBuilder &Remap) {
            if (Offset != None)
              Remap.insert(std::make_pair(Offset,
                                          static_cast<int>(BaseOffset - Offset)));
          };
          mapOffset(SLocOffset, OM->SLocEntryBaseOffset, SLocRemap);
          mapOffset(IdentifierIDOffset, OM->BaseIdentifierID, IdentifierRemap);
          mapOffset(MacroIDOffset, OM->BaseMacroID, MacroRemap);
          mapOffset(PreprocessedEntityIDOffset, OM->BasePreprocessedEntityID,
                    PreprocessedEntityRemap);
          mapOffset(SubmoduleIDOffset, OM->BaseSubmoduleID, SubmoduleRemap);
          mapOffset(SelectorIDOffset, OM->BaseSelectorID, SelectorRemap);
          mapOffset(DeclIDOffset, OM->BaseDeclID, DeclRemap);
          mapOffset(TypeIndexOffset, OM->BaseTypeIndex, TypeRemap);
  
          // Global -> local mappings.
          F.GlobalToLocalDeclIDs[OM] = DeclIDOffset;
        }
        break;
      }
  
      case SOURCE_MANAGER_LINE_TABLE:
        if (ParseLineTable(F, Record))
          return Failure;
        break;
  
      case SOURCE_LOCATION_PRELOADS: {
        // Need to transform from the local view (1-based IDs) to the global view,
        // which is based off F.SLocEntryBaseID.
        if (!F.PreloadSLocEntries.empty()) {
          Error("Multiple SOURCE_LOCATION_PRELOADS records in AST file");
          return Failure;
        }
        
        F.PreloadSLocEntries.swap(Record);
        break;
      }
  
      case EXT_VECTOR_DECLS:
        for (unsigned I = 0, N = Record.size(); I != N; ++I)
          ExtVectorDecls.push_back(getGlobalDeclID(F, Record[I]));
        break;
  
      case VTABLE_USES:
        if (Record.size() % 3 != 0) {
          Error("Invalid VTABLE_USES record");
          return Failure;
        }
          
        // Later tables overwrite earlier ones.
        // FIXME: Modules will have some trouble with this. This is clearly not
        // the right way to do this.
        VTableUses.clear();
          
        for (unsigned Idx = 0, N = Record.size(); Idx != N; /* In loop */) {
          VTableUses.push_back(getGlobalDeclID(F, Record[Idx++]));
          VTableUses.push_back(
            ReadSourceLocation(F, Record, Idx).getRawEncoding());
          VTableUses.push_back(Record[Idx++]);
        }
        break;
  
      case PENDING_IMPLICIT_INSTANTIATIONS:
        if (PendingInstantiations.size() % 2 != 0) {
          Error("Invalid existing PendingInstantiations");
          return Failure;
        }
  
        if (Record.size() % 2 != 0) {
          Error("Invalid PENDING_IMPLICIT_INSTANTIATIONS block");
          return Failure;
        }
  
        for (unsigned I = 0, N = Record.size(); I != N; /* in loop */) {
          PendingInstantiations.push_back(getGlobalDeclID(F, Record[I++]));
          PendingInstantiations.push_back(
            ReadSourceLocation(F, Record, I).getRawEncoding());
        }
        break;
  
      case SEMA_DECL_REFS:
        if (Record.size() != 2) {
          Error("Invalid SEMA_DECL_REFS block");
          return Failure;
        }
        for (unsigned I = 0, N = Record.size(); I != N; ++I)
          SemaDeclRefs.push_back(getGlobalDeclID(F, Record[I]));
        break;
  
      case PPD_ENTITIES_OFFSETS: {
        F.PreprocessedEntityOffsets = (const PPEntityOffset *)Blob.data();
        assert(Blob.size() % sizeof(PPEntityOffset) == 0);
        F.NumPreprocessedEntities = Blob.size() / sizeof(PPEntityOffset);
  
        unsigned LocalBasePreprocessedEntityID = Record[0];
        
        unsigned StartingID;
        if (!PP.getPreprocessingRecord())
          PP.createPreprocessingRecord();
        if (!PP.getPreprocessingRecord()->getExternalSource())
          PP.getPreprocessingRecord()->SetExternalSource(*this);
        StartingID 
          = PP.getPreprocessingRecord()
              ->allocateLoadedEntities(F.NumPreprocessedEntities);
        F.BasePreprocessedEntityID = StartingID;
  
        if (F.NumPreprocessedEntities > 0) {
          // Introduce the global -> local mapping for preprocessed entities in
          // this module.
          GlobalPreprocessedEntityMap.insert(std::make_pair(StartingID, &F));
         
          // Introduce the local -> global mapping for preprocessed entities in
          // this module.
          F.PreprocessedEntityRemap.insertOrReplace(
            std::make_pair(LocalBasePreprocessedEntityID,
              F.BasePreprocessedEntityID - LocalBasePreprocessedEntityID));
        }
  
        break;
      }
          
      case DECL_UPDATE_OFFSETS: {
        if (Record.size() % 2 != 0) {
          Error("invalid DECL_UPDATE_OFFSETS block in AST file");
          return Failure;
        }
        for (unsigned I = 0, N = Record.size(); I != N; I += 2) {
          GlobalDeclID ID = getGlobalDeclID(F, Record[I]);
          DeclUpdateOffsets[ID].push_back(std::make_pair(&F, Record[I + 1]));
  
          // If we've already loaded the decl, perform the updates when we finish
          // loading this block.
          if (Decl *D = GetExistingDecl(ID))
            PendingUpdateRecords.push_back(std::make_pair(ID, D));
        }
        break;
      }
  
      case OBJC_CATEGORIES_MAP: {
        if (F.LocalNumObjCCategoriesInMap != 0) {
          Error("duplicate OBJC_CATEGORIES_MAP record in AST file");
          return Failure;
        }
        
        F.LocalNumObjCCategoriesInMap = Record[0];
        F.ObjCCategoriesMap = (const ObjCCategoriesInfo *)Blob.data();
        break;
      }
          
      case OBJC_CATEGORIES:
        F.ObjCCategories.swap(Record);
        break;
  
      case DIAG_PRAGMA_MAPPINGS:
        if (F.PragmaDiagMappings.empty())
          F.PragmaDiagMappings.swap(Record);
        else
          F.PragmaDiagMappings.insert(F.PragmaDiagMappings.end(),
                                      Record.begin(), Record.end());
        break;
          
      case CUDA_SPECIAL_DECL_REFS:
        // Later tables overwrite earlier ones.
        // FIXME: Modules will have trouble with this.
        CUDASpecialDeclRefs.clear();
        for (unsigned I = 0, N = Record.size(); I != N; ++I)
          CUDASpecialDeclRefs.push_back(getGlobalDeclID(F, Record[I]));
        break;
  
      case HEADER_SEARCH_TABLE: {
        F.HeaderFileInfoTableData = Blob.data();
        F.LocalNumHeaderFileInfos = Record[1];
        if (Record[0]) {
          F.HeaderFileInfoTable
            = HeaderFileInfoLookupTable::Create(
                     (const unsigned char *)F.HeaderFileInfoTableData + Record[0],
                     (const unsigned char *)F.HeaderFileInfoTableData,
                     HeaderFileInfoTrait(*this, F, 
                                         &PP.getHeaderSearchInfo(),
                                         Blob.data() + Record[2]));
          
          PP.getHeaderSearchInfo().SetExternalSource(this);
          if (!PP.getHeaderSearchInfo().getExternalLookup())
            PP.getHeaderSearchInfo().SetExternalLookup(this);
        }
        break;
      }
          
      case FP_PRAGMA_OPTIONS:
        // Later tables overwrite earlier ones.
        FPPragmaOptions.swap(Record);
        break;
  
      case OPENCL_EXTENSIONS:
        // Later tables overwrite earlier ones.
        OpenCLExtensions.swap(Record);
        break;
  
      case TENTATIVE_DEFINITIONS:
        for (unsigned I = 0, N = Record.size(); I != N; ++I)
          TentativeDefinitions.push_back(getGlobalDeclID(F, Record[I]));
        break;
          
      case KNOWN_NAMESPACES:
        for (unsigned I = 0, N = Record.size(); I != N; ++I)
          KnownNamespaces.push_back(getGlobalDeclID(F, Record[I]));
        break;
  
      case UNDEFINED_BUT_USED:
        if (UndefinedButUsed.size() % 2 != 0) {
          Error("Invalid existing UndefinedButUsed");
          return Failure;
        }
  
        if (Record.size() % 2 != 0) {
          Error("invalid undefined-but-used record");
          return Failure;
        }
        for (unsigned I = 0, N = Record.size(); I != N; /* in loop */) {
          UndefinedButUsed.push_back(getGlobalDeclID(F, Record[I++]));
          UndefinedButUsed.push_back(
              ReadSourceLocation(F, Record, I).getRawEncoding());
        }
        break;
      case DELETE_EXPRS_TO_ANALYZE:
        for (unsigned I = 0, N = Record.size(); I != N;) {
          DelayedDeleteExprs.push_back(getGlobalDeclID(F, Record[I++]));
          const uint64_t Count = Record[I++];
          DelayedDeleteExprs.push_back(Count);
          for (uint64_t C = 0; C < Count; ++C) {
            DelayedDeleteExprs.push_back(ReadSourceLocation(F, Record, I).getRawEncoding());
            bool IsArrayForm = Record[I++] == 1;
            DelayedDeleteExprs.push_back(IsArrayForm);
          }
        }
        break;
  
      case IMPORTED_MODULES: {
        if (F.Kind != MK_ImplicitModule && F.Kind != MK_ExplicitModule) {
          // If we aren't loading a module (which has its own exports), make
          // all of the imported modules visible.
          // FIXME: Deal with macros-only imports.
          for (unsigned I = 0, N = Record.size(); I != N; /**/) {
            unsigned GlobalID = getGlobalSubmoduleID(F, Record[I++]);
            SourceLocation Loc = ReadSourceLocation(F, Record, I);
            if (GlobalID)
              ImportedModules.push_back(ImportedSubmodule(GlobalID, Loc));
          }
        }
        break;
      }
  
      case MACRO_OFFSET: {
        if (F.LocalNumMacros != 0) {
          Error("duplicate MACRO_OFFSET record in AST file");
          return Failure;
        }
        F.MacroOffsets = (const uint32_t *)Blob.data();
        F.LocalNumMacros = Record[0];
        unsigned LocalBaseMacroID = Record[1];
        F.BaseMacroID = getTotalNumMacros();
  
        if (F.LocalNumMacros > 0) {
          // Introduce the global -> local mapping for macros within this module.
          GlobalMacroMap.insert(std::make_pair(getTotalNumMacros() + 1, &F));
  
          // Introduce the local -> global mapping for macros within this module.
          F.MacroRemap.insertOrReplace(
            std::make_pair(LocalBaseMacroID,
                           F.BaseMacroID - LocalBaseMacroID));
  
          MacrosLoaded.resize(MacrosLoaded.size() + F.LocalNumMacros);
        }
        break;
      }
  
      case LATE_PARSED_TEMPLATE: {
        LateParsedTemplates.append(Record.begin(), Record.end());
        break;
      }
  
      case OPTIMIZE_PRAGMA_OPTIONS:
        if (Record.size() != 1) {
          Error("invalid pragma optimize record");
          return Failure;
        }
        OptimizeOffPragmaLocation = ReadSourceLocation(F, Record[0]);
        break;
  
      case MSSTRUCT_PRAGMA_OPTIONS:
        if (Record.size() != 1) {
          Error("invalid pragma ms_struct record");
          return Failure;
        }
        PragmaMSStructState = Record[0];
        break;
  
      case POINTERS_TO_MEMBERS_PRAGMA_OPTIONS:
        if (Record.size() != 2) {
          Error("invalid pragma ms_struct record");
          return Failure;
        }
        PragmaMSPointersToMembersState = Record[0];
        PointersToMembersPragmaLocation = ReadSourceLocation(F, Record[1]);
        break;
  
      case UNUSED_LOCAL_TYPEDEF_NAME_CANDIDATES:
        for (unsigned I = 0, N = Record.size(); I != N; ++I)
          UnusedLocalTypedefNameCandidates.push_back(
              getGlobalDeclID(F, Record[I]));
        break;
      }
    }
  }
  
  ASTReader::ASTReadResult
  ASTReader::ReadModuleMapFileBlock(RecordData &Record, ModuleFile &F,
                                    const ModuleFile *ImportedBy,
                                    unsigned ClientLoadCapabilities) {
    unsigned Idx = 0;
    F.ModuleMapPath = ReadPath(F, Record, Idx);
  
    if (F.Kind == MK_ExplicitModule) {
      // For an explicitly-loaded module, we don't care whether the original
      // module map file exists or matches.
      return Success;
    }
  
    // Try to resolve ModuleName in the current header search context and
    // verify that it is found in the same module map file as we saved. If the
    // top-level AST file is a main file, skip this check because there is no
    // usable header search context.
    assert(!F.ModuleName.empty() &&
           "MODULE_NAME should come before MODULE_MAP_FILE");
    if (F.Kind == MK_ImplicitModule &&
        (*ModuleMgr.begin())->Kind != MK_MainFile) {
      // An implicitly-loaded module file should have its module listed in some
      // module map file that we've already loaded.
      Module *M = PP.getHeaderSearchInfo().lookupModule(F.ModuleName);
      auto &Map = PP.getHeaderSearchInfo().getModuleMap();
      const FileEntry *ModMap = M ? Map.getModuleMapFileForUniquing(M) : nullptr;
      if (!ModMap) {
        assert(ImportedBy && "top-level import should be verified");
        if ((ClientLoadCapabilities & ARR_OutOfDate) == 0) {
          if (auto *ASTFE = M ? M->getASTFile() : nullptr)
            // This module was defined by an imported (explicit) module.
            Diag(diag::err_module_file_conflict) << F.ModuleName << F.FileName
                                                 << ASTFE->getName();
          else
            // This module was built with a different module map.
            Diag(diag::err_imported_module_not_found)
                << F.ModuleName << F.FileName << ImportedBy->FileName
                << F.ModuleMapPath;
        }
        return OutOfDate;
      }
  
      assert(M->Name == F.ModuleName && "found module with different name");
  
      // Check the primary module map file.
      const FileEntry *StoredModMap = FileMgr.getFile(F.ModuleMapPath);
      if (StoredModMap == nullptr || StoredModMap != ModMap) {
        assert(ModMap && "found module is missing module map file");
        assert(ImportedBy && "top-level import should be verified");
        if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
          Diag(diag::err_imported_module_modmap_changed)
            << F.ModuleName << ImportedBy->FileName
            << ModMap->getName() << F.ModuleMapPath;
        return OutOfDate;
      }
  
      llvm::SmallPtrSet<const FileEntry *, 1> AdditionalStoredMaps;
      for (unsigned I = 0, N = Record[Idx++]; I < N; ++I) {
        // FIXME: we should use input files rather than storing names.
        std::string Filename = ReadPath(F, Record, Idx);
        const FileEntry *F =
            FileMgr.getFile(Filename, false, false);
        if (F == nullptr) {
          if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
            Error("could not find file '" + Filename +"' referenced by AST file");
          return OutOfDate;
        }
        AdditionalStoredMaps.insert(F);
      }
  
      // Check any additional module map files (e.g. module.private.modulemap)
      // that are not in the pcm.
      if (auto *AdditionalModuleMaps = Map.getAdditionalModuleMapFiles(M)) {
        for (const FileEntry *ModMap : *AdditionalModuleMaps) {
          // Remove files that match
          // Note: SmallPtrSet::erase is really remove
          if (!AdditionalStoredMaps.erase(ModMap)) {
            if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
              Diag(diag::err_module_different_modmap)
                << F.ModuleName << /*new*/0 << ModMap->getName();
            return OutOfDate;
          }
        }
      }
  
      // Check any additional module map files that are in the pcm, but not
      // found in header search. Cases that match are already removed.
      for (const FileEntry *ModMap : AdditionalStoredMaps) {
        if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
          Diag(diag::err_module_different_modmap)
            << F.ModuleName << /*not new*/1 << ModMap->getName();
        return OutOfDate;
      }
    }
  
    if (Listener)
      Listener->ReadModuleMapFile(F.ModuleMapPath);
    return Success;
  }
  
  
  /// \brief Move the given method to the back of the global list of methods.
  static void moveMethodToBackOfGlobalList(Sema &S, ObjCMethodDecl *Method) {
    // Find the entry for this selector in the method pool.
    Sema::GlobalMethodPool::iterator Known
      = S.MethodPool.find(Method->getSelector());
    if (Known == S.MethodPool.end())
      return;
  
    // Retrieve the appropriate method list.
    ObjCMethodList &Start = Method->isInstanceMethod()? Known->second.first
                                                      : Known->second.second;
    bool Found = false;
    for (ObjCMethodList *List = &Start; List; List = List->getNext()) {
      if (!Found) {
        if (List->getMethod() == Method) {
          Found = true;
        } else {
          // Keep searching.
          continue;
        }
      }
  
      if (List->getNext())
        List->setMethod(List->getNext()->getMethod());
      else
        List->setMethod(Method);
    }
  }
  
  void ASTReader::makeNamesVisible(const HiddenNames &Names, Module *Owner) {
    assert(Owner->NameVisibility != Module::Hidden && "nothing to make visible?");
    for (Decl *D : Names) {
      bool wasHidden = D->Hidden;
      D->Hidden = false;
  
      if (wasHidden && SemaObj) {
        if (ObjCMethodDecl *Method = dyn_cast<ObjCMethodDecl>(D)) {
          moveMethodToBackOfGlobalList(*SemaObj, Method);
        }
      }
    }
  }
  
  void ASTReader::makeModuleVisible(Module *Mod,
                                    Module::NameVisibilityKind NameVisibility,
                                    SourceLocation ImportLoc) {
    // If we import anything from the module in any way, then it is used.
    markModuleUsed(Mod);
  
    llvm::SmallPtrSet<Module *, 4> Visited;
    SmallVector<Module *, 4> Stack;
    Stack.push_back(Mod);
    while (!Stack.empty()) {
      Mod = Stack.pop_back_val();
  
      if (NameVisibility <= Mod->NameVisibility) {
        // This module already has this level of visibility (or greater), so
        // there is nothing more to do.
        continue;
      }
  
      if (!Mod->isAvailable()) {
        // Modules that aren't available cannot be made visible.
        continue;
      }
  
      // Update the module's name visibility.
      Mod->NameVisibility = NameVisibility;
  
      // If we've already deserialized any names from this module,
      // mark them as visible.
      HiddenNamesMapType::iterator Hidden = HiddenNamesMap.find(Mod);
      if (Hidden != HiddenNamesMap.end()) {
        auto HiddenNames = std::move(*Hidden);
        HiddenNamesMap.erase(Hidden);
        makeNamesVisible(HiddenNames.second, HiddenNames.first);
        assert(HiddenNamesMap.find(Mod) == HiddenNamesMap.end() &&
               "making names visible added hidden names");
      }
  
      // Push any exported modules onto the stack to be marked as visible.
      SmallVector<Module *, 16> Exports;
      Mod->getExportedModules(Exports);
      for (SmallVectorImpl<Module *>::iterator
             I = Exports.begin(), E = Exports.end(); I != E; ++I) {
        Module *Exported = *I;
        if (Visited.insert(Exported).second)
          Stack.push_back(Exported);
      }
    }
  }
  
  bool ASTReader::loadGlobalIndex() {
    if (GlobalIndex)
      return false;
  
    if (TriedLoadingGlobalIndex || !UseGlobalIndex ||
        !Context.getLangOpts().Modules)
      return true;
    
    // Try to load the global index.
    TriedLoadingGlobalIndex = true;
    StringRef ModuleCachePath
      = getPreprocessor().getHeaderSearchInfo().getModuleCachePath();
    std::pair<GlobalModuleIndex *, GlobalModuleIndex::ErrorCode> Result
      = GlobalModuleIndex::readIndex(ModuleCachePath);
    if (!Result.first)
      return true;
  
    GlobalIndex.reset(Result.first);
    ModuleMgr.setGlobalIndex(GlobalIndex.get());
    return false;
  }
  
  bool ASTReader::isGlobalIndexUnavailable() const {
    return Context.getLangOpts().Modules && UseGlobalIndex &&
           !hasGlobalIndex() && TriedLoadingGlobalIndex;
  }
  
  static void updateModuleTimestamp(ModuleFile &MF) {
    // Overwrite the timestamp file contents so that file's mtime changes.
    std::string TimestampFilename = MF.getTimestampFilename();
    std::error_code EC;
    llvm::raw_fd_ostream OS(TimestampFilename, EC, llvm::sys::fs::F_Text);
    if (EC)
      return;
    OS << "Timestamp file\n";
  }
  
  /// \brief Given a cursor at the start of an AST file, scan ahead and drop the
  /// cursor into the start of the given block ID, returning false on success and
  /// true on failure.
  static bool SkipCursorToBlock(BitstreamCursor &Cursor, unsigned BlockID) {
    while (1) {
      llvm::BitstreamEntry Entry = Cursor.advance();
      switch (Entry.Kind) {
      case llvm::BitstreamEntry::Error:
      case llvm::BitstreamEntry::EndBlock:
        return true;
  
      case llvm::BitstreamEntry::Record:
        // Ignore top-level records.
        Cursor.skipRecord(Entry.ID);
        break;
  
      case llvm::BitstreamEntry::SubBlock:
        if (Entry.ID == BlockID) {
          if (Cursor.EnterSubBlock(BlockID))
            return true;
          // Found it!
          return false;
        }
  
        if (Cursor.SkipBlock())
          return true;
      }
    }
  }
  
  ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName,
                                              ModuleKind Type,
                                              SourceLocation ImportLoc,
                                              unsigned ClientLoadCapabilities) {
    llvm::SaveAndRestore<SourceLocation>
      SetCurImportLocRAII(CurrentImportLoc, ImportLoc);
  
    // Defer any pending actions until we get to the end of reading the AST file.
    Deserializing AnASTFile(this);
  
    // Bump the generation number.
    unsigned PreviousGeneration = incrementGeneration(Context);
  
    unsigned NumModules = ModuleMgr.size();
    SmallVector<ImportedModule, 4> Loaded;
    switch(ASTReadResult ReadResult = ReadASTCore(FileName, Type, ImportLoc,
                                                  /*ImportedBy=*/nullptr, Loaded,
                                                  0, 0, 0,
                                                  ClientLoadCapabilities)) {
    case Failure:
    case Missing:
    case OutOfDate:
    case VersionMismatch:
    case ConfigurationMismatch:
    case HadErrors: {
      llvm::SmallPtrSet<ModuleFile *, 4> LoadedSet;
      for (const ImportedModule &IM : Loaded)
        LoadedSet.insert(IM.Mod);
  
      ModuleMgr.removeModules(ModuleMgr.begin() + NumModules, ModuleMgr.end(),
                              LoadedSet,
                              Context.getLangOpts().Modules
                                ? &PP.getHeaderSearchInfo().getModuleMap()
                                : nullptr);
  
      // If we find that any modules are unusable, the global index is going
      // to be out-of-date. Just remove it.
      GlobalIndex.reset();
      ModuleMgr.setGlobalIndex(nullptr);
      return ReadResult;
    }
    case Success:
      break;
    }
  
    // Here comes stuff that we only do once the entire chain is loaded.
  
    // Load the AST blocks of all of the modules that we loaded.
    for (SmallVectorImpl<ImportedModule>::iterator M = Loaded.begin(),
                                                MEnd = Loaded.end();
         M != MEnd; ++M) {
      ModuleFile &F = *M->Mod;
  
      // Read the AST block.
      if (ASTReadResult Result = ReadASTBlock(F, ClientLoadCapabilities))
        return Result;
  
      // Read the extension blocks.
      while (!SkipCursorToBlock(F.Stream, EXTENSION_BLOCK_ID)) {
        if (ASTReadResult Result = ReadExtensionBlock(F))
          return Result;
      }
  
      // Once read, set the ModuleFile bit base offset and update the size in 
      // bits of all files we've seen.
      F.GlobalBitOffset = TotalModulesSizeInBits;
      TotalModulesSizeInBits += F.SizeInBits;
      GlobalBitOffsetsMap.insert(std::make_pair(F.GlobalBitOffset, &F));
      
      // Preload SLocEntries.
      for (unsigned I = 0, N = F.PreloadSLocEntries.size(); I != N; ++I) {
        int Index = int(F.PreloadSLocEntries[I] - 1) + F.SLocEntryBaseID;
        // Load it through the SourceManager and don't call ReadSLocEntry()
        // directly because the entry may have already been loaded in which case
        // calling ReadSLocEntry() directly would trigger an assertion in
        // SourceManager.
        SourceMgr.getLoadedSLocEntryByID(Index);
      }
  
      // Preload all the pending interesting identifiers by marking them out of
      // date.
      for (auto Offset : F.PreloadIdentifierOffsets) {
        const unsigned char *Data = reinterpret_cast<const unsigned char *>(
            F.IdentifierTableData + Offset);
  
        ASTIdentifierLookupTrait Trait(*this, F);
        auto KeyDataLen = Trait.ReadKeyDataLength(Data);
        auto Key = Trait.ReadKey(Data, KeyDataLen.first);
        auto &II = PP.getIdentifierTable().getOwn(Key);
        II.setOutOfDate(true);
  
        // Mark this identifier as being from an AST file so that we can track
        // whether we need to serialize it.
        markIdentifierFromAST(*this, II);
  
        // Associate the ID with the identifier so that the writer can reuse it.
        auto ID = Trait.ReadIdentifierID(Data + KeyDataLen.first);
        SetIdentifierInfo(ID, &II);
      }
    }
  
    // Setup the import locations and notify the module manager that we've
    // committed to these module files.
    for (SmallVectorImpl<ImportedModule>::iterator M = Loaded.begin(),
                                                MEnd = Loaded.end();
         M != MEnd; ++M) {
      ModuleFile &F = *M->Mod;
  
      ModuleMgr.moduleFileAccepted(&F);
  
      // Set the import location.
      F.DirectImportLoc = ImportLoc;
      // FIXME: We assume that locations from PCH / preamble do not need
      // any translation.
      if (!M->ImportedBy)
        F.ImportLoc = M->ImportLoc;
      else
        F.ImportLoc = TranslateSourceLocation(*M->ImportedBy, M->ImportLoc);
    }
  
    if (!Context.getLangOpts().CPlusPlus ||
        (Type != MK_ImplicitModule && Type != MK_ExplicitModule)) {
      // Mark all of the identifiers in the identifier table as being out of date,
      // so that various accessors know to check the loaded modules when the
      // identifier is used.
      //
      // For C++ modules, we don't need information on many identifiers (just
      // those that provide macros or are poisoned), so we mark all of
      // the interesting ones via PreloadIdentifierOffsets.
      for (IdentifierTable::iterator Id = PP.getIdentifierTable().begin(),
                                  IdEnd = PP.getIdentifierTable().end();
           Id != IdEnd; ++Id)
        Id->second->setOutOfDate(true);
    }
    // Mark selectors as out of date.
    for (auto Sel : SelectorGeneration)
      SelectorOutOfDate[Sel.first] = true;
    
    // Resolve any unresolved module exports.
    for (unsigned I = 0, N = UnresolvedModuleRefs.size(); I != N; ++I) {
      UnresolvedModuleRef &Unresolved = UnresolvedModuleRefs[I];
      SubmoduleID GlobalID = getGlobalSubmoduleID(*Unresolved.File,Unresolved.ID);
      Module *ResolvedMod = getSubmodule(GlobalID);
  
      switch (Unresolved.Kind) {
      case UnresolvedModuleRef::Conflict:
        if (ResolvedMod) {
          Module::Conflict Conflict;
          Conflict.Other = ResolvedMod;
          Conflict.Message = Unresolved.String.str();
          Unresolved.Mod->Conflicts.push_back(Conflict);
        }
        continue;
  
      case UnresolvedModuleRef::Import:
        if (ResolvedMod)
          Unresolved.Mod->Imports.insert(ResolvedMod);
        continue;
  
      case UnresolvedModuleRef::Export:
        if (ResolvedMod || Unresolved.IsWildcard)
          Unresolved.Mod->Exports.push_back(
            Module::ExportDecl(ResolvedMod, Unresolved.IsWildcard));
        continue;
      }
    }
    UnresolvedModuleRefs.clear();
  
    // FIXME: How do we load the 'use'd modules? They may not be submodules.
    // Might be unnecessary as use declarations are only used to build the
    // module itself.
    
    InitializeContext();
  
    if (SemaObj)
      UpdateSema();
  
    if (DeserializationListener)
      DeserializationListener->ReaderInitialized(this);
  
    ModuleFile &PrimaryModule = ModuleMgr.getPrimaryModule();
    if (PrimaryModule.OriginalSourceFileID.isValid()) {
      PrimaryModule.OriginalSourceFileID 
        = FileID::get(PrimaryModule.SLocEntryBaseID
                      + PrimaryModule.OriginalSourceFileID.getOpaqueValue() - 1);
  
      // If this AST file is a precompiled preamble, then set the
      // preamble file ID of the source manager to the file source file
      // from which the preamble was built.
      if (Type == MK_Preamble) {
        SourceMgr.setPreambleFileID(PrimaryModule.OriginalSourceFileID);
      } else if (Type == MK_MainFile) {
        SourceMgr.setMainFileID(PrimaryModule.OriginalSourceFileID);
      }
    }
    
    // For any Objective-C class definitions we have already loaded, make sure
    // that we load any additional categories.
    for (unsigned I = 0, N = ObjCClassesLoaded.size(); I != N; ++I) {
      loadObjCCategories(ObjCClassesLoaded[I]->getGlobalID(), 
                         ObjCClassesLoaded[I],
                         PreviousGeneration);
    }
  
    if (PP.getHeaderSearchInfo()
            .getHeaderSearchOpts()
            .ModulesValidateOncePerBuildSession) {
      // Now we are certain that the module and all modules it depends on are
      // up to date.  Create or update timestamp files for modules that are
      // located in the module cache (not for PCH files that could be anywhere
      // in the filesystem).
      for (unsigned I = 0, N = Loaded.size(); I != N; ++I) {
        ImportedModule &M = Loaded[I];
        if (M.Mod->Kind == MK_ImplicitModule) {
          updateModuleTimestamp(*M.Mod);
        }
      }
    }
  
    return Success;
  }
  
  static ASTFileSignature readASTFileSignature(llvm::BitstreamReader &StreamFile);
  
  /// \brief Whether \p Stream starts with the AST/PCH file magic number 'CPCH'.
  static bool startsWithASTFileMagic(BitstreamCursor &Stream) {
    return Stream.Read(8) == 'C' &&
           Stream.Read(8) == 'P' &&
           Stream.Read(8) == 'C' &&
           Stream.Read(8) == 'H';
  }
  
  static unsigned moduleKindForDiagnostic(ModuleKind Kind) {
    switch (Kind) {
    case MK_PCH:
      return 0; // PCH
    case MK_ImplicitModule:
    case MK_ExplicitModule:
      return 1; // module
    case MK_MainFile:
    case MK_Preamble:
      return 2; // main source file
    }
    llvm_unreachable("unknown module kind");
  }
  
  ASTReader::ASTReadResult
  ASTReader::ReadASTCore(StringRef FileName,
                         ModuleKind Type,
                         SourceLocation ImportLoc,
                         ModuleFile *ImportedBy,
                         SmallVectorImpl<ImportedModule> &Loaded,
                         off_t ExpectedSize, time_t ExpectedModTime,
                         ASTFileSignature ExpectedSignature,
                         unsigned ClientLoadCapabilities) {
    ModuleFile *M;
    std::string ErrorStr;
    ModuleManager::AddModuleResult AddResult
      = ModuleMgr.addModule(FileName, Type, ImportLoc, ImportedBy,
                            getGeneration(), ExpectedSize, ExpectedModTime,
                            ExpectedSignature, readASTFileSignature,
                            M, ErrorStr);
  
    switch (AddResult) {
    case ModuleManager::AlreadyLoaded:
      return Success;
  
    case ModuleManager::NewlyLoaded:
      // Load module file below.
      break;
  
    case ModuleManager::Missing:
      // The module file was missing; if the client can handle that, return
      // it.
      if (ClientLoadCapabilities & ARR_Missing)
        return Missing;
  
      // Otherwise, return an error.
      Diag(diag::err_module_file_not_found) << moduleKindForDiagnostic(Type)
                                            << FileName << ErrorStr.empty()
                                            << ErrorStr;
      return Failure;
  
    case ModuleManager::OutOfDate:
      // We couldn't load the module file because it is out-of-date. If the
      // client can handle out-of-date, return it.
      if (ClientLoadCapabilities & ARR_OutOfDate)
        return OutOfDate;
  
      // Otherwise, return an error.
      Diag(diag::err_module_file_out_of_date) << moduleKindForDiagnostic(Type)
                                              << FileName << ErrorStr.empty()
                                              << ErrorStr;
      return Failure;
    }
  
    assert(M && "Missing module file");
  
    // FIXME: This seems rather a hack. Should CurrentDir be part of the
    // module?
    if (FileName != "-") {
      CurrentDir = llvm::sys::path::parent_path(FileName);
      if (CurrentDir.empty()) CurrentDir = ".";
    }
  
    ModuleFile &F = *M;
    BitstreamCursor &Stream = F.Stream;
    PCHContainerRdr.ExtractPCH(F.Buffer->getMemBufferRef(), F.StreamFile);
    Stream.init(&F.StreamFile);
    F.SizeInBits = F.Buffer->getBufferSize() * 8;
    
    // Sniff for the signature.
    if (!startsWithASTFileMagic(Stream)) {
      Diag(diag::err_module_file_invalid) << moduleKindForDiagnostic(Type)
                                          << FileName;
      return Failure;
    }
  
    // This is used for compatibility with older PCH formats.
    bool HaveReadControlBlock = false;
    while (1) {
      llvm::BitstreamEntry Entry = Stream.advance();
      
      switch (Entry.Kind) {
      case llvm::BitstreamEntry::Error:
      case llvm::BitstreamEntry::Record:
      case llvm::BitstreamEntry::EndBlock:
        Error("invalid record at top-level of AST file");
        return Failure;
          
      case llvm::BitstreamEntry::SubBlock:
        break;
      }
  
      switch (Entry.ID) {
      case CONTROL_BLOCK_ID:
        HaveReadControlBlock = true;
        switch (ReadControlBlock(F, Loaded, ImportedBy, ClientLoadCapabilities)) {
        case Success:
          // Check that we didn't try to load a non-module AST file as a module.
          //
          // FIXME: Should we also perform the converse check? Loading a module as
          // a PCH file sort of works, but it's a bit wonky.
          if ((Type == MK_ImplicitModule || Type == MK_ExplicitModule) &&
              F.ModuleName.empty()) {
            auto Result = (Type == MK_ImplicitModule) ? OutOfDate : Failure;
            if (Result != OutOfDate ||
                (ClientLoadCapabilities & ARR_OutOfDate) == 0)
              Diag(diag::err_module_file_not_module) << FileName;
            return Result;
          }
          break;
  
        case Failure: return Failure;
        case Missing: return Missing;
        case OutOfDate: return OutOfDate;
        case VersionMismatch: return VersionMismatch;
        case ConfigurationMismatch: return ConfigurationMismatch;
        case HadErrors: return HadErrors;
        }
        break;
  
      case AST_BLOCK_ID:
        if (!HaveReadControlBlock) {
          if ((ClientLoadCapabilities & ARR_VersionMismatch) == 0)
            Diag(diag::err_pch_version_too_old);
          return VersionMismatch;
        }
  
        // Record that we've loaded this module.
        Loaded.push_back(ImportedModule(M, ImportedBy, ImportLoc));
        return Success;
  
      default:
        if (Stream.SkipBlock()) {
          Error("malformed block record in AST file");
          return Failure;
        }
        break;
      }
    }
  
    return Success;
  }
  
  /// Parse a record and blob containing module file extension metadata.
  static bool parseModuleFileExtensionMetadata(
                const SmallVectorImpl<uint64_t> &Record,
                StringRef Blob,
                ModuleFileExtensionMetadata &Metadata) {
    if (Record.size() < 4) return true;
  
    Metadata.MajorVersion = Record[0];
    Metadata.MinorVersion = Record[1];
  
    unsigned BlockNameLen = Record[2];
    unsigned UserInfoLen = Record[3];
  
    if (BlockNameLen + UserInfoLen > Blob.size()) return true;
  
    Metadata.BlockName = std::string(Blob.data(), Blob.data() + BlockNameLen);
    Metadata.UserInfo = std::string(Blob.data() + BlockNameLen,
                                    Blob.data() + BlockNameLen + UserInfoLen);
    return false;
  }
  
  ASTReader::ASTReadResult ASTReader::ReadExtensionBlock(ModuleFile &F) {
    BitstreamCursor &Stream = F.Stream;
  
    RecordData Record;
    while (true) {
      llvm::BitstreamEntry Entry = Stream.advance();
      switch (Entry.Kind) {
      case llvm::BitstreamEntry::SubBlock:
        if (Stream.SkipBlock())
          return Failure;
  
        continue;
  
      case llvm::BitstreamEntry::EndBlock:
        return Success;
  
      case llvm::BitstreamEntry::Error:
        return HadErrors;
  
      case llvm::BitstreamEntry::Record:
        break;
      }
  
      Record.clear();
      StringRef Blob;
      unsigned RecCode = Stream.readRecord(Entry.ID, Record, &Blob);
      switch (RecCode) {
      case EXTENSION_METADATA: {
        ModuleFileExtensionMetadata Metadata;
        if (parseModuleFileExtensionMetadata(Record, Blob, Metadata))
          return Failure;
  
        // Find a module file extension with this block name.
        auto Known = ModuleFileExtensions.find(Metadata.BlockName);
        if (Known == ModuleFileExtensions.end()) break;
  
        // Form a reader.
        if (auto Reader = Known->second->createExtensionReader(Metadata, *this,
                                                               F, Stream)) {
          F.ExtensionReaders.push_back(std::move(Reader));
        }
  
        break;
      }
      }
    }
  
    return Success;
  }
  
  void ASTReader::InitializeContext() {
    // If there's a listener, notify them that we "read" the translation unit.
    if (DeserializationListener)
      DeserializationListener->DeclRead(PREDEF_DECL_TRANSLATION_UNIT_ID, 
                                        Context.getTranslationUnitDecl());
  
    // FIXME: Find a better way to deal with collisions between these
    // built-in types. Right now, we just ignore the problem.
    
    // Load the special types.
    if (SpecialTypes.size() >= NumSpecialTypeIDs) {
      if (unsigned String = SpecialTypes[SPECIAL_TYPE_CF_CONSTANT_STRING]) {
        if (!Context.CFConstantStringTypeDecl)
          Context.setCFConstantStringType(GetType(String));
      }
      
      if (unsigned File = SpecialTypes[SPECIAL_TYPE_FILE]) {
        QualType FileType = GetType(File);
        if (FileType.isNull()) {
          Error("FILE type is NULL");
          return;
        }
        
        if (!Context.FILEDecl) {
          if (const TypedefType *Typedef = FileType->getAs<TypedefType>())
            Context.setFILEDecl(Typedef->getDecl());
          else {
            const TagType *Tag = FileType->getAs<TagType>();
            if (!Tag) {
              Error("Invalid FILE type in AST file");
              return;
            }
            Context.setFILEDecl(Tag->getDecl());
          }
        }
      }
      
      if (unsigned Jmp_buf = SpecialTypes[SPECIAL_TYPE_JMP_BUF]) {
        QualType Jmp_bufType = GetType(Jmp_buf);
        if (Jmp_bufType.isNull()) {
          Error("jmp_buf type is NULL");
          return;
        }
        
        if (!Context.jmp_bufDecl) {
          if (const TypedefType *Typedef = Jmp_bufType->getAs<TypedefType>())
            Context.setjmp_bufDecl(Typedef->getDecl());
          else {
            const TagType *Tag = Jmp_bufType->getAs<TagType>();
            if (!Tag) {
              Error("Invalid jmp_buf type in AST file");
              return;
            }
            Context.setjmp_bufDecl(Tag->getDecl());
          }
        }
      }
      
      if (unsigned Sigjmp_buf = SpecialTypes[SPECIAL_TYPE_SIGJMP_BUF]) {
        QualType Sigjmp_bufType = GetType(Sigjmp_buf);
        if (Sigjmp_bufType.isNull()) {
          Error("sigjmp_buf type is NULL");
          return;
        }
        
        if (!Context.sigjmp_bufDecl) {
          if (const TypedefType *Typedef = Sigjmp_bufType->getAs<TypedefType>())
            Context.setsigjmp_bufDecl(Typedef->getDecl());
          else {
            const TagType *Tag = Sigjmp_bufType->getAs<TagType>();
            assert(Tag && "Invalid sigjmp_buf type in AST file");
            Context.setsigjmp_bufDecl(Tag->getDecl());
          }
        }
      }
  
      if (unsigned ObjCIdRedef
            = SpecialTypes[SPECIAL_TYPE_OBJC_ID_REDEFINITION]) {
        if (Context.ObjCIdRedefinitionType.isNull())
          Context.ObjCIdRedefinitionType = GetType(ObjCIdRedef);
      }
  
      if (unsigned ObjCClassRedef
            = SpecialTypes[SPECIAL_TYPE_OBJC_CLASS_REDEFINITION]) {
        if (Context.ObjCClassRedefinitionType.isNull())
          Context.ObjCClassRedefinitionType = GetType(ObjCClassRedef);
      }
  
      if (unsigned ObjCSelRedef
            = SpecialTypes[SPECIAL_TYPE_OBJC_SEL_REDEFINITION]) {
        if (Context.ObjCSelRedefinitionType.isNull())
          Context.ObjCSelRedefinitionType = GetType(ObjCSelRedef);
      }
  
      if (unsigned Ucontext_t = SpecialTypes[SPECIAL_TYPE_UCONTEXT_T]) {
        QualType Ucontext_tType = GetType(Ucontext_t);
        if (Ucontext_tType.isNull()) {
          Error("ucontext_t type is NULL");
          return;
        }
  
        if (!Context.ucontext_tDecl) {
          if (const TypedefType *Typedef = Ucontext_tType->getAs<TypedefType>())
            Context.setucontext_tDecl(Typedef->getDecl());
          else {
            const TagType *Tag = Ucontext_tType->getAs<TagType>();
            assert(Tag && "Invalid ucontext_t type in AST file");
            Context.setucontext_tDecl(Tag->getDecl());
          }
        }
      }
    }
    
    ReadPragmaDiagnosticMappings(Context.getDiagnostics());
  
    // If there were any CUDA special declarations, deserialize them.
    if (!CUDASpecialDeclRefs.empty()) {
      assert(CUDASpecialDeclRefs.size() == 1 && "More decl refs than expected!");
      Context.setcudaConfigureCallDecl(
                             cast<FunctionDecl>(GetDecl(CUDASpecialDeclRefs[0])));
    }
  
    // Re-export any modules that were imported by a non-module AST file.
    // FIXME: This does not make macro-only imports visible again.
    for (auto &Import : ImportedModules) {
      if (Module *Imported = getSubmodule(Import.ID)) {
        makeModuleVisible(Imported, Module::AllVisible,
                          /*ImportLoc=*/Import.ImportLoc);
        if (Import.ImportLoc.isValid())
          PP.makeModuleVisible(Imported, Import.ImportLoc);
        // FIXME: should we tell Sema to make the module visible too?
      }
    }
    ImportedModules.clear();
  }
  
  void ASTReader::finalizeForWriting() {
    // Nothing to do for now.
  }
  
  /// \brief Reads and return the signature record from \p StreamFile's control
  /// block, or else returns 0.
  static ASTFileSignature readASTFileSignature(llvm::BitstreamReader &StreamFile){
    BitstreamCursor Stream(StreamFile);
    if (!startsWithASTFileMagic(Stream))
      return 0;
  
    // Scan for the CONTROL_BLOCK_ID block.
    if (SkipCursorToBlock(Stream, CONTROL_BLOCK_ID))
      return 0;
  
    // Scan for SIGNATURE inside the control block.
    ASTReader::RecordData Record;
    while (1) {
      llvm::BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
      if (Entry.Kind == llvm::BitstreamEntry::EndBlock ||
          Entry.Kind != llvm::BitstreamEntry::Record)
        return 0;
  
      Record.clear();
      StringRef Blob;
      if (SIGNATURE == Stream.readRecord(Entry.ID, Record, &Blob))
        return Record[0];
    }
  }
  
  /// \brief Retrieve the name of the original source file name
  /// directly from the AST file, without actually loading the AST
  /// file.
  std::string ASTReader::getOriginalSourceFile(
      const std::string &ASTFileName, FileManager &FileMgr,
      const PCHContainerReader &PCHContainerRdr, DiagnosticsEngine &Diags) {
    // Open the AST file.
    auto Buffer = FileMgr.getBufferForFile(ASTFileName);
    if (!Buffer) {
      Diags.Report(diag::err_fe_unable_to_read_pch_file)
          << ASTFileName << Buffer.getError().message();
      return std::string();
    }
  
    // Initialize the stream
    llvm::BitstreamReader StreamFile;
    PCHContainerRdr.ExtractPCH((*Buffer)->getMemBufferRef(), StreamFile);
    BitstreamCursor Stream(StreamFile);
  
    // Sniff for the signature.
    if (!startsWithASTFileMagic(Stream)) {
      Diags.Report(diag::err_fe_not_a_pch_file) << ASTFileName;
      return std::string();
    }
    
    // Scan for the CONTROL_BLOCK_ID block.
    if (SkipCursorToBlock(Stream, CONTROL_BLOCK_ID)) {
      Diags.Report(diag::err_fe_pch_malformed_block) << ASTFileName;
      return std::string();
    }
  
    // Scan for ORIGINAL_FILE inside the control block.
    RecordData Record;
    while (1) {
      llvm::BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
      if (Entry.Kind == llvm::BitstreamEntry::EndBlock)
        return std::string();
      
      if (Entry.Kind != llvm::BitstreamEntry::Record) {
        Diags.Report(diag::err_fe_pch_malformed_block) << ASTFileName;
        return std::string();
      }
      
      Record.clear();
      StringRef Blob;
      if (Stream.readRecord(Entry.ID, Record, &Blob) == ORIGINAL_FILE)
        return Blob.str();
    }
  }
  
  namespace {
    class SimplePCHValidator : public ASTReaderListener {
      const LangOptions &ExistingLangOpts;
      const TargetOptions &ExistingTargetOpts;
      const PreprocessorOptions &ExistingPPOpts;
      std::string ExistingModuleCachePath;
      FileManager &FileMgr;
  
    public:
      SimplePCHValidator(const LangOptions &ExistingLangOpts,
                         const TargetOptions &ExistingTargetOpts,
                         const PreprocessorOptions &ExistingPPOpts,
                         StringRef ExistingModuleCachePath,
                         FileManager &FileMgr)
        : ExistingLangOpts(ExistingLangOpts),
          ExistingTargetOpts(ExistingTargetOpts),
          ExistingPPOpts(ExistingPPOpts),
          ExistingModuleCachePath(ExistingModuleCachePath),
          FileMgr(FileMgr)
      {
      }
  
      bool ReadLanguageOptions(const LangOptions &LangOpts, bool Complain,
                               bool AllowCompatibleDifferences) override {
        return checkLanguageOptions(ExistingLangOpts, LangOpts, nullptr,
                                    AllowCompatibleDifferences);
      }
      bool ReadTargetOptions(const TargetOptions &TargetOpts, bool Complain,
                             bool AllowCompatibleDifferences) override {
        return checkTargetOptions(ExistingTargetOpts, TargetOpts, nullptr,
                                  AllowCompatibleDifferences);
      }
      bool ReadHeaderSearchOptions(const HeaderSearchOptions &HSOpts,
                                   StringRef SpecificModuleCachePath,
                                   bool Complain) override {
        return checkHeaderSearchOptions(HSOpts, SpecificModuleCachePath,
                                        ExistingModuleCachePath,
                                        nullptr, ExistingLangOpts);
      }
      bool ReadPreprocessorOptions(const PreprocessorOptions &PPOpts,
                                   bool Complain,
                                   std::string &SuggestedPredefines) override {
        return checkPreprocessorOptions(ExistingPPOpts, PPOpts, nullptr, FileMgr,
                                        SuggestedPredefines, ExistingLangOpts);
      }
    };
  }
  
  bool ASTReader::readASTFileControlBlock(
      StringRef Filename, FileManager &FileMgr,
      const PCHContainerReader &PCHContainerRdr,
      bool FindModuleFileExtensions,
      ASTReaderListener &Listener) {
    // Open the AST file.
    // FIXME: This allows use of the VFS; we do not allow use of the
    // VFS when actually loading a module.
    auto Buffer = FileMgr.getBufferForFile(Filename);
    if (!Buffer) {
      return true;
    }
  
    // Initialize the stream
    llvm::BitstreamReader StreamFile;
    PCHContainerRdr.ExtractPCH((*Buffer)->getMemBufferRef(), StreamFile);
    BitstreamCursor Stream(StreamFile);
  
    // Sniff for the signature.
    if (!startsWithASTFileMagic(Stream))
      return true;
  
    // Scan for the CONTROL_BLOCK_ID block.
    if (SkipCursorToBlock(Stream, CONTROL_BLOCK_ID))
      return true;
  
    bool NeedsInputFiles = Listener.needsInputFileVisitation();
    bool NeedsSystemInputFiles = Listener.needsSystemInputFileVisitation();
    bool NeedsImports = Listener.needsImportVisitation();
    BitstreamCursor InputFilesCursor;
  
    RecordData Record;
    std::string ModuleDir;
    bool DoneWithControlBlock = false;
    while (!DoneWithControlBlock) {
      llvm::BitstreamEntry Entry = Stream.advance();
  
      switch (Entry.Kind) {
      case llvm::BitstreamEntry::SubBlock: {
        switch (Entry.ID) {
        case OPTIONS_BLOCK_ID: {
          std::string IgnoredSuggestedPredefines;
          if (ReadOptionsBlock(Stream, ARR_ConfigurationMismatch | ARR_OutOfDate,
                               /*AllowCompatibleConfigurationMismatch*/ false,
                               Listener, IgnoredSuggestedPredefines) != Success)
            return true;
          break;
        }
  
        case INPUT_FILES_BLOCK_ID:
          InputFilesCursor = Stream;
          if (Stream.SkipBlock() ||
              (NeedsInputFiles &&
               ReadBlockAbbrevs(InputFilesCursor, INPUT_FILES_BLOCK_ID)))
            return true;
          break;
  
        default:
          if (Stream.SkipBlock())
            return true;
          break;
        }
  
        continue;
      }
  
      case llvm::BitstreamEntry::EndBlock:
        DoneWithControlBlock = true;
        break;
  
      case llvm::BitstreamEntry::Error:
        return true;
  
      case llvm::BitstreamEntry::Record:
        break;
      }
  
      if (DoneWithControlBlock) break;
  
      Record.clear();
      StringRef Blob;
      unsigned RecCode = Stream.readRecord(Entry.ID, Record, &Blob);
      switch ((ControlRecordTypes)RecCode) {
      case METADATA: {
        if (Record[0] != VERSION_MAJOR)
          return true;
  
        if (Listener.ReadFullVersionInformation(Blob))
          return true;
        
        break;
      }
      case MODULE_NAME:
        Listener.ReadModuleName(Blob);
        break;
      case MODULE_DIRECTORY:
        ModuleDir = Blob;
        break;
      case MODULE_MAP_FILE: {
        unsigned Idx = 0;
        auto Path = ReadString(Record, Idx);
        ResolveImportedPath(Path, ModuleDir);
        Listener.ReadModuleMapFile(Path);
        break;
      }
      case INPUT_FILE_OFFSETS: {
        if (!NeedsInputFiles)
          break;
  
        unsigned NumInputFiles = Record[0];
        unsigned NumUserFiles = Record[1];
        const uint64_t *InputFileOffs = (const uint64_t *)Blob.data();
        for (unsigned I = 0; I != NumInputFiles; ++I) {
          // Go find this input file.
          bool isSystemFile = I >= NumUserFiles;
  
          if (isSystemFile && !NeedsSystemInputFiles)
            break; // the rest are system input files
  
          BitstreamCursor &Cursor = InputFilesCursor;
          SavedStreamPosition SavedPosition(Cursor);
          Cursor.JumpToBit(InputFileOffs[I]);
  
          unsigned Code = Cursor.ReadCode();
          RecordData Record;
          StringRef Blob;
          bool shouldContinue = false;
          switch ((InputFileRecordTypes)Cursor.readRecord(Code, Record, &Blob)) {
          case INPUT_FILE:
            bool Overridden = static_cast<bool>(Record[3]);
            std::string Filename = Blob;
            ResolveImportedPath(Filename, ModuleDir);
            shouldContinue = Listener.visitInputFile(
                Filename, isSystemFile, Overridden, /*IsExplicitModule*/false);
            break;
          }
          if (!shouldContinue)
            break;
        }
        break;
      }
  
      case IMPORTS: {
        if (!NeedsImports)
          break;
  
        unsigned Idx = 0, N = Record.size();
        while (Idx < N) {
          // Read information about the AST file.
          Idx += 5; // ImportLoc, Size, ModTime, Signature
          std::string Filename = ReadString(Record, Idx);
          ResolveImportedPath(Filename, ModuleDir);
          Listener.visitImport(Filename);
        }
        break;
      }
  
      default:
        // No other validation to perform.
        break;
      }
    }
  
    // Look for module file extension blocks, if requested.
    if (FindModuleFileExtensions) {
      while (!SkipCursorToBlock(Stream, EXTENSION_BLOCK_ID)) {
        bool DoneWithExtensionBlock = false;
        while (!DoneWithExtensionBlock) {
         llvm::BitstreamEntry Entry = Stream.advance();
  
         switch (Entry.Kind) {
         case llvm::BitstreamEntry::SubBlock:
           if (Stream.SkipBlock())
             return true;
  
           continue;
  
         case llvm::BitstreamEntry::EndBlock:
           DoneWithExtensionBlock = true;
           continue;
  
         case llvm::BitstreamEntry::Error:
           return true;
  
         case llvm::BitstreamEntry::Record:
           break;
         }
  
         Record.clear();
         StringRef Blob;
         unsigned RecCode = Stream.readRecord(Entry.ID, Record, &Blob);
         switch (RecCode) {
         case EXTENSION_METADATA: {
           ModuleFileExtensionMetadata Metadata;
           if (parseModuleFileExtensionMetadata(Record, Blob, Metadata))
             return true;
  
           Listener.readModuleFileExtension(Metadata);
           break;
         }
         }
        }
      }
    }
  
    return false;
  }
  
  bool ASTReader::isAcceptableASTFile(
      StringRef Filename, FileManager &FileMgr,
      const PCHContainerReader &PCHContainerRdr, const LangOptions &LangOpts,
      const TargetOptions &TargetOpts, const PreprocessorOptions &PPOpts,
      std::string ExistingModuleCachePath) {
    SimplePCHValidator validator(LangOpts, TargetOpts, PPOpts,
                                 ExistingModuleCachePath, FileMgr);
    return !readASTFileControlBlock(Filename, FileMgr, PCHContainerRdr,
                                    /*FindModuleFileExtensions=*/false,
                                    validator);
  }
  
  ASTReader::ASTReadResult
  ASTReader::ReadSubmoduleBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
    // Enter the submodule block.
    if (F.Stream.EnterSubBlock(SUBMODULE_BLOCK_ID)) {
      Error("malformed submodule block record in AST file");
      return Failure;
    }
  
    ModuleMap &ModMap = PP.getHeaderSearchInfo().getModuleMap();
    bool First = true;
    Module *CurrentModule = nullptr;
    RecordData Record;
    while (true) {
      llvm::BitstreamEntry Entry = F.Stream.advanceSkippingSubblocks();
      
      switch (Entry.Kind) {
      case llvm::BitstreamEntry::SubBlock: // Handled for us already.
      case llvm::BitstreamEntry::Error:
        Error("malformed block record in AST file");
        return Failure;
      case llvm::BitstreamEntry::EndBlock:
        return Success;
      case llvm::BitstreamEntry::Record:
        // The interesting case.
        break;
      }
  
      // Read a record.
      StringRef Blob;
      Record.clear();
      auto Kind = F.Stream.readRecord(Entry.ID, Record, &Blob);
  
      if ((Kind == SUBMODULE_METADATA) != First) {
        Error("submodule metadata record should be at beginning of block");
        return Failure;
      }
      First = false;
  
      // Submodule information is only valid if we have a current module.
      // FIXME: Should we error on these cases?
      if (!CurrentModule && Kind != SUBMODULE_METADATA &&
          Kind != SUBMODULE_DEFINITION)
        continue;
  
      switch (Kind) {
      default:  // Default behavior: ignore.
        break;
  
      case SUBMODULE_DEFINITION: {
        if (Record.size() < 8) {
          Error("malformed module definition");
          return Failure;
        }
  
        StringRef Name = Blob;
        unsigned Idx = 0;
        SubmoduleID GlobalID = getGlobalSubmoduleID(F, Record[Idx++]);
        SubmoduleID Parent = getGlobalSubmoduleID(F, Record[Idx++]);
        bool IsFramework = Record[Idx++];
        bool IsExplicit = Record[Idx++];
        bool IsSystem = Record[Idx++];
        bool IsExternC = Record[Idx++];
        bool InferSubmodules = Record[Idx++];
        bool InferExplicitSubmodules = Record[Idx++];
        bool InferExportWildcard = Record[Idx++];
        bool ConfigMacrosExhaustive = Record[Idx++];
  
        Module *ParentModule = nullptr;
        if (Parent)
          ParentModule = getSubmodule(Parent);
  
        // Retrieve this (sub)module from the module map, creating it if
        // necessary.
        CurrentModule = ModMap.findOrCreateModule(Name, ParentModule, IsFramework,
                                                  IsExplicit).first;
  
        // FIXME: set the definition loc for CurrentModule, or call
        // ModMap.setInferredModuleAllowedBy()
  
        SubmoduleID GlobalIndex = GlobalID - NUM_PREDEF_SUBMODULE_IDS;
        if (GlobalIndex >= SubmodulesLoaded.size() ||
            SubmodulesLoaded[GlobalIndex]) {
          Error("too many submodules");
          return Failure;
        }
  
        if (!ParentModule) {
          if (const FileEntry *CurFile = CurrentModule->getASTFile()) {
            if (CurFile != F.File) {
              if (!Diags.isDiagnosticInFlight()) {
                Diag(diag::err_module_file_conflict)
                  << CurrentModule->getTopLevelModuleName()
                  << CurFile->getName()
                  << F.File->getName();
              }
              return Failure;
            }
          }
  
          CurrentModule->setASTFile(F.File);
        }
  
        CurrentModule->Signature = F.Signature;
        CurrentModule->IsFromModuleFile = true;
        CurrentModule->IsSystem = IsSystem || CurrentModule->IsSystem;
        CurrentModule->IsExternC = IsExternC;
        CurrentModule->InferSubmodules = InferSubmodules;
        CurrentModule->InferExplicitSubmodules = InferExplicitSubmodules;
        CurrentModule->InferExportWildcard = InferExportWildcard;
        CurrentModule->ConfigMacrosExhaustive = ConfigMacrosExhaustive;
        if (DeserializationListener)
          DeserializationListener->ModuleRead(GlobalID, CurrentModule);
        
        SubmodulesLoaded[GlobalIndex] = CurrentModule;
  
        // Clear out data that will be replaced by what is in the module file.
        CurrentModule->LinkLibraries.clear();
        CurrentModule->ConfigMacros.clear();
        CurrentModule->UnresolvedConflicts.clear();
        CurrentModule->Conflicts.clear();
  
        // The module is available unless it's missing a requirement; relevant
        // requirements will be (re-)added by SUBMODULE_REQUIRES records.
        // Missing headers that were present when the module was built do not
        // make it unavailable -- if we got this far, this must be an explicitly
        // imported module file.
        CurrentModule->Requirements.clear();
        CurrentModule->MissingHeaders.clear();
        CurrentModule->IsMissingRequirement =
            ParentModule && ParentModule->IsMissingRequirement;
        CurrentModule->IsAvailable = !CurrentModule->IsMissingRequirement;
        break;
      }
  
      case SUBMODULE_UMBRELLA_HEADER: {
        std::string Filename = Blob;
        ResolveImportedPath(F, Filename);
        if (auto *Umbrella = PP.getFileManager().getFile(Filename)) {
          if (!CurrentModule->getUmbrellaHeader())
            ModMap.setUmbrellaHeader(CurrentModule, Umbrella, Blob);
          else if (CurrentModule->getUmbrellaHeader().Entry != Umbrella) {
            // This can be a spurious difference caused by changing the VFS to
            // point to a different copy of the file, and it is too late to
            // to rebuild safely.
            // FIXME: If we wrote the virtual paths instead of the 'real' paths,
            // after input file validation only real problems would remain and we
            // could just error. For now, assume it's okay.
            break;
          }
        }
        break;
      }
          
      case SUBMODULE_HEADER:
      case SUBMODULE_EXCLUDED_HEADER:
      case SUBMODULE_PRIVATE_HEADER:
        // We lazily associate headers with their modules via the HeaderInfo table.
        // FIXME: Re-evaluate this section; maybe only store InputFile IDs instead
        // of complete filenames or remove it entirely.
        break;
  
      case SUBMODULE_TEXTUAL_HEADER:
      case SUBMODULE_PRIVATE_TEXTUAL_HEADER:
        // FIXME: Textual headers are not marked in the HeaderInfo table. Load
        // them here.
        break;
  
      case SUBMODULE_TOPHEADER: {
        CurrentModule->addTopHeaderFilename(Blob);
        break;
      }
  
      case SUBMODULE_UMBRELLA_DIR: {
        std::string Dirname = Blob;
        ResolveImportedPath(F, Dirname);
        if (auto *Umbrella = PP.getFileManager().getDirectory(Dirname)) {
          if (!CurrentModule->getUmbrellaDir())
            ModMap.setUmbrellaDir(CurrentModule, Umbrella, Blob);
          else if (CurrentModule->getUmbrellaDir().Entry != Umbrella) {
            if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
              Error("mismatched umbrella directories in submodule");
            return OutOfDate;
          }
        }
        break;
      }
          
      case SUBMODULE_METADATA: {
        F.BaseSubmoduleID = getTotalNumSubmodules();
        F.LocalNumSubmodules = Record[0];
        unsigned LocalBaseSubmoduleID = Record[1];
        if (F.LocalNumSubmodules > 0) {
          // Introduce the global -> local mapping for submodules within this 
          // module.
          GlobalSubmoduleMap.insert(std::make_pair(getTotalNumSubmodules()+1,&F));
          
          // Introduce the local -> global mapping for submodules within this 
          // module.
          F.SubmoduleRemap.insertOrReplace(
            std::make_pair(LocalBaseSubmoduleID,
                           F.BaseSubmoduleID - LocalBaseSubmoduleID));
  
          SubmodulesLoaded.resize(SubmodulesLoaded.size() + F.LocalNumSubmodules);
        }
        break;
      }
          
      case SUBMODULE_IMPORTS: {
        for (unsigned Idx = 0; Idx != Record.size(); ++Idx) {
          UnresolvedModuleRef Unresolved;
          Unresolved.File = &F;
          Unresolved.Mod = CurrentModule;
          Unresolved.ID = Record[Idx];
          Unresolved.Kind = UnresolvedModuleRef::Import;
          Unresolved.IsWildcard = false;
          UnresolvedModuleRefs.push_back(Unresolved);
        }
        break;
      }
  
      case SUBMODULE_EXPORTS: {
        for (unsigned Idx = 0; Idx + 1 < Record.size(); Idx += 2) {
          UnresolvedModuleRef Unresolved;
          Unresolved.File = &F;
          Unresolved.Mod = CurrentModule;
          Unresolved.ID = Record[Idx];
          Unresolved.Kind = UnresolvedModuleRef::Export;
          Unresolved.IsWildcard = Record[Idx + 1];
          UnresolvedModuleRefs.push_back(Unresolved);
        }
        
        // Once we've loaded the set of exports, there's no reason to keep 
        // the parsed, unresolved exports around.
        CurrentModule->UnresolvedExports.clear();
        break;
      }
      case SUBMODULE_REQUIRES: {
        CurrentModule->addRequirement(Blob, Record[0], Context.getLangOpts(),
                                      Context.getTargetInfo());
        break;
      }
  
      case SUBMODULE_LINK_LIBRARY:
        CurrentModule->LinkLibraries.push_back(
                                           Module::LinkLibrary(Blob, Record[0]));
        break;
  
      case SUBMODULE_CONFIG_MACRO:
        CurrentModule->ConfigMacros.push_back(Blob.str());
        break;
  
      case SUBMODULE_CONFLICT: {
        UnresolvedModuleRef Unresolved;
        Unresolved.File = &F;
        Unresolved.Mod = CurrentModule;
        Unresolved.ID = Record[0];
        Unresolved.Kind = UnresolvedModuleRef::Conflict;
        Unresolved.IsWildcard = false;
        Unresolved.String = Blob;
        UnresolvedModuleRefs.push_back(Unresolved);
        break;
      }
      }
    }
  }
  
  /// \brief Parse the record that corresponds to a LangOptions data
  /// structure.
  ///
  /// This routine parses the language options from the AST file and then gives
  /// them to the AST listener if one is set.
  ///
  /// \returns true if the listener deems the file unacceptable, false otherwise.
  bool ASTReader::ParseLanguageOptions(const RecordData &Record,
                                       bool Complain,
                                       ASTReaderListener &Listener,
                                       bool AllowCompatibleDifferences) {
    LangOptions LangOpts;
    unsigned Idx = 0;
  #define LANGOPT(Name, Bits, Default, Description) \
    LangOpts.Name = Record[Idx++];
  #define ENUM_LANGOPT(Name, Type, Bits, Default, Description) \
    LangOpts.set##Name(static_cast<LangOptions::Type>(Record[Idx++]));
  #include "clang/Basic/LangOptions.def"
  #define SANITIZER(NAME, ID)                                                    \
    LangOpts.Sanitize.set(SanitizerKind::ID, Record[Idx++]);
  #include "clang/Basic/Sanitizers.def"
  
    for (unsigned N = Record[Idx++]; N; --N)
      LangOpts.ModuleFeatures.push_back(ReadString(Record, Idx));
  
    ObjCRuntime::Kind runtimeKind = (ObjCRuntime::Kind) Record[Idx++];
    VersionTuple runtimeVersion = ReadVersionTuple(Record, Idx);
    LangOpts.ObjCRuntime = ObjCRuntime(runtimeKind, runtimeVersion);
  
    LangOpts.CurrentModule = ReadString(Record, Idx);
  
    // Comment options.
    for (unsigned N = Record[Idx++]; N; --N) {
      LangOpts.CommentOpts.BlockCommandNames.push_back(
        ReadString(Record, Idx));
    }
    LangOpts.CommentOpts.ParseAllComments = Record[Idx++];
  
    // OpenMP offloading options.
    for (unsigned N = Record[Idx++]; N; --N) {
      LangOpts.OMPTargetTriples.push_back(llvm::Triple(ReadString(Record, Idx)));
    }
  
    LangOpts.OMPHostIRFile = ReadString(Record, Idx);
  
    return Listener.ReadLanguageOptions(LangOpts, Complain,
                                        AllowCompatibleDifferences);
  }
  
  bool ASTReader::ParseTargetOptions(const RecordData &Record, bool Complain,
                                     ASTReaderListener &Listener,
                                     bool AllowCompatibleDifferences) {
    unsigned Idx = 0;
    TargetOptions TargetOpts;
    TargetOpts.Triple = ReadString(Record, Idx);
    TargetOpts.CPU = ReadString(Record, Idx);
    TargetOpts.ABI = ReadString(Record, Idx);
    for (unsigned N = Record[Idx++]; N; --N) {
      TargetOpts.FeaturesAsWritten.push_back(ReadString(Record, Idx));
    }
    for (unsigned N = Record[Idx++]; N; --N) {
      TargetOpts.Features.push_back(ReadString(Record, Idx));
    }
  
    return Listener.ReadTargetOptions(TargetOpts, Complain,
                                      AllowCompatibleDifferences);
  }
  
  bool ASTReader::ParseDiagnosticOptions(const RecordData &Record, bool Complain,
                                         ASTReaderListener &Listener) {
    IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts(new DiagnosticOptions);
    unsigned Idx = 0;
  #define DIAGOPT(Name, Bits, Default) DiagOpts->Name = Record[Idx++];
  #define ENUM_DIAGOPT(Name, Type, Bits, Default) \
    DiagOpts->set##Name(static_cast<Type>(Record[Idx++]));
  #include "clang/Basic/DiagnosticOptions.def"
  
    for (unsigned N = Record[Idx++]; N; --N)
      DiagOpts->Warnings.push_back(ReadString(Record, Idx));
    for (unsigned N = Record[Idx++]; N; --N)
      DiagOpts->Remarks.push_back(ReadString(Record, Idx));
  
    return Listener.ReadDiagnosticOptions(DiagOpts, Complain);
  }
  
  bool ASTReader::ParseFileSystemOptions(const RecordData &Record, bool Complain,
                                         ASTReaderListener &Listener) {
    FileSystemOptions FSOpts;
    unsigned Idx = 0;
    FSOpts.WorkingDir = ReadString(Record, Idx);
    return Listener.ReadFileSystemOptions(FSOpts, Complain);
  }
  
  bool ASTReader::ParseHeaderSearchOptions(const RecordData &Record,
                                           bool Complain,
                                           ASTReaderListener &Listener) {
    HeaderSearchOptions HSOpts;
    unsigned Idx = 0;
    HSOpts.Sysroot = ReadString(Record, Idx);
  
    // Include entries.
    for (unsigned N = Record[Idx++]; N; --N) {
      std::string Path = ReadString(Record, Idx);
      frontend::IncludeDirGroup Group
        = static_cast<frontend::IncludeDirGroup>(Record[Idx++]);
      bool IsFramework = Record[Idx++];
      bool IgnoreSysRoot = Record[Idx++];
      HSOpts.UserEntries.emplace_back(std::move(Path), Group, IsFramework,
                                      IgnoreSysRoot);
    }
  
    // System header prefixes.
    for (unsigned N = Record[Idx++]; N; --N) {
      std::string Prefix = ReadString(Record, Idx);
      bool IsSystemHeader = Record[Idx++];
      HSOpts.SystemHeaderPrefixes.emplace_back(std::move(Prefix), IsSystemHeader);
    }
  
    HSOpts.ResourceDir = ReadString(Record, Idx);
    HSOpts.ModuleCachePath = ReadString(Record, Idx);
    HSOpts.ModuleUserBuildPath = ReadString(Record, Idx);
    HSOpts.DisableModuleHash = Record[Idx++];
    HSOpts.UseBuiltinIncludes = Record[Idx++];
    HSOpts.UseStandardSystemIncludes = Record[Idx++];
    HSOpts.UseStandardCXXIncludes = Record[Idx++];
    HSOpts.UseLibcxx = Record[Idx++];
    std::string SpecificModuleCachePath = ReadString(Record, Idx);
  
    return Listener.ReadHeaderSearchOptions(HSOpts, SpecificModuleCachePath,
                                            Complain);
  }
  
  bool ASTReader::ParsePreprocessorOptions(const RecordData &Record,
                                           bool Complain,
                                           ASTReaderListener &Listener,
                                           std::string &SuggestedPredefines) {
    PreprocessorOptions PPOpts;
    unsigned Idx = 0;
  
    // Macro definitions/undefs
    for (unsigned N = Record[Idx++]; N; --N) {
      std::string Macro = ReadString(Record, Idx);
      bool IsUndef = Record[Idx++];
      PPOpts.Macros.push_back(std::make_pair(Macro, IsUndef));
    }
  
    // Includes
    for (unsigned N = Record[Idx++]; N; --N) {
      PPOpts.Includes.push_back(ReadString(Record, Idx));
    }
  
    // Macro Includes
    for (unsigned N = Record[Idx++]; N; --N) {
      PPOpts.MacroIncludes.push_back(ReadString(Record, Idx));
    }
  
    PPOpts.UsePredefines = Record[Idx++];
    PPOpts.DetailedRecord = Record[Idx++];
    PPOpts.ImplicitPCHInclude = ReadString(Record, Idx);
    PPOpts.ImplicitPTHInclude = ReadString(Record, Idx);
    PPOpts.ObjCXXARCStandardLibrary =
      static_cast<ObjCXXARCStandardLibraryKind>(Record[Idx++]);
    SuggestedPredefines.clear();
    return Listener.ReadPreprocessorOptions(PPOpts, Complain,
                                            SuggestedPredefines);
  }
  
  std::pair<ModuleFile *, unsigned>
  ASTReader::getModulePreprocessedEntity(unsigned GlobalIndex) {
    GlobalPreprocessedEntityMapType::iterator
    I = GlobalPreprocessedEntityMap.find(GlobalIndex);
    assert(I != GlobalPreprocessedEntityMap.end() && 
           "Corrupted global preprocessed entity map");
    ModuleFile *M = I->second;
    unsigned LocalIndex = GlobalIndex - M->BasePreprocessedEntityID;
    return std::make_pair(M, LocalIndex);
  }
  
  llvm::iterator_range<PreprocessingRecord::iterator>
  ASTReader::getModulePreprocessedEntities(ModuleFile &Mod) const {
    if (PreprocessingRecord *PPRec = PP.getPreprocessingRecord())
      return PPRec->getIteratorsForLoadedRange(Mod.BasePreprocessedEntityID,
                                               Mod.NumPreprocessedEntities);
  
    return llvm::make_range(PreprocessingRecord::iterator(),
                            PreprocessingRecord::iterator());
  }
  
  llvm::iterator_range<ASTReader::ModuleDeclIterator>
  ASTReader::getModuleFileLevelDecls(ModuleFile &Mod) {
    return llvm::make_range(
        ModuleDeclIterator(this, &Mod, Mod.FileSortedDecls),
        ModuleDeclIterator(this, &Mod,
                           Mod.FileSortedDecls + Mod.NumFileSortedDecls));
  }
  
  PreprocessedEntity *ASTReader::ReadPreprocessedEntity(unsigned Index) {
    PreprocessedEntityID PPID = Index+1;
    std::pair<ModuleFile *, unsigned> PPInfo = getModulePreprocessedEntity(Index);
    ModuleFile &M = *PPInfo.first;
    unsigned LocalIndex = PPInfo.second;
    const PPEntityOffset &PPOffs = M.PreprocessedEntityOffsets[LocalIndex];
  
    if (!PP.getPreprocessingRecord()) {
      Error("no preprocessing record");
      return nullptr;
    }
    
    SavedStreamPosition SavedPosition(M.PreprocessorDetailCursor);  
    M.PreprocessorDetailCursor.JumpToBit(PPOffs.BitOffset);
  
    llvm::BitstreamEntry Entry =
      M.PreprocessorDetailCursor.advance(BitstreamCursor::AF_DontPopBlockAtEnd);
    if (Entry.Kind != llvm::BitstreamEntry::Record)
      return nullptr;
  
    // Read the record.
    SourceRange Range(TranslateSourceLocation(M, PPOffs.getBegin()),
                      TranslateSourceLocation(M, PPOffs.getEnd()));
    PreprocessingRecord &PPRec = *PP.getPreprocessingRecord();
    StringRef Blob;
    RecordData Record;
    PreprocessorDetailRecordTypes RecType =
      (PreprocessorDetailRecordTypes)M.PreprocessorDetailCursor.readRecord(
                                            Entry.ID, Record, &Blob);
    switch (RecType) {
    case PPD_MACRO_EXPANSION: {
      bool isBuiltin = Record[0];
      IdentifierInfo *Name = nullptr;
      MacroDefinitionRecord *Def = nullptr;
      if (isBuiltin)
        Name = getLocalIdentifier(M, Record[1]);
      else {
        PreprocessedEntityID GlobalID =
            getGlobalPreprocessedEntityID(M, Record[1]);
        Def = cast<MacroDefinitionRecord>(
            PPRec.getLoadedPreprocessedEntity(GlobalID - 1));
      }
  
      MacroExpansion *ME;
      if (isBuiltin)
        ME = new (PPRec) MacroExpansion(Name, Range);
      else
        ME = new (PPRec) MacroExpansion(Def, Range);
  
      return ME;
    }
        
    case PPD_MACRO_DEFINITION: {
      // Decode the identifier info and then check again; if the macro is
      // still defined and associated with the identifier,
      IdentifierInfo *II = getLocalIdentifier(M, Record[0]);
      MacroDefinitionRecord *MD = new (PPRec) MacroDefinitionRecord(II, Range);
  
      if (DeserializationListener)
        DeserializationListener->MacroDefinitionRead(PPID, MD);
  
      return MD;
    }
        
    case PPD_INCLUSION_DIRECTIVE: {
      const char *FullFileNameStart = Blob.data() + Record[0];
      StringRef FullFileName(FullFileNameStart, Blob.size() - Record[0]);
      const FileEntry *File = nullptr;
      if (!FullFileName.empty())
        File = PP.getFileManager().getFile(FullFileName);
      
      // FIXME: Stable encoding
      InclusionDirective::InclusionKind Kind
        = static_cast<InclusionDirective::InclusionKind>(Record[2]);
      InclusionDirective *ID
        = new (PPRec) InclusionDirective(PPRec, Kind,
                                         StringRef(Blob.data(), Record[0]),
                                         Record[1], Record[3],
                                         File,
                                         Range);
      return ID;
    }
    }
  
    llvm_unreachable("Invalid PreprocessorDetailRecordTypes");
  }
  
  /// \brief \arg SLocMapI points at a chunk of a module that contains no
  /// preprocessed entities or the entities it contains are not the ones we are
  /// looking for. Find the next module that contains entities and return the ID
  /// of the first entry.
  PreprocessedEntityID ASTReader::findNextPreprocessedEntity(
                         GlobalSLocOffsetMapType::const_iterator SLocMapI) const {
    ++SLocMapI;
    for (GlobalSLocOffsetMapType::const_iterator
           EndI = GlobalSLocOffsetMap.end(); SLocMapI != EndI; ++SLocMapI) {
      ModuleFile &M = *SLocMapI->second;
      if (M.NumPreprocessedEntities)
        return M.BasePreprocessedEntityID;
    }
  
    return getTotalNumPreprocessedEntities();
  }
  
  namespace {
  
  struct PPEntityComp {
    const ASTReader &Reader;
    ModuleFile &M;
  
    PPEntityComp(const ASTReader &Reader, ModuleFile &M) : Reader(Reader), M(M) { }
  
    bool operator()(const PPEntityOffset &L, const PPEntityOffset &R) const {
      SourceLocation LHS = getLoc(L);
      SourceLocation RHS = getLoc(R);
      return Reader.getSourceManager().isBeforeInTranslationUnit(LHS, RHS);
    }
  
    bool operator()(const PPEntityOffset &L, SourceLocation RHS) const {
      SourceLocation LHS = getLoc(L);
      return Reader.getSourceManager().isBeforeInTranslationUnit(LHS, RHS);
    }
  
    bool operator()(SourceLocation LHS, const PPEntityOffset &R) const {
      SourceLocation RHS = getLoc(R);
      return Reader.getSourceManager().isBeforeInTranslationUnit(LHS, RHS);
    }
  
    SourceLocation getLoc(const PPEntityOffset &PPE) const {
      return Reader.TranslateSourceLocation(M, PPE.getBegin());
    }
  };
  
  }
  
  PreprocessedEntityID ASTReader::findPreprocessedEntity(SourceLocation Loc,
                                                         bool EndsAfter) const {
    if (SourceMgr.isLocalSourceLocation(Loc))
      return getTotalNumPreprocessedEntities();
  
    GlobalSLocOffsetMapType::const_iterator SLocMapI = GlobalSLocOffsetMap.find(
        SourceManager::MaxLoadedOffset - Loc.getOffset() - 1);
    assert(SLocMapI != GlobalSLocOffsetMap.end() &&
           "Corrupted global sloc offset map");
  
    if (SLocMapI->second->NumPreprocessedEntities == 0)
      return findNextPreprocessedEntity(SLocMapI);
  
    ModuleFile &M = *SLocMapI->second;
    typedef const PPEntityOffset *pp_iterator;
    pp_iterator pp_begin = M.PreprocessedEntityOffsets;
    pp_iterator pp_end = pp_begin + M.NumPreprocessedEntities;
  
    size_t Count = M.NumPreprocessedEntities;
    size_t Half;
    pp_iterator First = pp_begin;
    pp_iterator PPI;
  
    if (EndsAfter) {
      PPI = std::upper_bound(pp_begin, pp_end, Loc,
                             PPEntityComp(*this, M));
    } else {
      // Do a binary search manually instead of using std::lower_bound because
      // The end locations of entities may be unordered (when a macro expansion
      // is inside another macro argument), but for this case it is not important
      // whether we get the first macro expansion or its containing macro.
      while (Count > 0) {
        Half = Count / 2;
        PPI = First;
        std::advance(PPI, Half);
        if (SourceMgr.isBeforeInTranslationUnit(
                TranslateSourceLocation(M, PPI->getEnd()), Loc)) {
          First = PPI;
          ++First;
          Count = Count - Half - 1;
        } else
          Count = Half;
      }
    }
  
    if (PPI == pp_end)
      return findNextPreprocessedEntity(SLocMapI);
  
    return M.BasePreprocessedEntityID + (PPI - pp_begin);
  }
  
  /// \brief Returns a pair of [Begin, End) indices of preallocated
  /// preprocessed entities that \arg Range encompasses.
  std::pair<unsigned, unsigned>
      ASTReader::findPreprocessedEntitiesInRange(SourceRange Range) {
    if (Range.isInvalid())
      return std::make_pair(0,0);
    assert(!SourceMgr.isBeforeInTranslationUnit(Range.getEnd(),Range.getBegin()));
  
    PreprocessedEntityID BeginID =
        findPreprocessedEntity(Range.getBegin(), false);
    PreprocessedEntityID EndID = findPreprocessedEntity(Range.getEnd(), true);
    return std::make_pair(BeginID, EndID);
  }
  
  /// \brief Optionally returns true or false if the preallocated preprocessed
  /// entity with index \arg Index came from file \arg FID.
  Optional<bool> ASTReader::isPreprocessedEntityInFileID(unsigned Index,
                                                               FileID FID) {
    if (FID.isInvalid())
      return false;
  
    std::pair<ModuleFile *, unsigned> PPInfo = getModulePreprocessedEntity(Index);
    ModuleFile &M = *PPInfo.first;
    unsigned LocalIndex = PPInfo.second;
    const PPEntityOffset &PPOffs = M.PreprocessedEntityOffsets[LocalIndex];
    
    SourceLocation Loc = TranslateSourceLocation(M, PPOffs.getBegin());
    if (Loc.isInvalid())
      return false;
    
    if (SourceMgr.isInFileID(SourceMgr.getFileLoc(Loc), FID))
      return true;
    else
      return false;
  }
  
  namespace {
    /// \brief Visitor used to search for information about a header file.
    class HeaderFileInfoVisitor {
      const FileEntry *FE;
      
      Optional<HeaderFileInfo> HFI;
      
    public:
      explicit HeaderFileInfoVisitor(const FileEntry *FE)
        : FE(FE) { }
  
      bool operator()(ModuleFile &M) {
        HeaderFileInfoLookupTable *Table
          = static_cast<HeaderFileInfoLookupTable *>(M.HeaderFileInfoTable);
        if (!Table)
          return false;
  
        // Look in the on-disk hash table for an entry for this file name.
        HeaderFileInfoLookupTable::iterator Pos = Table->find(FE);
        if (Pos == Table->end())
          return false;
  
        HFI = *Pos;
        return true;
      }
      
      Optional<HeaderFileInfo> getHeaderFileInfo() const { return HFI; }
    };
  }
  
  HeaderFileInfo ASTReader::GetHeaderFileInfo(const FileEntry *FE) {
    HeaderFileInfoVisitor Visitor(FE);
    ModuleMgr.visit(Visitor);
    if (Optional<HeaderFileInfo> HFI = Visitor.getHeaderFileInfo())
      return *HFI;
    
    return HeaderFileInfo();
  }
  
  void ASTReader::ReadPragmaDiagnosticMappings(DiagnosticsEngine &Diag) {
    // FIXME: Make it work properly with modules.
    SmallVector<DiagnosticsEngine::DiagState *, 32> DiagStates;
    for (ModuleIterator I = ModuleMgr.begin(), E = ModuleMgr.end(); I != E; ++I) {
      ModuleFile &F = *(*I);
      unsigned Idx = 0;
      DiagStates.clear();
      assert(!Diag.DiagStates.empty());
      DiagStates.push_back(&Diag.DiagStates.front()); // the command-line one.
      while (Idx < F.PragmaDiagMappings.size()) {
        SourceLocation Loc = ReadSourceLocation(F, F.PragmaDiagMappings[Idx++]);
        unsigned DiagStateID = F.PragmaDiagMappings[Idx++];
        if (DiagStateID != 0) {
          Diag.DiagStatePoints.push_back(
                      DiagnosticsEngine::DiagStatePoint(DiagStates[DiagStateID-1],
                      FullSourceLoc(Loc, SourceMgr)));
          continue;
        }
        
        assert(DiagStateID == 0);
        // A new DiagState was created here.
        Diag.DiagStates.push_back(*Diag.GetCurDiagState());
        DiagnosticsEngine::DiagState *NewState = &Diag.DiagStates.back();
        DiagStates.push_back(NewState);
        Diag.DiagStatePoints.push_back(
            DiagnosticsEngine::DiagStatePoint(NewState,
                                              FullSourceLoc(Loc, SourceMgr)));
        while (1) {
          assert(Idx < F.PragmaDiagMappings.size() &&
                 "Invalid data, didn't find '-1' marking end of diag/map pairs");
          if (Idx >= F.PragmaDiagMappings.size()) {
            break; // Something is messed up but at least avoid infinite loop in
                   // release build.
          }
          unsigned DiagID = F.PragmaDiagMappings[Idx++];
          if (DiagID == (unsigned)-1) {
            break; // no more diag/map pairs for this location.
          }
          diag::Severity Map = (diag::Severity)F.PragmaDiagMappings[Idx++];
          DiagnosticMapping Mapping = Diag.makeUserMapping(Map, Loc);
          Diag.GetCurDiagState()->setMapping(DiagID, Mapping);
        }
      }
    }
  }
  
  /// \brief Get the correct cursor and offset for loading a type.
  ASTReader::RecordLocation ASTReader::TypeCursorForIndex(unsigned Index) {
    GlobalTypeMapType::iterator I = GlobalTypeMap.find(Index);
    assert(I != GlobalTypeMap.end() && "Corrupted global type map");
    ModuleFile *M = I->second;
    return RecordLocation(M, M->TypeOffsets[Index - M->BaseTypeIndex]);
  }
  
  /// \brief Read and return the type with the given index..
  ///
  /// The index is the type ID, shifted and minus the number of predefs. This
  /// routine actually reads the record corresponding to the type at the given
  /// location. It is a helper routine for GetType, which deals with reading type
  /// IDs.
  QualType ASTReader::readTypeRecord(unsigned Index) {
    RecordLocation Loc = TypeCursorForIndex(Index);
    BitstreamCursor &DeclsCursor = Loc.F->DeclsCursor;
  
    // Keep track of where we are in the stream, then jump back there
    // after reading this type.
    SavedStreamPosition SavedPosition(DeclsCursor);
  
    ReadingKindTracker ReadingKind(Read_Type, *this);
  
    // Note that we are loading a type record.
    Deserializing AType(this);
  
    unsigned Idx = 0;
    DeclsCursor.JumpToBit(Loc.Offset);
    RecordData Record;
    unsigned Code = DeclsCursor.ReadCode();
    switch ((TypeCode)DeclsCursor.readRecord(Code, Record)) {
    case TYPE_EXT_QUAL: {
      if (Record.size() != 2) {
        Error("Incorrect encoding of extended qualifier type");
        return QualType();
      }
      QualType Base = readType(*Loc.F, Record, Idx);
      Qualifiers Quals = Qualifiers::fromOpaqueValue(Record[Idx++]);
      return Context.getQualifiedType(Base, Quals);
    }
  
    case TYPE_COMPLEX: {
      if (Record.size() != 1) {
        Error("Incorrect encoding of complex type");
        return QualType();
      }
      QualType ElemType = readType(*Loc.F, Record, Idx);
      return Context.getComplexType(ElemType);
    }
  
    case TYPE_POINTER: {
      if (Record.size() != 1) {
        Error("Incorrect encoding of pointer type");
        return QualType();
      }
      QualType PointeeType = readType(*Loc.F, Record, Idx);
      return Context.getPointerType(PointeeType);
    }
  
    case TYPE_DECAYED: {
      if (Record.size() != 1) {
        Error("Incorrect encoding of decayed type");
        return QualType();
      }
      QualType OriginalType = readType(*Loc.F, Record, Idx);
      QualType DT = Context.getAdjustedParameterType(OriginalType);
      if (!isa<DecayedType>(DT))
        Error("Decayed type does not decay");
      return DT;
    }
  
    case TYPE_ADJUSTED: {
      if (Record.size() != 2) {
        Error("Incorrect encoding of adjusted type");
        return QualType();
      }
      QualType OriginalTy = readType(*Loc.F, Record, Idx);
      QualType AdjustedTy = readType(*Loc.F, Record, Idx);
      return Context.getAdjustedType(OriginalTy, AdjustedTy);
    }
  
    case TYPE_BLOCK_POINTER: {
      if (Record.size() != 1) {
        Error("Incorrect encoding of block pointer type");
        return QualType();
      }
      QualType PointeeType = readType(*Loc.F, Record, Idx);
      return Context.getBlockPointerType(PointeeType);
    }
  
    case TYPE_LVALUE_REFERENCE: {
      if (Record.size() != 2) {
        Error("Incorrect encoding of lvalue reference type");
        return QualType();
      }
      QualType PointeeType = readType(*Loc.F, Record, Idx);
      return Context.getLValueReferenceType(PointeeType, Record[1]);
    }
  
    case TYPE_RVALUE_REFERENCE: {
      if (Record.size() != 1) {
        Error("Incorrect encoding of rvalue reference type");
        return QualType();
      }
      QualType PointeeType = readType(*Loc.F, Record, Idx);
      return Context.getRValueReferenceType(PointeeType);
    }
  
    case TYPE_MEMBER_POINTER: {
      if (Record.size() != 2) {
        Error("Incorrect encoding of member pointer type");
        return QualType();
      }
      QualType PointeeType = readType(*Loc.F, Record, Idx);
      QualType ClassType = readType(*Loc.F, Record, Idx);
      if (PointeeType.isNull() || ClassType.isNull())
        return QualType();
      
      return Context.getMemberPointerType(PointeeType, ClassType.getTypePtr());
    }
  
    case TYPE_CONSTANT_ARRAY: {
      QualType ElementType = readType(*Loc.F, Record, Idx);
      ArrayType::ArraySizeModifier ASM = (ArrayType::ArraySizeModifier)Record[1];
      unsigned IndexTypeQuals = Record[2];
      unsigned Idx = 3;
      llvm::APInt Size = ReadAPInt(Record, Idx);
      return Context.getConstantArrayType(ElementType, Size,
                                           ASM, IndexTypeQuals);
    }
  
    case TYPE_INCOMPLETE_ARRAY: {
      QualType ElementType = readType(*Loc.F, Record, Idx);
      ArrayType::ArraySizeModifier ASM = (ArrayType::ArraySizeModifier)Record[1];
      unsigned IndexTypeQuals = Record[2];
      return Context.getIncompleteArrayType(ElementType, ASM, IndexTypeQuals);
    }
  
    case TYPE_VARIABLE_ARRAY: {
      QualType ElementType = readType(*Loc.F, Record, Idx);
      ArrayType::ArraySizeModifier ASM = (ArrayType::ArraySizeModifier)Record[1];
      unsigned IndexTypeQuals = Record[2];
      SourceLocation LBLoc = ReadSourceLocation(*Loc.F, Record[3]);
      SourceLocation RBLoc = ReadSourceLocation(*Loc.F, Record[4]);
      return Context.getVariableArrayType(ElementType, ReadExpr(*Loc.F),
                                           ASM, IndexTypeQuals,
                                           SourceRange(LBLoc, RBLoc));
    }
  
    case TYPE_VECTOR: {
      if (Record.size() != 3) {
        Error("incorrect encoding of vector type in AST file");
        return QualType();
      }
  
      QualType ElementType = readType(*Loc.F, Record, Idx);
      unsigned NumElements = Record[1];
      unsigned VecKind = Record[2];
      return Context.getVectorType(ElementType, NumElements,
                                    (VectorType::VectorKind)VecKind);
    }
  
    case TYPE_EXT_VECTOR: {
      if (Record.size() != 3) {
        Error("incorrect encoding of extended vector type in AST file");
        return QualType();
      }
  
      QualType ElementType = readType(*Loc.F, Record, Idx);
      unsigned NumElements = Record[1];
      return Context.getExtVectorType(ElementType, NumElements);
    }
  
    case TYPE_FUNCTION_NO_PROTO: {
      if (Record.size() != 6) {
        Error("incorrect encoding of no-proto function type");
        return QualType();
      }
      QualType ResultType = readType(*Loc.F, Record, Idx);
      FunctionType::ExtInfo Info(Record[1], Record[2], Record[3],
                                 (CallingConv)Record[4], Record[5]);
      return Context.getFunctionNoProtoType(ResultType, Info);
    }
  
    case TYPE_FUNCTION_PROTO: {
      QualType ResultType = readType(*Loc.F, Record, Idx);
  
      FunctionProtoType::ExtProtoInfo EPI;
      EPI.ExtInfo = FunctionType::ExtInfo(/*noreturn*/ Record[1],
                                          /*hasregparm*/ Record[2],
                                          /*regparm*/ Record[3],
                                          static_cast<CallingConv>(Record[4]),
                                          /*produces*/ Record[5]);
  
      unsigned Idx = 6;
  
      EPI.Variadic = Record[Idx++];
      EPI.HasTrailingReturn = Record[Idx++];
      EPI.TypeQuals = Record[Idx++];
      EPI.RefQualifier = static_cast<RefQualifierKind>(Record[Idx++]);
      SmallVector<QualType, 8> ExceptionStorage;
      readExceptionSpec(*Loc.F, ExceptionStorage, EPI.ExceptionSpec, Record, Idx);
  
      unsigned NumParams = Record[Idx++];
      SmallVector<QualType, 16> ParamTypes;
      for (unsigned I = 0; I != NumParams; ++I)
        ParamTypes.push_back(readType(*Loc.F, Record, Idx));
  
      SmallVector<FunctionProtoType::ExtParameterInfo, 4> ExtParameterInfos;
      if (Idx != Record.size()) {
        for (unsigned I = 0; I != NumParams; ++I)
          ExtParameterInfos.push_back(
            FunctionProtoType::ExtParameterInfo
                             ::getFromOpaqueValue(Record[Idx++]));
        EPI.ExtParameterInfos = ExtParameterInfos.data();
      }
  
      assert(Idx == Record.size());
  
      return Context.getFunctionType(ResultType, ParamTypes, EPI);
    }
  
    case TYPE_UNRESOLVED_USING: {
      unsigned Idx = 0;
      return Context.getTypeDeclType(
                    ReadDeclAs<UnresolvedUsingTypenameDecl>(*Loc.F, Record, Idx));
    }
        
    case TYPE_TYPEDEF: {
      if (Record.size() != 2) {
        Error("incorrect encoding of typedef type");
        return QualType();
      }
      unsigned Idx = 0;
      TypedefNameDecl *Decl = ReadDeclAs<TypedefNameDecl>(*Loc.F, Record, Idx);
      QualType Canonical = readType(*Loc.F, Record, Idx);
      if (!Canonical.isNull())
        Canonical = Context.getCanonicalType(Canonical);
      return Context.getTypedefType(Decl, Canonical);
    }
  
    case TYPE_TYPEOF_EXPR:
      return Context.getTypeOfExprType(ReadExpr(*Loc.F));
  
    case TYPE_TYPEOF: {
      if (Record.size() != 1) {
        Error("incorrect encoding of typeof(type) in AST file");
        return QualType();
      }
      QualType UnderlyingType = readType(*Loc.F, Record, Idx);
      return Context.getTypeOfType(UnderlyingType);
    }
  
    case TYPE_DECLTYPE: {
      QualType UnderlyingType = readType(*Loc.F, Record, Idx);
      return Context.getDecltypeType(ReadExpr(*Loc.F), UnderlyingType);
    }
  
    case TYPE_UNARY_TRANSFORM: {
      QualType BaseType = readType(*Loc.F, Record, Idx);
      QualType UnderlyingType = readType(*Loc.F, Record, Idx);
      UnaryTransformType::UTTKind UKind = (UnaryTransformType::UTTKind)Record[2];
      return Context.getUnaryTransformType(BaseType, UnderlyingType, UKind);
    }
  
    case TYPE_AUTO: {
      QualType Deduced = readType(*Loc.F, Record, Idx);
      AutoTypeKeyword Keyword = (AutoTypeKeyword)Record[Idx++];
      bool IsDependent = Deduced.isNull() ? Record[Idx++] : false;
      return Context.getAutoType(Deduced, Keyword, IsDependent);
    }
  
    case TYPE_RECORD: {
      if (Record.size() != 2) {
        Error("incorrect encoding of record type");
        return QualType();
      }
      unsigned Idx = 0;
      bool IsDependent = Record[Idx++];
      RecordDecl *RD = ReadDeclAs<RecordDecl>(*Loc.F, Record, Idx);
      RD = cast_or_null<RecordDecl>(RD->getCanonicalDecl());
      QualType T = Context.getRecordType(RD);
      const_cast<Type*>(T.getTypePtr())->setDependent(IsDependent);
      return T;
    }
  
    case TYPE_ENUM: {
      if (Record.size() != 2) {
        Error("incorrect encoding of enum type");
        return QualType();
      }
      unsigned Idx = 0;
      bool IsDependent = Record[Idx++];
      QualType T
        = Context.getEnumType(ReadDeclAs<EnumDecl>(*Loc.F, Record, Idx));
      const_cast<Type*>(T.getTypePtr())->setDependent(IsDependent);
      return T;
    }
  
    case TYPE_ATTRIBUTED: {
      if (Record.size() != 3) {
        Error("incorrect encoding of attributed type");
        return QualType();
      }
      QualType modifiedType = readType(*Loc.F, Record, Idx);
      QualType equivalentType = readType(*Loc.F, Record, Idx);
      AttributedType::Kind kind = static_cast<AttributedType::Kind>(Record[2]);
      return Context.getAttributedType(kind, modifiedType, equivalentType);
    }
  
    case TYPE_PAREN: {
      if (Record.size() != 1) {
        Error("incorrect encoding of paren type");
        return QualType();
      }
      QualType InnerType = readType(*Loc.F, Record, Idx);
      return Context.getParenType(InnerType);
    }
  
    case TYPE_PACK_EXPANSION: {
      if (Record.size() != 2) {
        Error("incorrect encoding of pack expansion type");
        return QualType();
      }
      QualType Pattern = readType(*Loc.F, Record, Idx);
      if (Pattern.isNull())
        return QualType();
      Optional<unsigned> NumExpansions;
      if (Record[1])
        NumExpansions = Record[1] - 1;
      return Context.getPackExpansionType(Pattern, NumExpansions);
    }
  
    case TYPE_ELABORATED: {
      unsigned Idx = 0;
      ElaboratedTypeKeyword Keyword = (ElaboratedTypeKeyword)Record[Idx++];
      NestedNameSpecifier *NNS = ReadNestedNameSpecifier(*Loc.F, Record, Idx);
      QualType NamedType = readType(*Loc.F, Record, Idx);
      return Context.getElaboratedType(Keyword, NNS, NamedType);
    }
  
    case TYPE_OBJC_INTERFACE: {
      unsigned Idx = 0;
      ObjCInterfaceDecl *ItfD
        = ReadDeclAs<ObjCInterfaceDecl>(*Loc.F, Record, Idx);
      return Context.getObjCInterfaceType(ItfD->getCanonicalDecl());
    }
  
    case TYPE_OBJC_OBJECT: {
      unsigned Idx = 0;
      QualType Base = readType(*Loc.F, Record, Idx);
      unsigned NumTypeArgs = Record[Idx++];
      SmallVector<QualType, 4> TypeArgs;
      for (unsigned I = 0; I != NumTypeArgs; ++I)
        TypeArgs.push_back(readType(*Loc.F, Record, Idx));
      unsigned NumProtos = Record[Idx++];
      SmallVector<ObjCProtocolDecl*, 4> Protos;
      for (unsigned I = 0; I != NumProtos; ++I)
        Protos.push_back(ReadDeclAs<ObjCProtocolDecl>(*Loc.F, Record, Idx));
      bool IsKindOf = Record[Idx++];
      return Context.getObjCObjectType(Base, TypeArgs, Protos, IsKindOf);
    }
  
    case TYPE_OBJC_OBJECT_POINTER: {
      unsigned Idx = 0;
      QualType Pointee = readType(*Loc.F, Record, Idx);
      return Context.getObjCObjectPointerType(Pointee);
    }
  
    case TYPE_SUBST_TEMPLATE_TYPE_PARM: {
      unsigned Idx = 0;
      QualType Parm = readType(*Loc.F, Record, Idx);
      QualType Replacement = readType(*Loc.F, Record, Idx);
      return Context.getSubstTemplateTypeParmType(
          cast<TemplateTypeParmType>(Parm),
          Context.getCanonicalType(Replacement));
    }
  
    case TYPE_SUBST_TEMPLATE_TYPE_PARM_PACK: {
      unsigned Idx = 0;
      QualType Parm = readType(*Loc.F, Record, Idx);
      TemplateArgument ArgPack = ReadTemplateArgument(*Loc.F, Record, Idx);
      return Context.getSubstTemplateTypeParmPackType(
                                                 cast<TemplateTypeParmType>(Parm),
                                                       ArgPack);
    }
  
    case TYPE_INJECTED_CLASS_NAME: {
      CXXRecordDecl *D = ReadDeclAs<CXXRecordDecl>(*Loc.F, Record, Idx);
      QualType TST = readType(*Loc.F, Record, Idx); // probably derivable
      // FIXME: ASTContext::getInjectedClassNameType is not currently suitable
      // for AST reading, too much interdependencies.
      const Type *T = nullptr;
      for (auto *DI = D; DI; DI = DI->getPreviousDecl()) {
        if (const Type *Existing = DI->getTypeForDecl()) {
          T = Existing;
          break;
        }
      }
      if (!T) {
        T = new (Context, TypeAlignment) InjectedClassNameType(D, TST);
        for (auto *DI = D; DI; DI = DI->getPreviousDecl())
          DI->setTypeForDecl(T);
      }
      return QualType(T, 0);
    }
  
    case TYPE_TEMPLATE_TYPE_PARM: {
      unsigned Idx = 0;
      unsigned Depth = Record[Idx++];
      unsigned Index = Record[Idx++];
      bool Pack = Record[Idx++];
      TemplateTypeParmDecl *D
        = ReadDeclAs<TemplateTypeParmDecl>(*Loc.F, Record, Idx);
      return Context.getTemplateTypeParmType(Depth, Index, Pack, D);
    }
  
    case TYPE_DEPENDENT_NAME: {
      unsigned Idx = 0;
      ElaboratedTypeKeyword Keyword = (ElaboratedTypeKeyword)Record[Idx++];
      NestedNameSpecifier *NNS = ReadNestedNameSpecifier(*Loc.F, Record, Idx);
      const IdentifierInfo *Name = GetIdentifierInfo(*Loc.F, Record, Idx);
      QualType Canon = readType(*Loc.F, Record, Idx);
      if (!Canon.isNull())
        Canon = Context.getCanonicalType(Canon);
      return Context.getDependentNameType(Keyword, NNS, Name, Canon);
    }
  
    case TYPE_DEPENDENT_TEMPLATE_SPECIALIZATION: {
      unsigned Idx = 0;
      ElaboratedTypeKeyword Keyword = (ElaboratedTypeKeyword)Record[Idx++];
      NestedNameSpecifier *NNS = ReadNestedNameSpecifier(*Loc.F, Record, Idx);
      const IdentifierInfo *Name = GetIdentifierInfo(*Loc.F, Record, Idx);
      unsigned NumArgs = Record[Idx++];
      SmallVector<TemplateArgument, 8> Args;
      Args.reserve(NumArgs);
      while (NumArgs--)
        Args.push_back(ReadTemplateArgument(*Loc.F, Record, Idx));
      return Context.getDependentTemplateSpecializationType(Keyword, NNS, Name,
                                                            Args);
    }
  
    case TYPE_DEPENDENT_SIZED_ARRAY: {
      unsigned Idx = 0;
  
      // ArrayType
      QualType ElementType = readType(*Loc.F, Record, Idx);
      ArrayType::ArraySizeModifier ASM
        = (ArrayType::ArraySizeModifier)Record[Idx++];
      unsigned IndexTypeQuals = Record[Idx++];
  
      // DependentSizedArrayType
      Expr *NumElts = ReadExpr(*Loc.F);
      SourceRange Brackets = ReadSourceRange(*Loc.F, Record, Idx);
  
      return Context.getDependentSizedArrayType(ElementType, NumElts, ASM,
                                                 IndexTypeQuals, Brackets);
    }
  
    case TYPE_TEMPLATE_SPECIALIZATION: {
      unsigned Idx = 0;
      bool IsDependent = Record[Idx++];
      TemplateName Name = ReadTemplateName(*Loc.F, Record, Idx);
      SmallVector<TemplateArgument, 8> Args;
      ReadTemplateArgumentList(Args, *Loc.F, Record, Idx);
      QualType Underlying = readType(*Loc.F, Record, Idx);
      QualType T;
      if (Underlying.isNull())
        T = Context.getCanonicalTemplateSpecializationType(Name, Args);
      else
        T = Context.getTemplateSpecializationType(Name, Args, Underlying);
      const_cast<Type*>(T.getTypePtr())->setDependent(IsDependent);
      return T;
    }
  
    case TYPE_ATOMIC: {
      if (Record.size() != 1) {
        Error("Incorrect encoding of atomic type");
        return QualType();
      }
      QualType ValueType = readType(*Loc.F, Record, Idx);
      return Context.getAtomicType(ValueType);
    }
  
    case TYPE_PIPE: {
      if (Record.size() != 1) {
        Error("Incorrect encoding of pipe type");
        return QualType();
      }
  
      // Reading the pipe element type.
      QualType ElementType = readType(*Loc.F, Record, Idx);
      return Context.getPipeType(ElementType);
    }
    }
    llvm_unreachable("Invalid TypeCode!");
  }
  
  void ASTReader::readExceptionSpec(ModuleFile &ModuleFile,
                                    SmallVectorImpl<QualType> &Exceptions,
                                    FunctionProtoType::ExceptionSpecInfo &ESI,
                                    const RecordData &Record, unsigned &Idx) {
    ExceptionSpecificationType EST =
        static_cast<ExceptionSpecificationType>(Record[Idx++]);
    ESI.Type = EST;
    if (EST == EST_Dynamic) {
      for (unsigned I = 0, N = Record[Idx++]; I != N; ++I)
        Exceptions.push_back(readType(ModuleFile, Record, Idx));
      ESI.Exceptions = Exceptions;
    } else if (EST == EST_ComputedNoexcept) {
      ESI.NoexceptExpr = ReadExpr(ModuleFile);
    } else if (EST == EST_Uninstantiated) {
      ESI.SourceDecl = ReadDeclAs<FunctionDecl>(ModuleFile, Record, Idx);
      ESI.SourceTemplate = ReadDeclAs<FunctionDecl>(ModuleFile, Record, Idx);
    } else if (EST == EST_Unevaluated) {
      ESI.SourceDecl = ReadDeclAs<FunctionDecl>(ModuleFile, Record, Idx);
    }
  }
  
  class clang::TypeLocReader : public TypeLocVisitor<TypeLocReader> {
    ASTReader &Reader;
    ModuleFile &F;
    const ASTReader::RecordData &Record;
    unsigned &Idx;
  
    SourceLocation ReadSourceLocation(const ASTReader::RecordData &R,
                                      unsigned &I) {
      return Reader.ReadSourceLocation(F, R, I);
    }
  
    template<typename T>
    T *ReadDeclAs(const ASTReader::RecordData &Record, unsigned &Idx) {
      return Reader.ReadDeclAs<T>(F, Record, Idx);
    }
    
  public:
    TypeLocReader(ASTReader &Reader, ModuleFile &F,
                  const ASTReader::RecordData &Record, unsigned &Idx)
      : Reader(Reader), F(F), Record(Record), Idx(Idx)
    { }
  
    // We want compile-time assurance that we've enumerated all of
    // these, so unfortunately we have to declare them first, then
    // define them out-of-line.
  #define ABSTRACT_TYPELOC(CLASS, PARENT)
  #define TYPELOC(CLASS, PARENT) \
    void Visit##CLASS##TypeLoc(CLASS##TypeLoc TyLoc);
  #include "clang/AST/TypeLocNodes.def"
  
    void VisitFunctionTypeLoc(FunctionTypeLoc);
    void VisitArrayTypeLoc(ArrayTypeLoc);
  };
  
  void TypeLocReader::VisitQualifiedTypeLoc(QualifiedTypeLoc TL) {
    // nothing to do
  }
  void TypeLocReader::VisitBuiltinTypeLoc(BuiltinTypeLoc TL) {
    TL.setBuiltinLoc(ReadSourceLocation(Record, Idx));
    if (TL.needsExtraLocalData()) {
      TL.setWrittenTypeSpec(static_cast<DeclSpec::TST>(Record[Idx++]));
      TL.setWrittenSignSpec(static_cast<DeclSpec::TSS>(Record[Idx++]));
      TL.setWrittenWidthSpec(static_cast<DeclSpec::TSW>(Record[Idx++]));
      TL.setModeAttr(Record[Idx++]);
    }
  }
  void TypeLocReader::VisitComplexTypeLoc(ComplexTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitPointerTypeLoc(PointerTypeLoc TL) {
    TL.setStarLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitDecayedTypeLoc(DecayedTypeLoc TL) {
    // nothing to do
  }
  void TypeLocReader::VisitAdjustedTypeLoc(AdjustedTypeLoc TL) {
    // nothing to do
  }
  void TypeLocReader::VisitBlockPointerTypeLoc(BlockPointerTypeLoc TL) {
    TL.setCaretLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitLValueReferenceTypeLoc(LValueReferenceTypeLoc TL) {
    TL.setAmpLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitRValueReferenceTypeLoc(RValueReferenceTypeLoc TL) {
    TL.setAmpAmpLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitMemberPointerTypeLoc(MemberPointerTypeLoc TL) {
    TL.setStarLoc(ReadSourceLocation(Record, Idx));
    TL.setClassTInfo(Reader.GetTypeSourceInfo(F, Record, Idx));
  }
  void TypeLocReader::VisitArrayTypeLoc(ArrayTypeLoc TL) {
    TL.setLBracketLoc(ReadSourceLocation(Record, Idx));
    TL.setRBracketLoc(ReadSourceLocation(Record, Idx));
    if (Record[Idx++])
      TL.setSizeExpr(Reader.ReadExpr(F));
    else
      TL.setSizeExpr(nullptr);
  }
  void TypeLocReader::VisitConstantArrayTypeLoc(ConstantArrayTypeLoc TL) {
    VisitArrayTypeLoc(TL);
  }
  void TypeLocReader::VisitIncompleteArrayTypeLoc(IncompleteArrayTypeLoc TL) {
    VisitArrayTypeLoc(TL);
  }
  void TypeLocReader::VisitVariableArrayTypeLoc(VariableArrayTypeLoc TL) {
    VisitArrayTypeLoc(TL);
  }
  void TypeLocReader::VisitDependentSizedArrayTypeLoc(
                                              DependentSizedArrayTypeLoc TL) {
    VisitArrayTypeLoc(TL);
  }
  void TypeLocReader::VisitDependentSizedExtVectorTypeLoc(
                                          DependentSizedExtVectorTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitVectorTypeLoc(VectorTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitExtVectorTypeLoc(ExtVectorTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitFunctionTypeLoc(FunctionTypeLoc TL) {
    TL.setLocalRangeBegin(ReadSourceLocation(Record, Idx));
    TL.setLParenLoc(ReadSourceLocation(Record, Idx));
    TL.setRParenLoc(ReadSourceLocation(Record, Idx));
    TL.setLocalRangeEnd(ReadSourceLocation(Record, Idx));
    for (unsigned i = 0, e = TL.getNumParams(); i != e; ++i) {
      TL.setParam(i, ReadDeclAs<ParmVarDecl>(Record, Idx));
    }
  }
  void TypeLocReader::VisitFunctionProtoTypeLoc(FunctionProtoTypeLoc TL) {
    VisitFunctionTypeLoc(TL);
  }
  void TypeLocReader::VisitFunctionNoProtoTypeLoc(FunctionNoProtoTypeLoc TL) {
    VisitFunctionTypeLoc(TL);
  }
  void TypeLocReader::VisitUnresolvedUsingTypeLoc(UnresolvedUsingTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitTypedefTypeLoc(TypedefTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitTypeOfExprTypeLoc(TypeOfExprTypeLoc TL) {
    TL.setTypeofLoc(ReadSourceLocation(Record, Idx));
    TL.setLParenLoc(ReadSourceLocation(Record, Idx));
    TL.setRParenLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitTypeOfTypeLoc(TypeOfTypeLoc TL) {
    TL.setTypeofLoc(ReadSourceLocation(Record, Idx));
    TL.setLParenLoc(ReadSourceLocation(Record, Idx));
    TL.setRParenLoc(ReadSourceLocation(Record, Idx));
    TL.setUnderlyingTInfo(Reader.GetTypeSourceInfo(F, Record, Idx));
  }
  void TypeLocReader::VisitDecltypeTypeLoc(DecltypeTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitUnaryTransformTypeLoc(UnaryTransformTypeLoc TL) {
    TL.setKWLoc(ReadSourceLocation(Record, Idx));
    TL.setLParenLoc(ReadSourceLocation(Record, Idx));
    TL.setRParenLoc(ReadSourceLocation(Record, Idx));
    TL.setUnderlyingTInfo(Reader.GetTypeSourceInfo(F, Record, Idx));
  }
  void TypeLocReader::VisitAutoTypeLoc(AutoTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitRecordTypeLoc(RecordTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitEnumTypeLoc(EnumTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitAttributedTypeLoc(AttributedTypeLoc TL) {
    TL.setAttrNameLoc(ReadSourceLocation(Record, Idx));
    if (TL.hasAttrOperand()) {
      SourceRange range;
      range.setBegin(ReadSourceLocation(Record, Idx));
      range.setEnd(ReadSourceLocation(Record, Idx));
      TL.setAttrOperandParensRange(range);
    }
    if (TL.hasAttrExprOperand()) {
      if (Record[Idx++])
        TL.setAttrExprOperand(Reader.ReadExpr(F));
      else
        TL.setAttrExprOperand(nullptr);
    } else if (TL.hasAttrEnumOperand())
      TL.setAttrEnumOperandLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitTemplateTypeParmTypeLoc(TemplateTypeParmTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitSubstTemplateTypeParmTypeLoc(
                                              SubstTemplateTypeParmTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitSubstTemplateTypeParmPackTypeLoc(
                                            SubstTemplateTypeParmPackTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitTemplateSpecializationTypeLoc(
                                             TemplateSpecializationTypeLoc TL) {
    TL.setTemplateKeywordLoc(ReadSourceLocation(Record, Idx));
    TL.setTemplateNameLoc(ReadSourceLocation(Record, Idx));
    TL.setLAngleLoc(ReadSourceLocation(Record, Idx));
    TL.setRAngleLoc(ReadSourceLocation(Record, Idx));
    for (unsigned i = 0, e = TL.getNumArgs(); i != e; ++i)
      TL.setArgLocInfo(i,
          Reader.GetTemplateArgumentLocInfo(F,
                                            TL.getTypePtr()->getArg(i).getKind(),
                                            Record, Idx));
  }
  void TypeLocReader::VisitParenTypeLoc(ParenTypeLoc TL) {
    TL.setLParenLoc(ReadSourceLocation(Record, Idx));
    TL.setRParenLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitElaboratedTypeLoc(ElaboratedTypeLoc TL) {
    TL.setElaboratedKeywordLoc(ReadSourceLocation(Record, Idx));
    TL.setQualifierLoc(Reader.ReadNestedNameSpecifierLoc(F, Record, Idx));
  }
  void TypeLocReader::VisitInjectedClassNameTypeLoc(InjectedClassNameTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitDependentNameTypeLoc(DependentNameTypeLoc TL) {
    TL.setElaboratedKeywordLoc(ReadSourceLocation(Record, Idx));
    TL.setQualifierLoc(Reader.ReadNestedNameSpecifierLoc(F, Record, Idx));
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitDependentTemplateSpecializationTypeLoc(
         DependentTemplateSpecializationTypeLoc TL) {
    TL.setElaboratedKeywordLoc(ReadSourceLocation(Record, Idx));
    TL.setQualifierLoc(Reader.ReadNestedNameSpecifierLoc(F, Record, Idx));
    TL.setTemplateKeywordLoc(ReadSourceLocation(Record, Idx));
    TL.setTemplateNameLoc(ReadSourceLocation(Record, Idx));
    TL.setLAngleLoc(ReadSourceLocation(Record, Idx));
    TL.setRAngleLoc(ReadSourceLocation(Record, Idx));
    for (unsigned I = 0, E = TL.getNumArgs(); I != E; ++I)
      TL.setArgLocInfo(I,
          Reader.GetTemplateArgumentLocInfo(F,
                                            TL.getTypePtr()->getArg(I).getKind(),
                                            Record, Idx));
  }
  void TypeLocReader::VisitPackExpansionTypeLoc(PackExpansionTypeLoc TL) {
    TL.setEllipsisLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitObjCInterfaceTypeLoc(ObjCInterfaceTypeLoc TL) {
    TL.setNameLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitObjCObjectTypeLoc(ObjCObjectTypeLoc TL) {
    TL.setHasBaseTypeAsWritten(Record[Idx++]);
    TL.setTypeArgsLAngleLoc(ReadSourceLocation(Record, Idx));
    TL.setTypeArgsRAngleLoc(ReadSourceLocation(Record, Idx));
    for (unsigned i = 0, e = TL.getNumTypeArgs(); i != e; ++i)
      TL.setTypeArgTInfo(i, Reader.GetTypeSourceInfo(F, Record, Idx));
    TL.setProtocolLAngleLoc(ReadSourceLocation(Record, Idx));
    TL.setProtocolRAngleLoc(ReadSourceLocation(Record, Idx));
    for (unsigned i = 0, e = TL.getNumProtocols(); i != e; ++i)
      TL.setProtocolLoc(i, ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitObjCObjectPointerTypeLoc(ObjCObjectPointerTypeLoc TL) {
    TL.setStarLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitAtomicTypeLoc(AtomicTypeLoc TL) {
    TL.setKWLoc(ReadSourceLocation(Record, Idx));
    TL.setLParenLoc(ReadSourceLocation(Record, Idx));
    TL.setRParenLoc(ReadSourceLocation(Record, Idx));
  }
  void TypeLocReader::VisitPipeTypeLoc(PipeTypeLoc TL) {
    TL.setKWLoc(ReadSourceLocation(Record, Idx));
  }
  
  TypeSourceInfo *ASTReader::GetTypeSourceInfo(ModuleFile &F,
                                               const RecordData &Record,
                                               unsigned &Idx) {
    QualType InfoTy = readType(F, Record, Idx);
    if (InfoTy.isNull())
      return nullptr;
  
    TypeSourceInfo *TInfo = getContext().CreateTypeSourceInfo(InfoTy);
    TypeLocReader TLR(*this, F, Record, Idx);
    for (TypeLoc TL = TInfo->getTypeLoc(); !TL.isNull(); TL = TL.getNextTypeLoc())
      TLR.Visit(TL);
    return TInfo;
  }
  
  QualType ASTReader::GetType(TypeID ID) {
    unsigned FastQuals = ID & Qualifiers::FastMask;
    unsigned Index = ID >> Qualifiers::FastWidth;
  
    if (Index < NUM_PREDEF_TYPE_IDS) {
      QualType T;
      switch ((PredefinedTypeIDs)Index) {
      case PREDEF_TYPE_NULL_ID:
        return QualType();
      case PREDEF_TYPE_VOID_ID:
        T = Context.VoidTy;
        break;
      case PREDEF_TYPE_BOOL_ID:
        T = Context.BoolTy;
        break;
  
      case PREDEF_TYPE_CHAR_U_ID:
      case PREDEF_TYPE_CHAR_S_ID:
        // FIXME: Check that the signedness of CharTy is correct!
        T = Context.CharTy;
        break;
  
      case PREDEF_TYPE_UCHAR_ID:
        T = Context.UnsignedCharTy;
        break;
      case PREDEF_TYPE_USHORT_ID:
        T = Context.UnsignedShortTy;
        break;
      case PREDEF_TYPE_UINT_ID:
        T = Context.UnsignedIntTy;
        break;
      case PREDEF_TYPE_ULONG_ID:
        T = Context.UnsignedLongTy;
        break;
      case PREDEF_TYPE_ULONGLONG_ID:
        T = Context.UnsignedLongLongTy;
        break;
      case PREDEF_TYPE_UINT128_ID:
        T = Context.UnsignedInt128Ty;
        break;
      case PREDEF_TYPE_SCHAR_ID:
        T = Context.SignedCharTy;
        break;
      case PREDEF_TYPE_WCHAR_ID:
        T = Context.WCharTy;
        break;
      case PREDEF_TYPE_SHORT_ID:
        T = Context.ShortTy;
        break;
      case PREDEF_TYPE_INT_ID:
        T = Context.IntTy;
        break;
      case PREDEF_TYPE_LONG_ID:
        T = Context.LongTy;
        break;
      case PREDEF_TYPE_LONGLONG_ID:
        T = Context.LongLongTy;
        break;
      case PREDEF_TYPE_INT128_ID:
        T = Context.Int128Ty;
        break;
      case PREDEF_TYPE_HALF_ID:
        T = Context.HalfTy;
        break;
      case PREDEF_TYPE_FLOAT_ID:
        T = Context.FloatTy;
        break;
      case PREDEF_TYPE_DOUBLE_ID:
        T = Context.DoubleTy;
        break;
      case PREDEF_TYPE_LONGDOUBLE_ID:
        T = Context.LongDoubleTy;
        break;
      case PREDEF_TYPE_FLOAT128_ID:
        T = Context.Float128Ty;
        break;
      case PREDEF_TYPE_OVERLOAD_ID:
        T = Context.OverloadTy;
        break;
      case PREDEF_TYPE_BOUND_MEMBER:
        T = Context.BoundMemberTy;
        break;
      case PREDEF_TYPE_PSEUDO_OBJECT:
        T = Context.PseudoObjectTy;
        break;
      case PREDEF_TYPE_DEPENDENT_ID:
        T = Context.DependentTy;
        break;
      case PREDEF_TYPE_UNKNOWN_ANY:
        T = Context.UnknownAnyTy;
        break;
      case PREDEF_TYPE_NULLPTR_ID:
        T = Context.NullPtrTy;
        break;
      case PREDEF_TYPE_CHAR16_ID:
        T = Context.Char16Ty;
        break;
      case PREDEF_TYPE_CHAR32_ID:
        T = Context.Char32Ty;
        break;
      case PREDEF_TYPE_OBJC_ID:
        T = Context.ObjCBuiltinIdTy;
        break;
      case PREDEF_TYPE_OBJC_CLASS:
        T = Context.ObjCBuiltinClassTy;
        break;
      case PREDEF_TYPE_OBJC_SEL:
        T = Context.ObjCBuiltinSelTy;
        break;
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
      case PREDEF_TYPE_##Id##_ID: \
        T = Context.SingletonId; \
        break;
  #include "clang/Basic/OpenCLImageTypes.def"
      case PREDEF_TYPE_SAMPLER_ID:
        T = Context.OCLSamplerTy;
        break;
      case PREDEF_TYPE_EVENT_ID:
        T = Context.OCLEventTy;
        break;
      case PREDEF_TYPE_CLK_EVENT_ID:
        T = Context.OCLClkEventTy;
        break;
      case PREDEF_TYPE_QUEUE_ID:
        T = Context.OCLQueueTy;
        break;
      case PREDEF_TYPE_NDRANGE_ID:
        T = Context.OCLNDRangeTy;
        break;
      case PREDEF_TYPE_RESERVE_ID_ID:
        T = Context.OCLReserveIDTy;
        break;
      case PREDEF_TYPE_AUTO_DEDUCT:
        T = Context.getAutoDeductType();
        break;
  
      case PREDEF_TYPE_AUTO_RREF_DEDUCT:
        T = Context.getAutoRRefDeductType();
        break;
  
      case PREDEF_TYPE_ARC_UNBRIDGED_CAST:
        T = Context.ARCUnbridgedCastTy;
        break;
  
      case PREDEF_TYPE_BUILTIN_FN:
        T = Context.BuiltinFnTy;
        break;
  
      case PREDEF_TYPE_OMP_ARRAY_SECTION:
        T = Context.OMPArraySectionTy;
        break;
      }
  
      assert(!T.isNull() && "Unknown predefined type");
      return T.withFastQualifiers(FastQuals);
    }
  
    Index -= NUM_PREDEF_TYPE_IDS;
    assert(Index < TypesLoaded.size() && "Type index out-of-range");
    if (TypesLoaded[Index].isNull()) {
      TypesLoaded[Index] = readTypeRecord(Index);
      if (TypesLoaded[Index].isNull())
        return QualType();
  
      TypesLoaded[Index]->setFromAST();
      if (DeserializationListener)
        DeserializationListener->TypeRead(TypeIdx::fromTypeID(ID),
                                          TypesLoaded[Index]);
    }
  
    return TypesLoaded[Index].withFastQualifiers(FastQuals);
  }
  
  QualType ASTReader::getLocalType(ModuleFile &F, unsigned LocalID) {
    return GetType(getGlobalTypeID(F, LocalID));
  }
  
  serialization::TypeID 
  ASTReader::getGlobalTypeID(ModuleFile &F, unsigned LocalID) const {
    unsigned FastQuals = LocalID & Qualifiers::FastMask;
    unsigned LocalIndex = LocalID >> Qualifiers::FastWidth;
    
    if (LocalIndex < NUM_PREDEF_TYPE_IDS)
      return LocalID;
  
    ContinuousRangeMap<uint32_t, int, 2>::iterator I
      = F.TypeRemap.find(LocalIndex - NUM_PREDEF_TYPE_IDS);
    assert(I != F.TypeRemap.end() && "Invalid index into type index remap");
    
    unsigned GlobalIndex = LocalIndex + I->second;
    return (GlobalIndex << Qualifiers::FastWidth) | FastQuals;
  }
  
  TemplateArgumentLocInfo
  ASTReader::GetTemplateArgumentLocInfo(ModuleFile &F,
                                        TemplateArgument::ArgKind Kind,
                                        const RecordData &Record,
                                        unsigned &Index) {
    switch (Kind) {
    case TemplateArgument::Expression:
      return ReadExpr(F);
    case TemplateArgument::Type:
      return GetTypeSourceInfo(F, Record, Index);
    case TemplateArgument::Template: {
      NestedNameSpecifierLoc QualifierLoc = ReadNestedNameSpecifierLoc(F, Record, 
                                                                       Index);
      SourceLocation TemplateNameLoc = ReadSourceLocation(F, Record, Index);
      return TemplateArgumentLocInfo(QualifierLoc, TemplateNameLoc,
                                     SourceLocation());
    }
    case TemplateArgument::TemplateExpansion: {
      NestedNameSpecifierLoc QualifierLoc = ReadNestedNameSpecifierLoc(F, Record, 
                                                                       Index);
      SourceLocation TemplateNameLoc = ReadSourceLocation(F, Record, Index);
      SourceLocation EllipsisLoc = ReadSourceLocation(F, Record, Index);
      return TemplateArgumentLocInfo(QualifierLoc, TemplateNameLoc, 
                                     EllipsisLoc);
    }
    case TemplateArgument::Null:
    case TemplateArgument::Integral:
    case TemplateArgument::Declaration:
    case TemplateArgument::NullPtr:
    case TemplateArgument::Pack:
      // FIXME: Is this right?
      return TemplateArgumentLocInfo();
    }
    llvm_unreachable("unexpected template argument loc");
  }
  
  TemplateArgumentLoc
  ASTReader::ReadTemplateArgumentLoc(ModuleFile &F,
                                     const RecordData &Record, unsigned &Index) {
    TemplateArgument Arg = ReadTemplateArgument(F, Record, Index);
  
    if (Arg.getKind() == TemplateArgument::Expression) {
      if (Record[Index++]) // bool InfoHasSameExpr.
        return TemplateArgumentLoc(Arg, TemplateArgumentLocInfo(Arg.getAsExpr()));
    }
    return TemplateArgumentLoc(Arg, GetTemplateArgumentLocInfo(F, Arg.getKind(),
                                                               Record, Index));
  }
  
  const ASTTemplateArgumentListInfo*
  ASTReader::ReadASTTemplateArgumentListInfo(ModuleFile &F,
                                             const RecordData &Record,
                                             unsigned &Index) {
    SourceLocation LAngleLoc = ReadSourceLocation(F, Record, Index);
    SourceLocation RAngleLoc = ReadSourceLocation(F, Record, Index);
    unsigned NumArgsAsWritten = Record[Index++];
    TemplateArgumentListInfo TemplArgsInfo(LAngleLoc, RAngleLoc);
    for (unsigned i = 0; i != NumArgsAsWritten; ++i)
      TemplArgsInfo.addArgument(ReadTemplateArgumentLoc(F, Record, Index));
    return ASTTemplateArgumentListInfo::Create(getContext(), TemplArgsInfo);
  }
  
  Decl *ASTReader::GetExternalDecl(uint32_t ID) {
    return GetDecl(ID);
  }
  
  template<typename TemplateSpecializationDecl>
  static void completeRedeclChainForTemplateSpecialization(Decl *D) {
    if (auto *TSD = dyn_cast<TemplateSpecializationDecl>(D))
      TSD->getSpecializedTemplate()->LoadLazySpecializations();
  }
  
  void ASTReader::CompleteRedeclChain(const Decl *D) {
    if (NumCurrentElementsDeserializing) {
      // We arrange to not care about the complete redeclaration chain while we're
      // deserializing. Just remember that the AST has marked this one as complete
      // but that it's not actually complete yet, so we know we still need to
      // complete it later.
      PendingIncompleteDeclChains.push_back(const_cast<Decl*>(D));
      return;
    }
  
    const DeclContext *DC = D->getDeclContext()->getRedeclContext();
  
    // If this is a named declaration, complete it by looking it up
    // within its context.
    //
    // FIXME: Merging a function definition should merge
    // all mergeable entities within it.
    if (isa<TranslationUnitDecl>(DC) || isa<NamespaceDecl>(DC) ||
        isa<CXXRecordDecl>(DC) || isa<EnumDecl>(DC)) {
      if (DeclarationName Name = cast<NamedDecl>(D)->getDeclName()) {
        if (!getContext().getLangOpts().CPlusPlus &&
            isa<TranslationUnitDecl>(DC)) {
          // Outside of C++, we don't have a lookup table for the TU, so update
          // the identifier instead. (For C++ modules, we don't store decls
          // in the serialized identifier table, so we do the lookup in the TU.)
          auto *II = Name.getAsIdentifierInfo();
          assert(II && "non-identifier name in C?");
          if (II->isOutOfDate())
            updateOutOfDateIdentifier(*II);
        } else
          DC->lookup(Name);
      } else if (needsAnonymousDeclarationNumber(cast<NamedDecl>(D))) {
        // Find all declarations of this kind from the relevant context.
        for (auto *DCDecl : cast<Decl>(D->getLexicalDeclContext())->redecls()) {
          auto *DC = cast<DeclContext>(DCDecl);
          SmallVector<Decl*, 8> Decls;
          FindExternalLexicalDecls(
              DC, [&](Decl::Kind K) { return K == D->getKind(); }, Decls);
        }
      }
    }
  
    if (auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(D))
      CTSD->getSpecializedTemplate()->LoadLazySpecializations();
    if (auto *VTSD = dyn_cast<VarTemplateSpecializationDecl>(D))
      VTSD->getSpecializedTemplate()->LoadLazySpecializations();
    if (auto *FD = dyn_cast<FunctionDecl>(D)) {
      if (auto *Template = FD->getPrimaryTemplate())
        Template->LoadLazySpecializations();
    }
  }
  
  CXXCtorInitializer **
  ASTReader::GetExternalCXXCtorInitializers(uint64_t Offset) {
    RecordLocation Loc = getLocalBitOffset(Offset);
    BitstreamCursor &Cursor = Loc.F->DeclsCursor;
    SavedStreamPosition SavedPosition(Cursor);
    Cursor.JumpToBit(Loc.Offset);
    ReadingKindTracker ReadingKind(Read_Decl, *this);
  
    RecordData Record;
    unsigned Code = Cursor.ReadCode();
    unsigned RecCode = Cursor.readRecord(Code, Record);
    if (RecCode != DECL_CXX_CTOR_INITIALIZERS) {
      Error("malformed AST file: missing C++ ctor initializers");
      return nullptr;
    }
  
    unsigned Idx = 0;
    return ReadCXXCtorInitializers(*Loc.F, Record, Idx);
  }
  
  CXXBaseSpecifier *ASTReader::GetExternalCXXBaseSpecifiers(uint64_t Offset) {
    RecordLocation Loc = getLocalBitOffset(Offset);
    BitstreamCursor &Cursor = Loc.F->DeclsCursor;
    SavedStreamPosition SavedPosition(Cursor);
    Cursor.JumpToBit(Loc.Offset);
    ReadingKindTracker ReadingKind(Read_Decl, *this);
    RecordData Record;
    unsigned Code = Cursor.ReadCode();
    unsigned RecCode = Cursor.readRecord(Code, Record);
    if (RecCode != DECL_CXX_BASE_SPECIFIERS) {
      Error("malformed AST file: missing C++ base specifiers");
      return nullptr;
    }
  
    unsigned Idx = 0;
    unsigned NumBases = Record[Idx++];
    void *Mem = Context.Allocate(sizeof(CXXBaseSpecifier) * NumBases);
    CXXBaseSpecifier *Bases = new (Mem) CXXBaseSpecifier [NumBases];
    for (unsigned I = 0; I != NumBases; ++I)
      Bases[I] = ReadCXXBaseSpecifier(*Loc.F, Record, Idx);
    return Bases;
  }
  
  serialization::DeclID 
  ASTReader::getGlobalDeclID(ModuleFile &F, LocalDeclID LocalID) const {
    if (LocalID < NUM_PREDEF_DECL_IDS)
      return LocalID;
  
    ContinuousRangeMap<uint32_t, int, 2>::iterator I
      = F.DeclRemap.find(LocalID - NUM_PREDEF_DECL_IDS);
    assert(I != F.DeclRemap.end() && "Invalid index into decl index remap");
    
    return LocalID + I->second;
  }
  
  bool ASTReader::isDeclIDFromModule(serialization::GlobalDeclID ID,
                                     ModuleFile &M) const {
    // Predefined decls aren't from any module.
    if (ID < NUM_PREDEF_DECL_IDS)
      return false;
  
    return ID - NUM_PREDEF_DECL_IDS >= M.BaseDeclID && 
           ID - NUM_PREDEF_DECL_IDS < M.BaseDeclID + M.LocalNumDecls;
  }
  
  ModuleFile *ASTReader::getOwningModuleFile(const Decl *D) {
    if (!D->isFromASTFile())
      return nullptr;
    GlobalDeclMapType::const_iterator I = GlobalDeclMap.find(D->getGlobalID());
    assert(I != GlobalDeclMap.end() && "Corrupted global declaration map");
    return I->second;
  }
  
  SourceLocation ASTReader::getSourceLocationForDeclID(GlobalDeclID ID) {
    if (ID < NUM_PREDEF_DECL_IDS)
      return SourceLocation();
  
    unsigned Index = ID - NUM_PREDEF_DECL_IDS;
  
    if (Index > DeclsLoaded.size()) {
      Error("declaration ID out-of-range for AST file");
      return SourceLocation();
    }
  
    if (Decl *D = DeclsLoaded[Index])
      return D->getLocation();
  
    SourceLocation Loc;
    DeclCursorForID(ID, Loc);
    return Loc;
  }
  
  static Decl *getPredefinedDecl(ASTContext &Context, PredefinedDeclIDs ID) {
    switch (ID) {
    case PREDEF_DECL_NULL_ID:
      return nullptr;
  
    case PREDEF_DECL_TRANSLATION_UNIT_ID:
      return Context.getTranslationUnitDecl();
  
    case PREDEF_DECL_OBJC_ID_ID:
      return Context.getObjCIdDecl();
  
    case PREDEF_DECL_OBJC_SEL_ID:
      return Context.getObjCSelDecl();
  
    case PREDEF_DECL_OBJC_CLASS_ID:
      return Context.getObjCClassDecl();
  
    case PREDEF_DECL_OBJC_PROTOCOL_ID:
      return Context.getObjCProtocolDecl();
  
    case PREDEF_DECL_INT_128_ID:
      return Context.getInt128Decl();
  
    case PREDEF_DECL_UNSIGNED_INT_128_ID:
      return Context.getUInt128Decl();
  
    case PREDEF_DECL_OBJC_INSTANCETYPE_ID:
      return Context.getObjCInstanceTypeDecl();
  
    case PREDEF_DECL_BUILTIN_VA_LIST_ID:
      return Context.getBuiltinVaListDecl();
  
    case PREDEF_DECL_VA_LIST_TAG:
      return Context.getVaListTagDecl();
  
    case PREDEF_DECL_BUILTIN_MS_VA_LIST_ID:
      return Context.getBuiltinMSVaListDecl();
  
    case PREDEF_DECL_EXTERN_C_CONTEXT_ID:
      return Context.getExternCContextDecl();
  
    case PREDEF_DECL_MAKE_INTEGER_SEQ_ID:
      return Context.getMakeIntegerSeqDecl();
  
    case PREDEF_DECL_CF_CONSTANT_STRING_ID:
      return Context.getCFConstantStringDecl();
  
    case PREDEF_DECL_CF_CONSTANT_STRING_TAG_ID:
      return Context.getCFConstantStringTagDecl();
  
    case PREDEF_DECL_TYPE_PACK_ELEMENT_ID:
      return Context.getTypePackElementDecl();
    }
    llvm_unreachable("PredefinedDeclIDs unknown enum value");
  }
  
  Decl *ASTReader::GetExistingDecl(DeclID ID) {
    if (ID < NUM_PREDEF_DECL_IDS) {
      Decl *D = getPredefinedDecl(Context, (PredefinedDeclIDs)ID);
      if (D) {
        // Track that we have merged the declaration with ID \p ID into the
        // pre-existing predefined declaration \p D.
        auto &Merged = KeyDecls[D->getCanonicalDecl()];
        if (Merged.empty())
          Merged.push_back(ID);
      }
      return D;
    }
  
    unsigned Index = ID - NUM_PREDEF_DECL_IDS;
  
    if (Index >= DeclsLoaded.size()) {
      assert(0 && "declaration ID out-of-range for AST file");
      Error("declaration ID out-of-range for AST file");
      return nullptr;
    }
  
    return DeclsLoaded[Index];
  }
  
  Decl *ASTReader::GetDecl(DeclID ID) {
    if (ID < NUM_PREDEF_DECL_IDS)
      return GetExistingDecl(ID);
  
    unsigned Index = ID - NUM_PREDEF_DECL_IDS;
  
    if (Index >= DeclsLoaded.size()) {
      assert(0 && "declaration ID out-of-range for AST file");
      Error("declaration ID out-of-range for AST file");
      return nullptr;
    }
  
    if (!DeclsLoaded[Index]) {
      ReadDeclRecord(ID);
      if (DeserializationListener)
        DeserializationListener->DeclRead(ID, DeclsLoaded[Index]);
    }
  
    return DeclsLoaded[Index];
  }
  
  DeclID ASTReader::mapGlobalIDToModuleFileGlobalID(ModuleFile &M, 
                                                    DeclID GlobalID) {
    if (GlobalID < NUM_PREDEF_DECL_IDS)
      return GlobalID;
    
    GlobalDeclMapType::const_iterator I = GlobalDeclMap.find(GlobalID);
    assert(I != GlobalDeclMap.end() && "Corrupted global declaration map");
    ModuleFile *Owner = I->second;
  
    llvm::DenseMap<ModuleFile *, serialization::DeclID>::iterator Pos
      = M.GlobalToLocalDeclIDs.find(Owner);
    if (Pos == M.GlobalToLocalDeclIDs.end())
      return 0;
        
    return GlobalID - Owner->BaseDeclID + Pos->second;
  }
  
  serialization::DeclID ASTReader::ReadDeclID(ModuleFile &F, 
                                              const RecordData &Record,
                                              unsigned &Idx) {
    if (Idx >= Record.size()) {
      Error("Corrupted AST file");
      return 0;
    }
    
    return getGlobalDeclID(F, Record[Idx++]);
  }
  
  /// \brief Resolve the offset of a statement into a statement.
  ///
  /// This operation will read a new statement from the external
  /// source each time it is called, and is meant to be used via a
  /// LazyOffsetPtr (which is used by Decls for the body of functions, etc).
  Stmt *ASTReader::GetExternalDeclStmt(uint64_t Offset) {
    // Switch case IDs are per Decl.
    ClearSwitchCaseIDs();
  
    // Offset here is a global offset across the entire chain.
    RecordLocation Loc = getLocalBitOffset(Offset);
    Loc.F->DeclsCursor.JumpToBit(Loc.Offset);
    return ReadStmtFromStream(*Loc.F);
  }
  
  void ASTReader::FindExternalLexicalDecls(
      const DeclContext *DC, llvm::function_ref<bool(Decl::Kind)> IsKindWeWant,
      SmallVectorImpl<Decl *> &Decls) {
    bool PredefsVisited[NUM_PREDEF_DECL_IDS] = {};
  
    auto Visit = [&] (ModuleFile *M, LexicalContents LexicalDecls) {
      assert(LexicalDecls.size() % 2 == 0 && "expected an even number of entries");
      for (int I = 0, N = LexicalDecls.size(); I != N; I += 2) {
        auto K = (Decl::Kind)+LexicalDecls[I];
        if (!IsKindWeWant(K))
          continue;
  
        auto ID = (serialization::DeclID)+LexicalDecls[I + 1];
  
        // Don't add predefined declarations to the lexical context more
        // than once.
        if (ID < NUM_PREDEF_DECL_IDS) {
          if (PredefsVisited[ID])
            continue;
  
          PredefsVisited[ID] = true;
        }
  
        if (Decl *D = GetLocalDecl(*M, ID)) {
          assert(D->getKind() == K && "wrong kind for lexical decl");
          if (!DC->isDeclInLexicalTraversal(D))
            Decls.push_back(D);
        }
      }
    };
  
    if (isa<TranslationUnitDecl>(DC)) {
      for (auto Lexical : TULexicalDecls)
        Visit(Lexical.first, Lexical.second);
    } else {
      auto I = LexicalDecls.find(DC);
      if (I != LexicalDecls.end())
        Visit(I->second.first, I->second.second);
    }
  
    ++NumLexicalDeclContextsRead;
  }
  
  namespace {
  
  class DeclIDComp {
    ASTReader &Reader;
    ModuleFile &Mod;
  
  public:
    DeclIDComp(ASTReader &Reader, ModuleFile &M) : Reader(Reader), Mod(M) {}
  
    bool operator()(LocalDeclID L, LocalDeclID R) const {
      SourceLocation LHS = getLocation(L);
      SourceLocation RHS = getLocation(R);
      return Reader.getSourceManager().isBeforeInTranslationUnit(LHS, RHS);
    }
  
    bool operator()(SourceLocation LHS, LocalDeclID R) const {
      SourceLocation RHS = getLocation(R);
      return Reader.getSourceManager().isBeforeInTranslationUnit(LHS, RHS);
    }
  
    bool operator()(LocalDeclID L, SourceLocation RHS) const {
      SourceLocation LHS = getLocation(L);
      return Reader.getSourceManager().isBeforeInTranslationUnit(LHS, RHS);
    }
  
    SourceLocation getLocation(LocalDeclID ID) const {
      return Reader.getSourceManager().getFileLoc(
              Reader.getSourceLocationForDeclID(Reader.getGlobalDeclID(Mod, ID)));
    }
  };
  
  }
  
  void ASTReader::FindFileRegionDecls(FileID File,
                                      unsigned Offset, unsigned Length,
                                      SmallVectorImpl<Decl *> &Decls) {
    SourceManager &SM = getSourceManager();
  
    llvm::DenseMap<FileID, FileDeclsInfo>::iterator I = FileDeclIDs.find(File);
    if (I == FileDeclIDs.end())
      return;
  
    FileDeclsInfo &DInfo = I->second;
    if (DInfo.Decls.empty())
      return;
  
    SourceLocation
      BeginLoc = SM.getLocForStartOfFile(File).getLocWithOffset(Offset);
    SourceLocation EndLoc = BeginLoc.getLocWithOffset(Length);
  
    DeclIDComp DIDComp(*this, *DInfo.Mod);
    ArrayRef<serialization::LocalDeclID>::iterator
      BeginIt = std::lower_bound(DInfo.Decls.begin(), DInfo.Decls.end(),
                                 BeginLoc, DIDComp);
    if (BeginIt != DInfo.Decls.begin())
      --BeginIt;
  
    // If we are pointing at a top-level decl inside an objc container, we need
    // to backtrack until we find it otherwise we will fail to report that the
    // region overlaps with an objc container.
    while (BeginIt != DInfo.Decls.begin() &&
           GetDecl(getGlobalDeclID(*DInfo.Mod, *BeginIt))
               ->isTopLevelDeclInObjCContainer())
      --BeginIt;
  
    ArrayRef<serialization::LocalDeclID>::iterator
      EndIt = std::upper_bound(DInfo.Decls.begin(), DInfo.Decls.end(),
                               EndLoc, DIDComp);
    if (EndIt != DInfo.Decls.end())
      ++EndIt;
    
    for (ArrayRef<serialization::LocalDeclID>::iterator
           DIt = BeginIt; DIt != EndIt; ++DIt)
      Decls.push_back(GetDecl(getGlobalDeclID(*DInfo.Mod, *DIt)));
  }
  
  bool
  ASTReader::FindExternalVisibleDeclsByName(const DeclContext *DC,
                                            DeclarationName Name) {
    assert(DC->hasExternalVisibleStorage() && DC == DC->getPrimaryContext() &&
           "DeclContext has no visible decls in storage");
    if (!Name)
      return false;
  
    auto It = Lookups.find(DC);
    if (It == Lookups.end())
      return false;
  
    Deserializing LookupResults(this);
  
    // Load the list of declarations.
    SmallVector<NamedDecl *, 64> Decls;
    for (DeclID ID : It->second.Table.find(Name)) {
      NamedDecl *ND = cast<NamedDecl>(GetDecl(ID));
      if (ND->getDeclName() == Name)
        Decls.push_back(ND);
    }
  
    ++NumVisibleDeclContextsRead;
    SetExternalVisibleDeclsForName(DC, Name, Decls);
    return !Decls.empty();
  }
  
  void ASTReader::completeVisibleDeclsMap(const DeclContext *DC) {
    if (!DC->hasExternalVisibleStorage())
      return;
  
    auto It = Lookups.find(DC);
    assert(It != Lookups.end() &&
           "have external visible storage but no lookup tables");
  
    DeclsMap Decls;
  
    for (DeclID ID : It->second.Table.findAll()) {
      NamedDecl *ND = cast<NamedDecl>(GetDecl(ID));
      Decls[ND->getDeclName()].push_back(ND);
    }
  
    ++NumVisibleDeclContextsRead;
  
    for (DeclsMap::iterator I = Decls.begin(), E = Decls.end(); I != E; ++I) {
      SetExternalVisibleDeclsForName(DC, I->first, I->second);
    }
    const_cast<DeclContext *>(DC)->setHasExternalVisibleStorage(false);
  }
  
  const serialization::reader::DeclContextLookupTable *
  ASTReader::getLoadedLookupTables(DeclContext *Primary) const {
    auto I = Lookups.find(Primary);
    return I == Lookups.end() ? nullptr : &I->second;
  }
  
  /// \brief Under non-PCH compilation the consumer receives the objc methods
  /// before receiving the implementation, and codegen depends on this.
  /// We simulate this by deserializing and passing to consumer the methods of the
  /// implementation before passing the deserialized implementation decl.
  static void PassObjCImplDeclToConsumer(ObjCImplDecl *ImplD,
                                         ASTConsumer *Consumer) {
    assert(ImplD && Consumer);
  
    for (auto *I : ImplD->methods())
      Consumer->HandleInterestingDecl(DeclGroupRef(I));
  
    Consumer->HandleInterestingDecl(DeclGroupRef(ImplD));
  }
  
  void ASTReader::PassInterestingDeclsToConsumer() {
    assert(Consumer);
  
    if (PassingDeclsToConsumer)
      return;
  
    // Guard variable to avoid recursively redoing the process of passing
    // decls to consumer.
    SaveAndRestore<bool> GuardPassingDeclsToConsumer(PassingDeclsToConsumer,
                                                     true);
  
    // Ensure that we've loaded all potentially-interesting declarations
    // that need to be eagerly loaded.
    for (auto ID : EagerlyDeserializedDecls)
      GetDecl(ID);
    EagerlyDeserializedDecls.clear();
  
    while (!InterestingDecls.empty()) {
      Decl *D = InterestingDecls.front();
      InterestingDecls.pop_front();
  
      // If we have found an interesting ImportDecl, then its imported module
      // is considered used.
      if (auto *ID = dyn_cast<ImportDecl>(D))
        markModuleUsed(ID->getImportedModule());
  
      PassInterestingDeclToConsumer(D);
    }
  }
  
  void ASTReader::markModuleUsed(Module *M) {
    M = M->getTopLevelModule();
    // Mark that interesting decls in this module should now be passed to the
    // consumer, and pass any pending decls.
    auto MInterestingDecls =
        UnimportedModuleInterestingDecls.insert(std::make_pair(M, nullptr)).first;
    if (auto *Decls = MInterestingDecls->second) {
      MInterestingDecls->second = nullptr;
      for (auto *D : *Decls) {
        Module *Owner = D->getImportedOwningModule();
        if (Owner)
          Owner = Owner->getTopLevelModule();
        if (Owner != M) {
          // Mark that this decl has been handed to the consumer in its original
          // module, and stop if it's already been removed from there.
          auto OwnerIt = UnimportedModuleInterestingDecls.find(Owner);
          if (OwnerIt == UnimportedModuleInterestingDecls.end() ||
              !OwnerIt->second)
            continue;
          auto NewEnd =
              std::remove(OwnerIt->second->begin(), OwnerIt->second->end(), D);
          if (NewEnd == OwnerIt->second->end())
            continue;
          OwnerIt->second->erase(NewEnd, OwnerIt->second->end());
        }
        InterestingDecls.push_back(D);
      }
    }
  }
  
  void ASTReader::addInterestingDecl(Decl *D,
                                     llvm::Optional<Module *> OwnerOverride) {
    Module *Owner = D->getImportedOwningModule();
    if (Owner)
      Owner = Owner->getTopLevelModule();
    Module *ExportedBy = OwnerOverride ? *OwnerOverride : Owner;
    if (ExportedBy)
      ExportedBy = ExportedBy->getTopLevelModule();
  
    auto It = ExportedBy ? UnimportedModuleInterestingDecls.find(ExportedBy)
                         : UnimportedModuleInterestingDecls.end();
    if (It == UnimportedModuleInterestingDecls.end())
      It = UnimportedModuleInterestingDecls.insert(
               std::make_pair(ExportedBy, new (Context) ModuleInterestingDecls))
           .first;
    ModuleInterestingDecls *Interesting = It->second;
  
    // If this declaration's module has been imported, hand it to the consumer.
    if (!ExportedBy || !Interesting) {
      if (Owner != ExportedBy) {
        // Mark that this decl has been handed to the consumer in its original
        // module, and stop if it's already been removed from there.
        auto OwnerIt = UnimportedModuleInterestingDecls.find(Owner);
        if (OwnerIt == UnimportedModuleInterestingDecls.end() || !OwnerIt->second)
          return;
        auto NewEnd =
            std::remove(OwnerIt->second->begin(), OwnerIt->second->end(), D);
        if (NewEnd == OwnerIt->second->end())
          return;
        OwnerIt->second->erase(NewEnd, OwnerIt->second->end());
      }
      InterestingDecls.push_back(D);
      return;
    }
    assert(Owner && "re-export of unowned decl");
  
    // If this is a re-export of another module's decl, check whether the decl
    // has already been handed to the consumer.
    if (Owner != ExportedBy) {
      auto OwnerIt = UnimportedModuleInterestingDecls.find(Owner);
      if (OwnerIt != UnimportedModuleInterestingDecls.end() &&
          (!OwnerIt->second ||
           std::find(OwnerIt->second->begin(), OwnerIt->second->end(), D) ==
               OwnerIt->second->end()))
        return;
    }
  
    Interesting->push_back(D);
  }
  
  void ASTReader::PassInterestingDeclToConsumer(Decl *D) {
    if (ObjCImplDecl *ImplD = dyn_cast<ObjCImplDecl>(D))
      PassObjCImplDeclToConsumer(ImplD, Consumer);
    else
      Consumer->HandleInterestingDecl(DeclGroupRef(D));
  }
  
  void ASTReader::StartTranslationUnit(ASTConsumer *Consumer) {
    this->Consumer = Consumer;
  
    if (Consumer)
      PassInterestingDeclsToConsumer();
  
    if (DeserializationListener)
      DeserializationListener->ReaderInitialized(this);
  }
  
  void ASTReader::PrintStats() {
    std::fprintf(stderr, "*** AST File Statistics:\n");
  
    unsigned NumTypesLoaded
      = TypesLoaded.size() - std::count(TypesLoaded.begin(), TypesLoaded.end(),
                                        QualType());
    unsigned NumDeclsLoaded
      = DeclsLoaded.size() - std::count(DeclsLoaded.begin(), DeclsLoaded.end(),
                                        (Decl *)nullptr);
    unsigned NumIdentifiersLoaded
      = IdentifiersLoaded.size() - std::count(IdentifiersLoaded.begin(),
                                              IdentifiersLoaded.end(),
                                              (IdentifierInfo *)nullptr);
    unsigned NumMacrosLoaded
      = MacrosLoaded.size() - std::count(MacrosLoaded.begin(),
                                         MacrosLoaded.end(),
                                         (MacroInfo *)nullptr);
    unsigned NumSelectorsLoaded
      = SelectorsLoaded.size() - std::count(SelectorsLoaded.begin(),
                                            SelectorsLoaded.end(),
                                            Selector());
  
    if (unsigned TotalNumSLocEntries = getTotalNumSLocs())
      std::fprintf(stderr, "  %u/%u source location entries read (%f%%)\n",
                   NumSLocEntriesRead, TotalNumSLocEntries,
                   ((float)NumSLocEntriesRead/TotalNumSLocEntries * 100));
    if (!TypesLoaded.empty())
      std::fprintf(stderr, "  %u/%u types read (%f%%)\n",
                   NumTypesLoaded, (unsigned)TypesLoaded.size(),
                   ((float)NumTypesLoaded/TypesLoaded.size() * 100));
    if (!DeclsLoaded.empty())
      std::fprintf(stderr, "  %u/%u declarations read (%f%%)\n",
                   NumDeclsLoaded, (unsigned)DeclsLoaded.size(),
                   ((float)NumDeclsLoaded/DeclsLoaded.size() * 100));
    if (!IdentifiersLoaded.empty())
      std::fprintf(stderr, "  %u/%u identifiers read (%f%%)\n",
                   NumIdentifiersLoaded, (unsigned)IdentifiersLoaded.size(),
                   ((float)NumIdentifiersLoaded/IdentifiersLoaded.size() * 100));
    if (!MacrosLoaded.empty())
      std::fprintf(stderr, "  %u/%u macros read (%f%%)\n",
                   NumMacrosLoaded, (unsigned)MacrosLoaded.size(),
                   ((float)NumMacrosLoaded/MacrosLoaded.size() * 100));
    if (!SelectorsLoaded.empty())
      std::fprintf(stderr, "  %u/%u selectors read (%f%%)\n",
                   NumSelectorsLoaded, (unsigned)SelectorsLoaded.size(),
                   ((float)NumSelectorsLoaded/SelectorsLoaded.size() * 100));
    if (TotalNumStatements)
      std::fprintf(stderr, "  %u/%u statements read (%f%%)\n",
                   NumStatementsRead, TotalNumStatements,
                   ((float)NumStatementsRead/TotalNumStatements * 100));
    if (TotalNumMacros)
      std::fprintf(stderr, "  %u/%u macros read (%f%%)\n",
                   NumMacrosRead, TotalNumMacros,
                   ((float)NumMacrosRead/TotalNumMacros * 100));
    if (TotalLexicalDeclContexts)
      std::fprintf(stderr, "  %u/%u lexical declcontexts read (%f%%)\n",
                   NumLexicalDeclContextsRead, TotalLexicalDeclContexts,
                   ((float)NumLexicalDeclContextsRead/TotalLexicalDeclContexts
                    * 100));
    if (TotalVisibleDeclContexts)
      std::fprintf(stderr, "  %u/%u visible declcontexts read (%f%%)\n",
                   NumVisibleDeclContextsRead, TotalVisibleDeclContexts,
                   ((float)NumVisibleDeclContextsRead/TotalVisibleDeclContexts
                    * 100));
    if (TotalNumMethodPoolEntries) {
      std::fprintf(stderr, "  %u/%u method pool entries read (%f%%)\n",
                   NumMethodPoolEntriesRead, TotalNumMethodPoolEntries,
                   ((float)NumMethodPoolEntriesRead/TotalNumMethodPoolEntries
                    * 100));
    }
    if (NumMethodPoolLookups) {
      std::fprintf(stderr, "  %u/%u method pool lookups succeeded (%f%%)\n",
                   NumMethodPoolHits, NumMethodPoolLookups,
                   ((float)NumMethodPoolHits/NumMethodPoolLookups * 100.0));
    }
    if (NumMethodPoolTableLookups) {
      std::fprintf(stderr, "  %u/%u method pool table lookups succeeded (%f%%)\n",
                   NumMethodPoolTableHits, NumMethodPoolTableLookups,
                   ((float)NumMethodPoolTableHits/NumMethodPoolTableLookups
                    * 100.0));
    }
  
    if (NumIdentifierLookupHits) {
      std::fprintf(stderr,
                   "  %u / %u identifier table lookups succeeded (%f%%)\n",
                   NumIdentifierLookupHits, NumIdentifierLookups,
                   (double)NumIdentifierLookupHits*100.0/NumIdentifierLookups);
    }
  
    if (GlobalIndex) {
      std::fprintf(stderr, "\n");
      GlobalIndex->printStats();
    }
    
    std::fprintf(stderr, "\n");
    dump();
    std::fprintf(stderr, "\n");
  }
  
  template<typename Key, typename ModuleFile, unsigned InitialCapacity>
  static void 
  dumpModuleIDMap(StringRef Name,
                  const ContinuousRangeMap<Key, ModuleFile *, 
                                           InitialCapacity> &Map) {
    if (Map.begin() == Map.end())
      return;
    
    typedef ContinuousRangeMap<Key, ModuleFile *, InitialCapacity> MapType;
    llvm::errs() << Name << ":\n";
    for (typename MapType::const_iterator I = Map.begin(), IEnd = Map.end(); 
         I != IEnd; ++I) {
      llvm::errs() << "  " << I->first << " -> " << I->second->FileName
        << "\n";
    }
  }
  
  LLVM_DUMP_METHOD void ASTReader::dump() {
    llvm::errs() << "*** PCH/ModuleFile Remappings:\n";
    dumpModuleIDMap("Global bit offset map", GlobalBitOffsetsMap);
    dumpModuleIDMap("Global source location entry map", GlobalSLocEntryMap);
    dumpModuleIDMap("Global type map", GlobalTypeMap);
    dumpModuleIDMap("Global declaration map", GlobalDeclMap);
    dumpModuleIDMap("Global identifier map", GlobalIdentifierMap);
    dumpModuleIDMap("Global macro map", GlobalMacroMap);
    dumpModuleIDMap("Global submodule map", GlobalSubmoduleMap);
    dumpModuleIDMap("Global selector map", GlobalSelectorMap);
    dumpModuleIDMap("Global preprocessed entity map", 
                    GlobalPreprocessedEntityMap);
    
    llvm::errs() << "\n*** PCH/Modules Loaded:";
    for (ModuleManager::ModuleConstIterator M = ModuleMgr.begin(), 
                                         MEnd = ModuleMgr.end();
         M != MEnd; ++M)
      (*M)->dump();
  }
  
  /// Return the amount of memory used by memory buffers, breaking down
  /// by heap-backed versus mmap'ed memory.
  void ASTReader::getMemoryBufferSizes(MemoryBufferSizes &sizes) const {
    for (ModuleConstIterator I = ModuleMgr.begin(),
        E = ModuleMgr.end(); I != E; ++I) {
      if (llvm::MemoryBuffer *buf = (*I)->Buffer.get()) {
        size_t bytes = buf->getBufferSize();
        switch (buf->getBufferKind()) {
          case llvm::MemoryBuffer::MemoryBuffer_Malloc:
            sizes.malloc_bytes += bytes;
            break;
          case llvm::MemoryBuffer::MemoryBuffer_MMap:
            sizes.mmap_bytes += bytes;
            break;
        }
      }
    }
  }
  
  void ASTReader::InitializeSema(Sema &S) {
    SemaObj = &S;
    S.addExternalSource(this);
  
    // Makes sure any declarations that were deserialized "too early"
    // still get added to the identifier's declaration chains.
    for (uint64_t ID : PreloadedDeclIDs) {
      NamedDecl *D = cast<NamedDecl>(GetDecl(ID));
      pushExternalDeclIntoScope(D, D->getDeclName());
    }
    PreloadedDeclIDs.clear();
  
    // FIXME: What happens if these are changed by a module import?
    if (!FPPragmaOptions.empty()) {
      assert(FPPragmaOptions.size() == 1 && "Wrong number of FP_PRAGMA_OPTIONS");
      SemaObj->FPFeatures.fp_contract = FPPragmaOptions[0];
    }
  
    // FIXME: What happens if these are changed by a module import?
    if (!OpenCLExtensions.empty()) {
      unsigned I = 0;
  #define OPENCLEXT(nm)  SemaObj->OpenCLFeatures.nm = OpenCLExtensions[I++];
  #include "clang/Basic/OpenCLExtensions.def"
  
      assert(OpenCLExtensions.size() == I && "Wrong number of OPENCL_EXTENSIONS");
    }
  
    UpdateSema();
  }
  
  void ASTReader::UpdateSema() {
    assert(SemaObj && "no Sema to update");
  
    // Load the offsets of the declarations that Sema references.
    // They will be lazily deserialized when needed.
    if (!SemaDeclRefs.empty()) {
      assert(SemaDeclRefs.size() % 2 == 0);
      for (unsigned I = 0; I != SemaDeclRefs.size(); I += 2) {
        if (!SemaObj->StdNamespace)
          SemaObj->StdNamespace = SemaDeclRefs[I];
        if (!SemaObj->StdBadAlloc)
          SemaObj->StdBadAlloc = SemaDeclRefs[I+1];
      }
      SemaDeclRefs.clear();
    }
  
    // Update the state of pragmas. Use the same API as if we had encountered the
    // pragma in the source.
    if(OptimizeOffPragmaLocation.isValid())
      SemaObj->ActOnPragmaOptimize(/* IsOn = */ false, OptimizeOffPragmaLocation);
    if (PragmaMSStructState != -1)
      SemaObj->ActOnPragmaMSStruct((PragmaMSStructKind)PragmaMSStructState);
    if (PointersToMembersPragmaLocation.isValid()) {
      SemaObj->ActOnPragmaMSPointersToMembers(
          (LangOptions::PragmaMSPointersToMembersKind)
              PragmaMSPointersToMembersState,
          PointersToMembersPragmaLocation);
    }
  }
  
  IdentifierInfo *ASTReader::get(StringRef Name) {
    // Note that we are loading an identifier.
    Deserializing AnIdentifier(this);
  
    IdentifierLookupVisitor Visitor(Name, /*PriorGeneration=*/0,
                                    NumIdentifierLookups,
                                    NumIdentifierLookupHits);
  
    // We don't need to do identifier table lookups in C++ modules (we preload
    // all interesting declarations, and don't need to use the scope for name
    // lookups). Perform the lookup in PCH files, though, since we don't build
    // a complete initial identifier table if we're carrying on from a PCH.
    if (Context.getLangOpts().CPlusPlus) {
      for (auto F : ModuleMgr.pch_modules())
        if (Visitor(*F))
          break;
    } else {
      // If there is a global index, look there first to determine which modules
      // provably do not have any results for this identifier.
      GlobalModuleIndex::HitSet Hits;
      GlobalModuleIndex::HitSet *HitsPtr = nullptr;
      if (!loadGlobalIndex()) {
        if (GlobalIndex->lookupIdentifier(Name, Hits)) {
          HitsPtr = &Hits;
        }
      }
  
      ModuleMgr.visit(Visitor, HitsPtr);
    }
  
    IdentifierInfo *II = Visitor.getIdentifierInfo();
    markIdentifierUpToDate(II);
    return II;
  }
  
  namespace clang {
    /// \brief An identifier-lookup iterator that enumerates all of the
    /// identifiers stored within a set of AST files.
    class ASTIdentifierIterator : public IdentifierIterator {
      /// \brief The AST reader whose identifiers are being enumerated.
      const ASTReader &Reader;
  
      /// \brief The current index into the chain of AST files stored in
      /// the AST reader.
      unsigned Index;
  
      /// \brief The current position within the identifier lookup table
      /// of the current AST file.
      ASTIdentifierLookupTable::key_iterator Current;
  
      /// \brief The end position within the identifier lookup table of
      /// the current AST file.
      ASTIdentifierLookupTable::key_iterator End;
  
      /// \brief Whether to skip any modules in the ASTReader.
      bool SkipModules;
  
    public:
      explicit ASTIdentifierIterator(const ASTReader &Reader,
                                     bool SkipModules = false);
  
      StringRef Next() override;
    };
  }
  
  ASTIdentifierIterator::ASTIdentifierIterator(const ASTReader &Reader,
                                               bool SkipModules)
      : Reader(Reader), Index(Reader.ModuleMgr.size()), SkipModules(SkipModules) {
  }
  
  StringRef ASTIdentifierIterator::Next() {
    while (Current == End) {
      // If we have exhausted all of our AST files, we're done.
      if (Index == 0)
        return StringRef();
  
      --Index;
      ModuleFile &F = Reader.ModuleMgr[Index];
      if (SkipModules && F.isModule())
        continue;
  
      ASTIdentifierLookupTable *IdTable =
          (ASTIdentifierLookupTable *)F.IdentifierLookupTable;
      Current = IdTable->key_begin();
      End = IdTable->key_end();
    }
  
    // We have any identifiers remaining in the current AST file; return
    // the next one.
    StringRef Result = *Current;
    ++Current;
    return Result;
  }
  
  namespace {
  /// A utility for appending two IdentifierIterators.
  class ChainedIdentifierIterator : public IdentifierIterator {
    std::unique_ptr<IdentifierIterator> Current;
    std::unique_ptr<IdentifierIterator> Queued;
  
  public:
    ChainedIdentifierIterator(std::unique_ptr<IdentifierIterator> First,
                              std::unique_ptr<IdentifierIterator> Second)
        : Current(std::move(First)), Queued(std::move(Second)) {}
  
    StringRef Next() override {
      if (!Current)
        return StringRef();
  
      StringRef result = Current->Next();
      if (!result.empty())
        return result;
  
      // Try the queued iterator, which may itself be empty.
      Current.reset();
      std::swap(Current, Queued);
      return Next();
    }
  };
  } // end anonymous namespace.
  
  IdentifierIterator *ASTReader::getIdentifiers() {
    if (!loadGlobalIndex()) {
      std::unique_ptr<IdentifierIterator> ReaderIter(
          new ASTIdentifierIterator(*this, /*SkipModules=*/true));
      std::unique_ptr<IdentifierIterator> ModulesIter(
          GlobalIndex->createIdentifierIterator());
      return new ChainedIdentifierIterator(std::move(ReaderIter),
                                           std::move(ModulesIter));
    }
  
    return new ASTIdentifierIterator(*this);
  }
  
  namespace clang { namespace serialization {
    class ReadMethodPoolVisitor {
      ASTReader &Reader;
      Selector Sel;
      unsigned PriorGeneration;
      unsigned InstanceBits;
      unsigned FactoryBits;
      bool InstanceHasMoreThanOneDecl;
      bool FactoryHasMoreThanOneDecl;
      SmallVector<ObjCMethodDecl *, 4> InstanceMethods;
      SmallVector<ObjCMethodDecl *, 4> FactoryMethods;
  
    public:
      ReadMethodPoolVisitor(ASTReader &Reader, Selector Sel,
                            unsigned PriorGeneration)
          : Reader(Reader), Sel(Sel), PriorGeneration(PriorGeneration),
            InstanceBits(0), FactoryBits(0), InstanceHasMoreThanOneDecl(false),
            FactoryHasMoreThanOneDecl(false) {}
  
      bool operator()(ModuleFile &M) {
        if (!M.SelectorLookupTable)
          return false;
        
        // If we've already searched this module file, skip it now.
        if (M.Generation <= PriorGeneration)
          return true;
  
        ++Reader.NumMethodPoolTableLookups;
        ASTSelectorLookupTable *PoolTable
          = (ASTSelectorLookupTable*)M.SelectorLookupTable;
        ASTSelectorLookupTable::iterator Pos = PoolTable->find(Sel);
        if (Pos == PoolTable->end())
          return false;
  
        ++Reader.NumMethodPoolTableHits;
        ++Reader.NumSelectorsRead;
        // FIXME: Not quite happy with the statistics here. We probably should
        // disable this tracking when called via LoadSelector.
        // Also, should entries without methods count as misses?
        ++Reader.NumMethodPoolEntriesRead;
        ASTSelectorLookupTrait::data_type Data = *Pos;
        if (Reader.DeserializationListener)
          Reader.DeserializationListener->SelectorRead(Data.ID, Sel);
  
        InstanceMethods.append(Data.Instance.begin(), Data.Instance.end());
        FactoryMethods.append(Data.Factory.begin(), Data.Factory.end());
        InstanceBits = Data.InstanceBits;
        FactoryBits = Data.FactoryBits;
        InstanceHasMoreThanOneDecl = Data.InstanceHasMoreThanOneDecl;
        FactoryHasMoreThanOneDecl = Data.FactoryHasMoreThanOneDecl;
        return true;
      }
      
      /// \brief Retrieve the instance methods found by this visitor.
      ArrayRef<ObjCMethodDecl *> getInstanceMethods() const { 
        return InstanceMethods; 
      }
  
      /// \brief Retrieve the instance methods found by this visitor.
      ArrayRef<ObjCMethodDecl *> getFactoryMethods() const { 
        return FactoryMethods;
      }
  
      unsigned getInstanceBits() const { return InstanceBits; }
      unsigned getFactoryBits() const { return FactoryBits; }
      bool instanceHasMoreThanOneDecl() const {
        return InstanceHasMoreThanOneDecl;
      }
      bool factoryHasMoreThanOneDecl() const { return FactoryHasMoreThanOneDecl; }
    };
  } } // end namespace clang::serialization
  
  /// \brief Add the given set of methods to the method list.
  static void addMethodsToPool(Sema &S, ArrayRef<ObjCMethodDecl *> Methods,
                               ObjCMethodList &List) {
    for (unsigned I = 0, N = Methods.size(); I != N; ++I) {
      S.addMethodToGlobalList(&List, Methods[I]);
    }
  }
                               
  void ASTReader::ReadMethodPool(Selector Sel) {
    // Get the selector generation and update it to the current generation.
    unsigned &Generation = SelectorGeneration[Sel];
    unsigned PriorGeneration = Generation;
    Generation = getGeneration();
    SelectorOutOfDate[Sel] = false;
    
    // Search for methods defined with this selector.
    ++NumMethodPoolLookups;
    ReadMethodPoolVisitor Visitor(*this, Sel, PriorGeneration);
    ModuleMgr.visit(Visitor);
  
    if (Visitor.getInstanceMethods().empty() &&
        Visitor.getFactoryMethods().empty())
      return;
  
    ++NumMethodPoolHits;
  
    if (!getSema())
      return;
    
    Sema &S = *getSema();
    Sema::GlobalMethodPool::iterator Pos
      = S.MethodPool.insert(std::make_pair(Sel, Sema::GlobalMethods())).first;
  
    Pos->second.first.setBits(Visitor.getInstanceBits());
    Pos->second.first.setHasMoreThanOneDecl(Visitor.instanceHasMoreThanOneDecl());
    Pos->second.second.setBits(Visitor.getFactoryBits());
    Pos->second.second.setHasMoreThanOneDecl(Visitor.factoryHasMoreThanOneDecl());
  
    // Add methods to the global pool *after* setting hasMoreThanOneDecl, since
    // when building a module we keep every method individually and may need to
    // update hasMoreThanOneDecl as we add the methods.
    addMethodsToPool(S, Visitor.getInstanceMethods(), Pos->second.first);
    addMethodsToPool(S, Visitor.getFactoryMethods(), Pos->second.second);
  }
  
  void ASTReader::updateOutOfDateSelector(Selector Sel) {
    if (SelectorOutOfDate[Sel])
      ReadMethodPool(Sel);
  }
  
  void ASTReader::ReadKnownNamespaces(
                            SmallVectorImpl<NamespaceDecl *> &Namespaces) {
    Namespaces.clear();
    
    for (unsigned I = 0, N = KnownNamespaces.size(); I != N; ++I) {
      if (NamespaceDecl *Namespace 
                  = dyn_cast_or_null<NamespaceDecl>(GetDecl(KnownNamespaces[I])))
        Namespaces.push_back(Namespace);
    }
  }
  
  void ASTReader::ReadUndefinedButUsed(
      llvm::MapVector<NamedDecl *, SourceLocation> &Undefined) {
    for (unsigned Idx = 0, N = UndefinedButUsed.size(); Idx != N;) {
      NamedDecl *D = cast<NamedDecl>(GetDecl(UndefinedButUsed[Idx++]));
      SourceLocation Loc =
          SourceLocation::getFromRawEncoding(UndefinedButUsed[Idx++]);
      Undefined.insert(std::make_pair(D, Loc));
    }
  }
  
  void ASTReader::ReadMismatchingDeleteExpressions(llvm::MapVector<
      FieldDecl *, llvm::SmallVector<std::pair<SourceLocation, bool>, 4>> &
                                                       Exprs) {
    for (unsigned Idx = 0, N = DelayedDeleteExprs.size(); Idx != N;) {
      FieldDecl *FD = cast<FieldDecl>(GetDecl(DelayedDeleteExprs[Idx++]));
      uint64_t Count = DelayedDeleteExprs[Idx++];
      for (uint64_t C = 0; C < Count; ++C) {
        SourceLocation DeleteLoc =
            SourceLocation::getFromRawEncoding(DelayedDeleteExprs[Idx++]);
        const bool IsArrayForm = DelayedDeleteExprs[Idx++];
        Exprs[FD].push_back(std::make_pair(DeleteLoc, IsArrayForm));
      }
    }
  }
  
  void ASTReader::ReadTentativeDefinitions(
                    SmallVectorImpl<VarDecl *> &TentativeDefs) {
    for (unsigned I = 0, N = TentativeDefinitions.size(); I != N; ++I) {
      VarDecl *Var = dyn_cast_or_null<VarDecl>(GetDecl(TentativeDefinitions[I]));
      if (Var)
        TentativeDefs.push_back(Var);
    }
    TentativeDefinitions.clear();
  }
  
  void ASTReader::ReadUnusedFileScopedDecls(
                                 SmallVectorImpl<const DeclaratorDecl *> &Decls) {
    for (unsigned I = 0, N = UnusedFileScopedDecls.size(); I != N; ++I) {
      DeclaratorDecl *D
        = dyn_cast_or_null<DeclaratorDecl>(GetDecl(UnusedFileScopedDecls[I]));
      if (D)
        Decls.push_back(D);
    }
    UnusedFileScopedDecls.clear();
  }
  
  void ASTReader::ReadDelegatingConstructors(
                                   SmallVectorImpl<CXXConstructorDecl *> &Decls) {
    for (unsigned I = 0, N = DelegatingCtorDecls.size(); I != N; ++I) {
      CXXConstructorDecl *D
        = dyn_cast_or_null<CXXConstructorDecl>(GetDecl(DelegatingCtorDecls[I]));
      if (D)
        Decls.push_back(D);
    }
    DelegatingCtorDecls.clear();
  }
  
  void ASTReader::ReadExtVectorDecls(SmallVectorImpl<TypedefNameDecl *> &Decls) {
    for (unsigned I = 0, N = ExtVectorDecls.size(); I != N; ++I) {
      TypedefNameDecl *D
        = dyn_cast_or_null<TypedefNameDecl>(GetDecl(ExtVectorDecls[I]));
      if (D)
        Decls.push_back(D);
    }
    ExtVectorDecls.clear();
  }
  
  void ASTReader::ReadUnusedLocalTypedefNameCandidates(
      llvm::SmallSetVector<const TypedefNameDecl *, 4> &Decls) {
    for (unsigned I = 0, N = UnusedLocalTypedefNameCandidates.size(); I != N;
         ++I) {
      TypedefNameDecl *D = dyn_cast_or_null<TypedefNameDecl>(
          GetDecl(UnusedLocalTypedefNameCandidates[I]));
      if (D)
        Decls.insert(D);
    }
    UnusedLocalTypedefNameCandidates.clear();
  }
  
  void ASTReader::ReadReferencedSelectors(
         SmallVectorImpl<std::pair<Selector, SourceLocation> > &Sels) {
    if (ReferencedSelectorsData.empty())
      return;
    
    // If there are @selector references added them to its pool. This is for
    // implementation of -Wselector.
    unsigned int DataSize = ReferencedSelectorsData.size()-1;
    unsigned I = 0;
    while (I < DataSize) {
      Selector Sel = DecodeSelector(ReferencedSelectorsData[I++]);
      SourceLocation SelLoc
        = SourceLocation::getFromRawEncoding(ReferencedSelectorsData[I++]);
      Sels.push_back(std::make_pair(Sel, SelLoc));
    }
    ReferencedSelectorsData.clear();
  }
  
  void ASTReader::ReadWeakUndeclaredIdentifiers(
         SmallVectorImpl<std::pair<IdentifierInfo *, WeakInfo> > &WeakIDs) {
    if (WeakUndeclaredIdentifiers.empty())
      return;
  
    for (unsigned I = 0, N = WeakUndeclaredIdentifiers.size(); I < N; /*none*/) {
      IdentifierInfo *WeakId 
        = DecodeIdentifierInfo(WeakUndeclaredIdentifiers[I++]);
      IdentifierInfo *AliasId 
        = DecodeIdentifierInfo(WeakUndeclaredIdentifiers[I++]);
      SourceLocation Loc
        = SourceLocation::getFromRawEncoding(WeakUndeclaredIdentifiers[I++]);
      bool Used = WeakUndeclaredIdentifiers[I++];
      WeakInfo WI(AliasId, Loc);
      WI.setUsed(Used);
      WeakIDs.push_back(std::make_pair(WeakId, WI));
    }
    WeakUndeclaredIdentifiers.clear();
  }
  
  void ASTReader::ReadUsedVTables(SmallVectorImpl<ExternalVTableUse> &VTables) {
    for (unsigned Idx = 0, N = VTableUses.size(); Idx < N; /* In loop */) {
      ExternalVTableUse VT;
      VT.Record = dyn_cast_or_null<CXXRecordDecl>(GetDecl(VTableUses[Idx++]));
      VT.Location = SourceLocation::getFromRawEncoding(VTableUses[Idx++]);
      VT.DefinitionRequired = VTableUses[Idx++];
      VTables.push_back(VT);
    }
    
    VTableUses.clear();
  }
  
  void ASTReader::ReadPendingInstantiations(
         SmallVectorImpl<std::pair<ValueDecl *, SourceLocation> > &Pending) {
    for (unsigned Idx = 0, N = PendingInstantiations.size(); Idx < N;) {
      ValueDecl *D = cast<ValueDecl>(GetDecl(PendingInstantiations[Idx++]));
      SourceLocation Loc
        = SourceLocation::getFromRawEncoding(PendingInstantiations[Idx++]);
  
      Pending.push_back(std::make_pair(D, Loc));
    }  
    PendingInstantiations.clear();
  }
  
  void ASTReader::ReadLateParsedTemplates(
      llvm::MapVector<const FunctionDecl *, LateParsedTemplate *> &LPTMap) {
    for (unsigned Idx = 0, N = LateParsedTemplates.size(); Idx < N;
         /* In loop */) {
      FunctionDecl *FD = cast<FunctionDecl>(GetDecl(LateParsedTemplates[Idx++]));
  
      LateParsedTemplate *LT = new LateParsedTemplate;
      LT->D = GetDecl(LateParsedTemplates[Idx++]);
  
      ModuleFile *F = getOwningModuleFile(LT->D);
      assert(F && "No module");
  
      unsigned TokN = LateParsedTemplates[Idx++];
      LT->Toks.reserve(TokN);
      for (unsigned T = 0; T < TokN; ++T)
        LT->Toks.push_back(ReadToken(*F, LateParsedTemplates, Idx));
  
      LPTMap.insert(std::make_pair(FD, LT));
    }
  
    LateParsedTemplates.clear();
  }
  
  void ASTReader::LoadSelector(Selector Sel) {
    // It would be complicated to avoid reading the methods anyway. So don't.
    ReadMethodPool(Sel);
  }
  
  void ASTReader::SetIdentifierInfo(IdentifierID ID, IdentifierInfo *II) {
    assert(ID && "Non-zero identifier ID required");
    assert(ID <= IdentifiersLoaded.size() && "identifier ID out of range");
    IdentifiersLoaded[ID - 1] = II;
    if (DeserializationListener)
      DeserializationListener->IdentifierRead(ID, II);
  }
  
  /// \brief Set the globally-visible declarations associated with the given
  /// identifier.
  ///
  /// If the AST reader is currently in a state where the given declaration IDs
  /// cannot safely be resolved, they are queued until it is safe to resolve
  /// them.
  ///
  /// \param II an IdentifierInfo that refers to one or more globally-visible
  /// declarations.
  ///
  /// \param DeclIDs the set of declaration IDs with the name @p II that are
  /// visible at global scope.
  ///
  /// \param Decls if non-null, this vector will be populated with the set of
  /// deserialized declarations. These declarations will not be pushed into
  /// scope.
  void
  ASTReader::SetGloballyVisibleDecls(IdentifierInfo *II,
                                const SmallVectorImpl<uint32_t> &DeclIDs,
                                     SmallVectorImpl<Decl *> *Decls) {
    if (NumCurrentElementsDeserializing && !Decls) {
      PendingIdentifierInfos[II].append(DeclIDs.begin(), DeclIDs.end());
      return;
    }
  
    for (unsigned I = 0, N = DeclIDs.size(); I != N; ++I) {
      if (!SemaObj) {
        // Queue this declaration so that it will be added to the
        // translation unit scope and identifier's declaration chain
        // once a Sema object is known.
        PreloadedDeclIDs.push_back(DeclIDs[I]);
        continue;
      }
  
      NamedDecl *D = cast<NamedDecl>(GetDecl(DeclIDs[I]));
  
      // If we're simply supposed to record the declarations, do so now.
      if (Decls) {
        Decls->push_back(D);
        continue;
      }
  
      // Introduce this declaration into the translation-unit scope
      // and add it to the declaration chain for this identifier, so
      // that (unqualified) name lookup will find it.
      pushExternalDeclIntoScope(D, II);
    }
  }
  
  IdentifierInfo *ASTReader::DecodeIdentifierInfo(IdentifierID ID) {
    if (ID == 0)
      return nullptr;
  
    if (IdentifiersLoaded.empty()) {
      Error("no identifier table in AST file");
      return nullptr;
    }
  
    ID -= 1;
    if (!IdentifiersLoaded[ID]) {
      GlobalIdentifierMapType::iterator I = GlobalIdentifierMap.find(ID + 1);
      assert(I != GlobalIdentifierMap.end() && "Corrupted global identifier map");
      ModuleFile *M = I->second;
      unsigned Index = ID - M->BaseIdentifierID;
      const char *Str = M->IdentifierTableData + M->IdentifierOffsets[Index];
  
      // All of the strings in the AST file are preceded by a 16-bit length.
      // Extract that 16-bit length to avoid having to execute strlen().
      // NOTE: 'StrLenPtr' is an 'unsigned char*' so that we load bytes as
      //  unsigned integers.  This is important to avoid integer overflow when
      //  we cast them to 'unsigned'.
      const unsigned char *StrLenPtr = (const unsigned char*) Str - 2;
      unsigned StrLen = (((unsigned) StrLenPtr[0])
                         | (((unsigned) StrLenPtr[1]) << 8)) - 1;
      auto &II = PP.getIdentifierTable().get(StringRef(Str, StrLen));
      IdentifiersLoaded[ID] = &II;
      markIdentifierFromAST(*this,  II);
      if (DeserializationListener)
        DeserializationListener->IdentifierRead(ID + 1, &II);
    }
  
    return IdentifiersLoaded[ID];
  }
  
  IdentifierInfo *ASTReader::getLocalIdentifier(ModuleFile &M, unsigned LocalID) {
    return DecodeIdentifierInfo(getGlobalIdentifierID(M, LocalID));
  }
  
  IdentifierID ASTReader::getGlobalIdentifierID(ModuleFile &M, unsigned LocalID) {
    if (LocalID < NUM_PREDEF_IDENT_IDS)
      return LocalID;
    
    ContinuousRangeMap<uint32_t, int, 2>::iterator I
      = M.IdentifierRemap.find(LocalID - NUM_PREDEF_IDENT_IDS);
    assert(I != M.IdentifierRemap.end() 
           && "Invalid index into identifier index remap");
    
    return LocalID + I->second;
  }
  
  MacroInfo *ASTReader::getMacro(MacroID ID) {
    if (ID == 0)
      return nullptr;
  
    if (MacrosLoaded.empty()) {
      Error("no macro table in AST file");
      return nullptr;
    }
  
    ID -= NUM_PREDEF_MACRO_IDS;
    if (!MacrosLoaded[ID]) {
      GlobalMacroMapType::iterator I
        = GlobalMacroMap.find(ID + NUM_PREDEF_MACRO_IDS);
      assert(I != GlobalMacroMap.end() && "Corrupted global macro map");
      ModuleFile *M = I->second;
      unsigned Index = ID - M->BaseMacroID;
      MacrosLoaded[ID] = ReadMacroRecord(*M, M->MacroOffsets[Index]);
      
      if (DeserializationListener)
        DeserializationListener->MacroRead(ID + NUM_PREDEF_MACRO_IDS,
                                           MacrosLoaded[ID]);
    }
  
    return MacrosLoaded[ID];
  }
  
  MacroID ASTReader::getGlobalMacroID(ModuleFile &M, unsigned LocalID) {
    if (LocalID < NUM_PREDEF_MACRO_IDS)
      return LocalID;
  
    ContinuousRangeMap<uint32_t, int, 2>::iterator I
      = M.MacroRemap.find(LocalID - NUM_PREDEF_MACRO_IDS);
    assert(I != M.MacroRemap.end() && "Invalid index into macro index remap");
  
    return LocalID + I->second;
  }
  
  serialization::SubmoduleID
  ASTReader::getGlobalSubmoduleID(ModuleFile &M, unsigned LocalID) {
    if (LocalID < NUM_PREDEF_SUBMODULE_IDS)
      return LocalID;
    
    ContinuousRangeMap<uint32_t, int, 2>::iterator I
      = M.SubmoduleRemap.find(LocalID - NUM_PREDEF_SUBMODULE_IDS);
    assert(I != M.SubmoduleRemap.end() 
           && "Invalid index into submodule index remap");
    
    return LocalID + I->second;
  }
  
  Module *ASTReader::getSubmodule(SubmoduleID GlobalID) {
    if (GlobalID < NUM_PREDEF_SUBMODULE_IDS) {
      assert(GlobalID == 0 && "Unhandled global submodule ID");
      return nullptr;
    }
    
    if (GlobalID > SubmodulesLoaded.size()) {
      Error("submodule ID out of range in AST file");
      return nullptr;
    }
    
    return SubmodulesLoaded[GlobalID - NUM_PREDEF_SUBMODULE_IDS];
  }
  
  Module *ASTReader::getModule(unsigned ID) {
    return getSubmodule(ID);
  }
  
  ModuleFile *ASTReader::getLocalModuleFile(ModuleFile &F, unsigned ID) {
    if (ID & 1) {
      // It's a module, look it up by submodule ID.
      auto I = GlobalSubmoduleMap.find(getGlobalSubmoduleID(F, ID >> 1));
      return I == GlobalSubmoduleMap.end() ? nullptr : I->second;
    } else {
      // It's a prefix (preamble, PCH, ...). Look it up by index.
      unsigned IndexFromEnd = ID >> 1;
      assert(IndexFromEnd && "got reference to unknown module file");
      return getModuleManager().pch_modules().end()[-IndexFromEnd];
    }
  }
  
  unsigned ASTReader::getModuleFileID(ModuleFile *F) {
    if (!F)
      return 1;
  
    // For a file representing a module, use the submodule ID of the top-level
    // module as the file ID. For any other kind of file, the number of such
    // files loaded beforehand will be the same on reload.
    // FIXME: Is this true even if we have an explicit module file and a PCH?
    if (F->isModule())
      return ((F->BaseSubmoduleID + NUM_PREDEF_SUBMODULE_IDS) << 1) | 1;
  
    auto PCHModules = getModuleManager().pch_modules();
    auto I = std::find(PCHModules.begin(), PCHModules.end(), F);
    assert(I != PCHModules.end() && "emitting reference to unknown file");
    return (I - PCHModules.end()) << 1;
  }
  
  llvm::Optional<ExternalASTSource::ASTSourceDescriptor>
  ASTReader::getSourceDescriptor(unsigned ID) {
    if (const Module *M = getSubmodule(ID))
      return ExternalASTSource::ASTSourceDescriptor(*M);
  
    // If there is only a single PCH, return it instead.
    // Chained PCH are not suported.
    if (ModuleMgr.size() == 1) {
      ModuleFile &MF = ModuleMgr.getPrimaryModule();
      StringRef ModuleName = llvm::sys::path::filename(MF.OriginalSourceFileName);
      StringRef FileName = llvm::sys::path::filename(MF.FileName);
      return ASTReader::ASTSourceDescriptor(ModuleName, MF.OriginalDir, FileName,
                                            MF.Signature);
    }
    return None;
  }
  
  Selector ASTReader::getLocalSelector(ModuleFile &M, unsigned LocalID) {
    return DecodeSelector(getGlobalSelectorID(M, LocalID));
  }
  
  Selector ASTReader::DecodeSelector(serialization::SelectorID ID) {
    if (ID == 0)
      return Selector();
  
    if (ID > SelectorsLoaded.size()) {
      Error("selector ID out of range in AST file");
      return Selector();
    }
  
    if (SelectorsLoaded[ID - 1].getAsOpaquePtr() == nullptr) {
      // Load this selector from the selector table.
      GlobalSelectorMapType::iterator I = GlobalSelectorMap.find(ID);
      assert(I != GlobalSelectorMap.end() && "Corrupted global selector map");
      ModuleFile &M = *I->second;
      ASTSelectorLookupTrait Trait(*this, M);
      unsigned Idx = ID - M.BaseSelectorID - NUM_PREDEF_SELECTOR_IDS;
      SelectorsLoaded[ID - 1] =
        Trait.ReadKey(M.SelectorLookupTableData + M.SelectorOffsets[Idx], 0);
      if (DeserializationListener)
        DeserializationListener->SelectorRead(ID, SelectorsLoaded[ID - 1]);
    }
  
    return SelectorsLoaded[ID - 1];
  }
  
  Selector ASTReader::GetExternalSelector(serialization::SelectorID ID) {
    return DecodeSelector(ID);
  }
  
  uint32_t ASTReader::GetNumExternalSelectors() {
    // ID 0 (the null selector) is considered an external selector.
    return getTotalNumSelectors() + 1;
  }
  
  serialization::SelectorID
  ASTReader::getGlobalSelectorID(ModuleFile &M, unsigned LocalID) const {
    if (LocalID < NUM_PREDEF_SELECTOR_IDS)
      return LocalID;
    
    ContinuousRangeMap<uint32_t, int, 2>::iterator I
      = M.SelectorRemap.find(LocalID - NUM_PREDEF_SELECTOR_IDS);
    assert(I != M.SelectorRemap.end() 
           && "Invalid index into selector index remap");
    
    return LocalID + I->second;
  }
  
  DeclarationName
  ASTReader::ReadDeclarationName(ModuleFile &F, 
                                 const RecordData &Record, unsigned &Idx) {
    DeclarationName::NameKind Kind = (DeclarationName::NameKind)Record[Idx++];
    switch (Kind) {
    case DeclarationName::Identifier:
      return DeclarationName(GetIdentifierInfo(F, Record, Idx));
  
    case DeclarationName::ObjCZeroArgSelector:
    case DeclarationName::ObjCOneArgSelector:
    case DeclarationName::ObjCMultiArgSelector:
      return DeclarationName(ReadSelector(F, Record, Idx));
  
    case DeclarationName::CXXConstructorName:
      return Context.DeclarationNames.getCXXConstructorName(
                            Context.getCanonicalType(readType(F, Record, Idx)));
  
    case DeclarationName::CXXDestructorName:
      return Context.DeclarationNames.getCXXDestructorName(
                            Context.getCanonicalType(readType(F, Record, Idx)));
  
    case DeclarationName::CXXConversionFunctionName:
      return Context.DeclarationNames.getCXXConversionFunctionName(
                            Context.getCanonicalType(readType(F, Record, Idx)));
  
    case DeclarationName::CXXOperatorName:
      return Context.DeclarationNames.getCXXOperatorName(
                                         (OverloadedOperatorKind)Record[Idx++]);
  
    case DeclarationName::CXXLiteralOperatorName:
      return Context.DeclarationNames.getCXXLiteralOperatorName(
                                         GetIdentifierInfo(F, Record, Idx));
  
    case DeclarationName::CXXUsingDirective:
      return DeclarationName::getUsingDirectiveName();
    }
  
    llvm_unreachable("Invalid NameKind!");
  }
  
  void ASTReader::ReadDeclarationNameLoc(ModuleFile &F,
                                         DeclarationNameLoc &DNLoc,
                                         DeclarationName Name,
                                        const RecordData &Record, unsigned &Idx) {
    switch (Name.getNameKind()) {
    case DeclarationName::CXXConstructorName:
    case DeclarationName::CXXDestructorName:
    case DeclarationName::CXXConversionFunctionName:
      DNLoc.NamedType.TInfo = GetTypeSourceInfo(F, Record, Idx);
      break;
  
    case DeclarationName::CXXOperatorName:
      DNLoc.CXXOperatorName.BeginOpNameLoc
          = ReadSourceLocation(F, Record, Idx).getRawEncoding();
      DNLoc.CXXOperatorName.EndOpNameLoc
          = ReadSourceLocation(F, Record, Idx).getRawEncoding();
      break;
  
    case DeclarationName::CXXLiteralOperatorName:
      DNLoc.CXXLiteralOperatorName.OpNameLoc
          = ReadSourceLocation(F, Record, Idx).getRawEncoding();
      break;
  
    case DeclarationName::Identifier:
    case DeclarationName::ObjCZeroArgSelector:
    case DeclarationName::ObjCOneArgSelector:
    case DeclarationName::ObjCMultiArgSelector:
    case DeclarationName::CXXUsingDirective:
      break;
    }
  }
  
  void ASTReader::ReadDeclarationNameInfo(ModuleFile &F,
                                          DeclarationNameInfo &NameInfo,
                                        const RecordData &Record, unsigned &Idx) {
    NameInfo.setName(ReadDeclarationName(F, Record, Idx));
    NameInfo.setLoc(ReadSourceLocation(F, Record, Idx));
    DeclarationNameLoc DNLoc;
    ReadDeclarationNameLoc(F, DNLoc, NameInfo.getName(), Record, Idx);
    NameInfo.setInfo(DNLoc);
  }
  
  void ASTReader::ReadQualifierInfo(ModuleFile &F, QualifierInfo &Info,
                                    const RecordData &Record, unsigned &Idx) {
    Info.QualifierLoc = ReadNestedNameSpecifierLoc(F, Record, Idx);
    unsigned NumTPLists = Record[Idx++];
    Info.NumTemplParamLists = NumTPLists;
    if (NumTPLists) {
      Info.TemplParamLists = new (Context) TemplateParameterList*[NumTPLists];
      for (unsigned i=0; i != NumTPLists; ++i)
        Info.TemplParamLists[i] = ReadTemplateParameterList(F, Record, Idx);
    }
  }
  
  TemplateName
  ASTReader::ReadTemplateName(ModuleFile &F, const RecordData &Record, 
                              unsigned &Idx) {
    TemplateName::NameKind Kind = (TemplateName::NameKind)Record[Idx++];
    switch (Kind) {
    case TemplateName::Template:
        return TemplateName(ReadDeclAs<TemplateDecl>(F, Record, Idx));
  
    case TemplateName::OverloadedTemplate: {
      unsigned size = Record[Idx++];
      UnresolvedSet<8> Decls;
      while (size--)
        Decls.addDecl(ReadDeclAs<NamedDecl>(F, Record, Idx));
  
      return Context.getOverloadedTemplateName(Decls.begin(), Decls.end());
    }
  
    case TemplateName::QualifiedTemplate: {
      NestedNameSpecifier *NNS = ReadNestedNameSpecifier(F, Record, Idx);
      bool hasTemplKeyword = Record[Idx++];
      TemplateDecl *Template = ReadDeclAs<TemplateDecl>(F, Record, Idx);
      return Context.getQualifiedTemplateName(NNS, hasTemplKeyword, Template);
    }
  
    case TemplateName::DependentTemplate: {
      NestedNameSpecifier *NNS = ReadNestedNameSpecifier(F, Record, Idx);
      if (Record[Idx++])  // isIdentifier
        return Context.getDependentTemplateName(NNS,
                                                 GetIdentifierInfo(F, Record, 
                                                                   Idx));
      return Context.getDependentTemplateName(NNS,
                                           (OverloadedOperatorKind)Record[Idx++]);
    }
  
    case TemplateName::SubstTemplateTemplateParm: {
      TemplateTemplateParmDecl *param
        = ReadDeclAs<TemplateTemplateParmDecl>(F, Record, Idx);
      if (!param) return TemplateName();
      TemplateName replacement = ReadTemplateName(F, Record, Idx);
      return Context.getSubstTemplateTemplateParm(param, replacement);
    }
        
    case TemplateName::SubstTemplateTemplateParmPack: {
      TemplateTemplateParmDecl *Param 
        = ReadDeclAs<TemplateTemplateParmDecl>(F, Record, Idx);
      if (!Param)
        return TemplateName();
      
      TemplateArgument ArgPack = ReadTemplateArgument(F, Record, Idx);
      if (ArgPack.getKind() != TemplateArgument::Pack)
        return TemplateName();
      
      return Context.getSubstTemplateTemplateParmPack(Param, ArgPack);
    }
    }
  
    llvm_unreachable("Unhandled template name kind!");
  }
  
  TemplateArgument ASTReader::ReadTemplateArgument(ModuleFile &F,
                                                   const RecordData &Record,
                                                   unsigned &Idx,
                                                   bool Canonicalize) {
    if (Canonicalize) {
      // The caller wants a canonical template argument. Sometimes the AST only
      // wants template arguments in canonical form (particularly as the template
      // argument lists of template specializations) so ensure we preserve that
      // canonical form across serialization.
      TemplateArgument Arg = ReadTemplateArgument(F, Record, Idx, false);
      return Context.getCanonicalTemplateArgument(Arg);
    }
  
    TemplateArgument::ArgKind Kind = (TemplateArgument::ArgKind)Record[Idx++];
    switch (Kind) {
    case TemplateArgument::Null:
      return TemplateArgument();
    case TemplateArgument::Type:
      return TemplateArgument(readType(F, Record, Idx));
    case TemplateArgument::Declaration: {
      ValueDecl *D = ReadDeclAs<ValueDecl>(F, Record, Idx);
      return TemplateArgument(D, readType(F, Record, Idx));
    }
    case TemplateArgument::NullPtr:
      return TemplateArgument(readType(F, Record, Idx), /*isNullPtr*/true);
    case TemplateArgument::Integral: {
      llvm::APSInt Value = ReadAPSInt(Record, Idx);
      QualType T = readType(F, Record, Idx);
      return TemplateArgument(Context, Value, T);
    }
    case TemplateArgument::Template: 
      return TemplateArgument(ReadTemplateName(F, Record, Idx));
    case TemplateArgument::TemplateExpansion: {
      TemplateName Name = ReadTemplateName(F, Record, Idx);
      Optional<unsigned> NumTemplateExpansions;
      if (unsigned NumExpansions = Record[Idx++])
        NumTemplateExpansions = NumExpansions - 1;
      return TemplateArgument(Name, NumTemplateExpansions);
    }
    case TemplateArgument::Expression:
      return TemplateArgument(ReadExpr(F));
    case TemplateArgument::Pack: {
      unsigned NumArgs = Record[Idx++];
      TemplateArgument *Args = new (Context) TemplateArgument[NumArgs];
      for (unsigned I = 0; I != NumArgs; ++I)
        Args[I] = ReadTemplateArgument(F, Record, Idx);
      return TemplateArgument(llvm::makeArrayRef(Args, NumArgs));
    }
    }
  
    llvm_unreachable("Unhandled template argument kind!");
  }
  
  TemplateParameterList *
  ASTReader::ReadTemplateParameterList(ModuleFile &F,
                                       const RecordData &Record, unsigned &Idx) {
    SourceLocation TemplateLoc = ReadSourceLocation(F, Record, Idx);
    SourceLocation LAngleLoc = ReadSourceLocation(F, Record, Idx);
    SourceLocation RAngleLoc = ReadSourceLocation(F, Record, Idx);
  
    unsigned NumParams = Record[Idx++];
    SmallVector<NamedDecl *, 16> Params;
    Params.reserve(NumParams);
    while (NumParams--)
      Params.push_back(ReadDeclAs<NamedDecl>(F, Record, Idx));
  
    TemplateParameterList* TemplateParams =
      TemplateParameterList::Create(Context, TemplateLoc, LAngleLoc,
                                    Params, RAngleLoc);
    return TemplateParams;
  }
  
  void
  ASTReader::
  ReadTemplateArgumentList(SmallVectorImpl<TemplateArgument> &TemplArgs,
                           ModuleFile &F, const RecordData &Record,
                           unsigned &Idx, bool Canonicalize) {
    unsigned NumTemplateArgs = Record[Idx++];
    TemplArgs.reserve(NumTemplateArgs);
    while (NumTemplateArgs--)
      TemplArgs.push_back(ReadTemplateArgument(F, Record, Idx, Canonicalize));
  }
  
  /// \brief Read a UnresolvedSet structure.
  void ASTReader::ReadUnresolvedSet(ModuleFile &F, LazyASTUnresolvedSet &Set,
                                    const RecordData &Record, unsigned &Idx) {
    unsigned NumDecls = Record[Idx++];
    Set.reserve(Context, NumDecls);
    while (NumDecls--) {
      DeclID ID = ReadDeclID(F, Record, Idx);
      AccessSpecifier AS = (AccessSpecifier)Record[Idx++];
      Set.addLazyDecl(Context, ID, AS);
    }
  }
  
  CXXBaseSpecifier
  ASTReader::ReadCXXBaseSpecifier(ModuleFile &F,
                                  const RecordData &Record, unsigned &Idx) {
    bool isVirtual = static_cast<bool>(Record[Idx++]);
    bool isBaseOfClass = static_cast<bool>(Record[Idx++]);
    AccessSpecifier AS = static_cast<AccessSpecifier>(Record[Idx++]);
    bool inheritConstructors = static_cast<bool>(Record[Idx++]);
    TypeSourceInfo *TInfo = GetTypeSourceInfo(F, Record, Idx);
    SourceRange Range = ReadSourceRange(F, Record, Idx);
    SourceLocation EllipsisLoc = ReadSourceLocation(F, Record, Idx);
    CXXBaseSpecifier Result(Range, isVirtual, isBaseOfClass, AS, TInfo, 
                            EllipsisLoc);
    Result.setInheritConstructors(inheritConstructors);
    return Result;
  }
  
  CXXCtorInitializer **
  ASTReader::ReadCXXCtorInitializers(ModuleFile &F, const RecordData &Record,
                                     unsigned &Idx) {
    unsigned NumInitializers = Record[Idx++];
    assert(NumInitializers && "wrote ctor initializers but have no inits");
    auto **CtorInitializers = new (Context) CXXCtorInitializer*[NumInitializers];
    for (unsigned i = 0; i != NumInitializers; ++i) {
      TypeSourceInfo *TInfo = nullptr;
      bool IsBaseVirtual = false;
      FieldDecl *Member = nullptr;
      IndirectFieldDecl *IndirectMember = nullptr;
  
      CtorInitializerType Type = (CtorInitializerType)Record[Idx++];
      switch (Type) {
      case CTOR_INITIALIZER_BASE:
        TInfo = GetTypeSourceInfo(F, Record, Idx);
        IsBaseVirtual = Record[Idx++];
        break;
  
      case CTOR_INITIALIZER_DELEGATING:
        TInfo = GetTypeSourceInfo(F, Record, Idx);
        break;
  
       case CTOR_INITIALIZER_MEMBER:
        Member = ReadDeclAs<FieldDecl>(F, Record, Idx);
        break;
  
       case CTOR_INITIALIZER_INDIRECT_MEMBER:
        IndirectMember = ReadDeclAs<IndirectFieldDecl>(F, Record, Idx);
        break;
      }
  
      SourceLocation MemberOrEllipsisLoc = ReadSourceLocation(F, Record, Idx);
      Expr *Init = ReadExpr(F);
      SourceLocation LParenLoc = ReadSourceLocation(F, Record, Idx);
      SourceLocation RParenLoc = ReadSourceLocation(F, Record, Idx);
      bool IsWritten = Record[Idx++];
      unsigned SourceOrderOrNumArrayIndices;
      SmallVector<VarDecl *, 8> Indices;
      if (IsWritten) {
        SourceOrderOrNumArrayIndices = Record[Idx++];
      } else {
        SourceOrderOrNumArrayIndices = Record[Idx++];
        Indices.reserve(SourceOrderOrNumArrayIndices);
        for (unsigned i=0; i != SourceOrderOrNumArrayIndices; ++i)
          Indices.push_back(ReadDeclAs<VarDecl>(F, Record, Idx));
      }
  
      CXXCtorInitializer *BOMInit;
      if (Type == CTOR_INITIALIZER_BASE) {
        BOMInit = new (Context)
            CXXCtorInitializer(Context, TInfo, IsBaseVirtual, LParenLoc, Init,
                               RParenLoc, MemberOrEllipsisLoc);
      } else if (Type == CTOR_INITIALIZER_DELEGATING) {
        BOMInit = new (Context)
            CXXCtorInitializer(Context, TInfo, LParenLoc, Init, RParenLoc);
      } else if (IsWritten) {
        if (Member)
          BOMInit = new (Context) CXXCtorInitializer(
              Context, Member, MemberOrEllipsisLoc, LParenLoc, Init, RParenLoc);
        else
          BOMInit = new (Context)
              CXXCtorInitializer(Context, IndirectMember, MemberOrEllipsisLoc,
                                 LParenLoc, Init, RParenLoc);
      } else {
        if (IndirectMember) {
          assert(Indices.empty() && "Indirect field improperly initialized");
          BOMInit = new (Context)
              CXXCtorInitializer(Context, IndirectMember, MemberOrEllipsisLoc,
                                 LParenLoc, Init, RParenLoc);
        } else {
          BOMInit = CXXCtorInitializer::Create(
              Context, Member, MemberOrEllipsisLoc, LParenLoc, Init, RParenLoc,
              Indices.data(), Indices.size());
        }
      }
  
      if (IsWritten)
        BOMInit->setSourceOrder(SourceOrderOrNumArrayIndices);
      CtorInitializers[i] = BOMInit;
    }
  
    return CtorInitializers;
  }
  
  NestedNameSpecifier *
  ASTReader::ReadNestedNameSpecifier(ModuleFile &F,
                                     const RecordData &Record, unsigned &Idx) {
    unsigned N = Record[Idx++];
    NestedNameSpecifier *NNS = nullptr, *Prev = nullptr;
    for (unsigned I = 0; I != N; ++I) {
      NestedNameSpecifier::SpecifierKind Kind
        = (NestedNameSpecifier::SpecifierKind)Record[Idx++];
      switch (Kind) {
      case NestedNameSpecifier::Identifier: {
        IdentifierInfo *II = GetIdentifierInfo(F, Record, Idx);
        NNS = NestedNameSpecifier::Create(Context, Prev, II);
        break;
      }
  
      case NestedNameSpecifier::Namespace: {
        NamespaceDecl *NS = ReadDeclAs<NamespaceDecl>(F, Record, Idx);
        NNS = NestedNameSpecifier::Create(Context, Prev, NS);
        break;
      }
  
      case NestedNameSpecifier::NamespaceAlias: {
        NamespaceAliasDecl *Alias =ReadDeclAs<NamespaceAliasDecl>(F, Record, Idx);
        NNS = NestedNameSpecifier::Create(Context, Prev, Alias);
        break;
      }
  
      case NestedNameSpecifier::TypeSpec:
      case NestedNameSpecifier::TypeSpecWithTemplate: {
        const Type *T = readType(F, Record, Idx).getTypePtrOrNull();
        if (!T)
          return nullptr;
  
        bool Template = Record[Idx++];
        NNS = NestedNameSpecifier::Create(Context, Prev, Template, T);
        break;
      }
  
      case NestedNameSpecifier::Global: {
        NNS = NestedNameSpecifier::GlobalSpecifier(Context);
        // No associated value, and there can't be a prefix.
        break;
      }
  
      case NestedNameSpecifier::Super: {
        CXXRecordDecl *RD = ReadDeclAs<CXXRecordDecl>(F, Record, Idx);
        NNS = NestedNameSpecifier::SuperSpecifier(Context, RD);
        break;
      }
      }
      Prev = NNS;
    }
    return NNS;
  }
  
  NestedNameSpecifierLoc
  ASTReader::ReadNestedNameSpecifierLoc(ModuleFile &F, const RecordData &Record, 
                                        unsigned &Idx) {
    unsigned N = Record[Idx++];
    NestedNameSpecifierLocBuilder Builder;
    for (unsigned I = 0; I != N; ++I) {
      NestedNameSpecifier::SpecifierKind Kind
        = (NestedNameSpecifier::SpecifierKind)Record[Idx++];
      switch (Kind) {
      case NestedNameSpecifier::Identifier: {
        IdentifierInfo *II = GetIdentifierInfo(F, Record, Idx);      
        SourceRange Range = ReadSourceRange(F, Record, Idx);
        Builder.Extend(Context, II, Range.getBegin(), Range.getEnd());
        break;
      }
  
      case NestedNameSpecifier::Namespace: {
        NamespaceDecl *NS = ReadDeclAs<NamespaceDecl>(F, Record, Idx);
        SourceRange Range = ReadSourceRange(F, Record, Idx);
        Builder.Extend(Context, NS, Range.getBegin(), Range.getEnd());
        break;
      }
  
      case NestedNameSpecifier::NamespaceAlias: {
        NamespaceAliasDecl *Alias =ReadDeclAs<NamespaceAliasDecl>(F, Record, Idx);
        SourceRange Range = ReadSourceRange(F, Record, Idx);
        Builder.Extend(Context, Alias, Range.getBegin(), Range.getEnd());
        break;
      }
  
      case NestedNameSpecifier::TypeSpec:
      case NestedNameSpecifier::TypeSpecWithTemplate: {
        bool Template = Record[Idx++];
        TypeSourceInfo *T = GetTypeSourceInfo(F, Record, Idx);
        if (!T)
          return NestedNameSpecifierLoc();
        SourceLocation ColonColonLoc = ReadSourceLocation(F, Record, Idx);
  
        // FIXME: 'template' keyword location not saved anywhere, so we fake it.
        Builder.Extend(Context, 
                       Template? T->getTypeLoc().getBeginLoc() : SourceLocation(),
                       T->getTypeLoc(), ColonColonLoc);
        break;
      }
  
      case NestedNameSpecifier::Global: {
        SourceLocation ColonColonLoc = ReadSourceLocation(F, Record, Idx);
        Builder.MakeGlobal(Context, ColonColonLoc);
        break;
      }
  
      case NestedNameSpecifier::Super: {
        CXXRecordDecl *RD = ReadDeclAs<CXXRecordDecl>(F, Record, Idx);
        SourceRange Range = ReadSourceRange(F, Record, Idx);
        Builder.MakeSuper(Context, RD, Range.getBegin(), Range.getEnd());
        break;
      }
      }
    }
  
    return Builder.getWithLocInContext(Context);
  }
  
  SourceRange
  ASTReader::ReadSourceRange(ModuleFile &F, const RecordData &Record,
                             unsigned &Idx) {
    SourceLocation beg = ReadSourceLocation(F, Record, Idx);
    SourceLocation end = ReadSourceLocation(F, Record, Idx);
    return SourceRange(beg, end);
  }
  
  /// \brief Read an integral value
  llvm::APInt ASTReader::ReadAPInt(const RecordData &Record, unsigned &Idx) {
    unsigned BitWidth = Record[Idx++];
    unsigned NumWords = llvm::APInt::getNumWords(BitWidth);
    llvm::APInt Result(BitWidth, NumWords, &Record[Idx]);
    Idx += NumWords;
    return Result;
  }
  
  /// \brief Read a signed integral value
  llvm::APSInt ASTReader::ReadAPSInt(const RecordData &Record, unsigned &Idx) {
    bool isUnsigned = Record[Idx++];
    return llvm::APSInt(ReadAPInt(Record, Idx), isUnsigned);
  }
  
  /// \brief Read a floating-point value
  llvm::APFloat ASTReader::ReadAPFloat(const RecordData &Record,
                                       const llvm::fltSemantics &Sem,
                                       unsigned &Idx) {
    return llvm::APFloat(Sem, ReadAPInt(Record, Idx));
  }
  
  // \brief Read a string
  std::string ASTReader::ReadString(const RecordData &Record, unsigned &Idx) {
    unsigned Len = Record[Idx++];
    std::string Result(Record.data() + Idx, Record.data() + Idx + Len);
    Idx += Len;
    return Result;
  }
  
  std::string ASTReader::ReadPath(ModuleFile &F, const RecordData &Record,
                                  unsigned &Idx) {
    std::string Filename = ReadString(Record, Idx);
    ResolveImportedPath(F, Filename);
    return Filename;
  }
  
  VersionTuple ASTReader::ReadVersionTuple(const RecordData &Record, 
                                           unsigned &Idx) {
    unsigned Major = Record[Idx++];
    unsigned Minor = Record[Idx++];
    unsigned Subminor = Record[Idx++];
    if (Minor == 0)
      return VersionTuple(Major);
    if (Subminor == 0)
      return VersionTuple(Major, Minor - 1);
    return VersionTuple(Major, Minor - 1, Subminor - 1);
  }
  
  CXXTemporary *ASTReader::ReadCXXTemporary(ModuleFile &F, 
                                            const RecordData &Record,
                                            unsigned &Idx) {
    CXXDestructorDecl *Decl = ReadDeclAs<CXXDestructorDecl>(F, Record, Idx);
    return CXXTemporary::Create(Context, Decl);
  }
  
  DiagnosticBuilder ASTReader::Diag(unsigned DiagID) {
    return Diag(CurrentImportLoc, DiagID);
  }
  
  DiagnosticBuilder ASTReader::Diag(SourceLocation Loc, unsigned DiagID) {
    return Diags.Report(Loc, DiagID);
  }
  
  /// \brief Retrieve the identifier table associated with the
  /// preprocessor.
  IdentifierTable &ASTReader::getIdentifierTable() {
    return PP.getIdentifierTable();
  }
  
  /// \brief Record that the given ID maps to the given switch-case
  /// statement.
  void ASTReader::RecordSwitchCaseID(SwitchCase *SC, unsigned ID) {
    assert((*CurrSwitchCaseStmts)[ID] == nullptr &&
           "Already have a SwitchCase with this ID");
    (*CurrSwitchCaseStmts)[ID] = SC;
  }
  
  /// \brief Retrieve the switch-case statement with the given ID.
  SwitchCase *ASTReader::getSwitchCaseWithID(unsigned ID) {
    assert((*CurrSwitchCaseStmts)[ID] != nullptr && "No SwitchCase with this ID");
    return (*CurrSwitchCaseStmts)[ID];
  }
  
  void ASTReader::ClearSwitchCaseIDs() {
    CurrSwitchCaseStmts->clear();
  }
  
  void ASTReader::ReadComments() {
    std::vector<RawComment *> Comments;
    for (SmallVectorImpl<std::pair<BitstreamCursor,
                                   serialization::ModuleFile *> >::iterator
         I = CommentsCursors.begin(),
         E = CommentsCursors.end();
         I != E; ++I) {
      Comments.clear();
      BitstreamCursor &Cursor = I->first;
      serialization::ModuleFile &F = *I->second;
      SavedStreamPosition SavedPosition(Cursor);
  
      RecordData Record;
      while (true) {
        llvm::BitstreamEntry Entry =
          Cursor.advanceSkippingSubblocks(BitstreamCursor::AF_DontPopBlockAtEnd);
  
        switch (Entry.Kind) {
        case llvm::BitstreamEntry::SubBlock: // Handled for us already.
        case llvm::BitstreamEntry::Error:
          Error("malformed block record in AST file");
          return;
        case llvm::BitstreamEntry::EndBlock:
          goto NextCursor;
        case llvm::BitstreamEntry::Record:
          // The interesting case.
          break;
        }
  
        // Read a record.
        Record.clear();
        switch ((CommentRecordTypes)Cursor.readRecord(Entry.ID, Record)) {
        case COMMENTS_RAW_COMMENT: {
          unsigned Idx = 0;
          SourceRange SR = ReadSourceRange(F, Record, Idx);
          RawComment::CommentKind Kind =
              (RawComment::CommentKind) Record[Idx++];
          bool IsTrailingComment = Record[Idx++];
          bool IsAlmostTrailingComment = Record[Idx++];
          Comments.push_back(new (Context) RawComment(
              SR, Kind, IsTrailingComment, IsAlmostTrailingComment,
              Context.getLangOpts().CommentOpts.ParseAllComments));
          break;
        }
        }
      }
    NextCursor:
      Context.Comments.addDeserializedComments(Comments);
    }
  }
  
  std::string ASTReader::getOwningModuleNameForDiagnostic(const Decl *D) {
    // If we know the owning module, use it.
    if (Module *M = D->getImportedOwningModule())
      return M->getFullModuleName();
  
    // Otherwise, use the name of the top-level module the decl is within.
    if (ModuleFile *M = getOwningModuleFile(D))
      return M->ModuleName;
  
    // Not from a module.
    return "";
  }
  
  void ASTReader::finishPendingActions() {
    while (!PendingIdentifierInfos.empty() ||
           !PendingIncompleteDeclChains.empty() || !PendingDeclChains.empty() ||
           !PendingMacroIDs.empty() || !PendingDeclContextInfos.empty() ||
           !PendingUpdateRecords.empty()) {
      // If any identifiers with corresponding top-level declarations have
      // been loaded, load those declarations now.
      typedef llvm::DenseMap<IdentifierInfo *, SmallVector<Decl *, 2> >
        TopLevelDeclsMap;
      TopLevelDeclsMap TopLevelDecls;
  
      while (!PendingIdentifierInfos.empty()) {
        IdentifierInfo *II = PendingIdentifierInfos.back().first;
        SmallVector<uint32_t, 4> DeclIDs =
            std::move(PendingIdentifierInfos.back().second);
        PendingIdentifierInfos.pop_back();
  
        SetGloballyVisibleDecls(II, DeclIDs, &TopLevelDecls[II]);
      }
  
      // For each decl chain that we wanted to complete while deserializing, mark
      // it as "still needs to be completed".
      for (unsigned I = 0; I != PendingIncompleteDeclChains.size(); ++I) {
        markIncompleteDeclChain(PendingIncompleteDeclChains[I]);
      }
      PendingIncompleteDeclChains.clear();
  
      // Load pending declaration chains.
      for (unsigned I = 0; I != PendingDeclChains.size(); ++I)
        loadPendingDeclChain(PendingDeclChains[I].first, PendingDeclChains[I].second);
      PendingDeclChains.clear();
  
      // Make the most recent of the top-level declarations visible.
      for (TopLevelDeclsMap::iterator TLD = TopLevelDecls.begin(),
             TLDEnd = TopLevelDecls.end(); TLD != TLDEnd; ++TLD) {
        IdentifierInfo *II = TLD->first;
        for (unsigned I = 0, N = TLD->second.size(); I != N; ++I) {
          pushExternalDeclIntoScope(cast<NamedDecl>(TLD->second[I]), II);
        }
      }
  
      // Load any pending macro definitions.
      for (unsigned I = 0; I != PendingMacroIDs.size(); ++I) {
        IdentifierInfo *II = PendingMacroIDs.begin()[I].first;
        SmallVector<PendingMacroInfo, 2> GlobalIDs;
        GlobalIDs.swap(PendingMacroIDs.begin()[I].second);
        // Initialize the macro history from chained-PCHs ahead of module imports.
        for (unsigned IDIdx = 0, NumIDs = GlobalIDs.size(); IDIdx != NumIDs;
             ++IDIdx) {
          const PendingMacroInfo &Info = GlobalIDs[IDIdx];
          if (Info.M->Kind != MK_ImplicitModule &&
              Info.M->Kind != MK_ExplicitModule)
            resolvePendingMacro(II, Info);
        }
        // Handle module imports.
        for (unsigned IDIdx = 0, NumIDs = GlobalIDs.size(); IDIdx != NumIDs;
             ++IDIdx) {
          const PendingMacroInfo &Info = GlobalIDs[IDIdx];
          if (Info.M->Kind == MK_ImplicitModule ||
              Info.M->Kind == MK_ExplicitModule)
            resolvePendingMacro(II, Info);
        }
      }
      PendingMacroIDs.clear();
  
      // Wire up the DeclContexts for Decls that we delayed setting until
      // recursive loading is completed.
      while (!PendingDeclContextInfos.empty()) {
        PendingDeclContextInfo Info = PendingDeclContextInfos.front();
        PendingDeclContextInfos.pop_front();
        DeclContext *SemaDC = cast<DeclContext>(GetDecl(Info.SemaDC));
        DeclContext *LexicalDC = cast<DeclContext>(GetDecl(Info.LexicalDC));
        Info.D->setDeclContextsImpl(SemaDC, LexicalDC, getContext());
      }
  
      // Perform any pending declaration updates.
      while (!PendingUpdateRecords.empty()) {
        auto Update = PendingUpdateRecords.pop_back_val();
        ReadingKindTracker ReadingKind(Read_Decl, *this);
        loadDeclUpdateRecords(Update.first, Update.second);
      }
    }
  
    // At this point, all update records for loaded decls are in place, so any
    // fake class definitions should have become real.
    assert(PendingFakeDefinitionData.empty() &&
           "faked up a class definition but never saw the real one");
  
    // If we deserialized any C++ or Objective-C class definitions, any
    // Objective-C protocol definitions, or any redeclarable templates, make sure
    // that all redeclarations point to the definitions. Note that this can only 
    // happen now, after the redeclaration chains have been fully wired.
    for (Decl *D : PendingDefinitions) {
      if (TagDecl *TD = dyn_cast<TagDecl>(D)) {
        if (const TagType *TagT = dyn_cast<TagType>(TD->getTypeForDecl())) {
          // Make sure that the TagType points at the definition.
          const_cast<TagType*>(TagT)->decl = TD;
        }
  
        if (auto RD = dyn_cast<CXXRecordDecl>(D)) {
          for (auto *R = getMostRecentExistingDecl(RD); R;
               R = R->getPreviousDecl()) {
            assert((R == D) ==
                       cast<CXXRecordDecl>(R)->isThisDeclarationADefinition() &&
                   "declaration thinks it's the definition but it isn't");
            cast<CXXRecordDecl>(R)->DefinitionData = RD->DefinitionData;
          }
        }
  
        continue;
      }
  
      if (auto ID = dyn_cast<ObjCInterfaceDecl>(D)) {
        // Make sure that the ObjCInterfaceType points at the definition.
        const_cast<ObjCInterfaceType *>(cast<ObjCInterfaceType>(ID->TypeForDecl))
          ->Decl = ID;
  
        for (auto *R = getMostRecentExistingDecl(ID); R; R = R->getPreviousDecl())
          cast<ObjCInterfaceDecl>(R)->Data = ID->Data;
  
        continue;
      }
  
      if (auto PD = dyn_cast<ObjCProtocolDecl>(D)) {
        for (auto *R = getMostRecentExistingDecl(PD); R; R = R->getPreviousDecl())
          cast<ObjCProtocolDecl>(R)->Data = PD->Data;
  
        continue;
      }
  
      auto RTD = cast<RedeclarableTemplateDecl>(D)->getCanonicalDecl();
      for (auto *R = getMostRecentExistingDecl(RTD); R; R = R->getPreviousDecl())
        cast<RedeclarableTemplateDecl>(R)->Common = RTD->Common;
    }
    PendingDefinitions.clear();
  
    // Load the bodies of any functions or methods we've encountered. We do
    // this now (delayed) so that we can be sure that the declaration chains
    // have been fully wired up (hasBody relies on this).
    // FIXME: We shouldn't require complete redeclaration chains here.
    for (PendingBodiesMap::iterator PB = PendingBodies.begin(),
                                 PBEnd = PendingBodies.end();
         PB != PBEnd; ++PB) {
      if (FunctionDecl *FD = dyn_cast<FunctionDecl>(PB->first)) {
        // FIXME: Check for =delete/=default?
        // FIXME: Complain about ODR violations here?
        if (!getContext().getLangOpts().Modules || !FD->hasBody())
          FD->setLazyBody(PB->second);
        continue;
      }
  
      ObjCMethodDecl *MD = cast<ObjCMethodDecl>(PB->first);
      if (!getContext().getLangOpts().Modules || !MD->hasBody())
        MD->setLazyBody(PB->second);
    }
    PendingBodies.clear();
  
    // Do some cleanup.
    for (auto *ND : PendingMergedDefinitionsToDeduplicate)
      getContext().deduplicateMergedDefinitonsFor(ND);
    PendingMergedDefinitionsToDeduplicate.clear();
  }
  
  void ASTReader::diagnoseOdrViolations() {
    if (PendingOdrMergeFailures.empty() && PendingOdrMergeChecks.empty())
      return;
  
    // Trigger the import of the full definition of each class that had any
    // odr-merging problems, so we can produce better diagnostics for them.
    // These updates may in turn find and diagnose some ODR failures, so take
    // ownership of the set first.
    auto OdrMergeFailures = std::move(PendingOdrMergeFailures);
    PendingOdrMergeFailures.clear();
    for (auto &Merge : OdrMergeFailures) {
      Merge.first->buildLookup();
      Merge.first->decls_begin();
      Merge.first->bases_begin();
      Merge.first->vbases_begin();
      for (auto *RD : Merge.second) {
        RD->decls_begin();
        RD->bases_begin();
        RD->vbases_begin();
      }
    }
  
    // For each declaration from a merged context, check that the canonical
    // definition of that context also contains a declaration of the same
    // entity.
    //
    // Caution: this loop does things that might invalidate iterators into
    // PendingOdrMergeChecks. Don't turn this into a range-based for loop!
    while (!PendingOdrMergeChecks.empty()) {
      NamedDecl *D = PendingOdrMergeChecks.pop_back_val();
  
      // FIXME: Skip over implicit declarations for now. This matters for things
      // like implicitly-declared special member functions. This isn't entirely
      // correct; we can end up with multiple unmerged declarations of the same
      // implicit entity.
      if (D->isImplicit())
        continue;
  
      DeclContext *CanonDef = D->getDeclContext();
  
      bool Found = false;
      const Decl *DCanon = D->getCanonicalDecl();
  
      for (auto RI : D->redecls()) {
        if (RI->getLexicalDeclContext() == CanonDef) {
          Found = true;
          break;
        }
      }
      if (Found)
        continue;
  
      // Quick check failed, time to do the slow thing. Note, we can't just
      // look up the name of D in CanonDef here, because the member that is
      // in CanonDef might not be found by name lookup (it might have been
      // replaced by a more recent declaration in the lookup table), and we
      // can't necessarily find it in the redeclaration chain because it might
      // be merely mergeable, not redeclarable.
      llvm::SmallVector<const NamedDecl*, 4> Candidates;
      for (auto *CanonMember : CanonDef->decls()) {
        if (CanonMember->getCanonicalDecl() == DCanon) {
          // This can happen if the declaration is merely mergeable and not
          // actually redeclarable (we looked for redeclarations earlier).
          //
          // FIXME: We should be able to detect this more efficiently, without
          // pulling in all of the members of CanonDef.
          Found = true;
          break;
        }
        if (auto *ND = dyn_cast<NamedDecl>(CanonMember))
          if (ND->getDeclName() == D->getDeclName())
            Candidates.push_back(ND);
      }
  
      if (!Found) {
        // The AST doesn't like TagDecls becoming invalid after they've been
        // completed. We only really need to mark FieldDecls as invalid here.
        if (!isa<TagDecl>(D))
          D->setInvalidDecl();
        
        // Ensure we don't accidentally recursively enter deserialization while
        // we're producing our diagnostic.
        Deserializing RecursionGuard(this);
  
        std::string CanonDefModule =
            getOwningModuleNameForDiagnostic(cast<Decl>(CanonDef));
        Diag(D->getLocation(), diag::err_module_odr_violation_missing_decl)
          << D << getOwningModuleNameForDiagnostic(D)
          << CanonDef << CanonDefModule.empty() << CanonDefModule;
  
        if (Candidates.empty())
          Diag(cast<Decl>(CanonDef)->getLocation(),
               diag::note_module_odr_violation_no_possible_decls) << D;
        else {
          for (unsigned I = 0, N = Candidates.size(); I != N; ++I)
            Diag(Candidates[I]->getLocation(),
                 diag::note_module_odr_violation_possible_decl)
              << Candidates[I];
        }
  
        DiagnosedOdrMergeFailures.insert(CanonDef);
      }
    }
  
    if (OdrMergeFailures.empty())
      return;
  
    // Ensure we don't accidentally recursively enter deserialization while
    // we're producing our diagnostics.
    Deserializing RecursionGuard(this);
  
    // Issue any pending ODR-failure diagnostics.
    for (auto &Merge : OdrMergeFailures) {
      // If we've already pointed out a specific problem with this class, don't
      // bother issuing a general "something's different" diagnostic.
      if (!DiagnosedOdrMergeFailures.insert(Merge.first).second)
        continue;
  
      bool Diagnosed = false;
      for (auto *RD : Merge.second) {
        // Multiple different declarations got merged together; tell the user
        // where they came from.
        if (Merge.first != RD) {
          // FIXME: Walk the definition, figure out what's different,
          // and diagnose that.
          if (!Diagnosed) {
            std::string Module = getOwningModuleNameForDiagnostic(Merge.first);
            Diag(Merge.first->getLocation(),
                 diag::err_module_odr_violation_different_definitions)
              << Merge.first << Module.empty() << Module;
            Diagnosed = true;
          }
  
          Diag(RD->getLocation(),
               diag::note_module_odr_violation_different_definitions)
            << getOwningModuleNameForDiagnostic(RD);
        }
      }
  
      if (!Diagnosed) {
        // All definitions are updates to the same declaration. This happens if a
        // module instantiates the declaration of a class template specialization
        // and two or more other modules instantiate its definition.
        //
        // FIXME: Indicate which modules had instantiations of this definition.
        // FIXME: How can this even happen?
        Diag(Merge.first->getLocation(),
             diag::err_module_odr_violation_different_instantiations)
          << Merge.first;
      }
    }
  }
  
  void ASTReader::StartedDeserializing() {
    if (++NumCurrentElementsDeserializing == 1 && ReadTimer.get()) 
      ReadTimer->startTimer();
  }
  
  void ASTReader::FinishedDeserializing() {
    assert(NumCurrentElementsDeserializing &&
           "FinishedDeserializing not paired with StartedDeserializing");
    if (NumCurrentElementsDeserializing == 1) {
      // We decrease NumCurrentElementsDeserializing only after pending actions
      // are finished, to avoid recursively re-calling finishPendingActions().
      finishPendingActions();
    }
    --NumCurrentElementsDeserializing;
  
    if (NumCurrentElementsDeserializing == 0) {
      // Propagate exception specification updates along redeclaration chains.
      while (!PendingExceptionSpecUpdates.empty()) {
        auto Updates = std::move(PendingExceptionSpecUpdates);
        PendingExceptionSpecUpdates.clear();
        for (auto Update : Updates) {
          auto *FPT = Update.second->getType()->castAs<FunctionProtoType>();
          auto ESI = FPT->getExtProtoInfo().ExceptionSpec;
          if (auto *Listener = Context.getASTMutationListener())
            Listener->ResolvedExceptionSpec(cast<FunctionDecl>(Update.second));
          for (auto *Redecl : Update.second->redecls())
            Context.adjustExceptionSpec(cast<FunctionDecl>(Redecl), ESI);
        }
      }
  
      if (ReadTimer)
        ReadTimer->stopTimer();
  
      diagnoseOdrViolations();
  
      // We are not in recursive loading, so it's safe to pass the "interesting"
      // decls to the consumer.
      if (Consumer)
        PassInterestingDeclsToConsumer();
    }
  }
  
  void ASTReader::pushExternalDeclIntoScope(NamedDecl *D, DeclarationName Name) {
    if (IdentifierInfo *II = Name.getAsIdentifierInfo()) {
      // Remove any fake results before adding any real ones.
      auto It = PendingFakeLookupResults.find(II);
      if (It != PendingFakeLookupResults.end()) {
        for (auto *ND : It->second)
          SemaObj->IdResolver.RemoveDecl(ND);
        // FIXME: this works around module+PCH performance issue.
        // Rather than erase the result from the map, which is O(n), just clear
        // the vector of NamedDecls.
        It->second.clear();
      }
    }
  
    if (SemaObj->IdResolver.tryAddTopLevelDecl(D, Name) && SemaObj->TUScope) {
      SemaObj->TUScope->AddDecl(D);
    } else if (SemaObj->TUScope) {
      // Adding the decl to IdResolver may have failed because it was already in
      // (even though it was not added in scope). If it is already in, make sure
      // it gets in the scope as well.
      if (std::find(SemaObj->IdResolver.begin(Name),
                    SemaObj->IdResolver.end(), D) != SemaObj->IdResolver.end())
        SemaObj->TUScope->AddDecl(D);
    }
  }
  
  ASTReader::ASTReader(
    Preprocessor &PP, ASTContext &Context,
    const PCHContainerReader &PCHContainerRdr,
    ArrayRef<IntrusiveRefCntPtr<ModuleFileExtension>> Extensions,
    StringRef isysroot, bool DisableValidation,
    bool AllowASTWithCompilerErrors,
    bool AllowConfigurationMismatch, bool ValidateSystemInputs,
    bool UseGlobalIndex,
    std::unique_ptr<llvm::Timer> ReadTimer)
      : Listener(new PCHValidator(PP, *this)), DeserializationListener(nullptr),
        OwnsDeserializationListener(false), SourceMgr(PP.getSourceManager()),
        FileMgr(PP.getFileManager()), PCHContainerRdr(PCHContainerRdr),
        Diags(PP.getDiagnostics()), SemaObj(nullptr), PP(PP), Context(Context),
        Consumer(nullptr), ModuleMgr(PP.getFileManager(), PCHContainerRdr),
        DummyIdResolver(PP),
        ReadTimer(std::move(ReadTimer)),
        PragmaMSStructState(-1),
        PragmaMSPointersToMembersState(-1),
        isysroot(isysroot), DisableValidation(DisableValidation),
        AllowASTWithCompilerErrors(AllowASTWithCompilerErrors),
        AllowConfigurationMismatch(AllowConfigurationMismatch),
        ValidateSystemInputs(ValidateSystemInputs),
        UseGlobalIndex(UseGlobalIndex), TriedLoadingGlobalIndex(false),
        CurrSwitchCaseStmts(&SwitchCaseStmts), NumSLocEntriesRead(0),
        TotalNumSLocEntries(0), NumStatementsRead(0), TotalNumStatements(0),
        NumMacrosRead(0), TotalNumMacros(0), NumIdentifierLookups(0),
        NumIdentifierLookupHits(0), NumSelectorsRead(0),
        NumMethodPoolEntriesRead(0), NumMethodPoolLookups(0),
        NumMethodPoolHits(0), NumMethodPoolTableLookups(0),
        NumMethodPoolTableHits(0), TotalNumMethodPoolEntries(0),
        NumLexicalDeclContextsRead(0), TotalLexicalDeclContexts(0),
        NumVisibleDeclContextsRead(0), TotalVisibleDeclContexts(0),
        TotalModulesSizeInBits(0), NumCurrentElementsDeserializing(0),
        PassingDeclsToConsumer(false), ReadingKind(Read_None) {
    SourceMgr.setExternalSLocEntrySource(this);
  
    for (const auto &Ext : Extensions) {
      auto BlockName = Ext->getExtensionMetadata().BlockName;
      auto Known = ModuleFileExtensions.find(BlockName);
      if (Known != ModuleFileExtensions.end()) {
        Diags.Report(diag::warn_duplicate_module_file_extension)
          << BlockName;
        continue;
      }
  
      ModuleFileExtensions.insert({BlockName, Ext});
    }
  }
  
  ASTReader::~ASTReader() {
    if (OwnsDeserializationListener)
      delete DeserializationListener;
  }
  
  IdentifierResolver &ASTReader::getIdResolver() {
    return SemaObj ? SemaObj->IdResolver : DummyIdResolver;
  }
  