1 files changed, 2128 insertions, 0 deletions

diff --git a/contrib/llvm-project/clang/lib/Frontend/CompilerInstance.cpp b/contrib/llvm-project/clang/lib/Frontend/CompilerInstance.cpp
new file mode 100644
index 000000000000..cf0267549e75
--- /dev/null
+++ b/contrib/llvm-project/clang/lib/Frontend/CompilerInstance.cpp
@@ -0,0 +1,2128 @@
+//===--- CompilerInstance.cpp ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/AST/ASTConsumer.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Decl.h"
+#include "clang/Basic/CharInfo.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/FileManager.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Basic/Stack.h"
+#include "clang/Basic/TargetInfo.h"
+#include "clang/Basic/Version.h"
+#include "clang/Config/config.h"
+#include "clang/Frontend/ChainedDiagnosticConsumer.h"
+#include "clang/Frontend/FrontendAction.h"
+#include "clang/Frontend/FrontendActions.h"
+#include "clang/Frontend/FrontendDiagnostic.h"
+#include "clang/Frontend/LogDiagnosticPrinter.h"
+#include "clang/Frontend/SerializedDiagnosticPrinter.h"
+#include "clang/Frontend/TextDiagnosticPrinter.h"
+#include "clang/Frontend/Utils.h"
+#include "clang/Frontend/VerifyDiagnosticConsumer.h"
+#include "clang/Lex/HeaderSearch.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Lex/PreprocessorOptions.h"
+#include "clang/Sema/CodeCompleteConsumer.h"
+#include "clang/Sema/Sema.h"
+#include "clang/Serialization/ASTReader.h"
+#include "clang/Serialization/GlobalModuleIndex.h"
+#include "clang/Serialization/InMemoryModuleCache.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/BuryPointer.h"
+#include "llvm/Support/CrashRecoveryContext.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/LockFileManager.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/Program.h"
+#include "llvm/Support/Signals.h"
+#include "llvm/Support/TimeProfiler.h"
+#include "llvm/Support/Timer.h"
+#include "llvm/Support/raw_ostream.h"
+#include <sys/stat.h>
+#include <system_error>
+#include <time.h>
+#include <utility>
+
+using namespace clang;
+
+CompilerInstance::CompilerInstance(
+    std::shared_ptr<PCHContainerOperations> PCHContainerOps,
+    InMemoryModuleCache *SharedModuleCache)
+    : ModuleLoader(/* BuildingModule = */ SharedModuleCache),
+      Invocation(new CompilerInvocation()),
+      ModuleCache(SharedModuleCache ? SharedModuleCache
+                                    : new InMemoryModuleCache),
+      ThePCHContainerOperations(std::move(PCHContainerOps)) {}
+
+CompilerInstance::~CompilerInstance() {
+  assert(OutputFiles.empty() && "Still output files in flight?");
+}
+
+void CompilerInstance::setInvocation(
+    std::shared_ptr<CompilerInvocation> Value) {
+  Invocation = std::move(Value);
+}
+
+bool CompilerInstance::shouldBuildGlobalModuleIndex() const {
+  return (BuildGlobalModuleIndex ||
+          (ModuleManager && ModuleManager->isGlobalIndexUnavailable() &&
+           getFrontendOpts().GenerateGlobalModuleIndex)) &&
+         !ModuleBuildFailed;
+}
+
+void CompilerInstance::setDiagnostics(DiagnosticsEngine *Value) {
+  Diagnostics = Value;
+}
+
+void CompilerInstance::setTarget(TargetInfo *Value) { Target = Value; }
+void CompilerInstance::setAuxTarget(TargetInfo *Value) { AuxTarget = Value; }
+
+void CompilerInstance::setFileManager(FileManager *Value) {
+  FileMgr = Value;
+}
+
+void CompilerInstance::setSourceManager(SourceManager *Value) {
+  SourceMgr = Value;
+}
+
+void CompilerInstance::setPreprocessor(std::shared_ptr<Preprocessor> Value) {
+  PP = std::move(Value);
+}
+
+void CompilerInstance::setASTContext(ASTContext *Value) {
+  Context = Value;
+
+  if (Context && Consumer)
+    getASTConsumer().Initialize(getASTContext());
+}
+
+void CompilerInstance::setSema(Sema *S) {
+  TheSema.reset(S);
+}
+
+void CompilerInstance::setASTConsumer(std::unique_ptr<ASTConsumer> Value) {
+  Consumer = std::move(Value);
+
+  if (Context && Consumer)
+    getASTConsumer().Initialize(getASTContext());
+}
+
+void CompilerInstance::setCodeCompletionConsumer(CodeCompleteConsumer *Value) {
+  CompletionConsumer.reset(Value);
+}
+
+std::unique_ptr<Sema> CompilerInstance::takeSema() {
+  return std::move(TheSema);
+}
+
+IntrusiveRefCntPtr<ASTReader> CompilerInstance::getModuleManager() const {
+  return ModuleManager;
+}
+void CompilerInstance::setModuleManager(IntrusiveRefCntPtr<ASTReader> Reader) {
+  assert(ModuleCache.get() == &Reader->getModuleManager().getModuleCache() &&
+         "Expected ASTReader to use the same PCM cache");
+  ModuleManager = std::move(Reader);
+}
+
+std::shared_ptr<ModuleDependencyCollector>
+CompilerInstance::getModuleDepCollector() const {
+  return ModuleDepCollector;
+}
+
+void CompilerInstance::setModuleDepCollector(
+    std::shared_ptr<ModuleDependencyCollector> Collector) {
+  ModuleDepCollector = std::move(Collector);
+}
+
+static void collectHeaderMaps(const HeaderSearch &HS,
+                              std::shared_ptr<ModuleDependencyCollector> MDC) {
+  SmallVector<std::string, 4> HeaderMapFileNames;
+  HS.getHeaderMapFileNames(HeaderMapFileNames);
+  for (auto &Name : HeaderMapFileNames)
+    MDC->addFile(Name);
+}
+
+static void collectIncludePCH(CompilerInstance &CI,
+                              std::shared_ptr<ModuleDependencyCollector> MDC) {
+  const PreprocessorOptions &PPOpts = CI.getPreprocessorOpts();
+  if (PPOpts.ImplicitPCHInclude.empty())
+    return;
+
+  StringRef PCHInclude = PPOpts.ImplicitPCHInclude;
+  FileManager &FileMgr = CI.getFileManager();
+  const DirectoryEntry *PCHDir = FileMgr.getDirectory(PCHInclude);
+  if (!PCHDir) {
+    MDC->addFile(PCHInclude);
+    return;
+  }
+
+  std::error_code EC;
+  SmallString<128> DirNative;
+  llvm::sys::path::native(PCHDir->getName(), DirNative);
+  llvm::vfs::FileSystem &FS = FileMgr.getVirtualFileSystem();
+  SimpleASTReaderListener Validator(CI.getPreprocessor());
+  for (llvm::vfs::directory_iterator Dir = FS.dir_begin(DirNative, EC), DirEnd;
+       Dir != DirEnd && !EC; Dir.increment(EC)) {
+    // Check whether this is an AST file. ASTReader::isAcceptableASTFile is not
+    // used here since we're not interested in validating the PCH at this time,
+    // but only to check whether this is a file containing an AST.
+    if (!ASTReader::readASTFileControlBlock(
+            Dir->path(), FileMgr, CI.getPCHContainerReader(),
+            /*FindModuleFileExtensions=*/false, Validator,
+            /*ValidateDiagnosticOptions=*/false))
+      MDC->addFile(Dir->path());
+  }
+}
+
+static void collectVFSEntries(CompilerInstance &CI,
+                              std::shared_ptr<ModuleDependencyCollector> MDC) {
+  if (CI.getHeaderSearchOpts().VFSOverlayFiles.empty())
+    return;
+
+  // Collect all VFS found.
+  SmallVector<llvm::vfs::YAMLVFSEntry, 16> VFSEntries;
+  for (const std::string &VFSFile : CI.getHeaderSearchOpts().VFSOverlayFiles) {
+    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Buffer =
+        llvm::MemoryBuffer::getFile(VFSFile);
+    if (!Buffer)
+      return;
+    llvm::vfs::collectVFSFromYAML(std::move(Buffer.get()),
+                                  /*DiagHandler*/ nullptr, VFSFile, VFSEntries);
+  }
+
+  for (auto &E : VFSEntries)
+    MDC->addFile(E.VPath, E.RPath);
+}
+
+// Diagnostics
+static void SetUpDiagnosticLog(DiagnosticOptions *DiagOpts,
+                               const CodeGenOptions *CodeGenOpts,
+                               DiagnosticsEngine &Diags) {
+  std::error_code EC;
+  std::unique_ptr<raw_ostream> StreamOwner;
+  raw_ostream *OS = &llvm::errs();
+  if (DiagOpts->DiagnosticLogFile != "-") {
+    // Create the output stream.
+    auto FileOS = llvm::make_unique<llvm::raw_fd_ostream>(
+        DiagOpts->DiagnosticLogFile, EC,
+        llvm::sys::fs::F_Append | llvm::sys::fs::F_Text);
+    if (EC) {
+      Diags.Report(diag::warn_fe_cc_log_diagnostics_failure)
+          << DiagOpts->DiagnosticLogFile << EC.message();
+    } else {
+      FileOS->SetUnbuffered();
+      OS = FileOS.get();
+      StreamOwner = std::move(FileOS);
+    }
+  }
+
+  // Chain in the diagnostic client which will log the diagnostics.
+  auto Logger = llvm::make_unique<LogDiagnosticPrinter>(*OS, DiagOpts,
+                                                        std::move(StreamOwner));
+  if (CodeGenOpts)
+    Logger->setDwarfDebugFlags(CodeGenOpts->DwarfDebugFlags);
+  if (Diags.ownsClient()) {
+    Diags.setClient(
+        new ChainedDiagnosticConsumer(Diags.takeClient(), std::move(Logger)));
+  } else {
+    Diags.setClient(
+        new ChainedDiagnosticConsumer(Diags.getClient(), std::move(Logger)));
+  }
+}
+
+static void SetupSerializedDiagnostics(DiagnosticOptions *DiagOpts,
+                                       DiagnosticsEngine &Diags,
+                                       StringRef OutputFile) {
+  auto SerializedConsumer =
+      clang::serialized_diags::create(OutputFile, DiagOpts);
+
+  if (Diags.ownsClient()) {
+    Diags.setClient(new ChainedDiagnosticConsumer(
+        Diags.takeClient(), std::move(SerializedConsumer)));
+  } else {
+    Diags.setClient(new ChainedDiagnosticConsumer(
+        Diags.getClient(), std::move(SerializedConsumer)));
+  }
+}
+
+void CompilerInstance::createDiagnostics(DiagnosticConsumer *Client,
+                                         bool ShouldOwnClient) {
+  Diagnostics = createDiagnostics(&getDiagnosticOpts(), Client,
+                                  ShouldOwnClient, &getCodeGenOpts());
+}
+
+IntrusiveRefCntPtr<DiagnosticsEngine>
+CompilerInstance::createDiagnostics(DiagnosticOptions *Opts,
+                                    DiagnosticConsumer *Client,
+                                    bool ShouldOwnClient,
+                                    const CodeGenOptions *CodeGenOpts) {
+  IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
+  IntrusiveRefCntPtr<DiagnosticsEngine>
+      Diags(new DiagnosticsEngine(DiagID, Opts));
+
+  // Create the diagnostic client for reporting errors or for
+  // implementing -verify.
+  if (Client) {
+    Diags->setClient(Client, ShouldOwnClient);
+  } else
+    Diags->setClient(new TextDiagnosticPrinter(llvm::errs(), Opts));
+
+  // Chain in -verify checker, if requested.
+  if (Opts->VerifyDiagnostics)
+    Diags->setClient(new VerifyDiagnosticConsumer(*Diags));
+
+  // Chain in -diagnostic-log-file dumper, if requested.
+  if (!Opts->DiagnosticLogFile.empty())
+    SetUpDiagnosticLog(Opts, CodeGenOpts, *Diags);
+
+  if (!Opts->DiagnosticSerializationFile.empty())
+    SetupSerializedDiagnostics(Opts, *Diags,
+                               Opts->DiagnosticSerializationFile);
+
+  // Configure our handling of diagnostics.
+  ProcessWarningOptions(*Diags, *Opts);
+
+  return Diags;
+}
+
+// File Manager
+
+FileManager *CompilerInstance::createFileManager(
+    IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS) {
+  if (!VFS)
+    VFS = FileMgr ? &FileMgr->getVirtualFileSystem()
+                  : createVFSFromCompilerInvocation(getInvocation(),
+                                                    getDiagnostics());
+  assert(VFS && "FileManager has no VFS?");
+  FileMgr = new FileManager(getFileSystemOpts(), std::move(VFS));
+  return FileMgr.get();
+}
+
+// Source Manager
+
+void CompilerInstance::createSourceManager(FileManager &FileMgr) {
+  SourceMgr = new SourceManager(getDiagnostics(), FileMgr);
+}
+
+// Initialize the remapping of files to alternative contents, e.g.,
+// those specified through other files.
+static void InitializeFileRemapping(DiagnosticsEngine &Diags,
+                                    SourceManager &SourceMgr,
+                                    FileManager &FileMgr,
+                                    const PreprocessorOptions &InitOpts) {
+  // Remap files in the source manager (with buffers).
+  for (const auto &RB : InitOpts.RemappedFileBuffers) {
+    // Create the file entry for the file that we're mapping from.
+    const FileEntry *FromFile =
+        FileMgr.getVirtualFile(RB.first, RB.second->getBufferSize(), 0);
+    if (!FromFile) {
+      Diags.Report(diag::err_fe_remap_missing_from_file) << RB.first;
+      if (!InitOpts.RetainRemappedFileBuffers)
+        delete RB.second;
+      continue;
+    }
+
+    // Override the contents of the "from" file with the contents of
+    // the "to" file.
+    SourceMgr.overrideFileContents(FromFile, RB.second,
+                                   InitOpts.RetainRemappedFileBuffers);
+  }
+
+  // Remap files in the source manager (with other files).
+  for (const auto &RF : InitOpts.RemappedFiles) {
+    // Find the file that we're mapping to.
+    const FileEntry *ToFile = FileMgr.getFile(RF.second);
+    if (!ToFile) {
+      Diags.Report(diag::err_fe_remap_missing_to_file) << RF.first << RF.second;
+      continue;
+    }
+
+    // Create the file entry for the file that we're mapping from.
+    const FileEntry *FromFile =
+        FileMgr.getVirtualFile(RF.first, ToFile->getSize(), 0);
+    if (!FromFile) {
+      Diags.Report(diag::err_fe_remap_missing_from_file) << RF.first;
+      continue;
+    }
+
+    // Override the contents of the "from" file with the contents of
+    // the "to" file.
+    SourceMgr.overrideFileContents(FromFile, ToFile);
+  }
+
+  SourceMgr.setOverridenFilesKeepOriginalName(
+      InitOpts.RemappedFilesKeepOriginalName);
+}
+
+// Preprocessor
+
+void CompilerInstance::createPreprocessor(TranslationUnitKind TUKind) {
+  const PreprocessorOptions &PPOpts = getPreprocessorOpts();
+
+  // The module manager holds a reference to the old preprocessor (if any).
+  ModuleManager.reset();
+
+  // Create the Preprocessor.
+  HeaderSearch *HeaderInfo =
+      new HeaderSearch(getHeaderSearchOptsPtr(), getSourceManager(),
+                       getDiagnostics(), getLangOpts(), &getTarget());
+  PP = std::make_shared<Preprocessor>(Invocation->getPreprocessorOptsPtr(),
+                                      getDiagnostics(), getLangOpts(),
+                                      getSourceManager(), *HeaderInfo, *this,
+                                      /*IdentifierInfoLookup=*/nullptr,
+                                      /*OwnsHeaderSearch=*/true, TUKind);
+  getTarget().adjust(getLangOpts());
+  PP->Initialize(getTarget(), getAuxTarget());
+
+  if (PPOpts.DetailedRecord)
+    PP->createPreprocessingRecord();
+
+  // Apply remappings to the source manager.
+  InitializeFileRemapping(PP->getDiagnostics(), PP->getSourceManager(),
+                          PP->getFileManager(), PPOpts);
+
+  // Predefine macros and configure the preprocessor.
+  InitializePreprocessor(*PP, PPOpts, getPCHContainerReader(),
+                         getFrontendOpts());
+
+  // Initialize the header search object.  In CUDA compilations, we use the aux
+  // triple (the host triple) to initialize our header search, since we need to
+  // find the host headers in order to compile the CUDA code.
+  const llvm::Triple *HeaderSearchTriple = &PP->getTargetInfo().getTriple();
+  if (PP->getTargetInfo().getTriple().getOS() == llvm::Triple::CUDA &&
+      PP->getAuxTargetInfo())
+    HeaderSearchTriple = &PP->getAuxTargetInfo()->getTriple();
+
+  ApplyHeaderSearchOptions(PP->getHeaderSearchInfo(), getHeaderSearchOpts(),
+                           PP->getLangOpts(), *HeaderSearchTriple);
+
+  PP->setPreprocessedOutput(getPreprocessorOutputOpts().ShowCPP);
+
+  if (PP->getLangOpts().Modules && PP->getLangOpts().ImplicitModules)
+    PP->getHeaderSearchInfo().setModuleCachePath(getSpecificModuleCachePath());
+
+  // Handle generating dependencies, if requested.
+  const DependencyOutputOptions &DepOpts = getDependencyOutputOpts();
+  if (!DepOpts.OutputFile.empty())
+    addDependencyCollector(std::make_shared<DependencyFileGenerator>(DepOpts));
+  if (!DepOpts.DOTOutputFile.empty())
+    AttachDependencyGraphGen(*PP, DepOpts.DOTOutputFile,
+                             getHeaderSearchOpts().Sysroot);
+
+  // If we don't have a collector, but we are collecting module dependencies,
+  // then we're the top level compiler instance and need to create one.
+  if (!ModuleDepCollector && !DepOpts.ModuleDependencyOutputDir.empty()) {
+    ModuleDepCollector = std::make_shared<ModuleDependencyCollector>(
+        DepOpts.ModuleDependencyOutputDir);
+  }
+
+  // If there is a module dep collector, register with other dep collectors
+  // and also (a) collect header maps and (b) TODO: input vfs overlay files.
+  if (ModuleDepCollector) {
+    addDependencyCollector(ModuleDepCollector);
+    collectHeaderMaps(PP->getHeaderSearchInfo(), ModuleDepCollector);
+    collectIncludePCH(*this, ModuleDepCollector);
+    collectVFSEntries(*this, ModuleDepCollector);
+  }
+
+  for (auto &Listener : DependencyCollectors)
+    Listener->attachToPreprocessor(*PP);
+
+  // Handle generating header include information, if requested.
+  if (DepOpts.ShowHeaderIncludes)
+    AttachHeaderIncludeGen(*PP, DepOpts);
+  if (!DepOpts.HeaderIncludeOutputFile.empty()) {
+    StringRef OutputPath = DepOpts.HeaderIncludeOutputFile;
+    if (OutputPath == "-")
+      OutputPath = "";
+    AttachHeaderIncludeGen(*PP, DepOpts,
+                           /*ShowAllHeaders=*/true, OutputPath,
+                           /*ShowDepth=*/false);
+  }
+
+  if (DepOpts.ShowIncludesDest != ShowIncludesDestination::None) {
+    AttachHeaderIncludeGen(*PP, DepOpts,
+                           /*ShowAllHeaders=*/true, /*OutputPath=*/"",
+                           /*ShowDepth=*/true, /*MSStyle=*/true);
+  }
+}
+
+std::string CompilerInstance::getSpecificModuleCachePath() {
+  // Set up the module path, including the hash for the
+  // module-creation options.
+  SmallString<256> SpecificModuleCache(getHeaderSearchOpts().ModuleCachePath);
+  if (!SpecificModuleCache.empty() && !getHeaderSearchOpts().DisableModuleHash)
+    llvm::sys::path::append(SpecificModuleCache,
+                            getInvocation().getModuleHash());
+  return SpecificModuleCache.str();
+}
+
+// ASTContext
+
+void CompilerInstance::createASTContext() {
+  Preprocessor &PP = getPreprocessor();
+  auto *Context = new ASTContext(getLangOpts(), PP.getSourceManager(),
+                                 PP.getIdentifierTable(), PP.getSelectorTable(),
+                                 PP.getBuiltinInfo());
+  Context->InitBuiltinTypes(getTarget(), getAuxTarget());
+  setASTContext(Context);
+}
+
+// ExternalASTSource
+
+void CompilerInstance::createPCHExternalASTSource(
+    StringRef Path, bool DisablePCHValidation, bool AllowPCHWithCompilerErrors,
+    void *DeserializationListener, bool OwnDeserializationListener) {
+  bool Preamble = getPreprocessorOpts().PrecompiledPreambleBytes.first != 0;
+  ModuleManager = createPCHExternalASTSource(
+      Path, getHeaderSearchOpts().Sysroot, DisablePCHValidation,
+      AllowPCHWithCompilerErrors, getPreprocessor(), getModuleCache(),
+      getASTContext(), getPCHContainerReader(),
+      getFrontendOpts().ModuleFileExtensions, DependencyCollectors,
+      DeserializationListener, OwnDeserializationListener, Preamble,
+      getFrontendOpts().UseGlobalModuleIndex);
+}
+
+IntrusiveRefCntPtr<ASTReader> CompilerInstance::createPCHExternalASTSource(
+    StringRef Path, StringRef Sysroot, bool DisablePCHValidation,
+    bool AllowPCHWithCompilerErrors, Preprocessor &PP,
+    InMemoryModuleCache &ModuleCache, ASTContext &Context,
+    const PCHContainerReader &PCHContainerRdr,
+    ArrayRef<std::shared_ptr<ModuleFileExtension>> Extensions,
+    ArrayRef<std::shared_ptr<DependencyCollector>> DependencyCollectors,
+    void *DeserializationListener, bool OwnDeserializationListener,
+    bool Preamble, bool UseGlobalModuleIndex) {
+  HeaderSearchOptions &HSOpts = PP.getHeaderSearchInfo().getHeaderSearchOpts();
+
+  IntrusiveRefCntPtr<ASTReader> Reader(new ASTReader(
+      PP, ModuleCache, &Context, PCHContainerRdr, Extensions,
+      Sysroot.empty() ? "" : Sysroot.data(), DisablePCHValidation,
+      AllowPCHWithCompilerErrors, /*AllowConfigurationMismatch*/ false,
+      HSOpts.ModulesValidateSystemHeaders, UseGlobalModuleIndex));
+
+  // We need the external source to be set up before we read the AST, because
+  // eagerly-deserialized declarations may use it.
+  Context.setExternalSource(Reader.get());
+
+  Reader->setDeserializationListener(
+      static_cast<ASTDeserializationListener *>(DeserializationListener),
+      /*TakeOwnership=*/OwnDeserializationListener);
+
+  for (auto &Listener : DependencyCollectors)
+    Listener->attachToASTReader(*Reader);
+
+  switch (Reader->ReadAST(Path,
+                          Preamble ? serialization::MK_Preamble
+                                   : serialization::MK_PCH,
+                          SourceLocation(),
+                          ASTReader::ARR_None)) {
+  case ASTReader::Success:
+    // Set the predefines buffer as suggested by the PCH reader. Typically, the
+    // predefines buffer will be empty.
+    PP.setPredefines(Reader->getSuggestedPredefines());
+    return Reader;
+
+  case ASTReader::Failure:
+    // Unrecoverable failure: don't even try to process the input file.
+    break;
+
+  case ASTReader::Missing:
+  case ASTReader::OutOfDate:
+  case ASTReader::VersionMismatch:
+  case ASTReader::ConfigurationMismatch:
+  case ASTReader::HadErrors:
+    // No suitable PCH file could be found. Return an error.
+    break;
+  }
+
+  Context.setExternalSource(nullptr);
+  return nullptr;
+}
+
+// Code Completion
+
+static bool EnableCodeCompletion(Preprocessor &PP,
+                                 StringRef Filename,
+                                 unsigned Line,
+                                 unsigned Column) {
+  // Tell the source manager to chop off the given file at a specific
+  // line and column.
+  const FileEntry *Entry = PP.getFileManager().getFile(Filename);
+  if (!Entry) {
+    PP.getDiagnostics().Report(diag::err_fe_invalid_code_complete_file)
+      << Filename;
+    return true;
+  }
+
+  // Truncate the named file at the given line/column.
+  PP.SetCodeCompletionPoint(Entry, Line, Column);
+  return false;
+}
+
+void CompilerInstance::createCodeCompletionConsumer() {
+  const ParsedSourceLocation &Loc = getFrontendOpts().CodeCompletionAt;
+  if (!CompletionConsumer) {
+    setCodeCompletionConsumer(
+      createCodeCompletionConsumer(getPreprocessor(),
+                                   Loc.FileName, Loc.Line, Loc.Column,
+                                   getFrontendOpts().CodeCompleteOpts,
+                                   llvm::outs()));
+    if (!CompletionConsumer)
+      return;
+  } else if (EnableCodeCompletion(getPreprocessor(), Loc.FileName,
+                                  Loc.Line, Loc.Column)) {
+    setCodeCompletionConsumer(nullptr);
+    return;
+  }
+}
+
+void CompilerInstance::createFrontendTimer() {
+  FrontendTimerGroup.reset(
+      new llvm::TimerGroup("frontend", "Clang front-end time report"));
+  FrontendTimer.reset(
+      new llvm::Timer("frontend", "Clang front-end timer",
+                      *FrontendTimerGroup));
+}
+
+CodeCompleteConsumer *
+CompilerInstance::createCodeCompletionConsumer(Preprocessor &PP,
+                                               StringRef Filename,
+                                               unsigned Line,
+                                               unsigned Column,
+                                               const CodeCompleteOptions &Opts,
+                                               raw_ostream &OS) {
+  if (EnableCodeCompletion(PP, Filename, Line, Column))
+    return nullptr;
+
+  // Set up the creation routine for code-completion.
+  return new PrintingCodeCompleteConsumer(Opts, OS);
+}
+
+void CompilerInstance::createSema(TranslationUnitKind TUKind,
+                                  CodeCompleteConsumer *CompletionConsumer) {
+  TheSema.reset(new Sema(getPreprocessor(), getASTContext(), getASTConsumer(),
+                         TUKind, CompletionConsumer));
+  // Attach the external sema source if there is any.
+  if (ExternalSemaSrc) {
+    TheSema->addExternalSource(ExternalSemaSrc.get());
+    ExternalSemaSrc->InitializeSema(*TheSema);
+  }
+}
+
+// Output Files
+
+void CompilerInstance::addOutputFile(OutputFile &&OutFile) {
+  OutputFiles.push_back(std::move(OutFile));
+}
+
+void CompilerInstance::clearOutputFiles(bool EraseFiles) {
+  for (OutputFile &OF : OutputFiles) {
+    if (!OF.TempFilename.empty()) {
+      if (EraseFiles) {
+        llvm::sys::fs::remove(OF.TempFilename);
+      } else {
+        SmallString<128> NewOutFile(OF.Filename);
+
+        // If '-working-directory' was passed, the output filename should be
+        // relative to that.
+        FileMgr->FixupRelativePath(NewOutFile);
+        if (std::error_code ec =
+                llvm::sys::fs::rename(OF.TempFilename, NewOutFile)) {
+          getDiagnostics().Report(diag::err_unable_to_rename_temp)
+            << OF.TempFilename << OF.Filename << ec.message();
+
+          llvm::sys::fs::remove(OF.TempFilename);
+        }
+      }
+    } else if (!OF.Filename.empty() && EraseFiles)
+      llvm::sys::fs::remove(OF.Filename);
+  }
+  OutputFiles.clear();
+  if (DeleteBuiltModules) {
+    for (auto &Module : BuiltModules)
+      llvm::sys::fs::remove(Module.second);
+    BuiltModules.clear();
+  }
+  NonSeekStream.reset();
+}
+
+std::unique_ptr<raw_pwrite_stream>
+CompilerInstance::createDefaultOutputFile(bool Binary, StringRef InFile,
+                                          StringRef Extension) {
+  return createOutputFile(getFrontendOpts().OutputFile, Binary,
+                          /*RemoveFileOnSignal=*/true, InFile, Extension,
+                          /*UseTemporary=*/true);
+}
+
+std::unique_ptr<raw_pwrite_stream> CompilerInstance::createNullOutputFile() {
+  return llvm::make_unique<llvm::raw_null_ostream>();
+}
+
+std::unique_ptr<raw_pwrite_stream>
+CompilerInstance::createOutputFile(StringRef OutputPath, bool Binary,
+                                   bool RemoveFileOnSignal, StringRef InFile,
+                                   StringRef Extension, bool UseTemporary,
+                                   bool CreateMissingDirectories) {
+  std::string OutputPathName, TempPathName;
+  std::error_code EC;
+  std::unique_ptr<raw_pwrite_stream> OS = createOutputFile(
+      OutputPath, EC, Binary, RemoveFileOnSignal, InFile, Extension,
+      UseTemporary, CreateMissingDirectories, &OutputPathName, &TempPathName);
+  if (!OS) {
+    getDiagnostics().Report(diag::err_fe_unable_to_open_output) << OutputPath
+                                                                << EC.message();
+    return nullptr;
+  }
+
+  // Add the output file -- but don't try to remove "-", since this means we are
+  // using stdin.
+  addOutputFile(
+      OutputFile((OutputPathName != "-") ? OutputPathName : "", TempPathName));
+
+  return OS;
+}
+
+std::unique_ptr<llvm::raw_pwrite_stream> CompilerInstance::createOutputFile(
+    StringRef OutputPath, std::error_code &Error, bool Binary,
+    bool RemoveFileOnSignal, StringRef InFile, StringRef Extension,
+    bool UseTemporary, bool CreateMissingDirectories,
+    std::string *ResultPathName, std::string *TempPathName) {
+  assert((!CreateMissingDirectories || UseTemporary) &&
+         "CreateMissingDirectories is only allowed when using temporary files");
+
+  std::string OutFile, TempFile;
+  if (!OutputPath.empty()) {
+    OutFile = OutputPath;
+  } else if (InFile == "-") {
+    OutFile = "-";
+  } else if (!Extension.empty()) {
+    SmallString<128> Path(InFile);
+    llvm::sys::path::replace_extension(Path, Extension);
+    OutFile = Path.str();
+  } else {
+    OutFile = "-";
+  }
+
+  std::unique_ptr<llvm::raw_fd_ostream> OS;
+  std::string OSFile;
+
+  if (UseTemporary) {
+    if (OutFile == "-")
+      UseTemporary = false;
+    else {
+      llvm::sys::fs::file_status Status;
+      llvm::sys::fs::status(OutputPath, Status);
+      if (llvm::sys::fs::exists(Status)) {
+        // Fail early if we can't write to the final destination.
+        if (!llvm::sys::fs::can_write(OutputPath)) {
+          Error = make_error_code(llvm::errc::operation_not_permitted);
+          return nullptr;
+        }
+
+        // Don't use a temporary if the output is a special file. This handles
+        // things like '-o /dev/null'
+        if (!llvm::sys::fs::is_regular_file(Status))
+          UseTemporary = false;
+      }
+    }
+  }
+
+  if (UseTemporary) {
+    // Create a temporary file.
+    // Insert -%%%%%%%% before the extension (if any), and because some tools
+    // (noticeable, clang's own GlobalModuleIndex.cpp) glob for build
+    // artifacts, also append .tmp.
+    StringRef OutputExtension = llvm::sys::path::extension(OutFile);
+    SmallString<128> TempPath =
+        StringRef(OutFile).drop_back(OutputExtension.size());
+    TempPath += "-%%%%%%%%";
+    TempPath += OutputExtension;
+    TempPath += ".tmp";
+    int fd;
+    std::error_code EC =
+        llvm::sys::fs::createUniqueFile(TempPath, fd, TempPath);
+
+    if (CreateMissingDirectories &&
+        EC == llvm::errc::no_such_file_or_directory) {
+      StringRef Parent = llvm::sys::path::parent_path(OutputPath);
+      EC = llvm::sys::fs::create_directories(Parent);
+      if (!EC) {
+        EC = llvm::sys::fs::createUniqueFile(TempPath, fd, TempPath);
+      }
+    }
+
+    if (!EC) {
+      OS.reset(new llvm::raw_fd_ostream(fd, /*shouldClose=*/true));
+      OSFile = TempFile = TempPath.str();
+    }
+    // If we failed to create the temporary, fallback to writing to the file
+    // directly. This handles the corner case where we cannot write to the
+    // directory, but can write to the file.
+  }
+
+  if (!OS) {
+    OSFile = OutFile;
+    OS.reset(new llvm::raw_fd_ostream(
+        OSFile, Error,
+        (Binary ? llvm::sys::fs::F_None : llvm::sys::fs::F_Text)));
+    if (Error)
+      return nullptr;
+  }
+
+  // Make sure the out stream file gets removed if we crash.
+  if (RemoveFileOnSignal)
+    llvm::sys::RemoveFileOnSignal(OSFile);
+
+  if (ResultPathName)
+    *ResultPathName = OutFile;
+  if (TempPathName)
+    *TempPathName = TempFile;
+
+  if (!Binary || OS->supportsSeeking())
+    return std::move(OS);
+
+  auto B = llvm::make_unique<llvm::buffer_ostream>(*OS);
+  assert(!NonSeekStream);
+  NonSeekStream = std::move(OS);
+  return std::move(B);
+}
+
+// Initialization Utilities
+
+bool CompilerInstance::InitializeSourceManager(const FrontendInputFile &Input){
+  return InitializeSourceManager(
+      Input, getDiagnostics(), getFileManager(), getSourceManager(),
+      hasPreprocessor() ? &getPreprocessor().getHeaderSearchInfo() : nullptr,
+      getDependencyOutputOpts(), getFrontendOpts());
+}
+
+// static
+bool CompilerInstance::InitializeSourceManager(
+    const FrontendInputFile &Input, DiagnosticsEngine &Diags,
+    FileManager &FileMgr, SourceManager &SourceMgr, HeaderSearch *HS,
+    DependencyOutputOptions &DepOpts, const FrontendOptions &Opts) {
+  SrcMgr::CharacteristicKind Kind =
+      Input.getKind().getFormat() == InputKind::ModuleMap
+          ? Input.isSystem() ? SrcMgr::C_System_ModuleMap
+                             : SrcMgr::C_User_ModuleMap
+          : Input.isSystem() ? SrcMgr::C_System : SrcMgr::C_User;
+
+  if (Input.isBuffer()) {
+    SourceMgr.setMainFileID(SourceMgr.createFileID(SourceManager::Unowned,
+                                                   Input.getBuffer(), Kind));
+    assert(SourceMgr.getMainFileID().isValid() &&
+           "Couldn't establish MainFileID!");
+    return true;
+  }
+
+  StringRef InputFile = Input.getFile();
+
+  // Figure out where to get and map in the main file.
+  if (InputFile != "-") {
+    const FileEntry *File = FileMgr.getFile(InputFile, /*OpenFile=*/true);
+    if (!File) {
+      Diags.Report(diag::err_fe_error_reading) << InputFile;
+      return false;
+    }
+
+    // The natural SourceManager infrastructure can't currently handle named
+    // pipes, but we would at least like to accept them for the main
+    // file. Detect them here, read them with the volatile flag so FileMgr will
+    // pick up the correct size, and simply override their contents as we do for
+    // STDIN.
+    if (File->isNamedPipe()) {
+      auto MB = FileMgr.getBufferForFile(File, /*isVolatile=*/true);
+      if (MB) {
+        // Create a new virtual file that will have the correct size.
+        File = FileMgr.getVirtualFile(InputFile, (*MB)->getBufferSize(), 0);
+        SourceMgr.overrideFileContents(File, std::move(*MB));
+      } else {
+        Diags.Report(diag::err_cannot_open_file) << InputFile
+                                                 << MB.getError().message();
+        return false;
+      }
+    }
+
+    SourceMgr.setMainFileID(
+        SourceMgr.createFileID(File, SourceLocation(), Kind));
+  } else {
+    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> SBOrErr =
+        llvm::MemoryBuffer::getSTDIN();
+    if (std::error_code EC = SBOrErr.getError()) {
+      Diags.Report(diag::err_fe_error_reading_stdin) << EC.message();
+      return false;
+    }
+    std::unique_ptr<llvm::MemoryBuffer> SB = std::move(SBOrErr.get());
+
+    const FileEntry *File = FileMgr.getVirtualFile(SB->getBufferIdentifier(),
+                                                   SB->getBufferSize(), 0);
+    SourceMgr.setMainFileID(
+        SourceMgr.createFileID(File, SourceLocation(), Kind));
+    SourceMgr.overrideFileContents(File, std::move(SB));
+  }
+
+  assert(SourceMgr.getMainFileID().isValid() &&
+         "Couldn't establish MainFileID!");
+  return true;
+}
+
+// High-Level Operations
+
+bool CompilerInstance::ExecuteAction(FrontendAction &Act) {
+  assert(hasDiagnostics() && "Diagnostics engine is not initialized!");
+  assert(!getFrontendOpts().ShowHelp && "Client must handle '-help'!");
+  assert(!getFrontendOpts().ShowVersion && "Client must handle '-version'!");
+
+  // FIXME: Take this as an argument, once all the APIs we used have moved to
+  // taking it as an input instead of hard-coding llvm::errs.
+  raw_ostream &OS = llvm::errs();
+
+  if (!Act.PrepareToExecute(*this))
+    return false;
+
+  // Create the target instance.
+  setTarget(TargetInfo::CreateTargetInfo(getDiagnostics(),
+                                         getInvocation().TargetOpts));
+  if (!hasTarget())
+    return false;
+
+  // Create TargetInfo for the other side of CUDA and OpenMP compilation.
+  if ((getLangOpts().CUDA || getLangOpts().OpenMPIsDevice) &&
+      !getFrontendOpts().AuxTriple.empty()) {
+    auto TO = std::make_shared<TargetOptions>();
+    TO->Triple = llvm::Triple::normalize(getFrontendOpts().AuxTriple);
+    TO->HostTriple = getTarget().getTriple().str();
+    setAuxTarget(TargetInfo::CreateTargetInfo(getDiagnostics(), TO));
+  }
+
+  // Inform the target of the language options.
+  //
+  // FIXME: We shouldn't need to do this, the target should be immutable once
+  // created. This complexity should be lifted elsewhere.
+  getTarget().adjust(getLangOpts());
+
+  // Adjust target options based on codegen options.
+  getTarget().adjustTargetOptions(getCodeGenOpts(), getTargetOpts());
+
+  if (auto *Aux = getAuxTarget())
+    getTarget().setAuxTarget(Aux);
+
+  // rewriter project will change target built-in bool type from its default.
+  if (getFrontendOpts().ProgramAction == frontend::RewriteObjC)
+    getTarget().noSignedCharForObjCBool();
+
+  // Validate/process some options.
+  if (getHeaderSearchOpts().Verbose)
+    OS << "clang -cc1 version " CLANG_VERSION_STRING
+       << " based upon " << BACKEND_PACKAGE_STRING
+       << " default target " << llvm::sys::getDefaultTargetTriple() << "\n";
+
+  if (getFrontendOpts().ShowTimers)
+    createFrontendTimer();
+
+  if (getFrontendOpts().ShowStats || !getFrontendOpts().StatsFile.empty())
+    llvm::EnableStatistics(false);
+
+  for (const FrontendInputFile &FIF : getFrontendOpts().Inputs) {
+    // Reset the ID tables if we are reusing the SourceManager and parsing
+    // regular files.
+    if (hasSourceManager() && !Act.isModelParsingAction())
+      getSourceManager().clearIDTables();
+
+    if (Act.BeginSourceFile(*this, FIF)) {
+      if (llvm::Error Err = Act.Execute()) {
+        consumeError(std::move(Err)); // FIXME this drops errors on the floor.
+      }
+      Act.EndSourceFile();
+    }
+  }
+
+  // Notify the diagnostic client that all files were processed.
+  getDiagnostics().getClient()->finish();
+
+  if (getDiagnosticOpts().ShowCarets) {
+    // We can have multiple diagnostics sharing one diagnostic client.
+    // Get the total number of warnings/errors from the client.
+    unsigned NumWarnings = getDiagnostics().getClient()->getNumWarnings();
+    unsigned NumErrors = getDiagnostics().getClient()->getNumErrors();
+
+    if (NumWarnings)
+      OS << NumWarnings << " warning" << (NumWarnings == 1 ? "" : "s");
+    if (NumWarnings && NumErrors)
+      OS << " and ";
+    if (NumErrors)
+      OS << NumErrors << " error" << (NumErrors == 1 ? "" : "s");
+    if (NumWarnings || NumErrors) {
+      OS << " generated";
+      if (getLangOpts().CUDA) {
+        if (!getLangOpts().CUDAIsDevice) {
+          OS << " when compiling for host";
+        } else {
+          OS << " when compiling for " << getTargetOpts().CPU;
+        }
+      }
+      OS << ".\n";
+    }
+  }
+
+  if (getFrontendOpts().ShowStats) {
+    if (hasFileManager()) {
+      getFileManager().PrintStats();
+      OS << '\n';
+    }
+    llvm::PrintStatistics(OS);
+  }
+  StringRef StatsFile = getFrontendOpts().StatsFile;
+  if (!StatsFile.empty()) {
+    std::error_code EC;
+    auto StatS = llvm::make_unique<llvm::raw_fd_ostream>(StatsFile, EC,
+                                                         llvm::sys::fs::F_Text);
+    if (EC) {
+      getDiagnostics().Report(diag::warn_fe_unable_to_open_stats_file)
+          << StatsFile << EC.message();
+    } else {
+      llvm::PrintStatisticsJSON(*StatS);
+    }
+  }
+
+  return !getDiagnostics().getClient()->getNumErrors();
+}
+
+/// Determine the appropriate source input kind based on language
+/// options.
+static InputKind::Language getLanguageFromOptions(const LangOptions &LangOpts) {
+  if (LangOpts.OpenCL)
+    return InputKind::OpenCL;
+  if (LangOpts.CUDA)
+    return InputKind::CUDA;
+  if (LangOpts.ObjC)
+    return LangOpts.CPlusPlus ? InputKind::ObjCXX : InputKind::ObjC;
+  return LangOpts.CPlusPlus ? InputKind::CXX : InputKind::C;
+}
+
+/// Compile a module file for the given module, using the options
+/// provided by the importing compiler instance. Returns true if the module
+/// was built without errors.
+static bool
+compileModuleImpl(CompilerInstance &ImportingInstance, SourceLocation ImportLoc,
+                  StringRef ModuleName, FrontendInputFile Input,
+                  StringRef OriginalModuleMapFile, StringRef ModuleFileName,
+                  llvm::function_ref<void(CompilerInstance &)> PreBuildStep =
+                      [](CompilerInstance &) {},
+                  llvm::function_ref<void(CompilerInstance &)> PostBuildStep =
+                      [](CompilerInstance &) {}) {
+  llvm::TimeTraceScope TimeScope("Module Compile", ModuleName);
+
+  // Construct a compiler invocation for creating this module.
+  auto Invocation =
+      std::make_shared<CompilerInvocation>(ImportingInstance.getInvocation());
+
+  PreprocessorOptions &PPOpts = Invocation->getPreprocessorOpts();
+
+  // For any options that aren't intended to affect how a module is built,
+  // reset them to their default values.
+  Invocation->getLangOpts()->resetNonModularOptions();
+  PPOpts.resetNonModularOptions();
+
+  // Remove any macro definitions that are explicitly ignored by the module.
+  // They aren't supposed to affect how the module is built anyway.
+  HeaderSearchOptions &HSOpts = Invocation->getHeaderSearchOpts();
+  PPOpts.Macros.erase(
+      std::remove_if(PPOpts.Macros.begin(), PPOpts.Macros.end(),
+                     [&HSOpts](const std::pair<std::string, bool> &def) {
+        StringRef MacroDef = def.first;
+        return HSOpts.ModulesIgnoreMacros.count(
+                   llvm::CachedHashString(MacroDef.split('=').first)) > 0;
+      }),
+      PPOpts.Macros.end());
+
+  // If the original compiler invocation had -fmodule-name, pass it through.
+  Invocation->getLangOpts()->ModuleName =
+      ImportingInstance.getInvocation().getLangOpts()->ModuleName;
+
+  // Note the name of the module we're building.
+  Invocation->getLangOpts()->CurrentModule = ModuleName;
+
+  // Make sure that the failed-module structure has been allocated in
+  // the importing instance, and propagate the pointer to the newly-created
+  // instance.
+  PreprocessorOptions &ImportingPPOpts
+    = ImportingInstance.getInvocation().getPreprocessorOpts();
+  if (!ImportingPPOpts.FailedModules)
+    ImportingPPOpts.FailedModules =
+        std::make_shared<PreprocessorOptions::FailedModulesSet>();
+  PPOpts.FailedModules = ImportingPPOpts.FailedModules;
+
+  // If there is a module map file, build the module using the module map.
+  // Set up the inputs/outputs so that we build the module from its umbrella
+  // header.
+  FrontendOptions &FrontendOpts = Invocation->getFrontendOpts();
+  FrontendOpts.OutputFile = ModuleFileName.str();
+  FrontendOpts.DisableFree = false;
+  FrontendOpts.GenerateGlobalModuleIndex = false;
+  FrontendOpts.BuildingImplicitModule = true;
+  FrontendOpts.OriginalModuleMap = OriginalModuleMapFile;
+  // Force implicitly-built modules to hash the content of the module file.
+  HSOpts.ModulesHashContent = true;
+  FrontendOpts.Inputs = {Input};
+
+  // Don't free the remapped file buffers; they are owned by our caller.
+  PPOpts.RetainRemappedFileBuffers = true;
+
+  Invocation->getDiagnosticOpts().VerifyDiagnostics = 0;
+  assert(ImportingInstance.getInvocation().getModuleHash() ==
+         Invocation->getModuleHash() && "Module hash mismatch!");
+
+  // Construct a compiler instance that will be used to actually create the
+  // module.  Since we're sharing an in-memory module cache,
+  // CompilerInstance::CompilerInstance is responsible for finalizing the
+  // buffers to prevent use-after-frees.
+  CompilerInstance Instance(ImportingInstance.getPCHContainerOperations(),
+                            &ImportingInstance.getModuleCache());
+  auto &Inv = *Invocation;
+  Instance.setInvocation(std::move(Invocation));
+
+  Instance.createDiagnostics(new ForwardingDiagnosticConsumer(
+                                   ImportingInstance.getDiagnosticClient()),
+                             /*ShouldOwnClient=*/true);
+
+  // Note that this module is part of the module build stack, so that we
+  // can detect cycles in the module graph.
+  Instance.setFileManager(&ImportingInstance.getFileManager());
+  Instance.createSourceManager(Instance.getFileManager());
+  SourceManager &SourceMgr = Instance.getSourceManager();
+  SourceMgr.setModuleBuildStack(
+    ImportingInstance.getSourceManager().getModuleBuildStack());
+  SourceMgr.pushModuleBuildStack(ModuleName,
+    FullSourceLoc(ImportLoc, ImportingInstance.getSourceManager()));
+
+  // If we're collecting module dependencies, we need to share a collector
+  // between all of the module CompilerInstances. Other than that, we don't
+  // want to produce any dependency output from the module build.
+  Instance.setModuleDepCollector(ImportingInstance.getModuleDepCollector());
+  Inv.getDependencyOutputOpts() = DependencyOutputOptions();
+
+  ImportingInstance.getDiagnostics().Report(ImportLoc,
+                                            diag::remark_module_build)
+    << ModuleName << ModuleFileName;
+
+  PreBuildStep(Instance);
+
+  // Execute the action to actually build the module in-place. Use a separate
+  // thread so that we get a stack large enough.
+  llvm::CrashRecoveryContext CRC;
+  CRC.RunSafelyOnThread(
+      [&]() {
+        GenerateModuleFromModuleMapAction Action;
+        Instance.ExecuteAction(Action);
+      },
+      DesiredStackSize);
+
+  PostBuildStep(Instance);
+
+  ImportingInstance.getDiagnostics().Report(ImportLoc,
+                                            diag::remark_module_build_done)
+    << ModuleName;
+
+  // Delete the temporary module map file.
+  // FIXME: Even though we're executing under crash protection, it would still
+  // be nice to do this with RemoveFileOnSignal when we can. However, that
+  // doesn't make sense for all clients, so clean this up manually.
+  Instance.clearOutputFiles(/*EraseFiles=*/true);
+
+  return !Instance.getDiagnostics().hasErrorOccurred();
+}
+
+static const FileEntry *getPublicModuleMap(const FileEntry *File,
+                                           FileManager &FileMgr) {
+  StringRef Filename = llvm::sys::path::filename(File->getName());
+  SmallString<128> PublicFilename(File->getDir()->getName());
+  if (Filename == "module_private.map")
+    llvm::sys::path::append(PublicFilename, "module.map");
+  else if (Filename == "module.private.modulemap")
+    llvm::sys::path::append(PublicFilename, "module.modulemap");
+  else
+    return nullptr;
+  return FileMgr.getFile(PublicFilename);
+}
+
+/// Compile a module file for the given module, using the options
+/// provided by the importing compiler instance. Returns true if the module
+/// was built without errors.
+static bool compileModuleImpl(CompilerInstance &ImportingInstance,
+                              SourceLocation ImportLoc,
+                              Module *Module,
+                              StringRef ModuleFileName) {
+  InputKind IK(getLanguageFromOptions(ImportingInstance.getLangOpts()),
+               InputKind::ModuleMap);
+
+  // Get or create the module map that we'll use to build this module.
+  ModuleMap &ModMap
+    = ImportingInstance.getPreprocessor().getHeaderSearchInfo().getModuleMap();
+  bool Result;
+  if (const FileEntry *ModuleMapFile =
+          ModMap.getContainingModuleMapFile(Module)) {
+    // Canonicalize compilation to start with the public module map. This is
+    // vital for submodules declarations in the private module maps to be
+    // correctly parsed when depending on a top level module in the public one.
+    if (const FileEntry *PublicMMFile = getPublicModuleMap(
+            ModuleMapFile, ImportingInstance.getFileManager()))
+      ModuleMapFile = PublicMMFile;
+
+    // Use the module map where this module resides.
+    Result = compileModuleImpl(
+        ImportingInstance, ImportLoc, Module->getTopLevelModuleName(),
+        FrontendInputFile(ModuleMapFile->getName(), IK, +Module->IsSystem),
+        ModMap.getModuleMapFileForUniquing(Module)->getName(),
+        ModuleFileName);
+  } else {
+    // FIXME: We only need to fake up an input file here as a way of
+    // transporting the module's directory to the module map parser. We should
+    // be able to do that more directly, and parse from a memory buffer without
+    // inventing this file.
+    SmallString<128> FakeModuleMapFile(Module->Directory->getName());
+    llvm::sys::path::append(FakeModuleMapFile, "__inferred_module.map");
+
+    std::string InferredModuleMapContent;
+    llvm::raw_string_ostream OS(InferredModuleMapContent);
+    Module->print(OS);
+    OS.flush();
+
+    Result = compileModuleImpl(
+        ImportingInstance, ImportLoc, Module->getTopLevelModuleName(),
+        FrontendInputFile(FakeModuleMapFile, IK, +Module->IsSystem),
+        ModMap.getModuleMapFileForUniquing(Module)->getName(),
+        ModuleFileName,
+        [&](CompilerInstance &Instance) {
+      std::unique_ptr<llvm::MemoryBuffer> ModuleMapBuffer =
+          llvm::MemoryBuffer::getMemBuffer(InferredModuleMapContent);
+      ModuleMapFile = Instance.getFileManager().getVirtualFile(
+          FakeModuleMapFile, InferredModuleMapContent.size(), 0);
+      Instance.getSourceManager().overrideFileContents(
+          ModuleMapFile, std::move(ModuleMapBuffer));
+    });
+  }
+
+  // We've rebuilt a module. If we're allowed to generate or update the global
+  // module index, record that fact in the importing compiler instance.
+  if (ImportingInstance.getFrontendOpts().GenerateGlobalModuleIndex) {
+    ImportingInstance.setBuildGlobalModuleIndex(true);
+  }
+
+  return Result;
+}
+
+static bool compileAndLoadModule(CompilerInstance &ImportingInstance,
+                                 SourceLocation ImportLoc,
+                                 SourceLocation ModuleNameLoc, Module *Module,
+                                 StringRef ModuleFileName) {
+  DiagnosticsEngine &Diags = ImportingInstance.getDiagnostics();
+
+  auto diagnoseBuildFailure = [&] {
+    Diags.Report(ModuleNameLoc, diag::err_module_not_built)
+        << Module->Name << SourceRange(ImportLoc, ModuleNameLoc);
+  };
+
+  // FIXME: have LockFileManager return an error_code so that we can
+  // avoid the mkdir when the directory already exists.
+  StringRef Dir = llvm::sys::path::parent_path(ModuleFileName);
+  llvm::sys::fs::create_directories(Dir);
+
+  while (1) {
+    unsigned ModuleLoadCapabilities = ASTReader::ARR_Missing;
+    llvm::LockFileManager Locked(ModuleFileName);
+    switch (Locked) {
+    case llvm::LockFileManager::LFS_Error:
+      // ModuleCache takes care of correctness and locks are only necessary for
+      // performance. Fallback to building the module in case of any lock
+      // related errors.
+      Diags.Report(ModuleNameLoc, diag::remark_module_lock_failure)
+          << Module->Name << Locked.getErrorMessage();
+      // Clear out any potential leftover.
+      Locked.unsafeRemoveLockFile();
+      LLVM_FALLTHROUGH;
+    case llvm::LockFileManager::LFS_Owned:
+      // We're responsible for building the module ourselves.
+      if (!compileModuleImpl(ImportingInstance, ModuleNameLoc, Module,
+                             ModuleFileName)) {
+        diagnoseBuildFailure();
+        return false;
+      }
+      break;
+
+    case llvm::LockFileManager::LFS_Shared:
+      // Someone else is responsible for building the module. Wait for them to
+      // finish.
+      switch (Locked.waitForUnlock()) {
+      case llvm::LockFileManager::Res_Success:
+        ModuleLoadCapabilities |= ASTReader::ARR_OutOfDate;
+        break;
+      case llvm::LockFileManager::Res_OwnerDied:
+        continue; // try again to get the lock.
+      case llvm::LockFileManager::Res_Timeout:
+        // Since ModuleCache takes care of correctness, we try waiting for
+        // another process to complete the build so clang does not do it done
+        // twice. If case of timeout, build it ourselves.
+        Diags.Report(ModuleNameLoc, diag::remark_module_lock_timeout)
+            << Module->Name;
+        // Clear the lock file so that future invocations can make progress.
+        Locked.unsafeRemoveLockFile();
+        continue;
+      }
+      break;
+    }
+
+    // Try to read the module file, now that we've compiled it.
+    ASTReader::ASTReadResult ReadResult =
+        ImportingInstance.getModuleManager()->ReadAST(
+            ModuleFileName, serialization::MK_ImplicitModule, ImportLoc,
+            ModuleLoadCapabilities);
+
+    if (ReadResult == ASTReader::OutOfDate &&
+        Locked == llvm::LockFileManager::LFS_Shared) {
+      // The module may be out of date in the presence of file system races,
+      // or if one of its imports depends on header search paths that are not
+      // consistent with this ImportingInstance.  Try again...
+      continue;
+    } else if (ReadResult == ASTReader::Missing) {
+      diagnoseBuildFailure();
+    } else if (ReadResult != ASTReader::Success &&
+               !Diags.hasErrorOccurred()) {
+      // The ASTReader didn't diagnose the error, so conservatively report it.
+      diagnoseBuildFailure();
+    }
+    return ReadResult == ASTReader::Success;
+  }
+}
+
+/// Diagnose differences between the current definition of the given
+/// configuration macro and the definition provided on the command line.
+static void checkConfigMacro(Preprocessor &PP, StringRef ConfigMacro,
+                             Module *Mod, SourceLocation ImportLoc) {
+  IdentifierInfo *Id = PP.getIdentifierInfo(ConfigMacro);
+  SourceManager &SourceMgr = PP.getSourceManager();
+
+  // If this identifier has never had a macro definition, then it could
+  // not have changed.
+  if (!Id->hadMacroDefinition())
+    return;
+  auto *LatestLocalMD = PP.getLocalMacroDirectiveHistory(Id);
+
+  // Find the macro definition from the command line.
+  MacroInfo *CmdLineDefinition = nullptr;
+  for (auto *MD = LatestLocalMD; MD; MD = MD->getPrevious()) {
+    // We only care about the predefines buffer.
+    FileID FID = SourceMgr.getFileID(MD->getLocation());
+    if (FID.isInvalid() || FID != PP.getPredefinesFileID())
+      continue;
+    if (auto *DMD = dyn_cast<DefMacroDirective>(MD))
+      CmdLineDefinition = DMD->getMacroInfo();
+    break;
+  }
+
+  auto *CurrentDefinition = PP.getMacroInfo(Id);
+  if (CurrentDefinition == CmdLineDefinition) {
+    // Macro matches. Nothing to do.
+  } else if (!CurrentDefinition) {
+    // This macro was defined on the command line, then #undef'd later.
+    // Complain.
+    PP.Diag(ImportLoc, diag::warn_module_config_macro_undef)
+      << true << ConfigMacro << Mod->getFullModuleName();
+    auto LatestDef = LatestLocalMD->getDefinition();
+    assert(LatestDef.isUndefined() &&
+           "predefined macro went away with no #undef?");
+    PP.Diag(LatestDef.getUndefLocation(), diag::note_module_def_undef_here)
+      << true;
+    return;
+  } else if (!CmdLineDefinition) {
+    // There was no definition for this macro in the predefines buffer,
+    // but there was a local definition. Complain.
+    PP.Diag(ImportLoc, diag::warn_module_config_macro_undef)
+      << false << ConfigMacro << Mod->getFullModuleName();
+    PP.Diag(CurrentDefinition->getDefinitionLoc(),
+            diag::note_module_def_undef_here)
+      << false;
+  } else if (!CurrentDefinition->isIdenticalTo(*CmdLineDefinition, PP,
+                                               /*Syntactically=*/true)) {
+    // The macro definitions differ.
+    PP.Diag(ImportLoc, diag::warn_module_config_macro_undef)
+      << false << ConfigMacro << Mod->getFullModuleName();
+    PP.Diag(CurrentDefinition->getDefinitionLoc(),
+            diag::note_module_def_undef_here)
+      << false;
+  }
+}
+
+/// Write a new timestamp file with the given path.
+static void writeTimestampFile(StringRef TimestampFile) {
+  std::error_code EC;
+  llvm::raw_fd_ostream Out(TimestampFile.str(), EC, llvm::sys::fs::F_None);
+}
+
+/// Prune the module cache of modules that haven't been accessed in
+/// a long time.
+static void pruneModuleCache(const HeaderSearchOptions &HSOpts) {
+  struct stat StatBuf;
+  llvm::SmallString<128> TimestampFile;
+  TimestampFile = HSOpts.ModuleCachePath;
+  assert(!TimestampFile.empty());
+  llvm::sys::path::append(TimestampFile, "modules.timestamp");
+
+  // Try to stat() the timestamp file.
+  if (::stat(TimestampFile.c_str(), &StatBuf)) {
+    // If the timestamp file wasn't there, create one now.
+    if (errno == ENOENT) {
+      writeTimestampFile(TimestampFile);
+    }
+    return;
+  }
+
+  // Check whether the time stamp is older than our pruning interval.
+  // If not, do nothing.
+  time_t TimeStampModTime = StatBuf.st_mtime;
+  time_t CurrentTime = time(nullptr);
+  if (CurrentTime - TimeStampModTime <= time_t(HSOpts.ModuleCachePruneInterval))
+    return;
+
+  // Write a new timestamp file so that nobody else attempts to prune.
+  // There is a benign race condition here, if two Clang instances happen to
+  // notice at the same time that the timestamp is out-of-date.
+  writeTimestampFile(TimestampFile);
+
+  // Walk the entire module cache, looking for unused module files and module
+  // indices.
+  std::error_code EC;
+  SmallString<128> ModuleCachePathNative;
+  llvm::sys::path::native(HSOpts.ModuleCachePath, ModuleCachePathNative);
+  for (llvm::sys::fs::directory_iterator Dir(ModuleCachePathNative, EC), DirEnd;
+       Dir != DirEnd && !EC; Dir.increment(EC)) {
+    // If we don't have a directory, there's nothing to look into.
+    if (!llvm::sys::fs::is_directory(Dir->path()))
+      continue;
+
+    // Walk all of the files within this directory.
+    for (llvm::sys::fs::directory_iterator File(Dir->path(), EC), FileEnd;
+         File != FileEnd && !EC; File.increment(EC)) {
+      // We only care about module and global module index files.
+      StringRef Extension = llvm::sys::path::extension(File->path());
+      if (Extension != ".pcm" && Extension != ".timestamp" &&
+          llvm::sys::path::filename(File->path()) != "modules.idx")
+        continue;
+
+      // Look at this file. If we can't stat it, there's nothing interesting
+      // there.
+      if (::stat(File->path().c_str(), &StatBuf))
+        continue;
+
+      // If the file has been used recently enough, leave it there.
+      time_t FileAccessTime = StatBuf.st_atime;
+      if (CurrentTime - FileAccessTime <=
+              time_t(HSOpts.ModuleCachePruneAfter)) {
+        continue;
+      }
+
+      // Remove the file.
+      llvm::sys::fs::remove(File->path());
+
+      // Remove the timestamp file.
+      std::string TimpestampFilename = File->path() + ".timestamp";
+      llvm::sys::fs::remove(TimpestampFilename);
+    }
+
+    // If we removed all of the files in the directory, remove the directory
+    // itself.
+    if (llvm::sys::fs::directory_iterator(Dir->path(), EC) ==
+            llvm::sys::fs::directory_iterator() && !EC)
+      llvm::sys::fs::remove(Dir->path());
+  }
+}
+
+void CompilerInstance::createModuleManager() {
+  if (!ModuleManager) {
+    if (!hasASTContext())
+      createASTContext();
+
+    // If we're implicitly building modules but not currently recursively
+    // building a module, check whether we need to prune the module cache.
+    if (getSourceManager().getModuleBuildStack().empty() &&
+        !getPreprocessor().getHeaderSearchInfo().getModuleCachePath().empty() &&
+        getHeaderSearchOpts().ModuleCachePruneInterval > 0 &&
+        getHeaderSearchOpts().ModuleCachePruneAfter > 0) {
+      pruneModuleCache(getHeaderSearchOpts());
+    }
+
+    HeaderSearchOptions &HSOpts = getHeaderSearchOpts();
+    std::string Sysroot = HSOpts.Sysroot;
+    const PreprocessorOptions &PPOpts = getPreprocessorOpts();
+    std::unique_ptr<llvm::Timer> ReadTimer;
+    if (FrontendTimerGroup)
+      ReadTimer = llvm::make_unique<llvm::Timer>("reading_modules",
+                                                 "Reading modules",
+                                                 *FrontendTimerGroup);
+    ModuleManager = new ASTReader(
+        getPreprocessor(), getModuleCache(), &getASTContext(),
+        getPCHContainerReader(), getFrontendOpts().ModuleFileExtensions,
+        Sysroot.empty() ? "" : Sysroot.c_str(), PPOpts.DisablePCHValidation,
+        /*AllowASTWithCompilerErrors=*/false,
+        /*AllowConfigurationMismatch=*/false,
+        HSOpts.ModulesValidateSystemHeaders,
+        getFrontendOpts().UseGlobalModuleIndex, std::move(ReadTimer));
+    if (hasASTConsumer()) {
+      ModuleManager->setDeserializationListener(
+        getASTConsumer().GetASTDeserializationListener());
+      getASTContext().setASTMutationListener(
+        getASTConsumer().GetASTMutationListener());
+    }
+    getASTContext().setExternalSource(ModuleManager);
+    if (hasSema())
+      ModuleManager->InitializeSema(getSema());
+    if (hasASTConsumer())
+      ModuleManager->StartTranslationUnit(&getASTConsumer());
+
+    for (auto &Listener : DependencyCollectors)
+      Listener->attachToASTReader(*ModuleManager);
+  }
+}
+
+bool CompilerInstance::loadModuleFile(StringRef FileName) {
+  llvm::Timer Timer;
+  if (FrontendTimerGroup)
+    Timer.init("preloading." + FileName.str(), "Preloading " + FileName.str(),
+               *FrontendTimerGroup);
+  llvm::TimeRegion TimeLoading(FrontendTimerGroup ? &Timer : nullptr);
+
+  // Helper to recursively read the module names for all modules we're adding.
+  // We mark these as known and redirect any attempt to load that module to
+  // the files we were handed.
+  struct ReadModuleNames : ASTReaderListener {
+    CompilerInstance &CI;
+    llvm::SmallVector<IdentifierInfo*, 8> LoadedModules;
+
+    ReadModuleNames(CompilerInstance &CI) : CI(CI) {}
+
+    void ReadModuleName(StringRef ModuleName) override {
+      LoadedModules.push_back(
+          CI.getPreprocessor().getIdentifierInfo(ModuleName));
+    }
+
+    void registerAll() {
+      for (auto *II : LoadedModules) {
+        CI.KnownModules[II] = CI.getPreprocessor()
+                                  .getHeaderSearchInfo()
+                                  .getModuleMap()
+                                  .findModule(II->getName());
+      }
+      LoadedModules.clear();
+    }
+
+    void markAllUnavailable() {
+      for (auto *II : LoadedModules) {
+        if (Module *M = CI.getPreprocessor()
+                            .getHeaderSearchInfo()
+                            .getModuleMap()
+                            .findModule(II->getName())) {
+          M->HasIncompatibleModuleFile = true;
+
+          // Mark module as available if the only reason it was unavailable
+          // was missing headers.
+          SmallVector<Module *, 2> Stack;
+          Stack.push_back(M);
+          while (!Stack.empty()) {
+            Module *Current = Stack.pop_back_val();
+            if (Current->IsMissingRequirement) continue;
+            Current->IsAvailable = true;
+            Stack.insert(Stack.end(),
+                         Current->submodule_begin(), Current->submodule_end());
+          }
+        }
+      }
+      LoadedModules.clear();
+    }
+  };
+
+  // If we don't already have an ASTReader, create one now.
+  if (!ModuleManager)
+    createModuleManager();
+
+  // If -Wmodule-file-config-mismatch is mapped as an error or worse, allow the
+  // ASTReader to diagnose it, since it can produce better errors that we can.
+  bool ConfigMismatchIsRecoverable =
+      getDiagnostics().getDiagnosticLevel(diag::warn_module_config_mismatch,
+                                          SourceLocation())
+        <= DiagnosticsEngine::Warning;
+
+  auto Listener = llvm::make_unique<ReadModuleNames>(*this);
+  auto &ListenerRef = *Listener;
+  ASTReader::ListenerScope ReadModuleNamesListener(*ModuleManager,
+                                                   std::move(Listener));
+
+  // Try to load the module file.
+  switch (ModuleManager->ReadAST(
+      FileName, serialization::MK_ExplicitModule, SourceLocation(),
+      ConfigMismatchIsRecoverable ? ASTReader::ARR_ConfigurationMismatch : 0)) {
+  case ASTReader::Success:
+    // We successfully loaded the module file; remember the set of provided
+    // modules so that we don't try to load implicit modules for them.
+    ListenerRef.registerAll();
+    return true;
+
+  case ASTReader::ConfigurationMismatch:
+    // Ignore unusable module files.
+    getDiagnostics().Report(SourceLocation(), diag::warn_module_config_mismatch)
+        << FileName;
+    // All modules provided by any files we tried and failed to load are now
+    // unavailable; includes of those modules should now be handled textually.
+    ListenerRef.markAllUnavailable();
+    return true;
+
+  default:
+    return false;
+  }
+}
+
+ModuleLoadResult
+CompilerInstance::loadModule(SourceLocation ImportLoc,
+                             ModuleIdPath Path,
+                             Module::NameVisibilityKind Visibility,
+                             bool IsInclusionDirective) {
+  // Determine what file we're searching from.
+  StringRef ModuleName = Path[0].first->getName();
+  SourceLocation ModuleNameLoc = Path[0].second;
+
+  // If we've already handled this import, just return the cached result.
+  // This one-element cache is important to eliminate redundant diagnostics
+  // when both the preprocessor and parser see the same import declaration.
+  if (ImportLoc.isValid() && LastModuleImportLoc == ImportLoc) {
+    // Make the named module visible.
+    if (LastModuleImportResult && ModuleName != getLangOpts().CurrentModule)
+      ModuleManager->makeModuleVisible(LastModuleImportResult, Visibility,
+                                       ImportLoc);
+    return LastModuleImportResult;
+  }
+
+  clang::Module *Module = nullptr;
+
+  // If we don't already have information on this module, load the module now.
+  llvm::DenseMap<const IdentifierInfo *, clang::Module *>::iterator Known
+    = KnownModules.find(Path[0].first);
+  if (Known != KnownModules.end()) {
+    // Retrieve the cached top-level module.
+    Module = Known->second;
+  } else if (ModuleName == getLangOpts().CurrentModule) {
+    // This is the module we're building.
+    Module = PP->getHeaderSearchInfo().lookupModule(
+        ModuleName, /*AllowSearch*/ true,
+        /*AllowExtraModuleMapSearch*/ !IsInclusionDirective);
+    /// FIXME: perhaps we should (a) look for a module using the module name
+    //  to file map (PrebuiltModuleFiles) and (b) diagnose if still not found?
+    //if (Module == nullptr) {
+    //  getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_found)
+    //    << ModuleName;
+    //  ModuleBuildFailed = true;
+    //  return ModuleLoadResult();
+    //}
+    Known = KnownModules.insert(std::make_pair(Path[0].first, Module)).first;
+  } else {
+    // Search for a module with the given name.
+    Module = PP->getHeaderSearchInfo().lookupModule(ModuleName, true,
+                                                    !IsInclusionDirective);
+    HeaderSearchOptions &HSOpts =
+        PP->getHeaderSearchInfo().getHeaderSearchOpts();
+
+    std::string ModuleFileName;
+    enum ModuleSource {
+      ModuleNotFound, ModuleCache, PrebuiltModulePath, ModuleBuildPragma
+    } Source = ModuleNotFound;
+
+    // Check to see if the module has been built as part of this compilation
+    // via a module build pragma.
+    auto BuiltModuleIt = BuiltModules.find(ModuleName);
+    if (BuiltModuleIt != BuiltModules.end()) {
+      ModuleFileName = BuiltModuleIt->second;
+      Source = ModuleBuildPragma;
+    }
+
+    // Try to load the module from the prebuilt module path.
+    if (Source == ModuleNotFound && (!HSOpts.PrebuiltModuleFiles.empty() ||
+                                     !HSOpts.PrebuiltModulePaths.empty())) {
+      ModuleFileName =
+        PP->getHeaderSearchInfo().getPrebuiltModuleFileName(ModuleName);
+      if (!ModuleFileName.empty())
+        Source = PrebuiltModulePath;
+    }
+
+    // Try to load the module from the module cache.
+    if (Source == ModuleNotFound && Module) {
+      ModuleFileName = PP->getHeaderSearchInfo().getCachedModuleFileName(Module);
+      Source = ModuleCache;
+    }
+
+    if (Source == ModuleNotFound) {
+      // We can't find a module, error out here.
+      getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_found)
+          << ModuleName << SourceRange(ImportLoc, ModuleNameLoc);
+      ModuleBuildFailed = true;
+      return ModuleLoadResult();
+    }
+
+    if (ModuleFileName.empty()) {
+      if (Module && Module->HasIncompatibleModuleFile) {
+        // We tried and failed to load a module file for this module. Fall
+        // back to textual inclusion for its headers.
+        return ModuleLoadResult::ConfigMismatch;
+      }
+
+      getDiagnostics().Report(ModuleNameLoc, diag::err_module_build_disabled)
+          << ModuleName;
+      ModuleBuildFailed = true;
+      return ModuleLoadResult();
+    }
+
+    // If we don't already have an ASTReader, create one now.
+    if (!ModuleManager)
+      createModuleManager();
+
+    llvm::Timer Timer;
+    if (FrontendTimerGroup)
+      Timer.init("loading." + ModuleFileName, "Loading " + ModuleFileName,
+                 *FrontendTimerGroup);
+    llvm::TimeRegion TimeLoading(FrontendTimerGroup ? &Timer : nullptr);
+    llvm::TimeTraceScope TimeScope("Module Load", ModuleName);
+
+    // Try to load the module file. If we are not trying to load from the
+    // module cache, we don't know how to rebuild modules.
+    unsigned ARRFlags = Source == ModuleCache ?
+                        ASTReader::ARR_OutOfDate | ASTReader::ARR_Missing :
+                        Source == PrebuiltModulePath ?
+                            0 :
+                            ASTReader::ARR_ConfigurationMismatch;
+    switch (ModuleManager->ReadAST(ModuleFileName,
+                                   Source == PrebuiltModulePath
+                                       ? serialization::MK_PrebuiltModule
+                                       : Source == ModuleBuildPragma
+                                             ? serialization::MK_ExplicitModule
+                                             : serialization::MK_ImplicitModule,
+                                   ImportLoc, ARRFlags)) {
+    case ASTReader::Success: {
+      if (Source != ModuleCache && !Module) {
+        Module = PP->getHeaderSearchInfo().lookupModule(ModuleName, true,
+                                                        !IsInclusionDirective);
+        if (!Module || !Module->getASTFile() ||
+            FileMgr->getFile(ModuleFileName) != Module->getASTFile()) {
+          // Error out if Module does not refer to the file in the prebuilt
+          // module path.
+          getDiagnostics().Report(ModuleNameLoc, diag::err_module_prebuilt)
+              << ModuleName;
+          ModuleBuildFailed = true;
+          KnownModules[Path[0].first] = nullptr;
+          return ModuleLoadResult();
+        }
+      }
+      break;
+    }
+
+    case ASTReader::OutOfDate:
+    case ASTReader::Missing: {
+      if (Source != ModuleCache) {
+        // We don't know the desired configuration for this module and don't
+        // necessarily even have a module map. Since ReadAST already produces
+        // diagnostics for these two cases, we simply error out here.
+        ModuleBuildFailed = true;
+        KnownModules[Path[0].first] = nullptr;
+        return ModuleLoadResult();
+      }
+
+      // The module file is missing or out-of-date. Build it.
+      assert(Module && "missing module file");
+      // Check whether there is a cycle in the module graph.
+      ModuleBuildStack ModPath = getSourceManager().getModuleBuildStack();
+      ModuleBuildStack::iterator Pos = ModPath.begin(), PosEnd = ModPath.end();
+      for (; Pos != PosEnd; ++Pos) {
+        if (Pos->first == ModuleName)
+          break;
+      }
+
+      if (Pos != PosEnd) {
+        SmallString<256> CyclePath;
+        for (; Pos != PosEnd; ++Pos) {
+          CyclePath += Pos->first;
+          CyclePath += " -> ";
+        }
+        CyclePath += ModuleName;
+
+        getDiagnostics().Report(ModuleNameLoc, diag::err_module_cycle)
+          << ModuleName << CyclePath;
+        return ModuleLoadResult();
+      }
+
+      // Check whether we have already attempted to build this module (but
+      // failed).
+      if (getPreprocessorOpts().FailedModules &&
+          getPreprocessorOpts().FailedModules->hasAlreadyFailed(ModuleName)) {
+        getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_built)
+          << ModuleName
+          << SourceRange(ImportLoc, ModuleNameLoc);
+        ModuleBuildFailed = true;
+        return ModuleLoadResult();
+      }
+
+      // Try to compile and then load the module.
+      if (!compileAndLoadModule(*this, ImportLoc, ModuleNameLoc, Module,
+                                ModuleFileName)) {
+        assert(getDiagnostics().hasErrorOccurred() &&
+               "undiagnosed error in compileAndLoadModule");
+        if (getPreprocessorOpts().FailedModules)
+          getPreprocessorOpts().FailedModules->addFailed(ModuleName);
+        KnownModules[Path[0].first] = nullptr;
+        ModuleBuildFailed = true;
+        return ModuleLoadResult();
+      }
+
+      // Okay, we've rebuilt and now loaded the module.
+      break;
+    }
+
+    case ASTReader::ConfigurationMismatch:
+      if (Source == PrebuiltModulePath)
+        // FIXME: We shouldn't be setting HadFatalFailure below if we only
+        // produce a warning here!
+        getDiagnostics().Report(SourceLocation(),
+                                diag::warn_module_config_mismatch)
+            << ModuleFileName;
+      // Fall through to error out.
+      LLVM_FALLTHROUGH;
+    case ASTReader::VersionMismatch:
+    case ASTReader::HadErrors:
+      ModuleLoader::HadFatalFailure = true;
+      // FIXME: The ASTReader will already have complained, but can we shoehorn
+      // that diagnostic information into a more useful form?
+      KnownModules[Path[0].first] = nullptr;
+      return ModuleLoadResult();
+
+    case ASTReader::Failure:
+      ModuleLoader::HadFatalFailure = true;
+      // Already complained, but note now that we failed.
+      KnownModules[Path[0].first] = nullptr;
+      ModuleBuildFailed = true;
+      return ModuleLoadResult();
+    }
+
+    // Cache the result of this top-level module lookup for later.
+    Known = KnownModules.insert(std::make_pair(Path[0].first, Module)).first;
+  }
+
+  // If we never found the module, fail.
+  if (!Module)
+    return ModuleLoadResult();
+
+  // Verify that the rest of the module path actually corresponds to
+  // a submodule.
+  bool MapPrivateSubModToTopLevel = false;
+  if (Path.size() > 1) {
+    for (unsigned I = 1, N = Path.size(); I != N; ++I) {
+      StringRef Name = Path[I].first->getName();
+      clang::Module *Sub = Module->findSubmodule(Name);
+
+      // If the user is requesting Foo.Private and it doesn't exist, try to
+      // match Foo_Private and emit a warning asking for the user to write
+      // @import Foo_Private instead. FIXME: remove this when existing clients
+      // migrate off of Foo.Private syntax.
+      if (!Sub && PP->getLangOpts().ImplicitModules && Name == "Private" &&
+          Module == Module->getTopLevelModule()) {
+        SmallString<128> PrivateModule(Module->Name);
+        PrivateModule.append("_Private");
+
+        SmallVector<std::pair<IdentifierInfo *, SourceLocation>, 2> PrivPath;
+        auto &II = PP->getIdentifierTable().get(
+            PrivateModule, PP->getIdentifierInfo(Module->Name)->getTokenID());
+        PrivPath.push_back(std::make_pair(&II, Path[0].second));
+
+        if (PP->getHeaderSearchInfo().lookupModule(PrivateModule, true,
+                                                   !IsInclusionDirective))
+          Sub =
+              loadModule(ImportLoc, PrivPath, Visibility, IsInclusionDirective);
+        if (Sub) {
+          MapPrivateSubModToTopLevel = true;
+          if (!getDiagnostics().isIgnored(
+                  diag::warn_no_priv_submodule_use_toplevel, ImportLoc)) {
+            getDiagnostics().Report(Path[I].second,
+                                    diag::warn_no_priv_submodule_use_toplevel)
+                << Path[I].first << Module->getFullModuleName() << PrivateModule
+                << SourceRange(Path[0].second, Path[I].second)
+                << FixItHint::CreateReplacement(SourceRange(Path[0].second),
+                                                PrivateModule);
+            getDiagnostics().Report(Sub->DefinitionLoc,
+                                    diag::note_private_top_level_defined);
+          }
+        }
+      }
+
+      if (!Sub) {
+        // Attempt to perform typo correction to find a module name that works.
+        SmallVector<StringRef, 2> Best;
+        unsigned BestEditDistance = (std::numeric_limits<unsigned>::max)();
+
+        for (clang::Module::submodule_iterator J = Module->submodule_begin(),
+                                            JEnd = Module->submodule_end();
+             J != JEnd; ++J) {
+          unsigned ED = Name.edit_distance((*J)->Name,
+                                           /*AllowReplacements=*/true,
+                                           BestEditDistance);
+          if (ED <= BestEditDistance) {
+            if (ED < BestEditDistance) {
+              Best.clear();
+              BestEditDistance = ED;
+            }
+
+            Best.push_back((*J)->Name);
+          }
+        }
+
+        // If there was a clear winner, user it.
+        if (Best.size() == 1) {
+          getDiagnostics().Report(Path[I].second,
+                                  diag::err_no_submodule_suggest)
+            << Path[I].first << Module->getFullModuleName() << Best[0]
+            << SourceRange(Path[0].second, Path[I-1].second)
+            << FixItHint::CreateReplacement(SourceRange(Path[I].second),
+                                            Best[0]);
+
+          Sub = Module->findSubmodule(Best[0]);
+        }
+      }
+
+      if (!Sub) {
+        // No submodule by this name. Complain, and don't look for further
+        // submodules.
+        getDiagnostics().Report(Path[I].second, diag::err_no_submodule)
+          << Path[I].first << Module->getFullModuleName()
+          << SourceRange(Path[0].second, Path[I-1].second);
+        break;
+      }
+
+      Module = Sub;
+    }
+  }
+
+  // Make the named module visible, if it's not already part of the module
+  // we are parsing.
+  if (ModuleName != getLangOpts().CurrentModule) {
+    if (!Module->IsFromModuleFile && !MapPrivateSubModToTopLevel) {
+      // We have an umbrella header or directory that doesn't actually include
+      // all of the headers within the directory it covers. Complain about
+      // this missing submodule and recover by forgetting that we ever saw
+      // this submodule.
+      // FIXME: Should we detect this at module load time? It seems fairly
+      // expensive (and rare).
+      getDiagnostics().Report(ImportLoc, diag::warn_missing_submodule)
+        << Module->getFullModuleName()
+        << SourceRange(Path.front().second, Path.back().second);
+
+      return ModuleLoadResult::MissingExpected;
+    }
+
+    // Check whether this module is available.
+    if (Preprocessor::checkModuleIsAvailable(getLangOpts(), getTarget(),
+                                             getDiagnostics(), Module)) {
+      getDiagnostics().Report(ImportLoc, diag::note_module_import_here)
+        << SourceRange(Path.front().second, Path.back().second);
+      LastModuleImportLoc = ImportLoc;
+      LastModuleImportResult = ModuleLoadResult();
+      return ModuleLoadResult();
+    }
+
+    ModuleManager->makeModuleVisible(Module, Visibility, ImportLoc);
+  }
+
+  // Check for any configuration macros that have changed.
+  clang::Module *TopModule = Module->getTopLevelModule();
+  for (unsigned I = 0, N = TopModule->ConfigMacros.size(); I != N; ++I) {
+    checkConfigMacro(getPreprocessor(), TopModule->ConfigMacros[I],
+                     Module, ImportLoc);
+  }
+
+  // Resolve any remaining module using export_as for this one.
+  getPreprocessor()
+      .getHeaderSearchInfo()
+      .getModuleMap()
+      .resolveLinkAsDependencies(TopModule);
+
+  LastModuleImportLoc = ImportLoc;
+  LastModuleImportResult = ModuleLoadResult(Module);
+  return LastModuleImportResult;
+}
+
+void CompilerInstance::loadModuleFromSource(SourceLocation ImportLoc,
+                                            StringRef ModuleName,
+                                            StringRef Source) {
+  // Avoid creating filenames with special characters.
+  SmallString<128> CleanModuleName(ModuleName);
+  for (auto &C : CleanModuleName)
+    if (!isAlphanumeric(C))
+      C = '_';
+
+  // FIXME: Using a randomized filename here means that our intermediate .pcm
+  // output is nondeterministic (as .pcm files refer to each other by name).
+  // Can this affect the output in any way?
+  SmallString<128> ModuleFileName;
+  if (std::error_code EC = llvm::sys::fs::createTemporaryFile(
+          CleanModuleName, "pcm", ModuleFileName)) {
+    getDiagnostics().Report(ImportLoc, diag::err_fe_unable_to_open_output)
+        << ModuleFileName << EC.message();
+    return;
+  }
+  std::string ModuleMapFileName = (CleanModuleName + ".map").str();
+
+  FrontendInputFile Input(
+      ModuleMapFileName,
+      InputKind(getLanguageFromOptions(*Invocation->getLangOpts()),
+                InputKind::ModuleMap, /*Preprocessed*/true));
+
+  std::string NullTerminatedSource(Source.str());
+
+  auto PreBuildStep = [&](CompilerInstance &Other) {
+    // Create a virtual file containing our desired source.
+    // FIXME: We shouldn't need to do this.
+    const FileEntry *ModuleMapFile = Other.getFileManager().getVirtualFile(
+        ModuleMapFileName, NullTerminatedSource.size(), 0);
+    Other.getSourceManager().overrideFileContents(
+        ModuleMapFile,
+        llvm::MemoryBuffer::getMemBuffer(NullTerminatedSource.c_str()));
+
+    Other.BuiltModules = std::move(BuiltModules);
+    Other.DeleteBuiltModules = false;
+  };
+
+  auto PostBuildStep = [this](CompilerInstance &Other) {
+    BuiltModules = std::move(Other.BuiltModules);
+  };
+
+  // Build the module, inheriting any modules that we've built locally.
+  if (compileModuleImpl(*this, ImportLoc, ModuleName, Input, StringRef(),
+                        ModuleFileName, PreBuildStep, PostBuildStep)) {
+    BuiltModules[ModuleName] = ModuleFileName.str();
+    llvm::sys::RemoveFileOnSignal(ModuleFileName);
+  }
+}
+
+void CompilerInstance::makeModuleVisible(Module *Mod,
+                                         Module::NameVisibilityKind Visibility,
+                                         SourceLocation ImportLoc) {
+  if (!ModuleManager)
+    createModuleManager();
+  if (!ModuleManager)
+    return;
+
+  ModuleManager->makeModuleVisible(Mod, Visibility, ImportLoc);
+}
+
+GlobalModuleIndex *CompilerInstance::loadGlobalModuleIndex(
+    SourceLocation TriggerLoc) {
+  if (getPreprocessor().getHeaderSearchInfo().getModuleCachePath().empty())
+    return nullptr;
+  if (!ModuleManager)
+    createModuleManager();
+  // Can't do anything if we don't have the module manager.
+  if (!ModuleManager)
+    return nullptr;
+  // Get an existing global index.  This loads it if not already
+  // loaded.
+  ModuleManager->loadGlobalIndex();
+  GlobalModuleIndex *GlobalIndex = ModuleManager->getGlobalIndex();
+  // If the global index doesn't exist, create it.
+  if (!GlobalIndex && shouldBuildGlobalModuleIndex() && hasFileManager() &&
+      hasPreprocessor()) {
+    llvm::sys::fs::create_directories(
+      getPreprocessor().getHeaderSearchInfo().getModuleCachePath());
+    if (llvm::Error Err = GlobalModuleIndex::writeIndex(
+            getFileManager(), getPCHContainerReader(),
+            getPreprocessor().getHeaderSearchInfo().getModuleCachePath())) {
+      // FIXME this drops the error on the floor. This code is only used for
+      // typo correction and drops more than just this one source of errors
+      // (such as the directory creation failure above). It should handle the
+      // error.
+      consumeError(std::move(Err));
+      return nullptr;
+    }
+    ModuleManager->resetForReload();
+    ModuleManager->loadGlobalIndex();
+    GlobalIndex = ModuleManager->getGlobalIndex();
+  }
+  // For finding modules needing to be imported for fixit messages,
+  // we need to make the global index cover all modules, so we do that here.
+  if (!HaveFullGlobalModuleIndex && GlobalIndex && !buildingModule()) {
+    ModuleMap &MMap = getPreprocessor().getHeaderSearchInfo().getModuleMap();
+    bool RecreateIndex = false;
+    for (ModuleMap::module_iterator I = MMap.module_begin(),
+        E = MMap.module_end(); I != E; ++I) {
+      Module *TheModule = I->second;
+      const FileEntry *Entry = TheModule->getASTFile();
+      if (!Entry) {
+        SmallVector<std::pair<IdentifierInfo *, SourceLocation>, 2> Path;
+        Path.push_back(std::make_pair(
+            getPreprocessor().getIdentifierInfo(TheModule->Name), TriggerLoc));
+        std::reverse(Path.begin(), Path.end());
+        // Load a module as hidden.  This also adds it to the global index.
+        loadModule(TheModule->DefinitionLoc, Path, Module::Hidden, false);
+        RecreateIndex = true;
+      }
+    }
+    if (RecreateIndex) {
+      if (llvm::Error Err = GlobalModuleIndex::writeIndex(
+              getFileManager(), getPCHContainerReader(),
+              getPreprocessor().getHeaderSearchInfo().getModuleCachePath())) {
+        // FIXME As above, this drops the error on the floor.
+        consumeError(std::move(Err));
+        return nullptr;
+      }
+      ModuleManager->resetForReload();
+      ModuleManager->loadGlobalIndex();
+      GlobalIndex = ModuleManager->getGlobalIndex();
+    }
+    HaveFullGlobalModuleIndex = true;
+  }
+  return GlobalIndex;
+}
+
+// Check global module index for missing imports.
+bool
+CompilerInstance::lookupMissingImports(StringRef Name,
+                                       SourceLocation TriggerLoc) {
+  // Look for the symbol in non-imported modules, but only if an error
+  // actually occurred.
+  if (!buildingModule()) {
+    // Load global module index, or retrieve a previously loaded one.
+    GlobalModuleIndex *GlobalIndex = loadGlobalModuleIndex(
+      TriggerLoc);
+
+    // Only if we have a global index.
+    if (GlobalIndex) {
+      GlobalModuleIndex::HitSet FoundModules;
+
+      // Find the modules that reference the identifier.
+      // Note that this only finds top-level modules.
+      // We'll let diagnoseTypo find the actual declaration module.
+      if (GlobalIndex->lookupIdentifier(Name, FoundModules))
+        return true;
+    }
+  }
+
+  return false;
+}
+void CompilerInstance::resetAndLeakSema() { llvm::BuryPointer(takeSema()); }
+
+void CompilerInstance::setExternalSemaSource(
+    IntrusiveRefCntPtr<ExternalSemaSource> ESS) {
+  ExternalSemaSrc = std::move(ESS);
+}