Cache Code Completion results from PCH files

- Add CompilerInvocation::getPCHHash
  This will be used when creating a unique filename for a persistent
  precompiled bridging header.

- Automatically generate and use a precompiled briding header
  When we're given both -import-objc-header and -pch-output-dir
  arguments, we will try to:
  - Validate what we think the PCH filename should be for the bridging
    header, based on the Swift PCH hash and the clang module hash.
    - If we're successful, we'll just use it.
    - If it's out of date or something else is wrong, we'll try to
      emit it.
  - This gives us a single filename which we can `stat` to check for the
    validity of our code completion cache, which is keyed off of module
    name, module filename, and module file age.

- Cache code completion results from imported modules
  If we just have a single .PCH file imported, we can use that file as
  part of the key used to cache declarations in a module.  Because
  multiple files can contribute to the __ObjC module, we've always given
  it the phony filename "<imports>", which never exists, so `stat`-ing it
  always fails and we never cache declarations in it.

  This is extremely problematic for projects with huge bridging headers.
  In the case where we have a single PCH import, this can bring warm code
  completion times down to about 500ms from over 2-3s, so it can provide a
  nice performance win for IDEs.

- Add a new test that performs two code-completion requests with a bridging header.
- Add some -pch-output-dir flags to existing SourceKit tests that import a bridging
  header.

rdar://problem/31198982

include/swift/AST/IRGenOptions.h

@@ -209,6 +209,12 @@ public:
       return OutputKind == IRGenOutputKind::LLVMAssembly;
     }
   }
+
+  /// Return a hash code of any components from these options that should
+  /// contribute to a Swift Bridging PCH hash.
+  llvm::hash_code getPCHHashComponents() const {
+    return llvm::hash_value(0);
+  }
 };
 
 } // end namespace swift

include/swift/AST/SILOptions.h

@@ -19,6 +19,7 @@
 #define SWIFT_AST_SILOPTIONS_H
 
 #include "swift/Basic/Sanitizers.h"
+#include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/StringRef.h"
 #include <string>
 #include <climits>
@@ -147,6 +148,11 @@ public:
 
   SILOptions() : Sanitize(SanitizerKind::None) {}
 
+  /// Return a hash code of any components from these options that should
+  /// contribute to a Swift Bridging PCH hash.
+  llvm::hash_code getPCHHashComponents() const {
+    return llvm::hash_value(0);
+  }
 };
 
 } // end namespace swift

include/swift/AST/SearchPathOptions.h

@@ -13,6 +13,8 @@
 #ifndef SWIFT_AST_SEARCHPATHOPTIONS_H
 #define SWIFT_AST_SEARCHPATHOPTIONS_H
 
+#include "llvm/ADT/Hashing.h"
+
 #include <string>
 #include <vector>
 
@@ -67,6 +69,26 @@ public:
 
   /// Don't look in for compiler-provided modules.
   bool SkipRuntimeLibraryImportPath = false;
+
+  /// Return a hash code of any components from these options that should
+  /// contribute to a Swift Bridging PCH hash.
+  llvm::hash_code getPCHHashComponents() const {
+    using llvm::hash_value;
+    using llvm::hash_combine;
+    auto Code = hash_value(SDKPath);
+    for (auto Import : ImportSearchPaths) {
+      Code = hash_combine(Code, Import);
+    }
+    for (const auto &FrameworkPath : FrameworkSearchPaths) {
+      Code = hash_combine(Code, FrameworkPath.Path);
+    }
+    for (auto LibraryPath : LibrarySearchPaths) {
+      Code = hash_combine(Code, LibraryPath);
+    }
+    Code = hash_combine(Code, RuntimeResourcePath);
+    Code = hash_combine(Code, RuntimeLibraryImportPath);
+    return Code;
+  }
 };
 
 }

include/swift/Basic/DiagnosticOptions.h

@@ -49,6 +49,13 @@ public:
 
   /// Treat all warnings as errors
   bool WarningsAsErrors = false;
+
+  /// Return a hash code of any components from these options that should
+  /// contribute to a Swift Bridging PCH hash.
+  llvm::hash_code getPCHHashComponents() const {
+    // Nothing here that contributes anything significant when emitting the PCH.
+    return llvm::hash_value(0);
+  }
 };
 
 } // end namespace swift

include/swift/Basic/LangOptions.h

@@ -22,9 +22,12 @@
 #include "swift/Basic/Version.h"
 #include "clang/Basic/VersionTuple.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Triple.h"
+#include "llvm/Support/raw_ostream.h"
 #include <string>
 #include <vector>
 
@@ -278,6 +281,17 @@ namespace swift {
       PlatformConditionKind Kind, StringRef Value,
       std::vector<StringRef> &suggestions);
 
+    /// Return a hash code of any components from these options that should
+    /// contribute to a Swift Bridging PCH hash.
+    llvm::hash_code getPCHHashComponents() const {
+      auto code = llvm::hash_value(Target.str());
+      SmallString<16> Scratch;
+      llvm::raw_svector_ostream OS(Scratch);
+      OS << EffectiveLanguageVersion;
+      code = llvm::hash_combine(code, OS.str());
+      return code;
+    }
+
   private:
     llvm::SmallVector<std::pair<PlatformConditionKind, std::string>,
                       NumPlatformConditionKind>

include/swift/ClangImporter/ClangImporter.h

@@ -31,6 +31,7 @@ namespace clang {
   class CodeGenOptions;
   class Decl;
   class DependencyCollector;
+  class DiagnosticConsumer;
   class EnumConstantDecl;
   class EnumDecl;
   class MacroInfo;
@@ -44,6 +45,7 @@ namespace clang {
 
 namespace swift {
 class ASTContext;
+class CompilerInvocation;
 class ClangImporterOptions;
 class ClangModuleUnit;
 class ClangNode;
@@ -78,14 +80,19 @@ public:
   /// \param ctx The ASTContext into which the module will be imported.
   /// The ASTContext's SearchPathOptions will be used for the Clang importer.
   ///
-  /// \param clangImporterOpts The options to use for the Clang importer.
+  /// \param importerOpts The options to use for the Clang importer.
+  ///
+  /// \param swiftPCHHash A hash of Swift's various options in a compiler
+  /// invocation, used to create a unique Bridging PCH if requested.
   ///
   /// \param tracker The object tracking files this compilation depends on.
   ///
   /// \returns a new Clang module importer, or null (with a diagnostic) if
   /// an error occurred.
   static std::unique_ptr<ClangImporter>
-  create(ASTContext &ctx, const ClangImporterOptions &clangImporterOpts,
+  create(ASTContext &ctx,
+         const ClangImporterOptions &importerOpts,
+         std::string swiftPCHHash = "",
          DependencyTracker *tracker = nullptr);
 
   ClangImporter(const ClangImporter &) = delete;
@@ -234,7 +241,14 @@ public:
   /// replica.
   ///
   /// \sa clang::GeneratePCHAction
-  bool emitBridgingPCH(StringRef headerPath, StringRef outputPCHPath);
+  bool emitBridgingPCH(StringRef headerPath,
+                       StringRef outputPCHPath,
+                       clang::DiagnosticConsumer *Diags = nullptr);
+
+  /// Returns true if a clang CompilerInstance can successfully read in a PCH,
+  /// assuming it exists, with the current options. This can be used to find out
+  /// if we need to persist a PCH for later reuse.
+  bool canReadPCH(StringRef PCHFilename);
 
   const clang::Module *getClangOwningModule(ClangNode Node) const;
   bool hasTypedef(const clang::Decl *typeDecl) const;
@@ -291,6 +305,13 @@ public:
 
   DeclName importName(const clang::NamedDecl *D,
                       clang::DeclarationName givenName);
+
+  Optional<std::string>
+  getOrCreatePCH(const ClangImporterOptions &ImporterOptions,
+                 const std::string &SwiftPCHHash);
+  Optional<std::string>
+  getPCHFilename(const ClangImporterOptions &ImporterOptions,
+                 const std::string &SwiftPCHHash);
 };
 
 ImportDecl *createImportDecl(ASTContext &Ctx, DeclContext *DC, ClangNode ClangN,

include/swift/ClangImporter/ClangImporterOptions.h

@@ -13,6 +13,8 @@
 #ifndef SWIFT_CLANGIMPORTER_CLANGIMPORTEROPTIONS_H
 #define SWIFT_CLANGIMPORTER_CLANGIMPORTEROPTIONS_H
 
+#include "llvm/ADT/Hashing.h"
+
 #include <string>
 #include <vector>
 
@@ -43,7 +45,7 @@ public:
   std::string PrecompiledHeaderOutputDir;
 
   /// \see Mode
-  enum class Modes {
+  enum class Modes : uint8_t {
     /// Set up Clang for importing modules into Swift and generating IR from
     /// Swift code.
     Normal,
@@ -84,6 +86,28 @@ public:
 
   /// When set, don't look for or load adapter modules.
   bool DisableAdapterModules = false;
+
+  /// Return a hash code of any components from these options that should
+  /// contribute to a Swift Bridging PCH hash.
+  llvm::hash_code getPCHHashComponents() const {
+    using llvm::hash_value;
+    using llvm::hash_combine;
+
+    auto Code = hash_value(ModuleCachePath);
+    // ExtraArgs ignored - already considered in Clang's module hashing.
+    Code = hash_combine(Code, OverrideResourceDir);
+    Code = hash_combine(Code, TargetCPU);
+    Code = hash_combine(Code, BridgingHeader);
+    Code = hash_combine(Code, PrecompiledHeaderOutputDir);
+    Code = hash_combine(Code, static_cast<uint8_t>(Mode));
+    Code = hash_combine(Code, DetailedPreprocessingRecord);
+    Code = hash_combine(Code, ImportForwardDeclarations);
+    Code = hash_combine(Code, InferImportAsMember);
+    Code = hash_combine(Code, DisableSwiftBridgeAttr);
+    Code = hash_combine(Code, DisableModulesValidateSystemHeaders);
+    Code = hash_combine(Code, DisableAdapterModules);
+    return Code;
+  }
 };
 
 } // end namespace swift

include/swift/Frontend/Frontend.h

@@ -292,6 +292,11 @@ public:
   bool isDelayedFunctionBodyParsing() const {
     return FrontendOpts.DelayedFunctionBodyParsing;
   }
+
+  /// Retrieve a module hash string that is suitable for uniquely
+  /// identifying the conditions under which the module was built, for use
+  /// in generating a cached PCH file for the bridging header.
+  std::string getPCHHash() const;
 };
 
 /// A class which manages the state and execution of the compiler.

include/swift/Frontend/FrontendOptions.h

@@ -14,6 +14,7 @@
 #define SWIFT_FRONTEND_FRONTENDOPTIONS_H
 
 #include "swift/AST/Module.h"
+#include "llvm/ADT/Hashing.h"
 
 #include <string>
 #include <vector>
@@ -305,6 +306,12 @@ public:
     OutputFilenames.clear();
     OutputFilenames.push_back(FileName);
   }
+
+  /// Return a hash code of any components from these options that should
+  /// contribute to a Swift Bridging PCH hash.
+  llvm::hash_code getPCHHashComponents() const {
+    return llvm::hash_value(0);
+  }
 };
 
 }

lib/Basic/LangOptions.cpp

@@ -18,6 +18,7 @@
 #include "swift/Basic/LangOptions.h"
 #include "swift/Basic/Range.h"
 #include "swift/Config.h"
+#include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/raw_ostream.h"
 #include <limits.h>

lib/ClangImporter/ClangImporter.cpp

@@ -145,27 +145,44 @@ namespace {
     ASTContext &Ctx;
     ClangImporter &Importer;
     ClangImporter::Implementation &Impl;
+    const ClangImporterOptions &ImporterOpts;
+    std::string SwiftPCHHash;
   public:
     explicit ParsingAction(ASTContext &ctx,
                            ClangImporter &importer,
-                           ClangImporter::Implementation &impl)
+                           ClangImporter::Implementation &impl,
-      : Ctx(ctx), Importer(importer), Impl(impl) {}
+                           const ClangImporterOptions &importerOpts,
+                           std::string swiftPCHHash)
+      : Ctx(ctx), Importer(importer), Impl(impl), ImporterOpts(importerOpts),
+        SwiftPCHHash(swiftPCHHash) {}
     std::unique_ptr<clang::ASTConsumer>
     CreateASTConsumer(clang::CompilerInstance &CI, StringRef InFile) override {
       return llvm::make_unique<HeaderParsingASTConsumer>(Impl);
     }
-    bool BeginSourceFileAction(CompilerInstance &CI,
+    bool BeginSourceFileAction(clang::CompilerInstance &CI,
                                StringRef Filename) override {
       // Prefer frameworks over plain headers.
       // We add search paths here instead of when building the initial invocation
       // so that (a) we use the same code as search paths for imported modules,
       // and (b) search paths are always added after -Xcc options.
       SearchPathOptions &searchPathOpts = Ctx.SearchPathOpts;
-      for (const auto &framepath : searchPathOpts.FrameworkSearchPaths)
+      for (const auto &framepath : searchPathOpts.FrameworkSearchPaths) {
         Importer.addSearchPath(framepath.Path, /*isFramework*/true,
                                framepath.IsSystem);
-      for (auto path : searchPathOpts.ImportSearchPaths)
+      }
+
+      for (auto path : searchPathOpts.ImportSearchPaths) {
         Importer.addSearchPath(path, /*isFramework*/false, /*isSystem=*/false);
+      }
+
+      auto PCH = Importer.getOrCreatePCH(ImporterOpts, SwiftPCHHash);
+      if (PCH.hasValue()) {
+        Impl.getClangInstance()->getPreprocessorOpts().ImplicitPCHInclude =
+            PCH.getValue();
+        Impl.IsReadingBridgingPCH = true;
+        Impl.setSinglePCHImport(PCH.getValue());
+      }
+
       return true;
     }
   };
@@ -692,11 +709,73 @@ addCommonInvocationArguments(std::vector<std::string> &invocationArgStrs,
     llvm::itostr(ctx.LangOpts.EffectiveLanguageVersion[0]));
 }
 
+bool ClangImporter::canReadPCH(StringRef PCHFilename) {
+  return clang::ASTReader::isAcceptableASTFile(PCHFilename,
+    Impl.Instance->getFileManager(),
+    Impl.Instance->getPCHContainerReader(),
+    Impl.Instance->getLangOpts(),
+    Impl.Instance->getTargetOpts(),
+    Impl.Instance->getPreprocessorOpts(),
+    Impl.Instance->getSpecificModuleCachePath());
+}
+
+Optional<std::string>
+ClangImporter::getPCHFilename(const ClangImporterOptions &ImporterOptions,
+                              const std::string &SwiftPCHHash) {
+  if (llvm::sys::path::extension(ImporterOptions.BridgingHeader)
+        .endswith(PCH_EXTENSION)) {
+    return ImporterOptions.BridgingHeader;
+  }
+
+  const auto &BridgingHeader = ImporterOptions.BridgingHeader;
+  const auto &PCHOutputDir = ImporterOptions.PrecompiledHeaderOutputDir;
+  if (SwiftPCHHash.empty() || BridgingHeader.empty() || PCHOutputDir.empty()) {
+    return None;
+  }
+
+  SmallString<256> PCHBasename { llvm::sys::path::filename(BridgingHeader) };
+  llvm::sys::path::replace_extension(PCHBasename, "");
+  PCHBasename.append("-swift_");
+  PCHBasename.append(SwiftPCHHash);
+  PCHBasename.append("-clang_");
+  PCHBasename.append(getClangModuleHash());
+  llvm::sys::path::replace_extension(PCHBasename, ".pch");
+  SmallString<256> PCHFilename { PCHOutputDir };
+  llvm::sys::path::append(PCHFilename, PCHBasename);
+  return PCHFilename.str().str();
+}
+
+
+Optional<std::string>
+ClangImporter::getOrCreatePCH(const ClangImporterOptions &ImporterOptions,
+                              const std::string &SwiftPCHHash) {
+  auto PCHFilename = getPCHFilename(ImporterOptions, SwiftPCHHash);
+  if (!PCHFilename.hasValue()) {
+    return None;
+  }
+  if (!canReadPCH(PCHFilename.getValue())) {
+    SmallString<256> Message;
+    llvm::raw_svector_ostream OS(Message);
+    auto Diags = new clang::TextDiagnosticPrinter {
+      llvm::errs(),
+      &Impl.Instance->getDiagnosticOpts()
+    };
+    auto FailedToEmit = emitBridgingPCH(ImporterOptions.BridgingHeader,
+                                        PCHFilename.getValue(),
+                                        Diags);
+    if (FailedToEmit) {
+      return None;
+    }
+  }
+
+  return PCHFilename.getValue();
+}
+
 std::unique_ptr<ClangImporter>
 ClangImporter::create(ASTContext &ctx,
                       const ClangImporterOptions &importerOpts,
+                      std::string swiftPCHHash,
                       DependencyTracker *tracker) {
-
   std::unique_ptr<ClangImporter> importer{
     new ClangImporter(ctx, importerOpts, tracker)
   };
@@ -731,6 +810,7 @@ ClangImporter::create(ASTContext &ctx,
 
   if (llvm::sys::path::extension(importerOpts.BridgingHeader).endswith(
         PCH_EXTENSION)) {
+    importer->Impl.setSinglePCHImport(importerOpts.BridgingHeader);
     importer->Impl.IsReadingBridgingPCH = true;
     if (tracker) {
       // Currently ignoring dependency on bridging .pch files because they are
@@ -751,8 +831,9 @@ ClangImporter::create(ASTContext &ctx,
     new ClangDiagnosticConsumer(importer->Impl, *diagnosticOpts,
                                 importerOpts.DumpClangDiagnostics)
   };
-  auto clangDiags = CompilerInstance::createDiagnostics(diagnosticOpts.get(),
+  auto clangDiags =
-                                                        diagClient.release());
+      clang::CompilerInstance::createDiagnostics(diagnosticOpts.get(),
+                                                 diagClient.release());
 
   // Create a new Clang compiler invocation.
   importer->Impl.Invocation =
@@ -794,7 +875,8 @@ ClangImporter::create(ASTContext &ctx,
       llvm::make_unique<clang::ObjectFilePCHContainerWriter>());
   PCHContainerOperations->registerReader(
       llvm::make_unique<clang::ObjectFilePCHContainerReader>());
-  importer->Impl.Instance.reset(new CompilerInstance(PCHContainerOperations));
+  importer->Impl.Instance.reset(
+      new clang::CompilerInstance(PCHContainerOperations));
   auto &instance = *importer->Impl.Instance;
   if (tracker)
     instance.addDependencyCollector(tracker->getClangCollector());
@@ -804,7 +886,9 @@ ClangImporter::create(ASTContext &ctx,
 
   // Create the associated action.
   importer->Impl.Action.reset(new ParsingAction(ctx, *importer,
-                                                importer->Impl));
+                                                importer->Impl,
+                                                importerOpts,
+                                                swiftPCHHash));
   auto *action = importer->Impl.Action.get();
 
   // Execute the action. We effectively inline most of
@@ -934,6 +1018,7 @@ bool ClangImporter::Implementation::importHeader(
     bool trackParsedSymbols,
     std::unique_ptr<llvm::MemoryBuffer> sourceBuffer,
     bool implicitImport) {
+
   // Don't even try to load the bridging header if the Clang AST is in a bad
   // state. It could cause a crash.
   auto &clangDiags = getClangASTContext().getDiagnostics();
@@ -1061,6 +1146,11 @@ bool ClangImporter::importHeader(StringRef header, ModuleDecl *adapter,
     return importBridgingHeader(header, adapter, diagLoc, false, true);
   }
 
+  // If we've made it to here, this is some header other than the bridging
+  // header, which means we can no longer rely on one file's modification time
+  // to invalid code completion caches. :-(
+  Impl.setSinglePCHImport(None);
+
   if (!cachedContents.empty() && cachedContents.back() == '\0')
     cachedContents = cachedContents.drop_back();
   std::unique_ptr<llvm::MemoryBuffer> sourceBuffer{
@@ -1082,6 +1172,7 @@ bool ClangImporter::importBridgingHeader(StringRef header, ModuleDecl *adapter,
     Impl.handleDeferredImports();
     return false;
   }
+
   clang::FileManager &fileManager = Impl.Instance->getFileManager();
   const clang::FileEntry *headerFile = fileManager.getFile(header,
                                                            /*OpenFile=*/true);
@@ -1152,7 +1243,8 @@ std::string ClangImporter::getBridgingHeaderContents(StringRef headerPath,
 
 bool
 ClangImporter::emitBridgingPCH(StringRef headerPath,
-                               StringRef outputPCHPath) {
+                               StringRef outputPCHPath,
+                               clang::DiagnosticConsumer *Diags) {
   auto invocation = std::make_shared<clang::CompilerInvocation>
     (clang::CompilerInvocation(*Impl.Invocation));
   invocation->getFrontendOpts().DisableFree = false;
@@ -1165,8 +1257,12 @@ ClangImporter::emitBridgingPCH(StringRef headerPath,
   clang::CompilerInstance emitInstance(
     Impl.Instance->getPCHContainerOperations());
   emitInstance.setInvocation(std::move(invocation));
-  emitInstance.createDiagnostics(&Impl.Instance->getDiagnosticClient(),
+
-                                 false);
+  auto ReusingDiags = Diags == nullptr;
+  if (ReusingDiags) {
+    Diags = &Impl.Instance->getDiagnosticClient();
+  }
+  emitInstance.createDiagnostics(Diags, /*ShouldOwnDiags=*/!ReusingDiags);
 
   clang::FileManager &fileManager = Impl.Instance->getFileManager();
   emitInstance.setFileManager(&fileManager);
@@ -2446,8 +2542,14 @@ void ClangModuleUnit::collectLinkLibraries(
 }
 
 StringRef ClangModuleUnit::getFilename() const {
-  if (!clangModule)
+  if (!clangModule) {
-    return "<imports>";
+    auto SinglePCH = owner.getSinglePCHImport();
+    if (SinglePCH.hasValue()) {
+      return SinglePCH.getValue();
+    } else {
+      return "<imports>";
+    }
+  }
   if (const clang::FileEntry *F = clangModule->getASTFile())
     if (!F->getName().empty())
       return F->getName();

lib/ClangImporter/ImporterImpl.h

@@ -29,6 +29,7 @@
 #include "swift/AST/Type.h"
 #include "swift/AST/ForeignErrorConvention.h"
 #include "swift/Basic/StringExtras.h"
+#include "swift/Strings.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclVisitor.h"
 #include "clang/Basic/IdentifierTable.h"
@@ -40,6 +41,7 @@
 #include "llvm/ADT/SmallBitVector.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/TinyPtrVector.h"
+#include "llvm/Support/Path.h"
 #include <set>
 
 namespace llvm {
@@ -386,6 +388,10 @@ public:
   llvm::DenseMap<std::pair<ObjCSelector, char>, unsigned>
     ActiveSelectors;
 
+  clang::CompilerInstance *getClangInstance() {
+    return Instance.get();
+  }
+
 private:
   /// \brief Generation number that is used for crude versioning.
   ///
@@ -532,6 +538,11 @@ private:
   /// after having set up a suitable Clang instance.
   std::unique_ptr<importer::NameImporter> nameImporter = nullptr;
 
+  /// If there is a single .PCH file imported into the __ObjC module, this
+  /// is the filename of that PCH. When other files are imported, this should
+  /// be llvm::None.
+  Optional<std::string> SinglePCHImport = None;
+
 public:
   importer::NameImporter &getNameImporter() {
     assert(nameImporter && "haven't finished initialization");
@@ -1158,6 +1169,22 @@ public:
 
   /// Dump the Swift-specific name lookup tables we generate.
   void dumpSwiftLookupTables();
+
+  void setSinglePCHImport(Optional<std::string> PCHFilename) {
+    if (PCHFilename.hasValue()) {
+      assert(llvm::sys::path::extension(PCHFilename.getValue())
+                 .endswith(PCH_EXTENSION) &&
+             "Single PCH imported filename doesn't have .pch extension!");
+    }
+    SinglePCHImport = PCHFilename;
+  }
+
+  /// If there was is a single .pch bridging header without other imported
+  /// files, we can provide the PCH filename for declaration caching,
+  /// especially in code completion. If there are other
+  Optional<std::string> getSinglePCHImport() const {
+    return SinglePCHImport;
+  }
 };
 
 namespace importer {

lib/Frontend/CompilerInvocation.cpp

@@ -1583,7 +1583,6 @@ bool CompilerInvocation::parseArgs(ArrayRef<const char *> Args,
   return false;
 }
 
-
 serialization::Status
 CompilerInvocation::loadFromSerializedAST(StringRef data) {
   serialization::ExtendedValidationInfo extendedInfo;

lib/Frontend/Frontend.cpp

@@ -27,6 +27,7 @@
 #include "swift/Parse/Lexer.h"
 #include "swift/SIL/SILModule.h"
 #include "swift/Serialization/SerializedModuleLoader.h"
+#include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Support/CommandLine.h"
@@ -35,6 +36,22 @@
 
 using namespace swift;
 
+std::string CompilerInvocation::getPCHHash() const {
+  using llvm::hash_code;
+  using llvm::hash_value;
+  using llvm::hash_combine;
+
+  auto Code = hash_value(LangOpts.getPCHHashComponents());
+  Code = hash_combine(Code, FrontendOpts.getPCHHashComponents());
+  Code = hash_combine(Code, ClangImporterOpts.getPCHHashComponents());
+  Code = hash_combine(Code, SearchPathOpts.getPCHHashComponents());
+  Code = hash_combine(Code, DiagnosticOpts.getPCHHashComponents());
+  Code = hash_combine(Code, SILOpts.getPCHHashComponents());
+  Code = hash_combine(Code, IRGenOpts.getPCHHashComponents());
+
+  return llvm::APInt(64, Code).toString(36, /*Signed=*/false);
+}
+
 void CompilerInstance::createSILModule(bool WholeModule) {
   assert(MainModule && "main module not created yet");
   TheSILModule = SILModule::createEmptyModule(getMainModule(),
@@ -103,6 +120,7 @@ bool CompilerInstance::setup(const CompilerInvocation &Invok) {
   // knowledge.
   auto clangImporter =
     ClangImporter::create(*Context, Invocation.getClangImporterOptions(),
+                          Invocation.getPCHHash(),
                           DepTracker);
   if (!clangImporter) {
     Diagnostics.diagnose(SourceLoc(), diag::error_clang_importer_create_fail);

lib/FrontendTool/FrontendTool.cpp

@@ -367,7 +367,8 @@ static bool performCompile(std::unique_ptr<CompilerInstance> &Instance,
     auto clangImporter = static_cast<ClangImporter *>(
       Instance->getASTContext().getClangModuleLoader());
     return clangImporter->emitBridgingPCH(
-      Invocation.getInputFilenames()[0], opts.getSingleOutputFilename());
+      Invocation.getInputFilenames()[0],
+      opts.getSingleOutputFilename());
   }
 
   IRGenOptions &IRGenOpts = Invocation.getIRGenOptions();

test/IDE/complete_with_header_import.swift

@@ -1,5 +1,9 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=TOP -import-objc-header %S/Inputs/header.h | %FileCheck %s -check-prefix=CHECK-TOP
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=TYPE -import-objc-header %S/Inputs/header.h | %FileCheck %s -check-prefix=CHECK-TYPE
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: %target-swift-ide-test -code-completion -pch-output-dir %t -source-filename %s -code-completion-token=TOP -import-objc-header %S/Inputs/header.h | %FileCheck %s -check-prefix=CHECK-TOP
+// RUN: %target-swift-ide-test -code-completion -pch-output-dir %t -source-filename %s -code-completion-token=TYPE -import-objc-header %S/Inputs/header.h | %FileCheck %s -check-prefix=CHECK-TYPE
+// RUN: stat %t/*.pch
 
 // REQUIRES: objc_interop
 

test/SourceKit/Mixed/complete_twice_bridging_header.swift

@@ -0,0 +1,13 @@
+// REQUIRES: objc_interop
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: %sourcekitd-test -req=complete -pos=8:5 %s -- %s -module-name Mixed -pch-output-dir %t -import-objc-header %S/Inputs/header.h == -req=complete -pos=8:5 %s -- %s -module-name Mixed -pch-output-dir %t -import-objc-header %S/Inputs/header.h | %FileCheck %s --check-prefix=CHECK-MEMBERS
+// RUN: %sourcekitd-test -req=complete -pos=9:1 %s -- %s -module-name Mixed -pch-output-dir %t -import-objc-header %S/Inputs/header.h == -req=complete -pos=9:1 %s -- %s -module-name Mixed -pch-output-dir %t -import-objc-header %S/Inputs/header.h | %FileCheck %s --check-prefix=CHECK-GLOBALS
+// RUN: stat %t/*.pch
+
+func foo(x: BaseInHead) {
+  x.
+}
+
+// CHECK-GLOBALS: doSomethingInHead(:)
+// CHECK-GLOBALS: test1(:)
+// CHECK-MEMBERS: doIt(:)

test/SourceKit/Mixed/cursor_mixed_header.swift

@@ -10,6 +10,10 @@ func test(_ b : BaseInHead) {
 
 // RUN: %sourcekitd-test -req=cursor -pos=3:7 %s -- %s %mcp_opt -module-name Mixed -import-objc-header %S/Inputs/header.h | %FileCheck %s
 
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: %sourcekitd-test -req=cursor -pos=3:7 %s -- %s %mcp_opt -module-name Mixed -pch-output-dir %t -import-objc-header %S/Inputs/header.h | %FileCheck %s
+// RUN: stat %t/*.pch
+
 // CHECK: source.lang.swift.ref.function.method.instance ({{.*}}Inputs/header.h:4:9-4:23)
 // CHECK: doIt(_:)
 // CHECK: c:objc(cs)BaseInHead(im)doIt:

tools/SourceKit/tools/sourcekitd/bin/XPC/Client/sourcekitd.cpp

@@ -17,6 +17,7 @@
 
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Mutex.h"
+#include "llvm/Support/TargetSelect.h"
 #include <chrono>
 #include <xpc/xpc.h>
 #include <dispatch/dispatch.h>
@@ -250,6 +251,11 @@ static void handleInterruptedConnection(xpc_object_t event, xpc_connection_t con
 void sourcekitd::initialize() {
   initializeTracing();
 
+  llvm::InitializeAllTargets();
+  llvm::InitializeAllTargetMCs();
+  llvm::InitializeAllAsmPrinters();
+  llvm::InitializeAllAsmParsers();
+
   assert(!GlobalConn);
   GlobalConn = xpc_connection_create(SOURCEKIT_XPCSERVICE_IDENTIFIER, nullptr);
 

tools/SourceKit/tools/sourcekitd/lib/API/Requests.cpp

@@ -35,6 +35,7 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/TargetSelect.h"
 #include <mutex>
 
 // FIXME: Portability.
@@ -149,6 +150,11 @@ static void onDocumentUpdateNotification(StringRef DocumentName) {
 static SourceKit::Context *GlobalCtx = nullptr;
 
 void sourcekitd::initialize() {
+  llvm::InitializeAllTargets();
+  llvm::InitializeAllTargetMCs();
+  llvm::InitializeAllAsmPrinters();
+  llvm::InitializeAllAsmParsers();
+
   GlobalCtx = new SourceKit::Context(sourcekitd::getRuntimeLibPath(),
                                      SourceKit::createSwiftLangSupport);
   GlobalCtx->getNotificationCenter().addDocumentUpdateNotificationReceiver(

tools/driver/modulewrap_main.cpp

@@ -168,7 +168,7 @@ int modulewrap_main(ArrayRef<const char *> Args, const char *Argv0,
   LangOpts.Target = Invocation.getTargetTriple();
   ASTContext ASTCtx(LangOpts, SearchPathOpts, SrcMgr, Instance.getDiags());
   ClangImporterOptions ClangImporterOpts;
-  ASTCtx.addModuleLoader(ClangImporter::create(ASTCtx, ClangImporterOpts),
+  ASTCtx.addModuleLoader(ClangImporter::create(ASTCtx, ClangImporterOpts, ""),
                          true);
   ModuleDecl *M = ModuleDecl::create(ASTCtx.getIdentifier("swiftmodule"), ASTCtx);
   SILOptions SILOpts;

tools/swift-ide-test/swift-ide-test.cpp

@@ -243,6 +243,10 @@ SwiftVersion("swift-version", llvm::cl::desc("Swift version"));
 static llvm::cl::opt<std::string>
 ModuleCachePath("module-cache-path", llvm::cl::desc("Clang module cache path"));
 
+static llvm::cl::opt<std::string>
+PCHOutputDir("pch-output-dir", llvm::cl::desc("place autogenerated PCH files in this directory"));
+
+
 static llvm::cl::opt<std::string>
     CompletionCachePath("completion-cache-path",
                         llvm::cl::desc("Code completion cache path"),
@@ -599,6 +603,7 @@ static int doCodeCompletion(const CompilerInvocation &InitInvok,
                << " at offset " << CodeCompletionOffset << "\n";
 
   CompilerInvocation Invocation(InitInvok);
+
   Invocation.setCodeCompletionPoint(CleanFile.get(), CodeCompletionOffset);
 
 
@@ -2973,6 +2978,8 @@ int main(int argc, char *argv[]) {
   }
   InitInvok.getClangImporterOptions().ModuleCachePath =
     options::ModuleCachePath;
+  InitInvok.getClangImporterOptions().PrecompiledHeaderOutputDir =
+    options::PCHOutputDir;
   InitInvok.setImportSearchPaths(options::ImportPaths);
   std::vector<SearchPathOptions::FrameworkSearchPath> FramePaths;
   for (const auto &path : options::FrameworkPaths) {
@@ -2986,6 +2993,8 @@ int main(int argc, char *argv[]) {
     options::EnableSourceImport;
   InitInvok.getFrontendOptions().ImplicitObjCHeaderPath =
     options::ImportObjCHeader;
+  InitInvok.getClangImporterOptions().BridgingHeader =
+    options::ImportObjCHeader;
   InitInvok.getLangOptions().EnableAccessControl =
     !options::DisableAccessControl;
   InitInvok.getLangOptions().CodeCompleteInitsInPostfixExpr |=

unittests/SourceKit/SwiftLang/CursorInfoTest.cpp

@@ -17,6 +17,7 @@
 #include "SourceKit/SwiftLang/Factory.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/TargetSelect.h"
 #include "gtest/gtest.h"
 
 using namespace SourceKit;
@@ -102,6 +103,10 @@ public:
   LangSupport &getLang() { return Ctx.getSwiftLangSupport(); }
 
   void SetUp() {
+    llvm::InitializeAllTargets();
+    llvm::InitializeAllTargetMCs();
+    llvm::InitializeAllAsmPrinters();
+    llvm::InitializeAllAsmParsers();
     NumTasks = 0;
   }