[Bridging PCH] Add ClangImporter::importBridgingPCH, call for .pch files.

Author: graydon

include/swift/ClangImporter/ClangImporter.h

@@ -209,6 +209,19 @@ class ClangImporter final : public ClangModuleLoader {
                             SourceLoc diagLoc = {},
                             bool trackParsedSymbols = false);
 
+  /// Imports an Objective-C PCH file into the shared imported header module.
+  ///
+  /// This is the "PCH variant" of importBridgingHeader; the provided PCH
+  /// needs to have been previously generated by emitBridgingPCH.
+  ///
+  /// \param pchFile The path of the PCH file to import.
+  /// \param adapter The module that depends on the contents of this header.
+  /// \param diagLoc A location to attach any diagnostics to if import fails.
+  ///
+  /// \sa importBridgingHeader
+  bool importBridgingPCH(StringRef pchFile, ModuleDecl *adapter,
+                         SourceLoc diagLoc = {});
+
   /// Returns the module that contains imports and declarations from all loaded
   /// Objective-C header files.
   ///

include/swift/ClangImporter/ClangImporterOptions.h

@@ -35,6 +35,9 @@ class ClangImporterOptions {
   /// Equivalent to Clang's -mcpu=.
   std::string TargetCPU;
 
+  // The bridging header or PCH that will be imported.
+  std::string BridgingHeader;
+
   /// \see Mode
   enum class Modes {
     /// Set up Clang for importing modules into Swift and generating IR from

lib/ClangImporter/ClangImporter.cpp

@@ -35,6 +35,7 @@
 #include "swift/Parse/Lexer.h"
 #include "swift/Parse/Parser.h"
 #include "swift/Config.h"
+#include "swift/Strings.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Mangle.h"
 #include "clang/Basic/CharInfo.h"
@@ -719,6 +720,15 @@ ClangImporter::create(ASTContext &ctx,
   auto ppTracker = llvm::make_unique<BridgingPPTracker>(importer->Impl);
   clangPP.addPPCallbacks(std::move(ppTracker));
 
+  // If we're going to load a bridging PCH, we need to know this now in order to
+  // clobber clangPP's predefined-macros buffer, otherwise it will provide macro
+  // definitions that collide with those in the PCH. This is actually simulating
+  // something clang does when it attaches to a PCH ASTReader as well, it's just
+  // interleaving the steps in an unusual order.
+  if (llvm::sys::path::extension(importerOpts.BridgingHeader).endswith(
+        PCH_EXTENSION))
+    clangPP.setPredefines("");
+
   instance.createModuleManager();
   instance.getModuleManager()->addListener(
          std::unique_ptr<clang::ASTReaderListener>(
@@ -926,6 +936,9 @@ bool ClangImporter::importHeader(StringRef header, Module *adapter,
 bool ClangImporter::importBridgingHeader(StringRef header, Module *adapter,
                                          SourceLoc diagLoc,
                                          bool trackParsedSymbols) {
+  if (llvm::sys::path::extension(header).endswith(PCH_EXTENSION)) {
+    return importBridgingPCH(header, adapter);
+  }
   clang::FileManager &fileManager = Impl.Instance->getFileManager();
   const clang::FileEntry *headerFile = fileManager.getFile(header,
                                                            /*OpenFile=*/true);
@@ -948,6 +961,29 @@ bool ClangImporter::importBridgingHeader(StringRef header, Module *adapter,
                            std::move(sourceBuffer));
 }
 
+bool ClangImporter::importBridgingPCH(StringRef pchFile, ModuleDecl *adapter,
+                                      SourceLoc diagLoc)
+{
+  clang::ASTReader &R = *Impl.Instance->getModuleManager();
+  SmallVector<clang::ASTReader::ImportedSubmodule, 2> Imports;
+  switch (R.ReadAST(pchFile, clang::serialization::MK_PCH,
+                    clang::SourceLocation(), 0, &Imports)) {
+  case clang::ASTReader::Success:
+    Impl.ImportedHeaderOwners.push_back(adapter);
+    for (auto I : Imports) {
+      clang::Module *CM = R.getSubmodule(I.ID);
+      assert(CM);
+      Impl.getClangPreprocessor().makeModuleVisible(CM, I.ImportLoc);
+      R.makeModuleVisible(CM, clang::Module::AllVisible, I.ImportLoc);
+      Module *M = Impl.finishLoadingClangModule(*this, CM, /*adapter=*/true);
+      Impl.ImportedHeaderExports.push_back({ /*filter=*/{}, M });
+    }
+    return false;
+  default:
+    return true;
+  }
+}
+
 std::string ClangImporter::getBridgingHeaderContents(StringRef headerPath,
                                                      off_t &fileSize,
                                                      time_t &fileModTime) {

lib/Frontend/CompilerInvocation.cpp

@@ -766,7 +766,7 @@ static bool ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
   Opts.ImportUnderlyingModule |= Args.hasArg(OPT_import_underlying_module);
   Opts.SILSerializeAll |= Args.hasArg(OPT_sil_serialize_all);
 
-  if (const Arg *A = Args.getLastArg(OPT_import_objc_header)) {
+  if (const Arg *A = Args.getLastArgNoClaim(OPT_import_objc_header)) {
     Opts.ImplicitObjCHeaderPath = A->getValue();
     Opts.SerializeBridgingHeader |=
       !Opts.PrimaryInput && !Opts.ModuleOutputPath.empty();
@@ -993,7 +993,8 @@ static bool ParseClangImporterArgs(ClangImporterOptions &Opts,
 
   if (Args.hasArg(OPT_embed_bitcode))
     Opts.Mode = ClangImporterOptions::Modes::EmbedBitcode;
-
+  if (auto *A = Args.getLastArg(OPT_import_objc_header))
+    Opts.BridgingHeader = A->getValue();
   Opts.DisableSwiftBridgeAttr |= Args.hasArg(OPT_disable_swift_bridge_attr);
 
   Opts.DisableModulesValidateSystemHeaders |= Args.hasArg(OPT_disable_modules_validate_system_headers);