Modules: Add LangOptions::CacheGeneratedPCH

Add an option to cache the generated PCH in the ModuleCache when
emitting it.  This protects clients that build PCHs and read them in the
same process, allowing them to avoid race conditions between parallel
jobs the same way that Clang's implicit module build system does.

rdar://problem/48740787

llvm-svn: 355950

clang/include/clang/Basic/LangOptions.def

@@ -154,6 +154,7 @@ BENIGN_ENUM_LANGOPT(CompilingModule, CompilingModuleKind, 2, CMK_None,
                     "compiling a module interface")
 BENIGN_LANGOPT(CompilingPCH, 1, 0, "building a pch")
 BENIGN_LANGOPT(BuildingPCHWithObjectFile, 1, 0, "building a pch which has a corresponding object file")
+BENIGN_LANGOPT(CacheGeneratedPCH, 1, 0, "cache generated PCH files in memory")
 COMPATIBLE_LANGOPT(ModulesDeclUse    , 1, 0, "require declaration of module uses")
 BENIGN_LANGOPT(ModulesSearchAll  , 1, 1, "searching even non-imported modules to find unresolved references")
 COMPATIBLE_LANGOPT(ModulesStrictDeclUse, 1, 0, "requiring declaration of module uses and all headers to be in modules")

clang/include/clang/Serialization/ASTWriter.h

@@ -570,7 +570,8 @@ public:
   /// the module but currently is merely a random 32-bit number.
   ASTFileSignature WriteAST(Sema &SemaRef, const std::string &OutputFile,
                             Module *WritingModule, StringRef isysroot,
-                            bool hasErrors = false);
+                            bool hasErrors = false,
+                            bool ShouldCacheASTInMemory = false);
 
   /// Emit a token.
   void AddToken(const Token &Tok, RecordDataImpl &Record);
@@ -974,6 +975,7 @@ class PCHGenerator : public SemaConsumer {
   llvm::BitstreamWriter Stream;
   ASTWriter Writer;
   bool AllowASTWithErrors;
+  bool ShouldCacheASTInMemory;
 
 protected:
   ASTWriter &getWriter() { return Writer; }
@@ -985,7 +987,8 @@ public:
                StringRef OutputFile, StringRef isysroot,
                std::shared_ptr<PCHBuffer> Buffer,
                ArrayRef<std::shared_ptr<ModuleFileExtension>> Extensions,
-               bool AllowASTWithErrors = false, bool IncludeTimestamps = true);
+               bool AllowASTWithErrors = false, bool IncludeTimestamps = true,
+               bool ShouldCacheASTInMemory = false);
   ~PCHGenerator() override;
 
   void InitializeSema(Sema &S) override { SemaPtr = &S; }

clang/lib/Frontend/FrontendActions.cpp

@@ -112,7 +112,7 @@ GeneratePCHAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
       CI.getPreprocessor(), CI.getModuleCache(), OutputFile, Sysroot, Buffer,
       FrontendOpts.ModuleFileExtensions,
       CI.getPreprocessorOpts().AllowPCHWithCompilerErrors,
-      FrontendOpts.IncludeTimestamps));
+      FrontendOpts.IncludeTimestamps, +CI.getLangOpts().CacheGeneratedPCH));
   Consumers.push_back(CI.getPCHContainerWriter().CreatePCHContainerGenerator(
       CI, InFile, OutputFile, std::move(OS), Buffer));
 
@@ -176,6 +176,8 @@ GenerateModuleAction::CreateASTConsumer(CompilerInstance &CI,
       CI.getFrontendOpts().ModuleFileExtensions,
       /*AllowASTWithErrors=*/false,
       /*IncludeTimestamps=*/
+      +CI.getFrontendOpts().BuildingImplicitModule,
+      /*ShouldCacheASTInMemory=*/
       +CI.getFrontendOpts().BuildingImplicitModule));
   Consumers.push_back(CI.getPCHContainerWriter().CreatePCHContainerGenerator(
       CI, InFile, OutputFile, std::move(OS), Buffer));

clang/lib/Serialization/ASTWriter.cpp

@@ -4596,7 +4596,8 @@ time_t ASTWriter::getTimestampForOutput(const FileEntry *E) const {
 ASTFileSignature ASTWriter::WriteAST(Sema &SemaRef,
                                      const std::string &OutputFile,
                                      Module *WritingModule, StringRef isysroot,
-                                     bool hasErrors) {
+                                     bool hasErrors,
+                                     bool ShouldCacheASTInMemory) {
   WritingAST = true;
 
   ASTHasCompilerErrors = hasErrors;
@@ -4620,7 +4621,7 @@ ASTFileSignature ASTWriter::WriteAST(Sema &SemaRef,
   this->BaseDirectory.clear();
 
   WritingAST = false;
-  if (SemaRef.Context.getLangOpts().ImplicitModules && WritingModule) {
+  if (ShouldCacheASTInMemory) {
     // Construct MemoryBuffer and update buffer manager.
     ModuleCache.addBuiltPCM(OutputFile,
                             llvm::MemoryBuffer::getMemBufferCopy(

clang/lib/Serialization/GeneratePCH.cpp

@@ -24,12 +24,14 @@ PCHGenerator::PCHGenerator(
     const Preprocessor &PP, InMemoryModuleCache &ModuleCache,
     StringRef OutputFile, StringRef isysroot, std::shared_ptr<PCHBuffer> Buffer,
     ArrayRef<std::shared_ptr<ModuleFileExtension>> Extensions,
-    bool AllowASTWithErrors, bool IncludeTimestamps)
+    bool AllowASTWithErrors, bool IncludeTimestamps,
+    bool ShouldCacheASTInMemory)
     : PP(PP), OutputFile(OutputFile), isysroot(isysroot.str()),
       SemaPtr(nullptr), Buffer(std::move(Buffer)), Stream(this->Buffer->Data),
       Writer(Stream, this->Buffer->Data, ModuleCache, Extensions,
              IncludeTimestamps),
-      AllowASTWithErrors(AllowASTWithErrors) {
+      AllowASTWithErrors(AllowASTWithErrors),
+      ShouldCacheASTInMemory(ShouldCacheASTInMemory) {
   this->Buffer->IsComplete = false;
 }
 
@@ -61,7 +63,8 @@ void PCHGenerator::HandleTranslationUnit(ASTContext &Ctx) {
       Writer.WriteAST(*SemaPtr, OutputFile, Module, isysroot,
                       // For serialization we are lenient if the errors were
                       // only warn-as-error kind.
-                      PP.getDiagnostics().hasUncompilableErrorOccurred());
+                      PP.getDiagnostics().hasUncompilableErrorOccurred(),
+                      ShouldCacheASTInMemory);
 
   Buffer->IsComplete = true;
 }

clang/unittests/Frontend/FrontendActionTest.cpp

@@ -6,18 +6,20 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Frontend/FrontendAction.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/CompilerInvocation.h"
-#include "clang/Frontend/FrontendAction.h"
 #include "clang/Frontend/FrontendActions.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Sema/Sema.h"
+#include "clang/Serialization/InMemoryModuleCache.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/ToolOutputFile.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -253,4 +255,40 @@ TEST(ASTFrontendAction, ExternalSemaSource) {
   EXPECT_EQ("This is a note", TDC->Note.str().str());
 }
 
+TEST(GeneratePCHFrontendAction, CacheGeneratedPCH) {
+  // Create a temporary file for writing out the PCH that will be cleaned up.
+  int PCHFD;
+  llvm::SmallString<128> PCHFilename;
+  ASSERT_FALSE(
+      llvm::sys::fs::createTemporaryFile("test.h", "pch", PCHFD, PCHFilename));
+  llvm::ToolOutputFile PCHFile(PCHFilename, PCHFD);
+
+  for (bool ShouldCache : {false, true}) {
+    auto Invocation = std::make_shared<CompilerInvocation>();
+    Invocation->getLangOpts()->CacheGeneratedPCH = ShouldCache;
+    Invocation->getPreprocessorOpts().addRemappedFile(
+        "test.h",
+        MemoryBuffer::getMemBuffer("int foo(void) { return 1; }\n").release());
+    Invocation->getFrontendOpts().Inputs.push_back(
+        FrontendInputFile("test.h", InputKind::C));
+    Invocation->getFrontendOpts().OutputFile = StringRef(PCHFilename);
+    Invocation->getFrontendOpts().ProgramAction = frontend::GeneratePCH;
+    Invocation->getTargetOpts().Triple = "x86_64-apple-darwin19.0.0";
+    CompilerInstance Compiler;
+    Compiler.setInvocation(std::move(Invocation));
+    Compiler.createDiagnostics();
+
+    GeneratePCHAction TestAction;
+    ASSERT_TRUE(Compiler.ExecuteAction(TestAction));
+
+    // Check whether the PCH was cached.
+    if (ShouldCache)
+      EXPECT_EQ(InMemoryModuleCache::Final,
+                Compiler.getModuleCache().getPCMState(PCHFilename));
+    else
+      EXPECT_EQ(InMemoryModuleCache::Unknown,
+                Compiler.getModuleCache().getPCMState(PCHFilename));
+  }
+}
+
 } // anonymous namespace