1 files changed, 41 insertions, 19 deletions

diff --git a/lib/Frontend/PrecompiledPreamble.cpp b/lib/Frontend/PrecompiledPreamble.cpp
index 7e1323fd83bb9..30ae2db26d862 100644
--- a/lib/Frontend/PrecompiledPreamble.cpp
+++ b/lib/Frontend/PrecompiledPreamble.cpp
@@ -40,7 +40,7 @@ namespace {
 StringRef getInMemoryPreamblePath() {
 #if defined(LLVM_ON_UNIX)
   return "/__clang_tmp/___clang_inmemory_preamble___";
-#elif defined(LLVM_ON_WIN32)
+#elif defined(_WIN32)
   return "C:\\__clang_tmp\\___clang_inmemory_preamble___";
 #else
 #warning "Unknown platform. Defaulting to UNIX-style paths for in-memory PCHs"
@@ -63,6 +63,16 @@ createVFSOverlayForPreamblePCH(StringRef PCHFilename,
   return Overlay;
 }
 
+class PreambleDependencyCollector : public DependencyCollector {
+public:
+  // We want to collect all dependencies for correctness. Avoiding the real
+  // system dependencies (e.g. stl from /usr/lib) would probably be a good idea,
+  // but there is no way to distinguish between those and the ones that can be
+  // spuriously added by '-isystem' (e.g. to suppress warnings from those
+  // headers).
+  bool needSystemDependencies() override { return true; }
+};
+
 /// Keeps a track of files to be deleted in destructor.
 class TemporaryFiles {
 public:
@@ -303,8 +313,6 @@ llvm::ErrorOr<PrecompiledPreamble> PrecompiledPreamble::Build(
 
   VFS =
       createVFSFromCompilerInvocation(Clang->getInvocation(), Diagnostics, VFS);
-  if (!VFS)
-    return BuildPreambleError::CouldntCreateVFSOverlay;
 
   // Create a file manager object to provide access to and cache the filesystem.
   Clang->setFileManager(new FileManager(Clang->getFileSystemOpts(), VFS));
@@ -313,7 +321,7 @@ llvm::ErrorOr<PrecompiledPreamble> PrecompiledPreamble::Build(
   Clang->setSourceManager(
       new SourceManager(Diagnostics, Clang->getFileManager()));
 
-  auto PreambleDepCollector = std::make_shared<DependencyCollector>();
+  auto PreambleDepCollector = std::make_shared<PreambleDependencyCollector>();
   Clang->addDependencyCollector(PreambleDepCollector);
 
   // Remap the main source file to the preamble buffer.
@@ -485,20 +493,15 @@ bool PrecompiledPreamble::CanReuse(const CompilerInvocation &Invocation,
 void PrecompiledPreamble::AddImplicitPreamble(
     CompilerInvocation &CI, IntrusiveRefCntPtr<vfs::FileSystem> &VFS,
     llvm::MemoryBuffer *MainFileBuffer) const {
-  assert(VFS && "VFS must not be null");
-
-  auto &PreprocessorOpts = CI.getPreprocessorOpts();
-
-  // Remap main file to point to MainFileBuffer.
-  auto MainFilePath = CI.getFrontendOpts().Inputs[0].getFile();
-  PreprocessorOpts.addRemappedFile(MainFilePath, MainFileBuffer);
-
-  // Configure ImpicitPCHInclude.
-  PreprocessorOpts.PrecompiledPreambleBytes.first = PreambleBytes.size();
-  PreprocessorOpts.PrecompiledPreambleBytes.second = PreambleEndsAtStartOfLine;
-  PreprocessorOpts.DisablePCHValidation = true;
+  PreambleBounds Bounds(PreambleBytes.size(), PreambleEndsAtStartOfLine);
+  configurePreamble(Bounds, CI, VFS, MainFileBuffer);
+}
 
-  setupPreambleStorage(Storage, PreprocessorOpts, VFS);
+void PrecompiledPreamble::OverridePreamble(
+    CompilerInvocation &CI, IntrusiveRefCntPtr<vfs::FileSystem> &VFS,
+    llvm::MemoryBuffer *MainFileBuffer) const {
+  auto Bounds = ComputePreambleBounds(*CI.getLangOpts(), MainFileBuffer, 0);
+  configurePreamble(Bounds, CI, VFS, MainFileBuffer);
 }
 
 PrecompiledPreamble::PrecompiledPreamble(
@@ -681,6 +684,27 @@ PrecompiledPreamble::PreambleFileHash::createForMemoryBuffer(
   return Result;
 }
 
+void PrecompiledPreamble::configurePreamble(
+    PreambleBounds Bounds, CompilerInvocation &CI,
+    IntrusiveRefCntPtr<vfs::FileSystem> &VFS,
+    llvm::MemoryBuffer *MainFileBuffer) const {
+  assert(VFS);
+
+  auto &PreprocessorOpts = CI.getPreprocessorOpts();
+
+  // Remap main file to point to MainFileBuffer.
+  auto MainFilePath = CI.getFrontendOpts().Inputs[0].getFile();
+  PreprocessorOpts.addRemappedFile(MainFilePath, MainFileBuffer);
+
+  // Configure ImpicitPCHInclude.
+  PreprocessorOpts.PrecompiledPreambleBytes.first = Bounds.Size;
+  PreprocessorOpts.PrecompiledPreambleBytes.second =
+      Bounds.PreambleEndsAtStartOfLine;
+  PreprocessorOpts.DisablePCHValidation = true;
+
+  setupPreambleStorage(Storage, PreprocessorOpts, VFS);
+}
+
 void PrecompiledPreamble::setupPreambleStorage(
     const PCHStorage &Storage, PreprocessorOptions &PreprocessorOpts,
     IntrusiveRefCntPtr<vfs::FileSystem> &VFS) {
@@ -740,8 +764,6 @@ std::string BuildPreambleErrorCategory::message(int condition) const {
     return "Could not create temporary file for PCH";
   case BuildPreambleError::CouldntCreateTargetInfo:
     return "CreateTargetInfo() return null";
-  case BuildPreambleError::CouldntCreateVFSOverlay:
-    return "Could not create VFS Overlay";
   case BuildPreambleError::BeginSourceFileFailed:
     return "BeginSourceFile() return an error";
   case BuildPreambleError::CouldntEmitPCH: