[libclang] Add a flag to create the precompiled preamble on the first parse.

Summary:
The current default is to create the preamble on the first reparse, aka
second parse. This is useful for clients that do not want to block when
opening a file because serializing the preamble takes a bit of time.
However, this makes the reparse much more expensive and that may be on the
critical path as it's the first interaction a user has with the source code.

YouCompleteMe currently optimizes for the first code interaction by parsing
the file twice when loaded. That's just unnecessarily slow and this flag
helps to avoid that.

Reviewers: doug.gregor, klimek

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D15490

llvm-svn: 255635

1 files changed, 19 insertions, 16 deletions

diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 0d5dd536589..e6ba29201f8 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -1725,9 +1725,10 @@ ASTUnit *ASTUnit::LoadFromCompilerInvocationAction(
     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
     IntrusiveRefCntPtr<DiagnosticsEngine> Diags, ASTFrontendAction *Action,
     ASTUnit *Unit, bool Persistent, StringRef ResourceFilesPath,
-    bool OnlyLocalDecls, bool CaptureDiagnostics, bool PrecompilePreamble,
-    bool CacheCodeCompletionResults, bool IncludeBriefCommentsInCodeCompletion,
-    bool UserFilesAreVolatile, std::unique_ptr<ASTUnit> *ErrAST) {
+    bool OnlyLocalDecls, bool CaptureDiagnostics,
+    unsigned PrecompilePreambleAfterNParses, bool CacheCodeCompletionResults,
+    bool IncludeBriefCommentsInCodeCompletion, bool UserFilesAreVolatile,
+    std::unique_ptr<ASTUnit> *ErrAST) {
   assert(CI && "A CompilerInvocation is required");
 
   std::unique_ptr<ASTUnit> OwnAST;
@@ -1746,8 +1747,8 @@ ASTUnit *ASTUnit::LoadFromCompilerInvocationAction(
   }
   AST->OnlyLocalDecls = OnlyLocalDecls;
   AST->CaptureDiagnostics = CaptureDiagnostics;
-  if (PrecompilePreamble)
-    AST->PreambleRebuildCounter = 2;
+  if (PrecompilePreambleAfterNParses > 0)
+    AST->PreambleRebuildCounter = PrecompilePreambleAfterNParses;
   AST->TUKind = Action ? Action->getTranslationUnitKind() : TU_Complete;
   AST->ShouldCacheCodeCompletionResults = CacheCodeCompletionResults;
   AST->IncludeBriefCommentsInCodeCompletion
@@ -1864,7 +1865,7 @@ ASTUnit *ASTUnit::LoadFromCompilerInvocationAction(
 
 bool ASTUnit::LoadFromCompilerInvocation(
     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
-    bool PrecompilePreamble) {
+    unsigned PrecompilePreambleAfterNParses) {
   if (!Invocation)
     return true;
   
@@ -1874,8 +1875,8 @@ bool ASTUnit::LoadFromCompilerInvocation(
   ProcessWarningOptions(getDiagnostics(), Invocation->getDiagnosticOpts());
 
   std::unique_ptr<llvm::MemoryBuffer> OverrideMainBuffer;
-  if (PrecompilePreamble) {
-    PreambleRebuildCounter = 2;
+  if (PrecompilePreambleAfterNParses > 0) {
+    PreambleRebuildCounter = PrecompilePreambleAfterNParses;
     OverrideMainBuffer =
         getMainBufferWithPrecompiledPreamble(PCHContainerOps, *Invocation);
   }
@@ -1894,9 +1895,10 @@ std::unique_ptr<ASTUnit> ASTUnit::LoadFromCompilerInvocation(
     CompilerInvocation *CI,
     std::shared_ptr<PCHContainerOperations> PCHContainerOps,
     IntrusiveRefCntPtr<DiagnosticsEngine> Diags, FileManager *FileMgr,
-    bool OnlyLocalDecls, bool CaptureDiagnostics, bool PrecompilePreamble,
-    TranslationUnitKind TUKind, bool CacheCodeCompletionResults,
-    bool IncludeBriefCommentsInCodeCompletion, bool UserFilesAreVolatile) {
+    bool OnlyLocalDecls, bool CaptureDiagnostics,
+    unsigned PrecompilePreambleAfterNParses, TranslationUnitKind TUKind,
+    bool CacheCodeCompletionResults, bool IncludeBriefCommentsInCodeCompletion,
+    bool UserFilesAreVolatile) {
   // Create the AST unit.
   std::unique_ptr<ASTUnit> AST(new ASTUnit(false));
   ConfigureDiags(Diags, *AST, CaptureDiagnostics);
@@ -1919,7 +1921,8 @@ std::unique_ptr<ASTUnit> ASTUnit::LoadFromCompilerInvocation(
     llvm::CrashRecoveryContextReleaseRefCleanup<DiagnosticsEngine> >
     DiagCleanup(Diags.get());
 
-  if (AST->LoadFromCompilerInvocation(PCHContainerOps, PrecompilePreamble))
+  if (AST->LoadFromCompilerInvocation(PCHContainerOps,
+                                      PrecompilePreambleAfterNParses))
     return nullptr;
   return AST;
 }
@@ -1930,12 +1933,11 @@ ASTUnit *ASTUnit::LoadFromCommandLine(
     IntrusiveRefCntPtr<DiagnosticsEngine> Diags, StringRef ResourceFilesPath,
     bool OnlyLocalDecls, bool CaptureDiagnostics,
     ArrayRef<RemappedFile> RemappedFiles, bool RemappedFilesKeepOriginalName,
-    bool PrecompilePreamble, TranslationUnitKind TUKind,
+    unsigned PrecompilePreambleAfterNParses, TranslationUnitKind TUKind,
     bool CacheCodeCompletionResults, bool IncludeBriefCommentsInCodeCompletion,
     bool AllowPCHWithCompilerErrors, bool SkipFunctionBodies,
     bool UserFilesAreVolatile, bool ForSerialization,
-    llvm::Optional<StringRef> ModuleFormat,
-    std::unique_ptr<ASTUnit> *ErrAST) {
+    llvm::Optional<StringRef> ModuleFormat, std::unique_ptr<ASTUnit> *ErrAST) {
   assert(Diags.get() && "no DiagnosticsEngine was provided");
 
   SmallVector<StoredDiagnostic, 4> StoredDiagnostics;
@@ -2002,7 +2004,8 @@ ASTUnit *ASTUnit::LoadFromCommandLine(
   llvm::CrashRecoveryContextCleanupRegistrar<ASTUnit>
     ASTUnitCleanup(AST.get());
 
-  if (AST->LoadFromCompilerInvocation(PCHContainerOps, PrecompilePreamble)) {
+  if (AST->LoadFromCompilerInvocation(PCHContainerOps,
+                                      PrecompilePreambleAfterNParses)) {
     // Some error occurred, if caller wants to examine diagnostics, pass it the
     // ASTUnit.
     if (ErrAST) {