Lazy deserialization of function bodies for PCH files. For the Carbon

"Hello, World!", this takes us from deserializing 6469
statements/expressions down to deserializing 1
statement/expression. It only translated into a 1% improvement on the
Carbon-prefixed 403.gcc, but (a) it's the right thing to do, and (b)
we expect this to matter more once we lazily deserialize identifiers.

llvm-svn: 69407

1 files changed, 10 insertions, 1 deletions

diff --git a/clang/lib/Frontend/PCHReader.cpp b/clang/lib/Frontend/PCHReader.cpp
index 5ea1f7c6c22..dc8d3fce34f 100644
--- a/clang/lib/Frontend/PCHReader.cpp
+++ b/clang/lib/Frontend/PCHReader.cpp
@@ -140,7 +140,7 @@ void PCHDeclReader::VisitEnumConstantDecl(EnumConstantDecl *ECD) {
 void PCHDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
   VisitValueDecl(FD);
   if (Record[Idx++])
-    FD->setBody(cast<CompoundStmt>(Reader.ReadStmt()));
+    FD->setLazyBody(Reader.getStream().GetCurrentBitNo());
   FD->setPreviousDeclaration(
                    cast_or_null<FunctionDecl>(Reader.GetDecl(Record[Idx++])));
   FD->setStorageClass((FunctionDecl::StorageClass)Record[Idx++]);
@@ -1880,6 +1880,15 @@ Decl *PCHReader::GetDecl(pch::DeclID ID) {
   return ReadDeclRecord(DeclOffsets[Index], Index);
 }
 
+Stmt *PCHReader::GetStmt(uint64_t Offset) {
+  // Keep track of where we are in the stream, then jump back there
+  // after reading this declaration.
+  SavedStreamPosition SavedPosition(Stream);
+
+  Stream.JumpToBit(Offset);
+  return ReadStmt();
+}
+
 bool PCHReader::ReadDeclsLexicallyInContext(DeclContext *DC,
                                   llvm::SmallVectorImpl<pch::DeclID> &Decls) {
   assert(DC->hasExternalLexicalStorage() &&