Implement semantic analysis and an AST representation for the named

return value optimization. Sema marks return statements with their
NRVO candidates (which may or may not end up using the NRVO), then, at
the end of a function body, computes and marks those variables that
can be allocated into the return slot.

I've checked this locally with some debugging statements (not
committed), but there won't be any tests until CodeGen comes along.

llvm-svn: 103865

4 files changed, 5 insertions, 0 deletions

diff --git a/clang/lib/Frontend/PCHReaderDecl.cpp b/clang/lib/Frontend/PCHReaderDecl.cpp
index 3f91d0cafb7..49010bf0d6d 100644
--- a/clang/lib/Frontend/PCHReaderDecl.cpp
+++ b/clang/lib/Frontend/PCHReaderDecl.cpp
@@ -435,6 +435,7 @@ void PCHDeclReader::VisitVarDecl(VarDecl *VD) {
   VD->setCXXDirectInitializer(Record[Idx++]);
   VD->setDeclaredInCondition(Record[Idx++]);
   VD->setExceptionVariable(Record[Idx++]);
+  VD->setNRVOVariable(Record[Idx++]);
   VD->setPreviousDeclaration(
                          cast_or_null<VarDecl>(Reader.GetDecl(Record[Idx++])));
   if (Record[Idx++])
diff --git a/clang/lib/Frontend/PCHReaderStmt.cpp b/clang/lib/Frontend/PCHReaderStmt.cpp
index 7595d03a15f..3931adbe8f2 100644
--- a/clang/lib/Frontend/PCHReaderStmt.cpp
+++ b/clang/lib/Frontend/PCHReaderStmt.cpp
@@ -291,6 +291,7 @@ unsigned PCHStmtReader::VisitReturnStmt(ReturnStmt *S) {
   VisitStmt(S);
   S->setRetValue(cast_or_null<Expr>(StmtStack.back()));
   S->setReturnLoc(SourceLocation::getFromRawEncoding(Record[Idx++]));
+  S->setNRVOCandidate(cast_or_null<VarDecl>(Reader.GetDecl(Record[Idx++])));
   return 1;
 }
 
diff --git a/clang/lib/Frontend/PCHWriterDecl.cpp b/clang/lib/Frontend/PCHWriterDecl.cpp
index 28a10ad6b0a..cc58e8ee465 100644
--- a/clang/lib/Frontend/PCHWriterDecl.cpp
+++ b/clang/lib/Frontend/PCHWriterDecl.cpp
@@ -415,6 +415,7 @@ void PCHDeclWriter::VisitVarDecl(VarDecl *D) {
   Record.push_back(D->hasCXXDirectInitializer());
   Record.push_back(D->isDeclaredInCondition());
   Record.push_back(D->isExceptionVariable());
+  Record.push_back(D->isNRVOVariable());
   Writer.AddDeclRef(D->getPreviousDeclaration(), Record);
   Record.push_back(D->getInit() ? 1 : 0);
   if (D->getInit())
@@ -683,6 +684,7 @@ void PCHWriter::WriteDeclsBlockAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(0));                       // hasCXXDirectInitializer
   Abv->Add(BitCodeAbbrevOp(0));                       // isDeclaredInCondition
   Abv->Add(BitCodeAbbrevOp(0));                       // isExceptionVariable
+  Abv->Add(BitCodeAbbrevOp(0));                       // isNRVOVariable
   Abv->Add(BitCodeAbbrevOp(0));                       // PrevDecl
   Abv->Add(BitCodeAbbrevOp(0));                       // HasInit
   // ParmVarDecl
diff --git a/clang/lib/Frontend/PCHWriterStmt.cpp b/clang/lib/Frontend/PCHWriterStmt.cpp
index a7f73a17fa6..a9ee43527ce 100644
--- a/clang/lib/Frontend/PCHWriterStmt.cpp
+++ b/clang/lib/Frontend/PCHWriterStmt.cpp
@@ -275,6 +275,7 @@ void PCHStmtWriter::VisitReturnStmt(ReturnStmt *S) {
   VisitStmt(S);
   Writer.WriteSubStmt(S->getRetValue());
   Writer.AddSourceLocation(S->getReturnLoc(), Record);
+  Writer.AddDeclRef(S->getNRVOCandidate(), Record);
   Code = pch::STMT_RETURN;
 }