Patch to optimize away copy constructor call when
appropriate.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@78267 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGCXX.cpp b/lib/CodeGen/CGCXX.cpp
index 5324cc6..0f76266 100644
--- a/lib/CodeGen/CGCXX.cpp
+++ b/lib/CodeGen/CGCXX.cpp
@@ -255,7 +255,20 @@
cast<CXXRecordDecl>(E->getType()->getAs<RecordType>()->getDecl());
if (RD->hasTrivialConstructor())
return;
-
+
+ // Code gen optimization to eliminate copy constructor and return
+ // its first argument instead.
+ const CXXConstructorDecl *CDecl = E->getConstructor();
+ if (E->getNumArgs() == 1 &&
+ CDecl->isCopyConstructor(getContext())) {
+ CXXConstructExpr::const_arg_iterator i = E->arg_begin();
+ const Expr *SubExpr = (*i);
+ // FIXME. Any other cases can be optimized away?
+ if (isa<CallExpr>(SubExpr) || isa<CXXTemporaryObjectExpr>(SubExpr)) {
+ EmitAggExpr(SubExpr, Dest, false);
+ return;
+ }
+ }
// Call the constructor.
EmitCXXConstructorCall(E->getConstructor(), Ctor_Complete, Dest,
E->arg_begin(), E->arg_end());