Implement the C++0x move optimization for Automatic Reference Counting
objects, so that we steal the retain count of a temporary __strong
pointer (zeroing out that temporary), eliding a retain/release
pair. Addresses <rdar://problem/9364932>.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133621 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGObjC.cpp b/lib/CodeGen/CGObjC.cpp
index a43f451..1849dee 100644
--- a/lib/CodeGen/CGObjC.cpp
+++ b/lib/CodeGen/CGObjC.cpp
@@ -2268,6 +2268,31 @@
// ultimate opaque expression.
const llvm::Type *resultType = 0;
+ // If we're loading retained from a __strong xvalue, we can avoid
+ // an extra retain/release pair by zeroing out the source of this
+ // "move" operation.
+ if (e->isXValue() &&
+ e->getType().getObjCLifetime() == Qualifiers::OCL_Strong) {
+ // Emit the lvalue
+ LValue lv = CGF.EmitLValue(e);
+
+ // Load the object pointer and cast it to the appropriate type.
+ QualType exprType = e->getType();
+ llvm::Value *result = CGF.EmitLoadOfLValue(lv, exprType).getScalarVal();
+
+ if (resultType)
+ result = CGF.Builder.CreateBitCast(result, resultType);
+
+ // Set the source pointer to NULL.
+ llvm::Value *null
+ = llvm::ConstantPointerNull::get(
+ cast<llvm::PointerType>(CGF.ConvertType(exprType)));
+ CGF.EmitStoreOfScalar(null, lv.getAddress(), lv.isVolatileQualified(),
+ lv.getAlignment(), exprType);
+
+ return TryEmitResult(result, true);
+ }
+
while (true) {
e = e->IgnoreParens();