Emit calls to objc_unsafeClaimAutoreleasedReturnValue when

reclaiming a call result in order to ignore it or assign it
to an __unsafe_unretained variable.  This avoids adding
an unwanted retain/release pair when the return value is
not actually returned autoreleased (e.g. when it is returned
from a nonatomic getter or a typical collection accessor).

This runtime function is only available on the latest Apple
OS releases; the backwards-compatibility story is that you
don't get the optimization unless your deployment target is
recent enough.  Sorry.

rdar://20530049

llvm-svn: 258962

1 files changed, 3 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 74087be3..00119c3 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -166,6 +166,9 @@ struct ObjCEntrypoints {
   /// id objc_storeWeak(id*, id);
   llvm::Constant *objc_storeWeak;
 
+  /// id objc_unsafeClaimAutoreleasedReturnValue(id);
+  llvm::Constant *objc_unsafeClaimAutoreleasedReturnValue;
+
   /// A void(void) inline asm to use to mark that the return value of
   /// a call will be immediately retain.
   llvm::InlineAsm *retainAutoreleasedReturnValueMarker;