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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@258962 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 0 deletions

diff --git a/include/clang/Basic/ObjCRuntime.h b/include/clang/Basic/ObjCRuntime.h
index cf51b146b1..6975b6c9bb 100644
--- a/include/clang/Basic/ObjCRuntime.h
+++ b/include/clang/Basic/ObjCRuntime.h
@@ -308,6 +308,23 @@ public:
     }
   }
 
+  /// Is objc_unsafeClaimAutoreleasedReturnValue available?
+  bool hasARCUnsafeClaimAutoreleasedReturnValue() const {
+    switch (getKind()) {
+    case MacOSX:
+      return getVersion() >= VersionTuple(10, 11);
+    case iOS:
+      return getVersion() >= VersionTuple(9);
+    case WatchOS:
+      return getVersion() >= VersionTuple(2);
+    case GNUstep:
+      return false;
+
+    default:
+      return false;
+    }
+  }
+
   /// \brief Try to parse an Objective-C runtime specification from the given
   /// string.
   ///