Merge pull request swiftlang#819 from al45tair/eng/PR-123945799

Remove objc_retainAutoreleasedReturnValue workaround.

Author: al45tair

src/swift/CMakeLists.txt

@@ -1,16 +1,3 @@
-
-# NOTE(compnerd) Today regardless of whether or not ObjC interop is enabled,
-# swift will use an autoreleased return value convention for certain CF
-# functions (including some that are used/related to dispatch). This means that
-# the swift compiler in callers to such functions will call the function, and
-# then pass the result of the function to objc_retainAutoreleasedReturnValue. In
-# a context where we have ObjC interop disabled, we do not have access to the
-# objc runtime so an implementation of objc_retainAutoreleasedReturnValue is not
-# available. To work around this, we provide a shim for
-# objc_retainAutoreleasedReturnValue in DispatchStubs.cc that just calls retain
-# on the object. Once we fix the swift compiler to switch to a different model
-# for handling these arguments with objc-interop disabled these shims can be
-# eliminated.
 add_library(DispatchStubs STATIC
   DispatchStubs.cc)
 target_include_directories(DispatchStubs PRIVATE

src/swift/DispatchStubs.cc

@@ -56,40 +56,3 @@ static void _dispatch_overlay_constructor() {
 }
 
 #endif /* USE_OBJC */
-
-#if !USE_OBJC
-DISPATCH_RUNTIME_STDLIB_INTERFACE
-extern "C" void * objc_retainAutoreleasedReturnValue(void *obj);
-#endif
-
-#if !USE_OBJC
-
-// For CF functions with 'Get' semantics, the compiler currently assumes that
-// the result is autoreleased and must be retained. It does so on all platforms
-// by emitting a call to objc_retainAutoreleasedReturnValue. On Darwin, this is
-// implemented by the ObjC runtime. On non-ObjC platforms, there is no runtime,
-// and therefore we have to stub it out here ourselves. The compiler will
-// eventually call swift_release to balance the retain below. This is a
-// workaround until the compiler no longer emits this callout on non-ObjC
-// platforms.
-extern "C"
-#if defined(_WIN32)
-__declspec(dllimport)
-#endif
-void swift_retain(void *);
-
-DISPATCH_RUNTIME_STDLIB_INTERFACE
-extern "C" void * objc_retainAutoreleasedReturnValue(void *obj) {
-    if (obj) {
-        swift_retain(obj);
-        return obj;
-    }
-    else return NULL;
-}
-
-#if defined(_WIN32)
-extern "C" void *(*__imp_objc_retainAutoreleasedReturnValue)(void *) =
-    &objc_retainAutoreleasedReturnValue;
-#endif
-
-#endif // !USE_OBJC