Fix fast-path test to work with subclasses correctly.

dtable.c

@@ -51,26 +51,25 @@ static void checkARCAccessors(Class cls)
 		autorelease = sel_registerName("autorelease");
 		isARC = sel_registerName("_ARCCompliantRetainRelease");
 	}
-	if (ownsMethod(cls, isARC))
-	{
-		objc_set_class_flag(cls, objc_class_flag_fast_arc);
-		return;
-	}
 	struct objc_slot *slot = objc_get_slot(cls, retain);
 	if (!ownsMethod(slot->owner, isARC))
 	{
 		objc_clear_class_flag(cls, objc_class_flag_fast_arc);
+		return;
 	}
 	slot = objc_get_slot(cls, release);
 	if (!ownsMethod(slot->owner, isARC))
 	{
 		objc_clear_class_flag(cls, objc_class_flag_fast_arc);
+		return;
 	}
 	slot = objc_get_slot(cls, autorelease);
 	if (!ownsMethod(slot->owner, isARC))
 	{
 		objc_clear_class_flag(cls, objc_class_flag_fast_arc);
+		return;
 	}
+	objc_set_class_flag(cls, objc_class_flag_fast_arc);
 }
 
 static void collectMethodsForMethodListToSparseArray(