JDK-8184795 disables compilation of LF as root if they return a value type. The reason is that the logic in CheckCastPPNode::Ideal() expects values to be returned in registers but if the called method is a lambda form, a value can be returned as an instance. The fix would require the logic in CheckCastPPNode::Ideal() to test if the returned value is a class pointer or not (tagged or not).