ObjectReference target, int offset,
ObjectReference target, Offset offset,
  public static ObjectReference performWriteInBarrierAtomic(                                           ObjectReference ref, Address slot,                                           ObjectReference target, int offset,                                           int locationMetadata, int mode)    throws InlinePragma {                                    Object obj = ref.toObject();    Object newObject = target.toObject();    Object oldObject;    do {      oldObject = VM_Magic.prepareObject(obj, offset);    } while (!VM_Magic.attemptObject(obj, offset, oldObject, newObject));    return ObjectReference.fromObject(oldObject);   }