src/hotspot/share/oops/oop.inline.hpp

rev 52211 : [mq]: 8212753-improve-forward-to-atomic

*** 368,397 ****
    markOop m = markOopDesc::encode_pointer_as_mark(p);
    assert(m->decode_pointer() == p, "encoding must be reversable");
    return cas_set_mark_raw(m, compare, order) == compare;
  }
  
! oop oopDesc::forward_to_atomic(oop p, atomic_memory_order order) {
!   markOop oldMark = mark_raw();
!   markOop forwardPtrMark = markOopDesc::encode_pointer_as_mark(p);
!   markOop curMark;
! 
!   assert(forwardPtrMark->decode_pointer() == p, "encoding must be reversable");
!   assert(sizeof(markOop) == sizeof(intptr_t), "CAS below requires this.");
! 
!   while (!oldMark->is_marked()) {
!     curMark = cas_set_mark_raw(forwardPtrMark, oldMark, order);
!     assert(is_forwarded(), "object should have been forwarded");
!     if (curMark == oldMark) {
        return NULL;
      }
-     // If the CAS was unsuccessful then curMark->is_marked()
-     // should return true as another thread has CAS'd in another
-     // forwarding pointer.
-     oldMark = curMark;
-   }
-   return forwardee();
  }
  
  // Note that the forwardee is not the same thing as the displaced_mark.
  // The forwardee is used when copying during scavenge and mark-sweep.
  // It does need to clear the low two locking- and GC-related bits.
--- 368,390 ----
    markOop m = markOopDesc::encode_pointer_as_mark(p);
    assert(m->decode_pointer() == p, "encoding must be reversable");
    return cas_set_mark_raw(m, compare, order) == compare;
  }
  
! oop oopDesc::forward_to_atomic(oop p, markOop compare, atomic_memory_order order) {
!   assert(UseConcMarkSweepGC || check_obj_alignment(p),
!          "forwarding to something not aligned");
!   assert(UseConcMarkSweepGC || Universe::heap()->is_in_reserved(p),
!          "forwarding to something not in heap");
!   markOop m = markOopDesc::encode_pointer_as_mark(p);
!   assert(m->decode_pointer() == p, "encoding must be reversable");
!   markOop old_mark = cas_set_mark_raw(m, compare, order);
!   if (old_mark == compare) {
      return NULL;
+   } else {
+     return (oop)old_mark->decode_pointer();
    }
  }
  
  // Note that the forwardee is not the same thing as the displaced_mark.
  // The forwardee is used when copying during scavenge and mark-sweep.
  // It does need to clear the low two locking- and GC-related bits.