src/share/vm/opto/library_call.cpp

rev 3081 : 7143491: G1 C2 CTW: assert(p2x->outcnt() == 2) failed: expects 2 users: Xor and URShift nodes
Summary: Adjust the assert and code in eliminate_card_mark() method for case when stored value is NULL.
Reviewed-by: iveresov

*** 2676,2686 ****
      break;
    case T_LONG:
      cas = _gvn.transform(new (C, 5) CompareAndSwapLNode(control(), mem, adr, newval, oldval));
      break;
    case T_OBJECT:
!      // reference stores need a store barrier.
      // (They don't if CAS fails, but it isn't worth checking.)
      pre_barrier(true /* do_load*/,
                  control(), base, adr, alias_idx, newval, value_type->make_oopptr(),
                  NULL /* pre_val*/,
                  T_OBJECT);
--- 2676,2692 ----
      break;
    case T_LONG:
      cas = _gvn.transform(new (C, 5) CompareAndSwapLNode(control(), mem, adr, newval, oldval));
      break;
    case T_OBJECT:
!     // Transformation of a value which could be NULL pointer (CastPP #NULL)
!     // could be delayed during Parse (for example, in adjust_map_after_if()).
!     // Execute transformation here to avoid barrier generation in such case.
!     if (_gvn.type(newval) == TypePtr::NULL_PTR)
!       newval = _gvn.makecon(TypePtr::NULL_PTR);
! 
!     // Reference stores need a store barrier.
      // (They don't if CAS fails, but it isn't worth checking.)
      pre_barrier(true /* do_load*/,
                  control(), base, adr, alias_idx, newval, value_type->make_oopptr(),
                  NULL /* pre_val*/,
                  T_OBJECT);