src/share/vm/opto/ifg.cpp

*** 525,534 ****
--- 525,550 ----
   */
  bool PhaseChaitin::remove_node_if_not_used(Block* b, uint location, Node* n, uint lid, IndexSet* liveout) {
    Node* def = n->in(0);
    if (!n->is_Proj() ||
        (_lrg_map.live_range_id(def) && !liveout->member(_lrg_map.live_range_id(def)))) {
+     if (n->is_MachProj()) {
+       // Don't remove KILL projections if their "defining" nodes have
+       // memory effects (have SCMemProj projection node) -
+       // they are not dead even when their result is not used.
+       // For example, compareAndSwapL (and other CAS) and EncodeISOArray nodes.
+       // The method add_input_to_liveout() keeps such nodes alive (put them on liveout list)
+       // when it sees SCMemProj node in a block. Unfortunately SCMemProj node could be placed
+       // in block in such order that KILL MachProj nodes are processed first.
+       uint cnt = def->outcnt();
+       for (uint i = 0; i < cnt; i++) {
+         Node* proj = def->raw_out(i);
+         if (proj->Opcode() == Op_SCMemProj) {
+           return false;
+         }
+       }
+     }
      b->remove_node(location);
      LRG& lrg = lrgs(lid);
      if (lrg._def == n) {
        lrg._def = 0;
      }