1393 // Sometimes in intrinsics, we implicitly know an object is not null

  1394 // (there's no actual null check) so we can cast it to not null. In

  1395 // the course of optimizations, the input to the cast can become null.

  1396 // In that case that data path will die and we need the control path

  1397 // to become dead as well to keep the graph consistent. So we have to

  1398 // add a check for null for which one branch can't be taken. It uses

  1399 // an Opaque4 node that will cause the check to be removed after loop

  1400 // opts so the test goes away and the compiled code doesn't execute a

  1401 // useless check.

  1402 Node* GraphKit::must_be_not_null(Node* value, bool do_replace_in_map) {

  1403   Node* chk = _gvn.transform(new CmpPNode(value, null()));

  1404   Node *tst = _gvn.transform(new BoolNode(chk, BoolTest::ne));

  1405   Node* opaq = _gvn.transform(new Opaque4Node(C, tst, intcon(1)));

  1406   IfNode *iff = new IfNode(control(), opaq, PROB_MAX, COUNT_UNKNOWN);

  1407   _gvn.set_type(iff, iff->Value(&_gvn));

  1408   Node *if_f = _gvn.transform(new IfFalseNode(iff));

  1409   Node *frame = _gvn.transform(new ParmNode(C->start(), TypeFunc::FramePtr));

  1410   Node *halt = _gvn.transform(new HaltNode(if_f, frame));

  1411   C->root()->add_req(halt);

  1412   Node *if_t = _gvn.transform(new IfTrueNode(iff));

  1413   set_control(if_t);

  1414   return cast_not_null(value, do_replace_in_map);

  1415 }

  1416