if (OPT_IR.SANITY_CHECK) VM.assert(bb.next == null); if (OPT_IR.SANITY_CHECK) VM.assert(bb.prev == null);
if (OPT_IR.SANITY_CHECK) VM._assert(bb.next == null); if (OPT_IR.SANITY_CHECK) VM._assert(bb.prev == null);
  void addLastInCodeOrder(OPT_BasicBlock bb) {    if (OPT_IR.SANITY_CHECK) VM.assert(bb.next == null);    if (OPT_IR.SANITY_CHECK) VM.assert(bb.prev == null);    if (_firstNode == null) {      _firstNode = bb;      _lastNode = bb;    } else {      _lastNode.append(bb);      _lastNode = bb;    }  }