We have a lot places which search for particular user node:

    Node* xorx = NULL;
    for (DUIterator_Fast imax, i = p2x->fast_outs(imax); i < imax; i++) {
      Node* u = p2x->fast_out(i);
      if (u->Opcode() == Op_XorX) {
        xorx = u;
        break;
      }
    }

      for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
        Node *use = n->fast_out(i);
        if (use->Opcode() == Op_SCMemProj) {
          n = use;
          break;
        }
      }

bool LoadStoreNode::result_not_used() const {
  for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
    Node *x = fast_out(i);
    if (x->Opcode() == Op_SCMemProj) continue;
    return false;
  }
  return true;
}

      uint cnt = def->outcnt();
      for (uint i = 0; i < cnt; i++) {
        Node* proj = def->raw_out(i);
        if (proj->Opcode() == Op_SCMemProj) {
          return false;
        }
      }


and so on.

Add new Node* Node::find_user(int opc) method to be used in such cases.