message: [grappler] Do not forward inputs to _Retval nodes
diff: @@ -285,6 +285,11 @@ bool ConstantFolding::ForwardInputs(NodeDef* node,
  if (IsControlInput(consumer_input)) {
  break;
  }
  + // It is illegal to add control dependencies to _Retval nodes, so we
  + // can't bypass value producing `node` and forward inputs to `consumer`.
  + if (IsRetval(*consumer)) {
  + break;
  + }
  int output_idx;
  const string input_node_name =
  ParseNodeName(consumer_input, &output_idx);
  