// old_ctrl_as_data otherwise the control edge from old_node to the constant
  // in ControlToData will be present in ctrl_edges.

  Output old_ctrl_as_data = ControlToData(s, old_node);
  Output new_ctrl_as_data = ControlToData(s, new_node);

  ops::Merge ctrl_merge_as_data(s.WithOpName("ctrl_merge"),
                                {old_ctrl_as_data, new_ctrl_as_data});