// dependencies present in the original graph.
      continue;
    }
    if (node_values_.find(input_node.id()) == node_values_.end())
      return errors::FailedPrecondition(
          "Graph not traversed in reverse post order; use seen before def!");
    mlir::Operation* inst = node_values_[input_node.id()];
    if (input_edge->IsControlEdge())