//    us from inferring XlaSendFromHost shape. But in `host_graph`, we already
//    removed those placeholder nodes.
// 2) Remove control edges.
// 3) Prune nodes that are not useful for shape inference.
Status RewriteShapeInferenceGraph(const string& shape_inference_graph_name,
                                  Graph* host_graph, Node* pivot_node,
                                  FunctionLibraryDefinition* fld) {