Function GetTheOnlyDataEdge

tensorflow/core/common_runtime/function.cc:1348–1374

If 'edges' contains only 1 non-control edge, returns it. Otherwise, returns a nullptr.

// If 'edges' contains only 1 non-control edge, returns it. Otherwise,
// returns a nullptr.
const Edge* GetTheOnlyDataEdge(const EdgeSet& edges) {
  const Edge* ret = nullptr;
  for (const Edge* e : edges) {
    if (e->IsControlEdge() || ret) {
      // Don't touch it if there is a control edge.
      return nullptr;
    }
    if (IsRefType(e->src()->output_type(e->src_output()))) {
      // Don't touch it if the identity node is effectively de-reffing
      // a ref.
      return nullptr;
    }
    if (IsRecv(e->src()) || IsSwitch(e->src()) ||
        IsFuseRecv(e->src())) {
      // Don't touch it if the identity is introduced for control flow.
      // Recv disables all its successors if it receives a dead signal.
      // When Recv has an outgoing control edge, the current executor
      // would not disable the destination. The current solution (see
      // graph_partition.cc) is to add an identity after Recv and change
      // the control edge to be from this identity node. So the identity
      // can't be removed.
      return nullptr;
    }
    ret = e;
  }
  return ret;
}
}  // end namespace

bool RemoveIdentityNodes(Graph* g) {