Method DetermineAncestorState

tensorflow/compiler/tf2xla/functionalize_cond.cc:1305–1337

}

Status FunctionalizeCond::DetermineAncestorState(Node* dst) {
  StateMap::AncestorId id = nullptr;
  StateMap::AncestorState state;

  auto insert = [&](StateMap::AncestorId id, Node* src) {
    auto other_id = state_map_.LookupAncestorId(src);
    if (other_id != id && other_id != nullptr) {
      state.insert(other_id->begin(), other_id->end());
    }
    if (IsMerge(src)) {
      state.insert({{src, 0}, AncestorNode::AncestorNodeType::kMerge});
    } else if (IsSwitch(src)) {
      OutputTensor pred;
      // For dead switch nodes, GetSwitchPredicate() will fail, and we use
      // the switch node directly as ancestor.
      if (GetSwitchPredicate(*src, &pred).ok()) {
        state.insert({pred, AncestorNode::AncestorNodeType::kPred});
      } else {
        state.insert({{src, 0}, AncestorNode::AncestorNodeType::kSwitch});
      }
    }
    return state_map_.GetAncestorId(state);
  };

  // Compute the union of all the switch/merge nodes that affects the input of
  // dst.
  for (auto e : dst->in_edges()) {
    Node* src = e->src();
    id = insert(id, src);
  }
  state_map_.ResetAncestorId(dst, id);
  return Status::OK();
}

void FunctionalizeCond::DeleteReachableAndDeadNodes(
    const std::vector<Node*>& merge_order) {