func::FuncOp ret = queue_.front();
    queue_.pop();
    queue_set_.erase(ret);
    return ret;
  }

  // Returns the current size of the queue.
  std::queue<func::FuncOp>::size_type QueueSize() const {
    return queue_.size();
  }

  Dialect* const tf_dialect_;

 private:
  // Returns whether the result of an operation could be updated to a new