bool Contains(Value resource) const {
    return resources_.find(resource) != resources_.end();
  }

  // Drops the given resource from lifting.
  void DropResource(Value resource) {
    resources_.erase(resource);
    written_resources_.remove(resource);
  }

  // Replaces all resource loads in all regions attached to the op.
  void ReplaceResourceLoads(bool read_only) {