// a tf_executor.NextIteration.Source/tf_executor.NextIteration.Sink will result
// in multiple passes over the tf_executor.graph to propagate devices in loops.
void PropagateDevicesInGraph(
    tf_executor::GraphOp graph,
    llvm::DenseMap<Value, llvm::StringRef>& value_to_device) {
  auto ops = graph.GetBody().without_terminator();

  bool updated_next_iteration = false;
  do {