message: Fix ophint_extraction topo sort.
  some like placeholder's operand is only value.
diff: @@ -378,6 +378,10 @@ void PreprocessTopoSortGraph(
  Operation* input_op = op.getOperand(i)->getDefiningOp();
  if (input_op) input_ops.insert(input_op);
  }
  + if (input_ops.empty()) {
  + init_queue->push(&op);
  + continue;
  + }
  operation_to_in_degrees->try_emplace(&op, input_ops.size());
  for (auto* input_op : input_ops) {
  auto preceeding_op_it = operation_to_ouputs->find(input_op);
  