for (auto p : llvm::zip(live_ins, outlined_func_block->getArguments())) {
    replaceAllUsesInRegionWith(std::get<0>(p), std::get<1>(p), op_region);
  }

  // Move all instructions in cluster_op into outlined_function's only block.
  auto& op_body = op.GetBody().getOperations();
  outlined_func_block->getOperations().splice(
      outlined_func_block->end(), op_body, op_body.begin(), op_body.end());