OpBuilder builder(op);
  Operation *new_op = Operation::create(
      op->getLoc(), op->getName(), new_result_types, op->getOperands(),
      op->getAttrs(), op->getPropertiesStorage(), op->getSuccessors(),
      op->getNumRegions());
  builder.insert(new_op);

  // Move region bodies to the new operation.
  for (auto it : llvm::zip(op->getRegions(), new_op->getRegions())) {

  Operation* new_op = Operation::create(
      op_->getLoc(), op_->getName(), new_result_types, op_->getOperands(),
      op_->getAttrs(), op_->getPropertiesStorage(), op_->getSuccessors(),
      op_->getNumRegions());
  builder.insert(new_op);

  // Move regions to the new op.
  for (auto it : llvm::zip(op_->getRegions(), new_op->getRegions())) {
    Region& old_region = std::get<0>(it);