auto return_val = entry.value();
    if (auto arg = mlir::dyn_cast<BlockArgument>(return_val)) {
      auto it = infos.find(arg.getArgNumber());
      if (it != infos.end() && !it->getSecond().used) {
        return_op->eraseOperand(entry.index() - skipped_retvals++);
      }
    }
  }
  llvm::BitVector indices_to_erase(func_op.getNumArguments());
  llvm::SmallVector<Type, 4> new_types;
  int64_t skipped_args = 0;