# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD 3-Clause license found in the
# LICENSE file in the root directory of this source tree.

import torch
import torch.distributed._functional_collectives as funcol
from torch.distributed._tensor import DTensor

from torchao.float8.float8_training_tensor import Float8TrainingTensor


def tensor_already_casted_to_fp8(tensor: torch.Tensor) -> bool:
    """
    Check if the tensor is already casted to fp8, works if the local
    tensor is wrapped in DTensor.
    """
    if isinstance(tensor, Float8TrainingTensor):
        return True
    elif isinstance(tensor, DTensor):
        # TODO: shall we stick to public API and directly use tensor.to_local() here?
        return tensor_already_casted_to_fp8(tensor._local_tensor)
    elif isinstance(tensor, funcol.AsyncCollectiveTensor):
        return tensor_already_casted_to_fp8(tensor.elem)

    return False