[export] Add export-safe LRU cache helper (#13290)

* [core] Add export-safe LRU cache helper

* torch version check!

---------

Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

Author: cbensimon

src/diffusers/hooks/context_parallel.py

@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import copy
-import functools
 import inspect
 from dataclasses import dataclass
 from typing import Type
@@ -32,7 +31,7 @@
     gather_size_by_comm,
 )
 from ..utils import get_logger
-from ..utils.torch_utils import maybe_allow_in_graph, unwrap_module
+from ..utils.torch_utils import lru_cache_unless_export, maybe_allow_in_graph, unwrap_module
 from .hooks import HookRegistry, ModelHook
 
 
@@ -327,7 +326,7 @@ def unshard_anything(
         return tensor
 
 
-@functools.lru_cache(maxsize=64)
+@lru_cache_unless_export(maxsize=64)
 def _fill_gather_shapes(shape: tuple[int], gather_dims: tuple[int], dim: int, world_size: int) -> list[list[int]]:
     gather_shapes = []
     for i in range(world_size):

src/diffusers/models/attention_dispatch.py

@@ -49,7 +49,7 @@
     is_xformers_version,
 )
 from ..utils.constants import DIFFUSERS_ATTN_BACKEND, DIFFUSERS_ATTN_CHECKS
-from ..utils.torch_utils import maybe_allow_in_graph
+from ..utils.torch_utils import lru_cache_unless_export, maybe_allow_in_graph
 from ._modeling_parallel import gather_size_by_comm
 
 
@@ -587,7 +587,7 @@ def _check_attention_backend_requirements(backend: AttentionBackendName) -> None
             )
 
 
-@functools.lru_cache(maxsize=128)
+@lru_cache_unless_export(maxsize=128)
 def _prepare_for_flash_attn_or_sage_varlen_without_mask(
     batch_size: int,
     seq_len_q: int,

src/diffusers/models/transformers/transformer_qwenimage.py

@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import functools
 import math
 from math import prod
 from typing import Any
@@ -25,7 +24,7 @@
 from ...configuration_utils import ConfigMixin, register_to_config
 from ...loaders import FromOriginalModelMixin, PeftAdapterMixin
 from ...utils import apply_lora_scale, deprecate, logging
-from ...utils.torch_utils import maybe_allow_in_graph
+from ...utils.torch_utils import lru_cache_unless_export, maybe_allow_in_graph
 from .._modeling_parallel import ContextParallelInput, ContextParallelOutput
 from ..attention import AttentionMixin, FeedForward
 from ..attention_dispatch import dispatch_attention_fn
@@ -307,7 +306,7 @@ def forward(
 
         return vid_freqs, txt_freqs
 
-    @functools.lru_cache(maxsize=128)
+    @lru_cache_unless_export(maxsize=128)
     def _compute_video_freqs(
         self, frame: int, height: int, width: int, idx: int = 0, device: torch.device = None
     ) -> torch.Tensor:
@@ -428,7 +427,7 @@ def forward(
 
         return vid_freqs, txt_freqs
 
-    @functools.lru_cache(maxsize=None)
+    @lru_cache_unless_export(maxsize=None)
     def _compute_video_freqs(self, frame, height, width, idx=0, device: torch.device = None):
         seq_lens = frame * height * width
         pos_freqs = self.pos_freqs.to(device) if device is not None else self.pos_freqs
@@ -450,7 +449,7 @@ def _compute_video_freqs(self, frame, height, width, idx=0, device: torch.device
         freqs = torch.cat([freqs_frame, freqs_height, freqs_width], dim=-1).reshape(seq_lens, -1)
         return freqs.clone().contiguous()
 
-    @functools.lru_cache(maxsize=None)
+    @lru_cache_unless_export(maxsize=None)
     def _compute_condition_freqs(self, frame, height, width, device: torch.device = None):
         seq_lens = frame * height * width
         pos_freqs = self.pos_freqs.to(device) if device is not None else self.pos_freqs

src/diffusers/utils/torch_utils.py

@@ -19,11 +19,16 @@
 
 import functools
 import os
+from typing import Callable, ParamSpec, TypeVar
 
 from . import logging
 from .import_utils import is_torch_available, is_torch_mlu_available, is_torch_npu_available, is_torch_version
 
 
+T = TypeVar("T")
+P = ParamSpec("P")
+
+
 if is_torch_available():
     import torch
     from torch.fft import fftn, fftshift, ifftn, ifftshift
@@ -333,5 +338,23 @@ def disable_full_determinism():
     torch.use_deterministic_algorithms(False)
 
 
+@functools.wraps(functools.lru_cache)
+def lru_cache_unless_export(maxsize=128, typed=False):
+    def outer_wrapper(fn: Callable[P, T]):
+        cached = functools.lru_cache(maxsize=maxsize, typed=typed)(fn)
+        if is_torch_version("<", "2.7.0"):
+            return cached
+
+        @functools.wraps(fn)
+        def inner_wrapper(*args: P.args, **kwargs: P.kwargs):
+            if torch.compiler.is_exporting():
+                return fn(*args, **kwargs)
+            return cached(*args, **kwargs)
+
+        return inner_wrapper
+
+    return outer_wrapper
+
+
 if is_torch_available():
     torch_device = get_device()