[rfc][compile] compile method for DiffusionPipeline (#11705)

* [rfc][compile] compile method for DiffusionPipeline

* Apply suggestions from code review
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

* Apply style fixes

* Update docs/source/en/optimization/fp16.md

* check

---------
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

docs/source/en/optimization/fp16.md

@@ -152,9 +152,39 @@ Compilation is slow the first time, but once compiled, it is significantly faste
 
 ### Regional compilation
 
-[Regional compilation](https://docs.pytorch.org/tutorials/recipes/regional_compilation.html) reduces the cold start compilation time by only compiling a specific repeated region (or block) of the model instead of the entire model. The compiler reuses the cached and compiled code for the other blocks.
 
-[Accelerate](https://huggingface.co/docs/accelerate/index) provides the [compile_regions](https://github.com/huggingface/accelerate/blob/273799c85d849a1954a4f2e65767216eb37fa089/src/accelerate/utils/other.py#L78) method for automatically compiling the repeated blocks of a `nn.Module` sequentially. The rest of the model is compiled separately.
+[Regional compilation](https://docs.pytorch.org/tutorials/recipes/regional_compilation.html) trims cold-start latency by compiling **only the small, frequently-repeated block(s)** of a model, typically a Transformer layer, enabling reuse of compiled artifacts for every subsequent occurrence.
+For many diffusion architectures this delivers the *same* runtime speed-ups as full-graph compilation yet cuts compile time by **8–10 ×**.
+
+To make this effortless, [`ModelMixin`] exposes [`ModelMixin.compile_repeated_blocks`] API, a helper that wraps `torch.compile` around any sub-modules you designate as repeatable:
+
+```py
+# pip install -U diffusers
+import torch
+from diffusers import StableDiffusionXLPipeline
+
+pipe = StableDiffusionXLPipeline.from_pretrained(
+    "stabilityai/stable-diffusion-xl-base-1.0",
+    torch_dtype=torch.float16,
+).to("cuda")
+
+# Compile only the repeated Transformer layers inside the UNet
+pipe.unet.compile_repeated_blocks(fullgraph=True)
+```
+
+To enable a new model with regional compilation, add a `_repeated_blocks` attribute to your model class containing the class names (as strings) of the blocks you want compiled:
+
+
+```py
+class MyUNet(ModelMixin):
+    _repeated_blocks = ("Transformer2DModel",)  # ← compiled by default
+```
+
+For more examples, see the reference [PR](https://github.com/huggingface/diffusers/pull/11705).
+
+**Relation to Accelerate compile_regions** There is also a separate API in [accelerate](https://huggingface.co/docs/accelerate/index) - [compile_regions](https://github.com/huggingface/accelerate/blob/273799c85d849a1954a4f2e65767216eb37fa089/src/accelerate/utils/other.py#L78). It takes a fully automatic approach: it walks the module, picks candidate blocks, then compiles the remaining graph separately. That hands-off experience is handy for quick experiments, but it also leaves fewer knobs when you want to fine-tune which blocks are compiled or adjust compilation flags.
+
+
 
 ```py
 # pip install -U accelerate
@@ -167,6 +197,8 @@ pipeline = StableDiffusionXLPipeline.from_pretrained(
 ).to("cuda")
 pipeline.unet = compile_regions(pipeline.unet, mode="reduce-overhead", fullgraph=True)
 ```
+`compile_repeated_blocks`, by contrast, is intentionally explicit. You list the repeated blocks once (via `_repeated_blocks`) and the helper compiles exactly those, nothing more. In practice this small dose of control hits a sweet spot for diffusion models: predictable behavior, easy reasoning about cache reuse, and still a one-liner for users.
+
 
 ### Graph breaks
 
@@ -241,4 +273,4 @@ An input is projected into three subspaces, represented by the projection matric
 
 ```py
 pipeline.fuse_qkv_projections()
-```
\ No newline at end of file
+```

src/diffusers/models/modeling_utils.py

@@ -266,6 +266,7 @@ class ModelMixin(torch.nn.Module, PushToHubMixin):
     _keep_in_fp32_modules = None
     _skip_layerwise_casting_patterns = None
     _supports_group_offloading = True
+    _repeated_blocks = []
 
     def __init__(self):
         super().__init__()
@@ -1404,6 +1405,39 @@ class ModelMixin(torch.nn.Module, PushToHubMixin):
         else:
             return super().float(*args)
 
+    def compile_repeated_blocks(self, *args, **kwargs):
+        """
+        Compiles *only* the frequently repeated sub-modules of a model (e.g. the Transformer layers) instead of
+        compiling the entire model. This technique—often called **regional compilation** (see the PyTorch recipe
+        https://docs.pytorch.org/tutorials/recipes/regional_compilation.html) can reduce end-to-end compile time
+        substantially, while preserving the runtime speed-ups you would expect from a full `torch.compile`.
+
+        The set of sub-modules to compile is discovered by the presence of **`_repeated_blocks`** attribute in the
+        model definition. Define this attribute on your model subclass as a list/tuple of class names (strings). Every
+        module whose class name matches will be compiled.
+
+        Once discovered, each matching sub-module is compiled by calling `submodule.compile(*args, **kwargs)`. Any
+        positional or keyword arguments you supply to `compile_repeated_blocks` are forwarded verbatim to
+        `torch.compile`.
+        """
+        repeated_blocks = getattr(self, "_repeated_blocks", None)
+
+        if not repeated_blocks:
+            raise ValueError(
+                "`_repeated_blocks` attribute is empty. "
+                f"Set `_repeated_blocks` for the class `{self.__class__.__name__}` to benefit from faster compilation. "
+            )
+        has_compiled_region = False
+        for submod in self.modules():
+            if submod.__class__.__name__ in repeated_blocks:
+                submod.compile(*args, **kwargs)
+                has_compiled_region = True
+
+        if not has_compiled_region:
+            raise ValueError(
+                f"Regional compilation failed because {repeated_blocks} classes are not found in the model. "
+            )
+
     @classmethod
     def _load_pretrained_model(
         cls,

src/diffusers/models/transformers/transformer_chroma.py

@@ -407,6 +407,7 @@ class ChromaTransformer2DModel(
 
     _supports_gradient_checkpointing = True
     _no_split_modules = ["ChromaTransformerBlock", "ChromaSingleTransformerBlock"]
+    _repeated_blocks = ["ChromaTransformerBlock", "ChromaSingleTransformerBlock"]
     _skip_layerwise_casting_patterns = ["pos_embed", "norm"]
 
     @register_to_config

src/diffusers/models/transformers/transformer_flux.py

@@ -227,6 +227,7 @@ class FluxTransformer2DModel(
     _supports_gradient_checkpointing = True
     _no_split_modules = ["FluxTransformerBlock", "FluxSingleTransformerBlock"]
     _skip_layerwise_casting_patterns = ["pos_embed", "norm"]
+    _repeated_blocks = ["FluxTransformerBlock", "FluxSingleTransformerBlock"]
 
     @register_to_config
     def __init__(

src/diffusers/models/transformers/transformer_hunyuan_video.py

@@ -870,6 +870,12 @@ class HunyuanVideoTransformer3DModel(ModelMixin, ConfigMixin, PeftAdapterMixin,
         "HunyuanVideoPatchEmbed",
         "HunyuanVideoTokenRefiner",
     ]
+    _repeated_blocks = [
+        "HunyuanVideoTransformerBlock",
+        "HunyuanVideoSingleTransformerBlock",
+        "HunyuanVideoPatchEmbed",
+        "HunyuanVideoTokenRefiner",
+    ]
 
     @register_to_config
     def __init__(

src/diffusers/models/transformers/transformer_ltx.py

@@ -328,6 +328,7 @@ class LTXVideoTransformer3DModel(ModelMixin, ConfigMixin, FromOriginalModelMixin
 
     _supports_gradient_checkpointing = True
     _skip_layerwise_casting_patterns = ["norm"]
+    _repeated_blocks = ["LTXVideoTransformerBlock"]
 
     @register_to_config
     def __init__(

src/diffusers/models/transformers/transformer_wan.py

@@ -345,6 +345,7 @@ class WanTransformer3DModel(ModelMixin, ConfigMixin, PeftAdapterMixin, FromOrigi
     _no_split_modules = ["WanTransformerBlock"]
     _keep_in_fp32_modules = ["time_embedder", "scale_shift_table", "norm1", "norm2", "norm3"]
     _keys_to_ignore_on_load_unexpected = ["norm_added_q"]
+    _repeated_blocks = ["WanTransformerBlock"]
 
     @register_to_config
     def __init__(

src/diffusers/models/unets/unet_2d_condition.py

@@ -167,6 +167,7 @@ class UNet2DConditionModel(
     _supports_gradient_checkpointing = True
     _no_split_modules = ["BasicTransformerBlock", "ResnetBlock2D", "CrossAttnUpBlock2D"]
     _skip_layerwise_casting_patterns = ["norm"]
+    _repeated_blocks = ["BasicTransformerBlock"]
 
     @register_to_config
     def __init__(

tests/models/test_modeling_common.py

@@ -1935,6 +1935,27 @@ class TorchCompileTesterMixin:
             _ = model(**inputs_dict)
             _ = model(**inputs_dict)
 
+    def test_torch_compile_repeated_blocks(self):
+        if self.model_class._repeated_blocks is None:
+            pytest.skip("Skipping test as the model class doesn't have `_repeated_blocks` set.")
+
+        init_dict, inputs_dict = self.prepare_init_args_and_inputs_for_common()
+
+        model = self.model_class(**init_dict).to(torch_device)
+        model.compile_repeated_blocks(fullgraph=True)
+
+        recompile_limit = 1
+        if self.model_class.__name__ == "UNet2DConditionModel":
+            recompile_limit = 2
+
+        with (
+            torch._inductor.utils.fresh_inductor_cache(),
+            torch._dynamo.config.patch(recompile_limit=recompile_limit),
+            torch.no_grad(),
+        ):
+            _ = model(**inputs_dict)
+            _ = model(**inputs_dict)
+
     def test_compile_with_group_offloading(self):
         torch._dynamo.config.cache_size_limit = 10000