[Bugfix] Add fake mode around passes (#23349)

Signed-off-by: angelayi <yiangela7@gmail.com>

vllm/compilation/activation_quant_fusion.py

@@ -10,6 +10,7 @@ from vllm.config import VllmConfig
 from vllm.logger import init_logger
 from vllm.platforms import current_platform
 
+from .inductor_pass import enable_fake_mode
 from .vllm_inductor_pass import VllmInductorPass
 
 logger = init_logger(__name__)
@@ -61,6 +62,7 @@ class ActivationQuantFusionPass(VllmInductorPass):
     https://github.com/pytorch/pytorch/pull/139321#issuecomment-2452354980
     """
 
+    @enable_fake_mode
     def __init__(self, config: VllmConfig):
         super().__init__(config)
 

vllm/compilation/collective_fusion.py

@@ -19,6 +19,7 @@ from vllm.logger import init_logger
 from vllm.platforms import current_platform
 from vllm.utils import direct_register_custom_op
 
+from .inductor_pass import enable_fake_mode
 from .vllm_inductor_pass import VllmInductorPass
 
 FP8_DTYPE = current_platform.fp8_dtype()
@@ -349,6 +350,7 @@ class AllGatherCutlassScaledMMPattern(BasePattern):
 
 class AsyncTPPass(VllmInductorPass):
 
+    @enable_fake_mode
     def __init__(self, config: VllmConfig):
         super().__init__(config)
 
@@ -1121,6 +1123,10 @@ class AllReduceFusionPass(VllmInductorPass):
             # in fallback path, when we don't use flashinfer
             fuse_rms_quant=config.compilation_config.pass_config.enable_fusion)
 
+        self.register_patterns()
+
+    @enable_fake_mode
+    def register_patterns(self):
         for epsilon in [1e-5, 1e-6]:
             AllReduceFusedRMSNormStaticQuantFP8Pattern(
                 epsilon,

vllm/compilation/fusion.py

@@ -17,6 +17,7 @@ from vllm.model_executor.layers.quantization.utils.quant_utils import (
 from vllm.platforms import current_platform
 
 from .fx_utils import find_getitem_maybe
+from .inductor_pass import enable_fake_mode
 from .multi_output_match import MultiOutputMatch
 from .vllm_inductor_pass import VllmInductorPass
 
@@ -528,6 +529,7 @@ class FusionPass(VllmInductorPass):
             cls._instance.pass_config = config.compilation_config.pass_config
         return cls._instance
 
+    @enable_fake_mode
     def __init__(self, config: VllmConfig):
         assert self.__class__._instance is None, \
             "FusionPass singleton instance already exists"

vllm/compilation/fusion_attn.py

@@ -7,8 +7,6 @@ import torch
 import torch._inductor.pattern_matcher as pm
 from torch._higher_order_ops.auto_functionalize import auto_functionalized
 from torch._inductor.pattern_matcher import PatternMatcherPass
-from torch._subclasses.fake_tensor import (FakeTensorMode,
-                                           unset_fake_temporarily)
 
 from vllm.attention import Attention
 from vllm.config import VllmConfig, get_layers_from_vllm_config
@@ -19,6 +17,7 @@ from vllm.platforms import current_platform
 from vllm.utils import round_up
 
 from .fusion import QUANT_OPS, empty_bf16, empty_fp32, empty_i32
+from .inductor_pass import enable_fake_mode
 from .vllm_inductor_pass import VllmInductorPass
 
 logger = init_logger(__name__)
@@ -139,16 +138,13 @@ class AttentionFp8StaticQuantPattern(AttentionQuantPattern):
                                       output_block_scale=None)
             return RESHAPE_OP(at1[1], [-1, self.num_heads * self.head_size])
 
-        # Need custom fake mode, otherwise tracing happens with real tensors.
-        # That would not work for the unified_attention custom op.
-        with unset_fake_temporarily(), FakeTensorMode():
         inputs = [
             empty_bf16(5, self.num_heads, self.head_size),  # q
             empty_bf16(5, self.num_heads, self.head_size),  # k
             empty_bf16(5, self.num_heads, self.head_size),  # v
             empty_bf16(5, self.num_heads, self.head_size),  # attn_output
-                self.empty_quant(5, self.num_heads *
-                                 self.head_size),  # quant_output
+            self.empty_quant(5,
+                             self.num_heads * self.head_size),  # quant_output
             empty_fp32(1, 1)  # scale
         ]
 
@@ -219,9 +215,6 @@ class AttentionNvfp4QuantPattern(AttentionQuantPattern):
                                 [-1, self.num_heads * self.head_size // 2])
             return output, at2[2]
 
-        # Need custom fake mode, otherwise tracing happens with real tensors.
-        # That would not work for the unified_attention custom op.
-        with unset_fake_temporarily(), FakeTensorMode():
         inputs = [
             empty_bf16(5, self.num_heads, self.head_size),  # q
             empty_bf16(5, self.num_heads, self.head_size),  # k
@@ -229,8 +222,7 @@ class AttentionNvfp4QuantPattern(AttentionQuantPattern):
             empty_bf16(5, self.num_heads, self.head_size),  # output_attn
             self.empty_quant(5, self.num_heads * self.head_size //
                              2),  # output_quant
-                empty_i32(128,
-                          round_up(self.num_heads * self.head_size // 16,
+            empty_i32(128, round_up(self.num_heads * self.head_size // 16,
                                     4)),  # output_scale
             empty_fp32(1, 1),  # input_scale
         ]
@@ -255,6 +247,7 @@ class AttnFusionPass(VllmInductorPass):
     support are attention kernels, which need to support fusing output quant.
     """
 
+    @enable_fake_mode
     def __init__(self, config: VllmConfig):
         super().__init__(config)
 

vllm/compilation/inductor_pass.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
+import functools
 import hashlib
 import inspect
 import json
@@ -10,6 +11,8 @@ from typing import Any, Callable, Optional, Union
 
 import torch
 from torch import fx
+from torch._subclasses.fake_tensor import (FakeTensorMode,
+                                           unset_fake_temporarily)
 
 from vllm.utils import is_torch_equal_or_newer
 
@@ -114,3 +117,20 @@ class CallableInductorPass(InductorPass):
 
     def uuid(self) -> Any:
         return self._uuid
+
+
+def enable_fake_mode(fn: Callable[..., Any]) -> Callable[..., Any]:
+    """
+    Applies a FakeTensorMode context. This is useful when you don't want to
+    create or run things with real tensors.
+    """
+
+    @functools.wraps(fn)
+    def fn_new(*args, **kwargs) -> Any:
+        with torch._guards.tracing(
+                None), unset_fake_temporarily(), FakeTensorMode():
+            result = fn(*args, **kwargs)
+
+        return result
+
+    return fn_new

vllm/compilation/sequence_parallelism.py

@@ -14,6 +14,7 @@ from vllm.distributed.parallel_state import (
 from vllm.logger import init_logger
 from vllm.platforms import current_platform
 
+from .inductor_pass import enable_fake_mode
 from .vllm_inductor_pass import VllmInductorPass
 
 logger = init_logger(__name__)
@@ -436,6 +437,7 @@ class SequenceParallelismPass(VllmInductorPass):
     performance.
     """
 
+    @enable_fake_mode
     def __init__(self, config: VllmConfig):
         super().__init__(config)