Add fake mode in verifier (#5805)

Summary:
Pull Request resolved: #5805

Hopefully fixes https://fb.workplace.com/groups/pytorch.edge.users/permalink/1605630670307220/

Reviewed By: larryliu0820

Differential Revision: D63734251

fbshipit-source-id: 854750227b64125a3609245c6cfcbff26b71f26a

Author: angelayi

exir/tests/test_tracer.py

@@ -100,6 +100,17 @@ def f(x: torch.Tensor) -> torch.Tensor:
             any(node.meta.get("stack_trace", None) for node in traced_f.graph.nodes)
         )
 
+    def test_ones(self) -> None:
+        class M(torch.nn.Module):
+            def forward(self, x):
+                y = torch.ones(x.shape[0])
+                return x + y
+
+        ep = torch.export.export(
+            M(), (torch.ones(3),), dynamic_shapes={"x": {0: torch.export.Dim("x")}}
+        )
+        exir.to_edge(ep)
+
     def test_possible_input_mutation(self) -> None:
         def f(x: torch.Tensor) -> torch.Tensor:
             return torch.add(torch.ones(5), torch.ones(5), out=x)

exir/verification/verifier.py

@@ -7,6 +7,7 @@
 import itertools
 import operator
 import types
+from contextlib import nullcontext
 from typing import Any, List, Optional, Tuple, Type
 
 import torch
@@ -19,6 +20,7 @@
     RunHigherOrderOperatorError,
 )
 from torch._dispatch.python import enable_python_dispatcher
+from torch._export.utils import _detect_fake_mode_from_gm
 
 from torch._export.verifier import SpecViolationError, Verifier
 from torch._ops import OpOverload
@@ -161,8 +163,9 @@ def extract_input(node: torch.fx.Node) -> Optional[FakeTensor]:
 def _check_tensor_args_matching_op_allowed_dtype(gm: GraphModule) -> None:
     validator = EdgeOpArgValidator(gm)
     inputs = _get_inputs(gm)
+    fake_mode = _detect_fake_mode_from_gm(gm) or nullcontext()
     try:
-        with enable_python_dispatcher():
+        with enable_python_dispatcher(), fake_mode:
             validator.run(*inputs)
     except RunHigherOrderOperatorError:
         # NB: ignore higher order operator in the graph.