[Feature][CI]: compare `func` & `no_func` outputs in test_functionalization.py (#35481)

Signed-off-by: Bhuminjay <bhuminjaysoni@gmail.com>
Signed-off-by: Bhuminjay Soni <Soni5Happy@gmail.com>
Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com>

tests/compile/passes/test_functionalization.py

@@ -309,12 +309,15 @@ def test_fix_functionalization(
         model = model_class()
         inputs_func = model.example_inputs()
         inputs_no_func = copy.deepcopy(inputs_func)
-        model_func = model_class()
-        model_no_func = copy.deepcopy(model_func)
+        model_func = copy.deepcopy(model)
+        model_no_func = copy.deepcopy(model)
         model_func = torch.compile(model_func, backend=backend_func)
         model_no_func = torch.compile(model_no_func, backend=backend_no_func)
-        model_func(*inputs_func)
-        model_no_func(*inputs_no_func)
+
+        # deepcopy inputs to prevent potential in place mutation
+        outputs_func = model_func(*copy.deepcopy(inputs_func))
+        outputs_no_func = model_no_func(*copy.deepcopy(inputs_no_func))
+        torch.testing.assert_close(outputs_func, outputs_no_func)
 
         # check if the functionalization pass is applied
         for op in model.ops_in_model(do_fusion):
@@ -332,8 +335,3 @@ def test_fix_functionalization(
                     found[op] = True
         assert all(found[op] for op in model.ops_in_model(do_fusion))
         assert all(not found.get(op) for op in model.ops_not_in_model())
-
-        # TODO (Rohan138): compare the outputs from model_func and model_no_func
-        # currently runs into errors while comparing `TestFusedAddRMSNorm`
-        # Linked issue: https://github.com/vllm-project/vllm/issues/34996
-        # torch.testing.assert_close(outputs_func, outputs_no_func)