Revert "[dynamo][exceptions] Use exception subclass whenever possible (#134610)"

This reverts commit 880e3d18a4.

Reverted https://github.com/pytorch/pytorch/pull/134610 on behalf of https://github.com/ZainRizvi due to Sorry, I had to revert this in order to revert another PR ([comment](https://github.com/pytorch/pytorch/pull/134610#issuecomment-2316568553))

test/dynamo/test_exceptions.py

@@ -267,29 +267,6 @@ class ExceptionTests(torch._dynamo.test_case.TestCase):
         x = torch.ones(4)
         self.assertEqual(mod(x), opt_mod(x))
 
-    def test_attribute_error_from_getattr(self):
-        class Mock:
-            def __init__(self):
-                self.a = 5
-
-            def __getattr__(self, name):
-                if name != "a":
-                    raise AttributeError("missing")
-                return self.__dict__["a"]
-
-        mock = Mock()
-
-        def fn(x):
-            if hasattr(mock, "b"):
-                return torch.cos(x)
-            return torch.sin(x)
-
-        opt_fn = torch.compile(fn, backend="eager", fullgraph=True)
-        x = torch.randn(4)
-        ref = fn(x)
-        res = opt_fn(x)
-        self.assertEqual(ref, res)
-
     def test_stop_iteration(self):
         def zip_longest(*iterables, fillvalue=None):
             # Get the iterators for each iterable

torch/_dynamo/symbolic_convert.py

@@ -1379,10 +1379,9 @@ class InstructionTranslatorBase(
 
             # 2) when user raises exception instance
             if isinstance(val, variables.ExceptionVariable):
-                if observed_exception_type := exc.observed_exception_map.get(
-                    val.exc_type
-                ):
-                    raise observed_exception_type(f"raised exception {val}")
+                if val.exc_type is StopIteration:
+                    # StopIteration is used to find the end of iteration while tracing __next__
+                    raise exc.ObservedUserStopIteration(f"raised exception {val}")
                 raise exc.ObservedException(f"raised exception {val}")
             unimplemented(f"raise {exc}")
         else: