[dynamo][guards] De-dupe DUPLICATE_INPUT guard (pytorch#134354)

Hard to write a test.

Pull Request resolved: pytorch#134354
Approved by: https://github.com/jansel
ghstack dependencies: pytorch#134272

torch/_dynamo/guards.py

@@ -575,6 +575,8 @@ def __init__(
             str, torch._C._dynamo.guards.GuardManager
         ] = {}
 
+        self._cached_duplicate_input_guards: Set[Tuple[str, str]] = set()
+
     def guard_on_dict_keys_and_ignore_order(self, example_value, guard):
         dict_mgr = self.get_guard_manager(guard)
         if isinstance(dict_mgr, DictGuardManager):
@@ -1663,6 +1665,13 @@ def DUPLICATE_INPUT(self, guard, source_b):
         self._set_guard_export_info(guard, code)
 
         if config.enable_cpp_guard_manager:
+            # Check that the guard has not been inserted already
+            key = (ref_a, ref_b)
+            if key in self._cached_duplicate_input_guards:
+                return
+            self._cached_duplicate_input_guards.add((ref_a, ref_b))
+            self._cached_duplicate_input_guards.add((ref_b, ref_a))
+
             install_object_aliasing_guard(
                 self.get_guard_manager(guard),
                 self.get_guard_manager_from_source(source_b),