Use atomics to load valid bit for inline values in _GUARD_DORV_VALUES_INST_ATTR_FROM_DICT

Author: mpage

Python/bytecodes.c

@@ -3216,7 +3216,8 @@ dummy_func(
         op(_GUARD_DORV_VALUES_INST_ATTR_FROM_DICT, (owner -- owner)) {
             PyObject *owner_o = PyStackRef_AsPyObjectBorrow(owner);
             assert(Py_TYPE(owner_o)->tp_flags & Py_TPFLAGS_INLINE_VALUES);
-            DEOPT_IF(!_PyObject_InlineValues(owner_o)->valid);
+            PyDictValues *ivs = _PyObject_InlineValues(owner_o);
+            DEOPT_IF(!FT_ATOMIC_LOAD_UINT8(ivs->valid));
         }
 
         op(_GUARD_KEYS_VERSION, (keys_version/2, owner -- owner)) {