bpo-40575: Avoid unnecessary overhead in _PyDict_GetItemIdWithError() (GH-20018)

scoder · web-flow · commit 6067d4bc3ce5 · 2020-05-11T06:04:31.000+02:00
Avoid unnecessary overhead in _PyDict_GetItemIdWithError() by calling
_PyDict_GetItem_KnownHash() instead of the more generic PyDict_GetItemWithError(),
since we already know the hash of interned strings.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
@@ -1492,7 +1492,9 @@ _PyDict_GetItemIdWithError(PyObject *dp, struct _Py_Identifier *key)
     kv = _PyUnicode_FromId(key); /* borrowed */
     if (kv == NULL)
         return NULL;
-    return PyDict_GetItemWithError(dp, kv);
+    Py_hash_t hash = ((PyASCIIObject *) kv)->hash;
+    assert (hash != -1);  /* interned strings have their hash value initialised */
+    return _PyDict_GetItem_KnownHash(dp, kv, hash);
 }
 
 PyObject *
