gh-145044: avoid calling Py_DECREF in unsafe_object_compare on immortal objects

Misc/NEWS.d/next/Core_and_Builtins/2026-02-20-16-49-28.gh-issue-145044.20DoM5.rst

@@ -0,0 +1,2 @@
+The function ``unsafe_object_compare()`` in :file:`Objects/listobject.c` has been optimized to avoid unnecessary reference count decrements on boolean results. This reduces overhead on tight comparison loops, improving :class:`list` sort performance by approximately 1%.
+Patch by Benedikt Johannes.

Objects/listobject.c

@@ -2774,8 +2774,8 @@ unsafe_object_compare(PyObject *v, PyObject *w, MergeState *ms)
     }
     else {
         res = PyObject_IsTrue(res_obj);
+        Py_DECREF(res_obj);
     }
-    Py_DECREF(res_obj);
 
     /* Note that we can't assert
      *     res == PyObject_RichCompareBool(v, w, Py_LT);