gh-134584: Eliminate redundant refcounting from _CALL{_BUILTIN_O, _METHOD_DESCRIPTOR_O}

Lib/test/test_capi/test_opt.py

@@ -2201,7 +2201,8 @@ def test_call_builtin_o(self):
         def testfunc(n):
             x = 0
             for _ in range(n):
-                y = abs(1)
+                my_abs = abs
+                y = my_abs(1)
                 x += y
             return x
 
@@ -2210,7 +2211,26 @@ def testfunc(n):
         self.assertIsNotNone(ex)
         uops = get_opnames(ex)
         self.assertIn("_CALL_BUILTIN_O", uops)
-        self.assertIn("_POP_TOP", uops)
+        self.assertNotIn("_POP_TOP", uops)
+        self.assertIn("_POP_TOP_NOP", uops)
+
+    def test_call_method_descriptor_o(self):
+        def testfunc(n):
+            x = 0
+            for _ in range(n):
+                y = (1, 2, 3)
+                z = y.count(2)
+                x += z
+            return x
+
+        res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
+        self.assertEqual(res, TIER2_THRESHOLD)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        pop_tops = [opname for opname in iter_opnames(ex) if opname == "_POP_TOP"]
+        self.assertIn("_CALL_METHOD_DESCRIPTOR_O", uops)
+        self.assertIn("_POP_TOP_NOP", uops)
+        self.assertLessEqual(len(pop_tops), 1)
 
     def test_get_len_with_const_tuple(self):
         def testfunc(n):

Python/bytecodes.c

@@ -4170,7 +4170,7 @@ dummy_func(
             _CALL_BUILTIN_CLASS +
             _CHECK_PERIODIC_AT_END;
 
-        op(_CALL_BUILTIN_O, (callable, self_or_null, args[oparg] -- res, a, c)) {
+        op(_CALL_BUILTIN_O, (callable, self_or_null, args[oparg] -- res, c, s)) {
             /* Builtin METH_O functions */
             PyObject *callable_o = PyStackRef_AsPyObjectBorrow(callable);
 
@@ -4193,8 +4193,8 @@ dummy_func(
             if (res_o == NULL) {
                 ERROR_NO_POP();
             }
-            a = arg;
             c = callable;
+            s = args[0];
             INPUTS_DEAD();
             res = PyStackRef_FromPyObjectSteal(res_o);
         }
@@ -4362,7 +4362,7 @@ dummy_func(
             none = PyStackRef_None;
         }
 
-         op(_CALL_METHOD_DESCRIPTOR_O, (callable, self_or_null, args[oparg] -- res)) {
+         op(_CALL_METHOD_DESCRIPTOR_O, (callable, self_or_null, args[oparg] -- res, c, s, a)) {
             PyObject *callable_o = PyStackRef_AsPyObjectBorrow(callable);
 
             int total_args = oparg;
@@ -4390,15 +4390,23 @@ dummy_func(
                                   PyStackRef_AsPyObjectBorrow(arg_stackref));
             _Py_LeaveRecursiveCallTstate(tstate);
             assert((res_o != NULL) ^ (_PyErr_Occurred(tstate) != NULL));
-            DECREF_INPUTS();
-            ERROR_IF(res_o == NULL);
+            if (res_o == NULL) {
+                ERROR_NO_POP();
+            }
+            c = callable;
+            s = arguments[0];
+            a = arguments[1];
+            INPUTS_DEAD();
             res = PyStackRef_FromPyObjectSteal(res_o);
         }
 
         macro(CALL_METHOD_DESCRIPTOR_O) =
             unused/1 +
             unused/2 +
             _CALL_METHOD_DESCRIPTOR_O +
+            POP_TOP +
+            POP_TOP +
+            POP_TOP +
             _CHECK_PERIODIC_AT_END;
 
         op(_CALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS, (callable, self_or_null, args[oparg] -- res)) {