gh-134584: Remove redundant refcount for BINARY_OP_SUBSCR_DICT

Author: caje731

Lib/test/test_capi/test_opt.py

@@ -1975,6 +1975,23 @@ def testfunc(n):
         self.assertLessEqual(count_ops(ex, "_POP_TOP"), 2)
         self.assertLessEqual(count_ops(ex, "_POP_TOP_INT"), 1)
 
+    def test_binary_op_subscr_dict(self):
+        def testfunc(n):
+            x = 0
+            d = {'a': 1, 'b': 2}
+            for _ in range(n):
+                v = d['a']  # _BINARY_OP_SUBSCR_DICT
+                if v == 1:
+                    x += 1
+            return x
+
+        res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
+        self.assertEqual(res, TIER2_THRESHOLD)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        self.assertIn("_BINARY_OP_SUBSCR_DICT", uops)
+        self.assertLessEqual(count_ops(ex, "_POP_TOP"), 2)
+
     def test_call_type_1_guards_removed(self):
         def testfunc(n):
             x = 0

Python/bytecodes.c

@@ -1056,9 +1056,9 @@ dummy_func(
         }
 
         macro(BINARY_OP_SUBSCR_DICT) =
-            _GUARD_NOS_DICT + unused/5 + _BINARY_OP_SUBSCR_DICT;
+            _GUARD_NOS_DICT + unused/5 + _BINARY_OP_SUBSCR_DICT + POP_TOP + POP_TOP;
 
-        op(_BINARY_OP_SUBSCR_DICT, (dict_st, sub_st -- res)) {
+        op(_BINARY_OP_SUBSCR_DICT, (dict_st, sub_st -- res, ds, ss)) {
             PyObject *sub = PyStackRef_AsPyObjectBorrow(sub_st);
             PyObject *dict = PyStackRef_AsPyObjectBorrow(dict_st);
 
@@ -1069,9 +1069,11 @@ dummy_func(
             if (rc == 0) {
                 _PyErr_SetKeyError(sub);
             }
-            DECREF_INPUTS();
+            INPUTS_DEAD();
             ERROR_IF(rc <= 0); // not found or error
             res = PyStackRef_FromPyObjectSteal(res_o);
+            ds = dict_st;
+            ss = sub_st;
         }
 
         op(_BINARY_OP_SUBSCR_CHECK_FUNC, (container, unused -- container, unused, getitem)) {

Python/executor_cases.c.h

@@ -380,6 +380,13 @@ dummy_func(void) {
         ss = sub_st;
     }
 
+    op(_BINARY_OP_SUBSCR_DICT, (dict_st, sub_st -- res, ds, ss)) {
+        res = sym_new_not_null(ctx);
+        ds = dict_st;
+        ss = sub_st;
+        INPUTS_DEAD();
+    }
+
     op(_TO_BOOL, (value -- res)) {
         int already_bool = optimize_to_bool(this_instr, ctx, value, &res, false);
         if (!already_bool) {