gh-134584: Eliminate redundant refcounting from _STORE_SUBSCR_DICT (GH-142712)

Co-authored-by: Ken Jin <[email protected]>

Author: corona10

Include/internal/pycore_opcode_metadata.h

@@ -2525,10 +2525,29 @@ def testfunc(n):
         self.assertEqual(res, 10)
         self.assertIsNotNone(ex)
         uops = get_opnames(ex)
+        self.assertIn("_STORE_SUBSCR_LIST_INT", uops)
         self.assertNotIn("_POP_TOP", uops)
         self.assertNotIn("_POP_TOP_INT", uops)
         self.assertIn("_POP_TOP_NOP", uops)
 
+    def test_store_susbscr_dict(self):
+        def testfunc(n):
+            d = {}
+            for _ in range(n):
+                d['a'] = 1
+                d['b'] = 2
+                d['c'] = 3
+                d['d'] = 4
+            return sum(d.values())
+
+        res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
+        self.assertEqual(res, 10)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        self.assertIn("_STORE_SUBSCR_DICT", uops)
+        self.assertNotIn("_POP_TOP", uops)
+        self.assertIn("_POP_TOP_NOP", uops)
+
     def test_attr_promotion_failure(self):
         # We're not testing for any specific uops here, just
         # testing it doesn't crash.

Include/internal/pycore_uop_ids.h

@@ -1158,18 +1158,22 @@ dummy_func(
         }
 
         macro(STORE_SUBSCR_DICT) =
-            _GUARD_NOS_DICT + unused/1 + _STORE_SUBSCR_DICT;
+            _GUARD_NOS_DICT + unused/1 + _STORE_SUBSCR_DICT + POP_TOP;
 
-        op(_STORE_SUBSCR_DICT, (value, dict_st, sub -- )) {
+        op(_STORE_SUBSCR_DICT, (value, dict_st, sub -- st)) {
             PyObject *dict = PyStackRef_AsPyObjectBorrow(dict_st);
 
             assert(PyDict_CheckExact(dict));
             STAT_INC(STORE_SUBSCR, hit);
             int err = _PyDict_SetItem_Take2((PyDictObject *)dict,
                                             PyStackRef_AsPyObjectSteal(sub),
                                             PyStackRef_AsPyObjectSteal(value));
-            PyStackRef_CLOSE(dict_st);
-            ERROR_IF(err);
+            if (err) {
+                PyStackRef_CLOSE(dict_st);
+                ERROR_IF(1);
+            }
+            DEAD(dict_st);
+            st = dict_st;
         }
 
         inst(DELETE_SUBSCR, (container, sub --)) {

Include/internal/pycore_uop_metadata.h

@@ -109,6 +109,11 @@ dummy_func(void) {
         ss = sub_st;
     }
 
+    op(_STORE_SUBSCR_DICT, (value, dict_st, sub -- st)) {
+        (void)value;
+        st = dict_st;
+    }
+
     op(_PUSH_NULL, (-- res)) {
         res = sym_new_null(ctx);
     }