gh-134584: Eliminate redundant refcounting from _STORE_SUBSCR_LIST_INT (gh-142703)

Author: corona10

Include/internal/pycore_opcode_metadata.h

@@ -2499,6 +2499,24 @@ def testfunc(n):
         self.assertNotIn("_GUARD_TOS_INT", uops)
         self.assertNotIn("_GUARD_NOS_INT", uops)
 
+    def test_store_subscr_int(self):
+        def testfunc(n):
+            l = [0, 0, 0, 0]
+            for _ in range(n):
+                l[0] = 1
+                l[1] = 2
+                l[2] = 3
+                l[3] = 4
+            return sum(l)
+
+        res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
+        self.assertEqual(res, 10)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        self.assertNotIn("_POP_TOP", uops)
+        self.assertNotIn("_POP_TOP_INT", 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

@@ -1126,9 +1126,9 @@ dummy_func(
         macro(STORE_SUBSCR) = _SPECIALIZE_STORE_SUBSCR + _STORE_SUBSCR;
 
         macro(STORE_SUBSCR_LIST_INT) =
-            _GUARD_TOS_INT + _GUARD_NOS_LIST + unused/1 + _STORE_SUBSCR_LIST_INT;
+            _GUARD_TOS_INT + _GUARD_NOS_LIST + unused/1 + _STORE_SUBSCR_LIST_INT + _POP_TOP_INT + POP_TOP;
 
-        op(_STORE_SUBSCR_LIST_INT, (value, list_st, sub_st -- )) {
+        op(_STORE_SUBSCR_LIST_INT, (value, list_st, sub_st -- ls, ss)) {
             PyObject *sub = PyStackRef_AsPyObjectBorrow(sub_st);
             PyObject *list = PyStackRef_AsPyObjectBorrow(list_st);
 
@@ -1151,9 +1151,9 @@ dummy_func(
                                         PyStackRef_AsPyObjectSteal(value));
             assert(old_value != NULL);
             UNLOCK_OBJECT(list);  // unlock before decrefs!
-            PyStackRef_CLOSE_SPECIALIZED(sub_st, _PyLong_ExactDealloc);
-            DEAD(sub_st);
-            PyStackRef_CLOSE(list_st);
+            INPUTS_DEAD();
+            ls = list_st;
+            ss = sub_st;
             Py_DECREF(old_value);
         }
 

Include/internal/pycore_uop_metadata.h

@@ -103,6 +103,12 @@ dummy_func(void) {
         GETLOCAL(oparg) = value;
     }
 
+    op(_STORE_SUBSCR_LIST_INT, (value, list_st, sub_st -- ls, ss)) {
+        (void)value;
+        ls = list_st;
+        ss = sub_st;
+    }
+
     op(_PUSH_NULL, (-- res)) {
         res = sym_new_null(ctx);
     }
@@ -529,6 +535,12 @@ dummy_func(void) {
         }
     }
 
+    op(_POP_TOP_INT, (value --)) {
+        if (PyJitRef_IsBorrowed(value)) {
+            REPLACE_OP(this_instr, _POP_TOP_NOP, 0, 0);
+        }
+    }
+
     op(_COPY, (bottom, unused[oparg-1] -- bottom, unused[oparg-1], top)) {
         assert(oparg > 0);
         top = bottom;