gh-134584: Eliminate redundant refcounting from _CALL_TUPLE_1

Lib/test/test_capi/test_opt.py

@@ -1925,6 +1925,21 @@ def testfunc(n):
         uops = get_opnames(ex)
         self.assertNotIn("_GUARD_IS_NOT_NONE_POP", uops)
 
+    def test_call_tuple_1_pop_top(self):
+        def testfunc(n):
+            x = 0
+            for _ in range(n):
+                t = tuple(())
+                x += len(t) == 0
+            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("_CALL_TUPLE_1", uops)
+        self.assertIn("_POP_TOP_NOP", uops)
+
     def test_call_str_1(self):
         def testfunc(n):
             x = 0

Misc/NEWS.d/next/Core_and_Builtins/2025-06-23-22-52-20.gh-issue-134584.qbiQfG.rst

@@ -0,0 +1 @@
+Eliminate redundant refcounting from ``_CALL_TUPLE_1``. Patch by Noam Cohen

Python/bytecodes.c

@@ -4068,17 +4068,14 @@ dummy_func(
             DEOPT_IF(callable_o != (PyObject *)&PyTuple_Type);
         }
 
-        op(_CALL_TUPLE_1, (callable, null, arg -- res)) {
+        op(_CALL_TUPLE_1, (callable, null, arg -- res, a)) {
             PyObject *arg_o = PyStackRef_AsPyObjectBorrow(arg);
 
             assert(oparg == 1);
             STAT_INC(CALL, hit);
             PyObject *res_o = PySequence_Tuple(arg_o);
-            DEAD(null);
-            DEAD(callable);
-            (void)callable; // Silence compiler warnings about unused variables
-            (void)null;
-            PyStackRef_CLOSE(arg);
+            a = arg;
+            INPUTS_DEAD();
             ERROR_IF(res_o == NULL);
             res = PyStackRef_FromPyObjectSteal(res_o);
         }
@@ -4089,6 +4086,7 @@ dummy_func(
             _GUARD_NOS_NULL +
             _GUARD_CALLABLE_TUPLE_1 +
             _CALL_TUPLE_1 +
+            POP_TOP +
             _CHECK_PERIODIC_AT_END;
 
         op(_CHECK_AND_ALLOCATE_OBJECT, (type_version/2, callable, self_or_null, unused[oparg] -- callable, self_or_null, unused[oparg])) {
@@ -5455,6 +5453,12 @@ dummy_func(
             }
         }
 
+        label(pop_3_error) {
+            stack_pointer -= 3;
+            assert(WITHIN_STACK_BOUNDS());
+            goto error;
+        }
+
         label(pop_2_error) {
             stack_pointer -= 2;
             assert(WITHIN_STACK_BOUNDS());

Python/optimizer_bytecodes.c

@@ -1097,7 +1097,7 @@ dummy_func(void) {
         }
     }
 
-    op(_CALL_TUPLE_1, (callable, null, arg -- res)) {
+    op(_CALL_TUPLE_1, (callable, null, arg -- res, a)) {
         if (sym_matches_type(arg, &PyTuple_Type)) {
             // e.g. tuple((1, 2)) or tuple(foo) where foo is known to be a tuple
             // Note: we must strip the reference information because it goes
@@ -1107,6 +1107,7 @@ dummy_func(void) {
         else {
             res = sym_new_type(ctx, &PyTuple_Type);
         }
+        a = arg;
     }
 
     op(_GUARD_TOS_LIST, (tos -- tos)) {