gh-134584: Eliminate redundant refcounting from _CALL_LEN

Author: corona10

Include/internal/pycore_opcode_metadata.h

@@ -1967,6 +1967,7 @@ def testfunc(n):
         self.assertIn("_CALL_LEN", uops)
         self.assertNotIn("_GUARD_NOS_INT", uops)
         self.assertNotIn("_GUARD_TOS_INT", uops)
+        self.assertIn("_POP_TOP_NOP", uops)
 
     def test_call_len_known_length_small_int(self):
         def testfunc(n):

Lib/test/test_capi/test_opt.py

@@ -4315,18 +4315,20 @@ dummy_func(
             unused/2 +
             _GUARD_NOS_NULL +
             _GUARD_CALLABLE_LEN +
-            _CALL_LEN;
+            _CALL_LEN +
+            POP_TOP +
+            POP_TOP;
 
         op(_GUARD_CALLABLE_LEN, (callable, unused, unused -- callable, unused, unused)){
             PyObject *callable_o = PyStackRef_AsPyObjectBorrow(callable);
             PyInterpreterState *interp = tstate->interp;
             DEOPT_IF(callable_o != interp->callable_cache.len);
         }
 
-        op(_CALL_LEN, (callable, null, arg -- res)) {
+        op(_CALL_LEN, (callable, null, arg -- res, a, c)) {
             /* len(o) */
-            (void)null;
             STAT_INC(CALL, hit);
+            INPUTS_DEAD();
             PyObject *arg_o = PyStackRef_AsPyObjectBorrow(arg);
             Py_ssize_t len_i = PyObject_Length(arg_o);
             if (len_i < 0) {
@@ -4337,10 +4339,9 @@ dummy_func(
             if (res_o == NULL) {
                 ERROR_NO_POP();
             }
-            PyStackRef_CLOSE(arg);
-            DEAD(null);
-            PyStackRef_CLOSE(callable);
             res = PyStackRef_FromPyObjectSteal(res_o);
+            a = arg;
+            c = callable;
         }
 
         op(_GUARD_CALLABLE_ISINSTANCE, (callable, unused, unused, unused -- callable, unused, unused, unused)) {

Python/bytecodes.c

@@ -1178,7 +1178,7 @@ dummy_func(void) {
         sym_set_const(callable, (PyObject *)&PyUnicode_Type);
     }
 
-    op(_CALL_LEN, (callable, null, arg -- res)) {
+    op(_CALL_LEN, (callable, null, arg -- res, a, c)) {
         res = sym_new_type(ctx, &PyLong_Type);
         int tuple_length = sym_tuple_length(arg);
         if (tuple_length >= 0) {
@@ -1193,6 +1193,8 @@ dummy_func(void) {
             res = sym_new_const(ctx, temp);
             Py_DECREF(temp);
         }
+        a = arg;
+        c = callable;
     }
 
     op(_GET_LEN, (obj -- obj, len)) {