[3.15] gh-149481: skip FOR_ITER inline specialization for Python __next__ (GH-149491) (#149523)

gh-149481: skip `FOR_ITER` inline specialization for Python `__next__` (GH-149491)
(cherry picked from commit 49918f5)

Co-authored-by: Neko Asakura <neko.asakura@outlook.com>
Co-authored-by: Savannah Ostrowski <savannah@python.org>
Co-authored-by: Stan Ulbrych <stan@python.org>

Author: 4 people

Include/internal/pycore_typeobject.h

@@ -122,6 +122,8 @@ extern PyObject* _Py_BaseObject_RichCompare(PyObject* self, PyObject* other, int
 extern PyObject* _Py_slot_tp_getattro(PyObject *self, PyObject *name);
 extern PyObject* _Py_slot_tp_getattr_hook(PyObject *self, PyObject *name);
 
+extern int _PyType_HasSlotTpIternext(PyTypeObject *type);
+
 extern PyTypeObject _PyBufferWrapper_Type;
 
 PyAPI_FUNC(PyObject*) _PySuper_Lookup(PyTypeObject *su_type, PyObject *su_obj,

Lib/test/test_capi/test_opt.py

@@ -598,7 +598,8 @@ def testfunc(n, m):
         ex = get_first_executor(testfunc)
         self.assertIsNotNone(ex)
         uops = get_opnames(ex)
-        self.assertIn("_ITER_NEXT_INLINE", uops)
+        self.assertIn("_FOR_ITER_TIER_TWO", uops)
+        self.assertNotIn("_ITER_NEXT_INLINE", uops)
 
 
 @requires_specialization

Objects/typeobject.c

@@ -11079,6 +11079,12 @@ slot_tp_iternext(PyObject *self)
     return vectorcall_method(&_Py_ID(__next__), stack, 1);
 }
 
+int
+_PyType_HasSlotTpIternext(PyTypeObject *type)
+{
+    return type->tp_iternext == slot_tp_iternext;
+}
+
 static PyObject *
 slot_tp_descr_get(PyObject *self, PyObject *obj, PyObject *type)
 {

Python/optimizer_bytecodes.c

@@ -2,6 +2,7 @@
 #include "pycore_long.h"
 #include "pycore_opcode_utils.h"
 #include "pycore_optimizer.h"
+#include "pycore_typeobject.h"
 #include "pycore_uops.h"
 #include "pycore_uop_ids.h"
 #include "internal/pycore_moduleobject.h"
@@ -1459,7 +1460,8 @@ dummy_func(void) {
             type = sym_get_probable_type(iter);
             definite = false;
         }
-        if (type != NULL && type != &PyGen_Type && type->tp_iternext != NULL) {
+        if (type != NULL && type != &PyGen_Type && type->tp_iternext != NULL
+            && !_PyType_HasSlotTpIternext(type)) {
             PyType_Watch(TYPE_WATCHER_ID, (PyObject *)type);
             _Py_BloomFilter_Add(dependencies, type);
             if (!definite) {