GH-120507: Lower the `BEFORE_WITH` and `BEFORE_ASYNC_WITH` instructions. (#120640)

* Remove BEFORE_WITH and BEFORE_ASYNC_WITH instructions.

* Add LOAD_SPECIAL instruction

* Reimplement `with` and `async with` statements using LOAD_SPECIAL

1 files changed, 28 insertions, 0 deletions

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 958f424..a380e74 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -2705,6 +2705,34 @@ _PyObject_LookupSpecial(PyObject *self, PyObject *attr)
     return res;
 }
 
+/* Steals a reference to self */
+PyObject *
+_PyObject_LookupSpecialMethod(PyObject *self, PyObject *attr, PyObject **self_or_null)
+{
+    PyObject *res;
+
+    res = _PyType_LookupRef(Py_TYPE(self), attr);
+    if (res == NULL) {
+        Py_DECREF(self);
+        *self_or_null = NULL;
+        return NULL;
+    }
+
+    if (_PyType_HasFeature(Py_TYPE(res), Py_TPFLAGS_METHOD_DESCRIPTOR)) {
+        /* Avoid temporary PyMethodObject */
+        *self_or_null = self;
+    }
+    else {
+        descrgetfunc f = Py_TYPE(res)->tp_descr_get;
+        if (f != NULL) {
+            Py_SETREF(res, f(res, self, (PyObject *)(Py_TYPE(self))));
+        }
+        *self_or_null = NULL;
+        Py_DECREF(self);
+    }
+    return res;
+}
+
 PyObject *
 _PyObject_LookupSpecialId(PyObject *self, _Py_Identifier *attrid)
 {