>  I noticed that my patch uses Py_TYPE(self)->tp_hash, whereas normal
>  processing of slot_tp_hash() uses lookup_method(self,"__hash__",hash_str).
>
>  I am almost sure that both expressions return the same value.
>  Is this correct? Py_TYPE(self)->tp_hash seems much faster.

HERE BE DRAGONS

There are cases where Py_TYPE(self)->tp_hash is the function currently
executing (some wrapper(s) in typeobject.c). OTOH, lookup_method(...)
finds the Python code in the class __dict__s along the MRO.