> BTW, what do you think about using __int128 when available?  That way we can also optimize twodigit PyLongs.

__int128 is not always available and it will add too much of complexity for possible less gain. There is many ways to optimize the code and we should to choose those of them that have the best gain/complexity ratio.

Lets split the patch on smaller parts: 1) direct using long-specialized functions in ceval.c, and 2) optimize the fast path in these functions, and test them separately and combined. May be only one way will add a gain.