[Python-Dev] Python 3 optimizations continued...

[stefan brunthaler]

> I think that you must deal with big endianess because some RISC can't handle
> at all data in little endian format.
>
> In WPython I have wrote some macros which handle both endianess, but lacking
> big endian machines I never had the opportunity to verify if something was
> wrong.
>
I am sorry for the temporal lapse of not getting back to this directly
yesterday, we were just heading out for lunch and I figured it only
out then but immediately forgot it on our way back to the lab...

So, as I have already said, I evaluated my optimizations on x86
(little-endian) and PowerPC 970 (big-endian) and I did not have to
change any of my instruction decoding during interpretation. (The only
nasty bug I still remember vividly was that while on gcc for x86 the
data type char defaults to signed, whereas it defaults to unsigned on
PowerPC's gcc.) When I have time and access to a PowerPC machine again
(an ARM might be interesting, too), I will take a look at the
generated assembly code to figure out why this is working. (I have
some ideas why it might work without changing the code.)

If I run into any problems, I'll gladly contact you :)

BTW: AFAIR, we emailed last year regarding wpython and IIRC your
optimizations could primarily be summarized as clever
superinstructions. I have not implemented anything in that area at all
(and have in fact not even touched the compiler and its peephole
optimizer), but if parts my implementation gets in, I am sure that you
could add some of your work on top of that, too.

Cheers,
--stefan