[Python-Dev] Python 3 optimizations continued... (original) (raw)

stefan brunthaler stefan at brunthaler.net
Wed Aug 31 18:54:41 CEST 2011

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

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