Re: [PATCH] aes-i586-asm.S optimization

[James Morris]

On Thu, 12 Aug 2004, Denis Vlasenko wrote:

> formatting.patch:
> renames macro parameters to more understandable ones
> fixes wrong comment (code does not use MMX)

This looks good, thanks.

> 
> opt.patch:
> convert fwd_rnd into pair of fwd_rnd1,fwd_rnd2 which use
> r0,r2 in mirror-image fashion, thus eliminating the need
> to do "mov r0,r2". After testing, same can be done
> to inv_rnd.

This bumped performance on a P4 Xeon by about 5%, which is pretty good.  
How much more would you expect again with inv_rnd?

> Both patches are only compile tested. First one produces bit-identical
> object file. Second one, understandably, not.
> 
> PS: why aes-i586-asm.S? it is valid _386_ code (no Pentium ops used AFAICS).

My understanding is that the code is generally optimized for Pentium, 
although that could be wrong.  I'll check with the original author.

> PPS: your code is very easy to understand. It was a joy hacking on it :)

It's Brian Gladman's code (converted to gas format by Linus).


- James
-- 
James Morris
<jmorris@xxxxxxxxxx>


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