Date: Sun, 24 May 2015 06:45:02 +0300 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: AVX2 On Fri, May 22, 2015 at 06:26:45PM +0200, magnum wrote: > I noticed the contest AVX2 core patch and tried applying it to Jumbo. It > works like a champ, including with Deepika's formats. Can I commit this > to bleeding for now? You may, but I'm afraid it breaks a few things: It replaces 256-bit AVX with AVX2, rather than adds AVX2 as an extra for capable CPUs. This might result in AVX2 use attempted in AVX builds. Even if not, it'd make 256-bit AVX no longer available for 32-bit builds with AVX (and without AVX2), which might result in slightly worse performance on Sandy/Ivy Bridge and Bulldozer/Piledriver when running 32-bit OS. I previously used 256-bit AVX on those as a way to partially compensate for 32-bit mode's lower register count. I might choose to drop this anyway, though. IIRC, it also reduces DES_bs_cpt from 32 to 16 unconditionally. This should be wrapped in #ifdef __AVX2__ (or maybe this value should come from the arch-specific .h files instead). Trivial to fix, indeed. I've been meaning to add AVX2 detection to CPU_detect in x86-64.S and x86.S. Right now, I guess it will crash when run on a CPU not supporting AVX2. > >BTW I'm not sure why I never noticed this, but what does the -16 in > >AVX-16 or AVX2-16 mean? > > This still beats me, I'm curious! I initially added SSE2-16 to refer to AMD64's revision of SSE2 with 16 registers. I felt it wasn't the same SSE2, differing to an extent even greater than e.g. SSE2 and SSE3 do. So I felt it needed to be specified differently. Perhaps we're past that point now, with everyone else saying just SSE2, etc., and perhaps some other indication of 32-bit vs. 64-bit build (or just the architecture identifier from configure, to provide even more info on non-x86 builds?) would be worthwhile instead. Alexander
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