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Re: Some thoughts about steerring commitee work
- From: Ira Rosen <IRAR at il dot ibm dot com>
- To: "Daniel Berlin" <dberlin at dberlin dot org>
- Cc: Dorit Nuzman <DORIT at il dot ibm dot com>, "Vladimir N. Makarov" <vmakarov at redhat dot com>, "Eric Botcazou" <ebotcazou at libertysurf dot fr>, gcc at gcc dot gnu dot org, "H. J. Lu" <hjl at lucon dot org>, "Ian Lance Taylor" <iant at google dot com>
- Date: Sun, 17 Jun 2007 15:11:20 +0300
- Subject: Re: Some thoughts about steerring commitee work
"Daniel Berlin" <dberlin@dberlin.org> wrote on 16/06/2007:
> On 6/16/07, Dorit Nuzman <DORIT@il.ibm.com> wrote:
>
> > Do you have specific examples where SLP helps performance out of loops?
>
> hash calculations.
>
> For md5, you can get a 2x performance improvement by straight-line
> vectorizing it
> sha1 is about 2-2.5x
>
> (This assumes you do good pack/unpack placement using something like
> lazy code motion)
>
> See, for example, http://arctic.org/~dean/crypto/sha1.html
>
> (The page is out of date, the technique they explain where they are
> doing straight line computation of the hash in parallel, is exactly
> what SLP would provide out of loops)
I looked at the above page (and also at MD5 and SHA1 implementations). I
found only computations inside loops.
Could you please explain what exactly you refer to as SLP out of loops in
this benchmark?
Thanks,
Ira