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Re: Some thoughts about steerring commitee work
- From: "Daniel Berlin" <dberlin at dberlin dot org>
- To: "Dorit Nuzman" <DORIT at il dot ibm dot com>
- Cc: "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: Sat, 16 Jun 2007 12:13:17 -0400
- Subject: Re: Some thoughts about steerring commitee work
- References: <46735A20.6080101@redhat.com> <OF457928D7.042936D0-ONC22572FC.00554879-C22572FC.00572314@il.ibm.com>
On 6/16/07, Dorit Nuzman <DORIT@il.ibm.com> wrote:
> H. J. Lu wrote:
>
> >On Fri, Jun 15, 2007 at 06:21:53PM -0700, Ian Lance Taylor wrote:
> Vectorizer is a big a project and may be we will see more improvements
> in future. They promissed implement SLP two years ago and now I see it
> happens. It would be nice to see it not only in loops.
>
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(The page is out of date, the technique they explain where they are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)