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Re: Some thoughts about steerring commitee work
- From: Dorit Nuzman <DORIT at il dot ibm dot com>
- To: "H. J. Lu" <hjl at lucon dot org>
- Cc: Eric Botcazou <ebotcazou at libertysurf dot fr>, gcc at gcc dot gnu dot org, Ian Lance Taylor <iant at google dot com>, "Vladimir N. Makarov" <vmakarov at redhat dot com>
- Date: Sat, 16 Jun 2007 18:54:46 +0300
- Subject: Re: Some thoughts about steerring commitee work
> On Fri, Jun 15, 2007 at 11:33:52PM -0400, Vladimir N. Makarov wrote:
> > H. J. Lu wrote:
> >
...
> > >
> > >
> > A mount ago I did some measurements of the effect of the vectorizer for
> > Core2 in 64-bit mode. Unfortunately, I saw small improvement (as I
> > remember less than 1% for SPECInt2000).
>
> Vectorizer works only when there are vector instructions available
> which vectorizer can take advantage of. Adding -mssse3 should make
> vectorizer to work a little bit better. SSE4 will improve vectorizer
> even more.
>
> >
> > 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.
>
> There are quite a few known simple cases which vectorizer fails to
> vectorize.
by "known" you mean there are open missed-optimization PRs for them? (if
not - please feel free to open PRs for them!)
thanks,
dorit
> Also, not all x86 vector instructions are supported by
> vectorizer.
>
>
> H.J.