[sldev] RFC: Vectorisation control patch

[Paul TBBle Hampson]

On Thu, Aug 16, 2007 at 08:32:46AM -0700, Dzonatas wrote:
> Paul TBBle Hampson wrote:

> >Either way, I think it's a good vote in support of trying all the
> >relevant hand-tuned vectorisations, the gcc autovectorisation, and the
> >non-vectorised code at each run. I'm not totally clear on how expensive
> >that is, but I presume not very, given that to be an optimisation target
> >this routine would have to be called an awful lot anyway.

> Auto-vectorization is only supported by certain compilers. It can't be
> used universally for general open source. It also lacks some operation
> to do fast transformations, which means we still have to use
> hand-coded vectorization to do those.

> Auto-vectorization is nice to speed up general loops, but it doesn't
> make sense to use it to get the fastest inner loop.

My point here is that every time I even mention hand-written Altivec
code, someone points out that Altivec auto-vectorises the _vec code
well enough that it's not worth doing.

Are you now saying that that's not the case? That it would be worth
trying to find some speed gain in the viewer by throwing some time into
the code?

-- 
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Paul "TBBle" Hampson, B.Sc, LPI, MCSE
Very-later-year Asian Studies student, ANU
The Boss, Bubblesworth Pty Ltd (ABN: 51 095 284 361)
Paul.Hampson at Pobox.com

Of course Pacman didn't influence us as kids. If it did,
we'd be running around in darkened rooms, popping pills and
listening to repetitive music.
 -- Kristian Wilson, Nintendo, Inc, 1989

License: http://creativecommons.org/licenses/by/2.1/au/
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