Re: PowerPC optional instructions
Re: PowerPC optional instructions
- Subject: Re: PowerPC optional instructions
- From: Urs Heckmann <email@hidden>
- Date: Wed, 26 May 2004 10:51:06 +0200
Hiya Os,
the reciprocal estimate is a bit tricky, as the precision varies from
processor to processor. I think I've read it's only like a 256th on a
G5 (maybe in the SIMD engine only?), so it's a bit noisy even with some
iterations of Newton-Raphson refinement.
I'm using these special instructions quite a lot, like the reciprocal
square root estimate (frsqrte), the float select (fsel) etc. without
problems so far. Of coure, every compiler makes use of fmadds, fabs
etc. anyway.
However, it's a pity that the vector extensions aren't available on G3
machines. These rock.
Cheers,
;) Urs
Am 26.05.2004 um 00:50 schrieb Os:
Hi,
while optimising my code, I came across a compiler warning that the
'fres' (reciprocal estimate) instruction is optional in the PowerPC
architecture.
Can anyone point me at a list of which optional instructions are
supported on which Apple processors?
I'm only really interested in supporting G3s and above.
cheers,
os.
email@hidden
http://www.collective.co.uk/
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