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From: Vincent Lefevre <vincent+gcc@vinc17.org>
To: gcc@gcc.gnu.org
Subject: Re: Optimizing floating point *(2^c) and /(2^c)
Date: Wed, 31 Mar 2010 12:03:00 -0000	[thread overview]
Message-ID: <20100331092539.GL14245@prunille.vinc17.org> (raw)
In-Reply-To: <alpine.DEB.2.00.1003311046030.26351@stedding.saclay.inria.fr>

On 2010-03-31 11:04:03 +0200, Marc Glisse wrote:
> IMHO this transformation mostly makes sense for the
> -ffinite-math-only case where you can replace: "put a constant and
> multiply/divide" by "put a constant and add/sub" and never care
> about extracting the exponent, overflowing, or anything else. And in
> that case, it does look like a nice optimization.

I suppose that this could be interesting only if a same register
can be seen as a FP one and an integer one (for the addition on
the exponent field), hoping that mixing both kinds of operations
won't stall the pipeline.

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)

  reply	other threads:[~2010-03-31  9:25 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-29 17:38 Jeroen Van Der Bossche
2010-03-29 20:30 ` Geert Bosch
2010-03-29 22:43   ` Tim Prince
2010-03-31 15:29     ` Geert Bosch
2010-03-30 19:03   ` Jeroen Van Der Bossche
2010-03-31  6:07     ` Vincent Lefevre
2010-03-31  9:25       ` Marc Glisse
2010-03-31 12:03         ` Vincent Lefevre [this message]
2010-04-01 16:21           ` Paolo Bonzini

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