From: Christian Keil <c.keil@tu-harburg.de>
To: gcc-help@gcc.gnu.org
Subject: Re: Floating point optimizations
Date: Fri, 04 Apr 2008 15:48:00 -0000 [thread overview]
Message-ID: <47F61927.8030705@tu-harburg.de> (raw)
In-Reply-To: <20080403172718.GA4451@endeed2.ispras.ru>
Alexander Monakov schrieb:
> This transformation is indeed included into -ffast-math. I checked with
>
> $ gcc --version
> gcc (GCC) 4.1.1 20070105 (Red Hat 4.1.1-52)
>
> and it does eliminate the calculation. What does generated assembly code look
> like in your case? Note you may as well check on this code:
>
> double f(double a, double c)
> {
> return c - (c - a);
> }
That's interesting. After your answer I checked with a gcc from Fedora
Core (Werewolf) and this removes it also. It seems like a backported
enhancement from vanilla gcc, version 4.3.0 does it as well.
Cheers,
Christian
--
Christian Keil /"\
Institute for Reliable Computing \ / ASCII Ribbon Campaign
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next prev parent reply other threads:[~2008-04-04 12:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-03 17:00 Christian Keil
2008-04-03 17:27 ` John Fine
2008-04-04 12:04 ` Christian Keil
2008-04-03 18:24 ` Alexander Monakov
2008-04-04 15:48 ` Christian Keil [this message]
2008-04-05 1:15 ` Tim Prince
2008-04-05 13:07 ` Andrew Haley
2008-04-05 13:32 ` NightStrike
2008-04-05 19:05 ` Tim Prince
2008-04-05 21:26 ` me22
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