From: Jakub Jelinek <jakub@redhat.com>
To: Jamie Lokier <jamie@shareable.org>
Cc: Daniel Forrest <forrest@lmcg.wisc.edu>, linux-kernel@vger.kernel.org
Subject: Re: Somewhat OT: gcc, x86, -ffast-math, and Linux
Date: Sat, 27 Mar 2004 10:13:41 -0500 [thread overview]
Message-ID: <20040327151341.GP31589@devserv.devel.redhat.com> (raw)
In-Reply-To: <20040327142459.GF21884@mail.shareable.org>
On Sat, Mar 27, 2004 at 02:24:59PM +0000, Jamie Lokier wrote:
> GCC's manual claims that fsin, fcos and fsqrt instructions are only
> used if the -funsafe-math-optimizations flag is also used, if the GCC
> version is >= 2.6.1. However you may find that Glibc's <math.h> ends
> up using those instructions when -ffast-math is used alone.
Well, -ffast-math sets -funsafe-math-optimizations, unless you do
-ffast-math -fno-unsafe-math-optimizations, so the difference is not that
big. glibc math inlines will be eventually replaced by GCC builtins as soon
as GCC is known to optimize at least as good as glibc's math inlines and so
even that difference will cease to exist.
Jakub
next prev parent reply other threads:[~2004-03-27 15:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-26 20:54 Somewhat OT: gcc, x86, -ffast-math, and Linux Daniel Forrest
2004-03-26 21:26 ` Richard B. Johnson
2004-03-26 21:45 ` Andy Isaacson
2004-03-27 14:24 ` Jamie Lokier
2004-03-27 15:13 ` Jakub Jelinek [this message]
2004-03-29 8:47 ` Eric W. Biederman
2004-03-31 7:14 ` J.A. Magallon
-- strict thread matches above, loose matches on Subject: below --
2004-03-27 14:48 Nick Warne
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