From: Jakub Jelinek <jakub@redhat.com>
To: Jan Hubicka <jh@suse.cz>
Cc: Gabriel Dos Reis <gdr@integrable-solutions.net>,
Richard Henderson <rth@redhat.com>,
gcc-patches@gcc.gnu.org, aj@suse.de
Subject: Re: Converting floor to rint
Date: Thu, 07 Nov 2002 01:32:00 -0000 [thread overview]
Message-ID: <20021107043221.K10988@devserv.devel.redhat.com> (raw)
In-Reply-To: <20021107092112.GF7964@kam.mff.cuni.cz>; from jh@suse.cz on Thu, Nov 07, 2002 at 10:21:12AM +0100
On Thu, Nov 07, 2002 at 10:21:12AM +0100, Jan Hubicka wrote:
> > | On the related note. How bad would you consider converting
> > | floor(x) into rint(x-0.5) in the fast-math mode?
> >
> > If you think you do want to do that transformation, then I would
> > prefer this
> >
> > floor(x) -> nearbyint(x-0.5)
> >
> > | That transformation would do a miracles for i386, where rint is faster
> > | than floor by quite a lot and should suffice for 3D application in
> > | reliablility. I can imagine it to fail only for very large numbers...
> >
> > Not really. floor(1) == 1 and rint(1 - 0.5) maybe be 0 or 1 depending
> > on the current rounding mode.
> Hmm, is rint really expected to be dependent on the rouding mode?
> Man page claims:
> The nearbyint functions round their argument to an integer value
> in floating point format, using the current
> rounding direction and without raising the inexact
> exception.
>
> The rint functions do the same, but will raise the
> inexact exception when the result differs in value
> from the argument.
>
> I can builtinize nearbyint too if it makes sense. I am bit confused by
> rint. Does it imply that rint will raise exception for any non-integral
> arugment?
If FE_INEXACT is enabled, yes.
Jakub
next prev parent reply other threads:[~2002-11-07 9:32 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-11-05 9:14 Simplify floating point conversions Jan Hubicka
2002-11-05 9:38 ` Richard Henderson
2002-11-05 9:42 ` Jan Hubicka
2002-11-06 1:23 ` Simplify floating point conversions II Jan Hubicka
2002-11-06 3:08 ` Michael Matz
2002-11-06 4:36 ` Jan Hubicka
2002-11-06 9:54 ` Jan Hubicka
2002-11-06 10:09 ` Richard Henderson
2002-11-06 13:11 ` Jan Hubicka
2002-11-06 13:19 ` Jan Hubicka
2002-11-06 13:35 ` Gabriel Dos Reis
2002-11-06 13:36 ` Jan Hubicka
2002-11-06 14:06 ` Gabriel Dos Reis
2002-11-06 14:29 ` Converting floor to rint Jan Hubicka
2002-11-06 14:47 ` Richard Henderson
2002-11-06 14:53 ` Jan Hubicka
2002-11-06 14:55 ` Gabriel Dos Reis
2002-11-07 1:21 ` Jan Hubicka
2002-11-07 1:32 ` Jakub Jelinek [this message]
2002-11-07 1:33 ` Gabriel Dos Reis
2002-11-07 1:44 ` Jan Hubicka
2002-11-07 1:52 ` Jakub Jelinek
2002-11-07 1:54 ` Jan Hubicka
2002-11-07 2:04 ` Jan Hubicka
2002-11-07 4:47 ` Gabriel Dos Reis
2002-11-07 4:56 ` Jan Hubicka
2002-11-07 5:14 ` Andreas Schwab
2002-11-07 5:27 ` Gabriel Dos Reis
2002-11-07 5:31 ` Jan Hubicka
2002-11-07 5:35 ` Andreas Schwab
2002-11-07 5:22 ` Gabriel Dos Reis
2002-11-07 5:43 ` Andreas Schwab
2002-11-07 6:23 ` Gabriel Dos Reis
2002-11-07 7:01 ` Jan Hubicka
2002-11-07 7:18 ` Gabriel Dos Reis
2002-11-06 13:48 ` Simplify floating point conversions III Jan Hubicka
2002-11-06 14:55 ` Richard Henderson
2002-11-07 2:54 ` Simplify floating point conversions IV Jan Hubicka
2002-11-18 15:01 ` Richard Henderson
2002-11-05 11:14 ` Simplify floating point conversions Geoff Keating
2002-11-06 1:09 ` Jan Hubicka
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