From: Zdenek Dvorak <rakdver@atrey.karlin.mff.cuni.cz>
To: Paolo Carlini <pcarlini@suse.de>
Cc: Andrew Pinski <pinskia@physics.uc.edu>,
Scott Robert Ladd <coyote@coyotegulch.com>,
gcc@gcc.gnu.org
Subject: Re: GCC beaten by ICC in stupid trig test!
Date: Mon, 15 Mar 2004 13:29:00 -0000 [thread overview]
Message-ID: <20040315132907.GA25288@atrey.karlin.mff.cuni.cz> (raw)
In-Reply-To: <405592D6.3060200@suse.de>
Hello,
> >The reason why still is that ICC will just unroll the loop to be "r =
> >doit(a)*100000000.0" so that is the reasons why
> >ICC is better than GCC at doing this stupid trig test (note this is
> >transformation
> >is only valid if fast-math is on as you loose precision).
>
> In the meanwhile we have learned that the real reason why Icc performs
> better then mainline gcc is the use of an iterative SSE instruction
> (see Dan Nicolaescu message).
>
> On the other hand, gcc-lno "appear" to perform as well as Icc because of
> the unrolling trick (just checked that gcc-lno transforms the loop to
> the trivial:
>
> 8048470: 40 inc %eax
> 8048471: d8 c1 fadd %st(1),%st
> 8048473: 3d 00 e1 f5 05 cmp $0x5f5e100,%eax
> 8048478: 75 f6 jne 8048470 <main+0x20>)
>
> Now, my question is: why gcc-lno is doing that also when -ffast-math is
> *not* passed???
doing what? I do not see any loop related optimization here.
Zdenek
next prev parent reply other threads:[~2004-03-15 13:29 UTC|newest]
Thread overview: 116+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-14 23:40 GCC viciously beaten by ICC in " Scott Robert Ladd
2004-03-14 23:49 ` Gabriel Dos Reis
2004-03-15 1:47 ` Scott Robert Ladd
2004-03-15 0:11 ` Paolo Carlini
2004-03-15 1:47 ` Scott Robert Ladd
2004-03-15 2:07 ` Daniel Berlin
2004-03-15 2:30 ` Scott Robert Ladd
2004-03-15 2:31 ` Daniel Berlin
2004-03-15 2:38 ` Scott Robert Ladd
2004-03-15 10:00 ` Sebastian Pop
2004-03-15 0:12 ` GCC beaten by ICC in stupid " Andrew Pinski
2004-03-15 0:32 ` Paolo Carlini
2004-03-15 1:31 ` Scott Robert Ladd
2004-03-15 2:36 ` Scott Robert Ladd
2004-03-15 11:25 ` Paolo Carlini
2004-03-15 11:31 ` Paolo Carlini
2004-03-15 13:29 ` Zdenek Dvorak [this message]
2004-03-15 13:42 ` Paolo Carlini
2004-03-15 13:51 ` Zdenek Dvorak
2004-03-15 13:55 ` Paolo Carlini
2004-03-15 14:00 ` Zdenek Dvorak
2004-03-15 14:05 ` Joseph S. Myers
2004-03-15 14:13 ` Paolo Carlini
2004-03-15 14:18 ` Zdenek Dvorak
2004-03-15 14:29 ` Segher Boessenkool
2004-03-15 14:28 ` Joseph S. Myers
2004-03-15 1:55 ` GCC viciously beaten by ICC in " Roger Sayle
2004-03-15 2:22 ` Dan Nicolaescu
2004-03-15 12:05 ` Stelios Xanthakis
2004-03-15 18:22 ` Dan Nicolaescu
2004-03-15 2:41 ` Kaveh R. Ghazi
2004-03-15 6:06 ` Andreas Jaeger
2004-03-15 8:57 ` Gabriel Dos Reis
2004-03-15 2:41 ` Scott Robert Ladd
2004-03-15 3:05 ` Gabriel Dos Reis
2004-03-15 14:47 ` Segher Boessenkool
2004-03-15 17:44 ` Geert Bosch
2004-03-15 17:46 ` Geert Bosch
2004-03-15 3:01 ` Gabriel Dos Reis
2004-03-15 4:06 ` Scott Robert Ladd
2004-03-15 5:15 ` James Morrison
2004-03-15 8:20 ` Jakub Jelinek
2004-03-15 18:13 ` Joe Buck
2004-03-16 13:31 ` Jakub Jelinek
2004-03-15 7:42 ` Ranjit Mathew
2004-03-15 19:00 ` Toon Moene
2004-03-15 19:44 ` Laurent GUERBY
2004-03-15 16:06 GCC beaten by ICC in stupid " Robert Dewar
2004-03-16 8:45 ` Per Abrahamsen
2004-03-17 0:09 ` Robert Dewar
2004-03-17 0:36 ` Scott Robert Ladd
2004-03-17 5:53 ` Gabriel Dos Reis
2004-03-17 7:21 ` Robert Dewar
2004-03-17 9:10 ` Gabriel Dos Reis
2004-03-21 16:55 ` Robert Dewar
2004-03-23 19:38 ` Joe Buck
2004-03-23 19:58 ` Gabriel Dos Reis
2004-03-23 20:49 ` Laurent GUERBY
2004-03-24 8:17 ` Toon Moene
2004-03-24 13:50 ` Robert Dewar
2004-03-24 18:25 ` Paul Koning
2004-03-24 18:51 ` Robert Dewar
2004-03-25 18:18 ` Per Abrahamsen
2004-03-27 1:26 ` Robert Dewar
2004-03-24 18:56 ` Joe Buck
2004-03-24 19:10 ` Robert Dewar
2004-03-24 19:14 ` Richard Guenther
2004-03-24 19:39 ` Paul Brook
2004-03-24 19:45 ` Dave Korn
2004-03-24 20:57 ` Paul Brook
2004-03-25 6:14 ` Robert Dewar
2004-03-25 18:32 ` Scott Robert Ladd
2004-03-27 1:28 ` Robert Dewar
2004-03-17 14:51 ` Per Abrahamsen
2004-03-17 15:18 ` Gabriel Dos Reis
2004-03-17 16:05 ` Per Abrahamsen
2004-03-16 12:14 ` Scott Robert Ladd
2004-03-17 0:19 ` Robert Dewar
2004-03-24 19:04 Bradley Lucier
2004-03-24 19:29 ` Joe Buck
2004-03-24 19:43 ` Bradley Lucier
2004-03-24 19:50 ` Joe Buck
2004-03-24 23:48 ` Toon Moene
2004-03-25 0:02 ` Toon Moene
2004-03-25 0:11 ` Roger Sayle
2004-03-25 5:56 ` Scott Robert Ladd
2004-03-25 6:07 ` Bradley Lucier
2004-03-25 8:18 ` Robert Dewar
2004-03-25 16:15 ` Roger Sayle
2004-03-25 16:36 ` David Edelsohn
2004-03-25 17:09 ` Scott Robert Ladd
2004-03-25 17:47 ` David Edelsohn
2004-03-25 18:03 ` Scott Robert Ladd
2004-03-26 1:29 ` Toon Moene
2004-03-27 0:23 ` Daniel Egger
2004-03-27 0:50 ` Laurent GUERBY
2004-03-27 0:55 ` Joe Buck
2004-03-27 0:58 ` Laurent GUERBY
2004-03-27 1:16 ` Joe Buck
2004-03-25 5:36 ` Gabriel Dos Reis
2004-03-25 8:46 ` Robert Dewar
2004-03-25 5:34 ` Gabriel Dos Reis
2004-03-25 7:24 ` Robert Dewar
2004-03-25 8:28 ` Gabriel Dos Reis
2004-03-25 18:19 ` Per Abrahamsen
2004-03-24 20:14 ` Paul Koning
2004-03-24 21:00 ` Joe Buck
2004-03-24 22:20 ` Dale Johannesen
2004-03-24 21:07 ` Joseph S. Myers
2004-03-24 21:38 ` Joe Buck
2004-03-24 21:44 ` Joe Buck
2004-03-24 22:49 ` Joseph S. Myers
2004-03-24 22:19 ` Richard Guenther
2004-03-24 22:21 ` Dale Johannesen
2004-03-25 7:29 ` Robert Dewar
2004-03-25 16:51 Wolfgang Bangerth
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