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From: Andrew Pinski <pinskia@gmail.com>
To: "jak@jak-linux.org" <gcc-bugzilla@gcc.gnu.org>
Cc: "gcc-bugs@gcc.gnu.org" <gcc-bugs@gcc.gnu.org>
Subject: Re: [Bug c/46186] Clang creates code running 1600 times faster than gcc's
Date: Tue, 26 Oct 2010 15:56:00 -0000 [thread overview]
Message-ID: <7F0406A6-2B6A-4230-8DCC-81A5F362BA58@gmail.com> (raw)
In-Reply-To: <4cc6e60b.2811970a.71aa.016aSMTPIN_ADDED@mx.google.com>
On Oct 26, 2010, at 7:30 AM, "jak@jak-linux.org" <gcc-bugzilla@gcc.gnu.org
> wrote:
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46186
>
> --- Comment #1 from Julian Andres Klode <jak@jak-linux.org>
> 2010-10-26 14:30:24 UTC ---
> Created attachment 22162
> --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22162
> Clang's assember
This multiplication transformation is incorrect if the loop wraps
(unsigned always wraps; never overflows). Gcc is correct in its speed.
Though -O3 is faster but not because of multiplication but rather
constant propatagtion. So this bug is invalid and some one should
report a bug to llvm folks about this.
>
> Attaching the assembler output from clang, it should help understand
> which
> optimizations clang does (and improve gcc to do them as well).
next prev parent reply other threads:[~2010-10-26 15:56 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-26 14:27 [Bug c/46186] New: " jak@jak-linux.org
2010-10-26 14:30 ` [Bug c/46186] " jak@jak-linux.org
2010-10-26 14:31 ` paolo.carlini at oracle dot com
2010-10-26 14:33 ` jak@jak-linux.org
2010-10-26 14:47 ` redi at gcc dot gnu.org
2010-10-26 14:53 ` jak@jak-linux.org
2010-10-26 14:59 ` dominiq at lps dot ens.fr
2010-10-26 15:00 ` jak@jak-linux.org
2010-10-26 15:26 ` jak@jak-linux.org
2010-10-26 15:29 ` redi at gcc dot gnu.org
2010-10-26 15:37 ` jakub at gcc dot gnu.org
2010-10-26 15:43 ` paolo.carlini at oracle dot com
2010-10-26 15:56 ` pinskia at gmail dot com
[not found] ` <4cc6e60b.2811970a.71aa.016aSMTPIN_ADDED@mx.google.com>
2010-10-26 15:56 ` Andrew Pinski [this message]
2010-10-26 16:36 ` dominiq at lps dot ens.fr
2010-10-26 16:59 ` jakub at gcc dot gnu.org
2010-10-26 17:15 ` dominiq at lps dot ens.fr
2010-10-26 18:44 ` jakub at gcc dot gnu.org
2010-10-26 18:54 ` dominiq at lps dot ens.fr
2010-10-26 19:12 ` jakub at gcc dot gnu.org
2010-10-26 20:30 ` joseph at codesourcery dot com
2010-10-26 21:00 ` jakub at gcc dot gnu.org
2010-10-26 21:07 ` dominiq at lps dot ens.fr
2010-10-29 21:07 ` tg at mirbsd dot org
2010-10-29 21:44 ` [Bug tree-optimization/46186] " sebpop at gmail dot com
2010-10-29 21:59 ` joseph at codesourcery dot com
2014-02-16 13:13 ` jackie.rosen at hushmail dot com
2021-08-28 23:42 ` pinskia at gcc dot gnu.org
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