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From: "tg at mirbsd dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/46186] Clang creates code running 1600 times faster than gcc's
Date: Fri, 29 Oct 2010 21:07:00 -0000 [thread overview]
Message-ID: <20101029210700.-cvGjvkmwvrJO9mSR0RTERKLUbwMkOtyLRYqQYDtiAg@z> (raw)
In-Reply-To: <bug-46186-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46186
Thorsten Glaser <tg at mirbsd dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |tg at mirbsd dot org
--- Comment #22 from Thorsten Glaser <tg at mirbsd dot org> 2010-10-29 21:06:44 UTC ---
(In reply to comment #19)
> It's a bit more complicated than that, in that you can't just compute
> (b*(b-1)-a*(a-1)) mod 2^n, then divide by 2, as that will lose the top
> bit. (I haven't checked exactly what the generated code is doing here.)
Haven’t checked either, but in i386 asm, using RCR instead of SHR would work
if the carry flag is correct after the sequence calculating that (or SAR).
next prev parent reply other threads:[~2010-10-29 21:07 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
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 [this message]
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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