Message-ID: <47387E32.4050206@t-online.de>
Date: Mon, 12 Nov 2007 17:24:18 +0100
From: Bernd Schmidt <bernds_cb1@t-online.de>
User-Agent: Thunderbird 2.0.0.6 (X11/20070810)
MIME-Version: 1.0
To: Adrian Bunk <bunk@kernel.org>
CC: Sam Ravnborg <sam@ravnborg.org>, linux-kernel@vger.kernel.org
Subject: Re: [RFC: 2.6 patch] add -fno-tree-scev-cprop to KBUILD_CFLAGS
References: <20071111064829.GG21669@stusta.de>
In-Reply-To: <20071111064829.GG21669@stusta.de>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1121
Lines: 34

Adrian Bunk wrote:
> The gcc from svn that will become gcc 4.3 generates libgcc calls in 
> cases like the following (on 32bit architectures):
> 
> <--  snip  -->
> 
> static inline void timespec_add_ns(struct timespec *a, u64 ns)
> {
> ...
>         while(ns >= NSEC_PER_SEC) {
>                 ns -= NSEC_PER_SEC;
>                 a->tv_sec++;
>         }
> ...
> 
> <--  snip  -->
> 
> It can make sense to emit assembler code doing division for such C code -
> that doesn't seem to be something that would generally be wrong.

It can be a pretty huge performance regression, so gcc ought to be fixed.


Bernd
-- 
This footer brought to you by insane German lawmakers.
Analog Devices GmbH      Wilhelm-Wagenfeld-Str. 6      80807 Muenchen
Sitz der Gesellschaft Muenchen, Registergericht Muenchen HRB 40368
Geschaeftsfuehrer Thomas Wessel, William A. Martin, Margaret Seif
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/