From: Andi Kleen <ak@suse.de>
To: Serge Belyshev <belyshev@depni.sinp.msu.ru>
Cc: patches@x86-64.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH]: x86_64: Remove unnecessary cast in prefetch()
Date: Fri, 7 Sep 2007 08:18:03 +0100 [thread overview]
Message-ID: <200709070818.03995.ak@suse.de> (raw)
In-Reply-To: <87tzq7cwnt.fsf@depni.sinp.msu.ru>
On Thursday 06 September 2007 22:27, Serge Belyshev wrote:
> It is ok to call prefetch() function with NULL argument, as specifically
> commented in include/linux/prefetch.h. But in standard C, it is invalid to
> dereference NULL pointer (see C99 standard 6.5.3.2 paragraph 4 and note
> #84). Newer gcc versions (4.3 and above) will use that to conclude that "x"
> argument is non-null and thus wreaking havok everywhere prefetch() was
> inlined. Fixed by removing cast and changing asm constraint.
>
> This can be fixed better by using gcc's __builtin_prefetch().
I changed it to just use that. Thanks.
It seems like gcc 3.1/3.2 already supported it and that's the earliest gcc
still supported so it can be used unconditionally.
-Andi
next prev parent reply other threads:[~2007-09-07 7:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-06 21:27 [PATCH]: x86_64: Remove unnecessary cast in prefetch() Serge Belyshev
2007-09-07 7:18 ` Andi Kleen [this message]
2007-09-15 6:40 ` Serge Belyshev
2007-09-15 20:01 ` Andi Kleen
2007-09-15 21:16 ` Serge Belyshev
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