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Date: Sat, 28 Jun 2008 12:09:13 +1000 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Marius Strobl <marius@alchemy.franken.de>
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Cc: cvs-src@freebsd.org, Christoph Mallon <christoph.mallon@gmx.de>,
	src-committers@freebsd.org, cvs-all@freebsd.org
Subject: Re: cvs commit: src/sys/sparc64/include in_cksum.h
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On Sat, 28 Jun 2008, Marius Strobl wrote:

> On Fri, Jun 27, 2008 at 09:58:31PM +0200, Christoph Mallon wrote:
>>
>> This approach seems wrong to me and I think it works only by chance. The
>
> I wasn't aware that the clobber list allows to explicitly specify
> the condition codes, thanks for the hint. Though it unfortunately
> took me longer than two days to verify it's effect on the generated
> code; sparc64 could still have been one of the archs where "cc" has
> no effect.

I think it still only works by chance.

> Besides I don't think using "__volatile" for this is
> that wrong, given that the sparc64 code generated by using "cc"
> and "__volatile" is nearly identical and given that at least i386
> relies on "__volatile" telling GCC that the inline assembler uses
> the condition codes since quite some time. So the condition codes
> are probably part of what GCC treats as "important side-effects".

No, the comments in the i386 version are rotted bits left over from
old failing attempts to fix this problem.

Bruce