From owner-freebsd-hackers  Mon Nov 26  9:43:46 2001
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Date: Mon, 26 Nov 2001 09:43:32 -0800 (PST)
From: John Baldwin <jhb@FreeBSD.org>
To: David Xu <davidx@viasoft.com.cn>
Subject: Re: add some constraints in cpufunc.h
Cc: freebsd-hackers@FreeBSD.org
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On 22-Nov-01 David Xu wrote:
> According to GCC manual of inline assembler instruction,  it says if your
> instruction
> changes condition code register(on X86,  it's cpu flag register, and a simple
> addl 
> instruction can affect it),  you'd put cc there, I have reviewed some source
> header
> files of bus management,  they all have cc constraint,  but others not,  and
> some 
> lines lost __volatile__  keyword,  GCC can feel free to optimize them and 
> re-order 
> or delete these lines when it thinks this is a right decision,  this could be
> dangerous
> when high optimizing option is turned on.

Bah, fair enough.  There are probably several places that are missing "cc".  I
doubt that there are very many bugs from this though, since "cc" is clobbered
very often during normal program flow.

-- 

John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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