linux-kernel - Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64()

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Message-ID: <4BC5D19A.8000605@redhat.com>
Date:	Wed, 14 Apr 2010 17:30:50 +0300
From:	Avi Kivity <avi@...hat.com>
To:	David Howells <dhowells@...hat.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matthew Wilcox <matthew@....cx>,
	Ralf Baechle <ralf@...ux-mips.org>, mingo@...e.hu,
	tglx@...utronix.de, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64()

On 04/14/2010 02:49 PM, David Howells wrote:
> Matthew Wilcox<matthew@....cx>  wrote:
>
>    
>> I don't know whether we can get it /documented/, but the architect I
>> asked said "We'll never get away with reverting to the older behavior,
>> so in essence the architecture is set to not overwrite."
>>      
> Does that mean we can rely on it?  Linus?
>    

Even if Intel processors behave that way, other processors (real and 
emulated) use those manuals as a specification.  Emulated processors are 
unlikely to touch an undefined register, but real processors may.

(qemu tcg appears not to touch the output)

-- 
error compiling committee.c: too many arguments to function

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