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

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Message-ID: <alpine.LFD.2.00.1003261042580.3721@i5.linux-foundation.org>
Date:	Fri, 26 Mar 2010 10:45:05 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Howells <dhowells@...hat.com>
cc:	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 Fri, 26 Mar 2010, David Howells wrote:
> 
> Hmmm...  My ancient Borland Assembler dead-tree manual doesn't mention that.

I went back and checked the old Intel 386 docs from -92 or something, and 
it was "undefined" in there too. So at least Intel seems to have been very 
consistent on this.

That said, maybe all implementations actually do the "don't touch" thing. 

But I do have this memory of us doing this ten+ years ago, though, and 
having to check the ZF after all. Which is why I reacted to the patch in 
the first place and checked the documentation.

			Linus
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