linux-kernel - Re: [PATCH 2/8] i386: bitops: Rectify bogus "Ir" constraints

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Date:	Mon, 23 Jul 2007 18:30:40 +0200
From:	Andi Kleen <ak@...e.de>
To:	Satyam Sharma <ssatyam@....iitk.ac.in>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>, jh@...e.cz
Subject: Re: [PATCH 2/8] i386: bitops: Rectify bogus "Ir" constraints


> Whoa, thanks for explaining that to me -- I didn't know, obviously. I had
> just written a test program that used "Ir" with an automatic variable
> defined in the inline function (as is the case with these bitops) and
> observed that even when I gave > 32 values, it would still work -- hence
> my conclusion.
> 
> However, the patch still stands, does it not? [ I will modify the
> changelog, obviously. ] The thing is that we don't want to limit
> @nr to <= 31 in the first place, or am I wrong again? :-)

These bit operations only allow 8 bit immediates, so 0..255 would
be correct. N might work from the 4.1 docs, but I don't know if it works 
in all old supported gccs (3.2+)

However I is definitely not wrong and most bit numbers are small anyways.

-Andi
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