linux-kernel - Re: [PATCH 1/3] Fix Unlikely(x) == y

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Message-ID: <20080218184027.429cf47b@laptopd505.fenrus.org>
Date:	Mon, 18 Feb 2008 18:40:27 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Andi Kleen <andi@...stfloor.org>, Willy Tarreau <w@....eu>,
	Roel Kluin <12o3l@...cali.nl>, geoffrey.levand@...sony.com,
	linuxppc-dev@...abs.org, cbe-oss-dev@...abs.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] Fix Unlikely(x) == y

On Tue, 19 Feb 2008 13:33:53 +1100
Nick Piggin <nickpiggin@...oo.com.au> wrote:
> 
> Actually one thing I don't like about gcc is that I think it still
> emits cmovs for likely/unlikely branches, which is silly (the gcc
> developers seem to be in love with that instruction). If that goes
> away, then branch hints may be even better.

only for -Os and only if the result is smaller afaik.
(cmov tends to be a performance loss most of the time so for -O2 and such it
isn't used as far as I know.. it does make for nice small code however ;-)

 


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