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

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Message-ID: <de8d50360802181122k63410760y9a61f4c42ff251f8@mail.gmail.com>
Date:	Mon, 18 Feb 2008 11:22:18 -0800
From:	"Andrew Pinski" <pinskia@...il.com>
To:	"Geert Uytterhoeven" <Geert.Uytterhoeven@...ycom.com>
Cc:	"Adrian Bunk" <bunk@...nel.org>, "Roel Kluin" <12o3l@...cali.nl>,
	lkml <linux-kernel@...r.kernel.org>, cbe-oss-dev@...abs.org,
	linuxppc-dev@...abs.org, "Willy Tarreau" <w@....eu>,
	"Arjan van de Ven" <arjan@...radead.org>
Subject: Re: [Cbe-oss-dev] [PATCH 1/3] Fix Unlikely(x) == y

On Feb 18, 2008 6:01 AM, Geert Uytterhoeven
<Geert.Uytterhoeven@...ycom.com> wrote:
> > This means it generates faster code with a current gcc for your platform.
> >
> > But a future gcc might e.g. replace the whole loop with a division
> > (gcc SVN head (that will soon become gcc 4.3) already does
> > transformations like replacing loops with divisions [1]).

Yes but the issue is one optimization inside GCC does not take into
account the probability in one case.

And really there is a bug in the linux kernel for not implementing the
long long divide function (or really using libgcc) but that is a
different story and is part of the issue there anyways.

-- Pinski
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