linux-kernel - Re: if (unlikely(...)) == unnecessary?

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Message-ID: <alpine.DEB.1.10.0901281130020.21401@alien.or.mcafeemobile.com>
Date:	Wed, 28 Jan 2009 11:41:16 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Chris Snook <csnook@...hat.com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: if (unlikely(...)) == unnecessary?

On Wed, 28 Jan 2009, Chris Snook wrote:

> Davide Libenzi wrote:
> > I noticed that GCC >= 3.3 (not tried the ones before) automatically branches
> > out the "if" code (and follow-through the "else" code, if there). Is that a
> > coincidence or a rule we can rely on going forward?
> 
> That's the default behavior, but there are lots of things that can cause it to
> behave differently.

Please don't keep me hanging. What are they (just a few of the "lots" 
that makes GCC follow-through "if" code)?

- Davide

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