Subject: Re: [PATCH] 2.4.22pre10: {,un}likely_p() macros for pointers
From: Albert Cahalan <albert@users.sf.net>
To: Andrew Morton OSDL <akpm@osdl.org>
Cc: Albert Cahalan <albert@users.sourceforge.net>, willy@w.ods.org,
       chip@pobox.com,
       linux-kernel mailing list <linux-kernel@vger.kernel.org>,
       davem@redhat.com
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Date: 11 Aug 2003 19:13:58 -0400
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On Mon, 2003-08-11 at 14:55, Andrew Morton wrote:
> Albert Cahalan <albert@users.sourceforge.net> wrote:
> >
> > -#define likely(x)	__builtin_expect((x),1)
> > -#define unlikely(x)	__builtin_expect((x),0)
> > +#define likely(x)	__builtin_expect(!!(x),1)
> > +#define unlikely(x)	__builtin_expect(!!(x),0)
> 
> Odd.  I thought we fixed that ages ago.
> 
> Being a simple soul, I prefer __builtin_expect((x) != 0, 1).

That's much harder to read. The !! is a nice
neat idiom. The other way requires a bit of thought.
(is that == or !=, a 0 or 1, and what does that
compute to?)

The !! is visually distinctive. It has only one use.
When you see it, you instantly know that a value is
being converted to the pure boolean form.


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