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From: Andreas Schwab <schwab@suse.de>
To: James Antill <james@and.org>
Cc: Andi Kleen <ak@suse.de>, linux-kernel@vger.kernel.org
Subject: Re: Linux 2.4.10-pre11 -- __builtin_expect
Date: 27 Sep 2001 14:51:44 +0200	[thread overview]
Message-ID: <jezo7gu78f.fsf@sykes.suse.de> (raw)
In-Reply-To: <20010918031813.57E1062ABC@oscar.casa.dyndns.org.suse.lists.linux.kernel> <E15jBLy-0008UF-00@the-village.bc.nu.suse.lists.linux.kernel> <9o6j9l$461$1@cesium.transmeta.com.suse.lists.linux.kernel> <oup4rq0bwww.fsf_-_@pigdrop.muc.suse.de> <jeelp4rbtf.fsf@sykes.suse.de> <20010918143827.A16003@gruyere.muc.suse.de> <nn3d59qzho.fsf@code.and.org>
In-Reply-To: <nn3d59qzho.fsf@code.and.org> (James Antill's message of "26 Sep 2001 19:54:59 -0400")

James Antill <james@and.org> writes:

|> Andi Kleen <ak@suse.de> writes:
|> 
|> > Good point. I somehow assumed that __builtin_expect would just signify
|> > a boolean, but if I read gcc source correctly this was wrong.
|> 
|>  Yeh, it's a long so you'll get no cast warnings too.
|> 
|> > Here is an updated patch.
|> 
|> [snip ... ]
|> 
|> > --- include/linux/kernel.h-LIKELY	Tue Sep 18 11:12:20 2001
|> > +++ include/linux/kernel.h	Tue Sep 18 14:35:17 2001
|> > @@ -171,4 +171,14 @@
|> >  	char _f[20-2*sizeof(long)-sizeof(int)];	/* Padding: libc5 uses this.. */
|> >  };
|> >  
|> > +
|> > +/* This loses on a few early 2.96 snapshots, but hopefully nobody uses them anymore. */ 
|> > +#if __GNUC__ > 2 || (__GNUC__ == 2 && _GNUC_MINOR__ == 96)
|> > +#define likely(x)  __builtin_expect(!!(x), 1) 
|> > +#define unlikely(x)  __builtin_expect((x), 0) 
|> 
|>  unlikely() also needs to be...
|> 
|> #define unlikely(x)  __builtin_expect(!(x), 1) 
|> 
|> ...or...
|> 
|> #define unlikely(x)  __builtin_expect(!!(x), 0) 

This is not needed, since only 0 is the likely value and !! does not
change that.

Andreas.

-- 
Andreas Schwab                                  "And now for something
Andreas.Schwab@suse.de				completely different."
SuSE Labs, SuSE GmbH, Schanzäckerstr. 10, D-90443 Nürnberg
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5

  reply	other threads:[~2001-09-27 12:51 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20010918031813.57E1062ABC@oscar.casa.dyndns.org.suse.lists.linux.kernel>
     [not found] ` <E15jBLy-0008UF-00@the-village.bc.nu.suse.lists.linux.kernel>
     [not found]   ` <9o6j9l$461$1@cesium.transmeta.com.suse.lists.linux.kernel>
2001-09-18 10:44     ` Andi Kleen
2001-09-18 11:13       ` Andreas Schwab
2001-09-18 12:38         ` Andi Kleen
2001-09-26 23:54           ` James Antill
2001-09-27 12:51             ` Andreas Schwab [this message]
2001-09-27 15:41               ` James Antill
2001-09-27 16:28                 ` Andreas Schwab
2001-10-04 18:52                   ` Richard Henderson
2001-10-08  6:17                     ` James Antill
2001-09-18 20:11         ` Horst von Brand

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