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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
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From: Andreas Schwab <schwab@suse.de>
Date: 27 Sep 2001 18:28:08 +0200
In-Reply-To: <nnvgi4prod.fsf@code.and.org> (James Antill's message of "27 Sep 2001 11:41:22 -0400")
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James Antill <james@and.org> writes:

|> Andreas Schwab <schwab@suse.de> writes:
|> 
|> > James Antill <james@and.org> writes:
|> > 
|> > |>  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.
|> 
|>  Yes it is, given the code...
|> 
|> struct blah *ptr = NULL;
|> 
|> if (unlikely(ptr))
|> 
|> ...you'll get a warning from gcc because you are implicitly converting
|> from a pointer to a long.

You're right, seems like __builtin_expect is really only defined for pure
boolean values.

Andreas.

-- 
Andreas Schwab                                  "And now for something
Andreas.Schwab@suse.de				completely different."
SuSE Labs, SuSE GmbH, Schanzäckerstr. 10, D-90443 Nürnberg
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