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Date: Thu, 02 Nov 2000 13:14:49 +0100
From: Martin Dalecki <dalecki@evision-ventures.com>
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To: Richard Henderson <rth@twiddle.net>
CC: tytso@mit.edu, Jakub Jelinek <jakub@redhat.com>,
        Horst von Brand <vonbrand@sleipnir.valparaiso.cl>,
        linux-kernel@vger.kernel.org
Subject: Re: 2.4.0-test10-pre6: Use of abs()
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Richard Henderson wrote:
> 
> On Wed, Nov 01, 2000 at 09:46:19AM -0500, tytso@mit.edu wrote:
> > What versions of gcc produce the built-in functions?
> 
> 2.95 and previous.  In 2.96 somewhere we fixed a bug that
> automatically prototypes these builtin functions for you;
> ie with current code you get an undeclared function warning.
> 
> > And does it do so for *all* platforms?  (i.e., PPC, Alpha,
> > IA64, etc., etc., etc.)
> 
> Yes.  The thing about abs, though, is that it's "int abs(int)"
> which does naughty things with longs on 64-bit targets.  You're
> much better off writing (x < 0 ? -x : x) directly.

Thank's for answering it... I was already looking up the GCC source for
an exact answer ;-). However what's the difference in respect of
optimization between unrolling the abs function by hand and
relying on the built in?
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