From: Alexey Dobriyan <adobriyan@gmail.com>
To: Randy Dunlap <rdunlap@xenotime.net>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
behlendorf1@llnl.gov, oleg@redhat.com
Subject: Re: [PATCH] remove abs64()
Date: Wed, 13 Apr 2011 00:14:53 +0300 [thread overview]
Message-ID: <20110412211452.GA20135@p183> (raw)
In-Reply-To: <20110412140726.3f4f2a7b.rdunlap@xenotime.net>
On Tue, Apr 12, 2011 at 02:07:26PM -0700, Randy Dunlap wrote:
> On Wed, 13 Apr 2011 00:00:45 +0300 Alexey Dobriyan wrote:
>
> > We don't need no stinking abs64() given some GCC extensions
> > (especially __builtin_choose_expr()).
> >
> > One abs() implementation is better than two abs() implementations.
>
> questionable.
Come on, what's so special in 64-bit types?
> > --- a/include/linux/kernel.h
> > +++ b/include/linux/kernel.h
> > -#define abs64(x) ({ \
> > - s64 __x = (x); \
> > - (__x < 0) ? -__x : __x; \
> > - })
> > +#define abs(x) \
> > +({ \
> > + typeof(x) _x = (x); \
> > + \
> > + __builtin_choose_expr( \
> > + __builtin_types_compatible_p(typeof(_x), signed char), \
> > + (unsigned char)({ _x < 0 ? -_x : _x; }), \
> that is better?
Infinitely better.
sizeof(abs(x)) == sizeof(x) for one thing.
Implementation is ugly, but, hey, one can't do better in C.
next prev parent reply other threads:[~2011-04-12 21:14 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-12 21:00 [PATCH] remove abs64() Alexey Dobriyan
2011-04-12 21:07 ` Randy Dunlap
2011-04-12 21:10 ` Andrew Morton
2011-04-12 21:16 ` Alexey Dobriyan
2011-04-12 21:33 ` Andrew Morton
2011-04-12 21:40 ` Randy Dunlap
2011-04-12 21:14 ` Alexey Dobriyan [this message]
2011-04-13 14:27 ` Oleg Nesterov
2011-04-13 18:48 ` Andrew Morton
2011-04-13 20:20 ` Oleg Nesterov
2011-04-13 20:26 ` Andrew Morton
2011-04-13 20:36 ` Alexey Dobriyan
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