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Date: Tue, 21 Oct 2014 23:36:21 +0200
From: Luigi Rizzo <rizzo@iet.unipi.it>
To: Andriy Gapon <avg@freebsd.org>
Subject: Re: svn commit: r273274 - head/sys/netpfil/ipfw
Message-ID: <20141021213621.GA70907@onelab2.iet.unipi.it>
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User-Agent: Mutt/1.5.20 (2009-06-14)
Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
 src-committers@freebsd.org, "Alexander V. Chernikov" <melifaro@freebsd.org>
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On Sun, Oct 19, 2014 at 03:02:07PM +0300, Andriy Gapon wrote:
> On 19/10/2014 14:15, Alexander V. Chernikov wrote:
> > +static uint32_t
> > +roundup2p(uint32_t v)
> > +{
> > +
> > +	v--;
> > +	v |= v >> 1;
> > +	v |= v >> 2;
> > +	v |= v >> 4;
> > +	v |= v >> 8;
> > +	v |= v >> 16;
> > +	v++;
> > +
> > +	return (v);
> > +}
> 
> I think that on platforms where an optimized version of fls() is available that
> would work faster than this cool piece of bit magic.

This code is not performance critical. I wouldn't bother optimizing it.

Rather, since this code must be platform independent, I'd like
to give it a name that does not conflict with any builtin.

cheers
luigi
>