Re: [KJ] anyone interested in the "power of 2" stuff?

[Vignesh Babu BM <vignesh.babu@wipro.com>]

I have a doubt:
There are instances as follows:

/* ASIC location registers should be 0 or have only a single bit set. */
    if (   (iobase_reg  & (iobase_reg - 1))

here and in other similar situations the variables values vary from 0
and above
In such checks the above might be more optimized...as the is_power_of_2
will
1. check for 0 and fail that
2. check for even and pass it
3. or if it is odd...fail it

op 1 would be done followed by op 2/3

The code would be like
if(!iobase_reg && !is_power_of_2(iobase_reg))
---where we are checking for 0 at 2 places-both inside and outside of
is_power_of_2

But the n & (n-1) is just one step.
Is this not more optimised?

What would you suggest here?

On Fri, 2007-02-09 at 07:39 -0500, Robert P. J. Day wrote:
> On Fri, 9 Feb 2007, Vignesh Babu BM wrote:
> 
> >
> > On Thu, 2007-02-08 at 17:17 -0500, Robert P. J. Day wrote:
> >
> > > http://fsdev.net/wiki/index.php?title=Power_of_2_stuff
> > >
> > >   any takers?
> > >
> > > rday
> > >
> >
> > I would take that up rday.
> 
> ok, have at it, and keep us up to date on the wiki page.
> 
> rday
> 
> p.s.  note that we still haven't formalized the rounding stuff so, as
> i mention in the wiki page, the only changes should involve *just*
> strict power of 2 testing, and not as part of a larger bit of code
> that's trying to round, or anything like that.
> 
-- 
Regards,  
Vignesh Babu BM  
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