Re: [PATCH 0/10] use safer test on the result of find_first_zero_bit

[Julia Lawall <julia.lawall@lip6.fr>]

On Wed, 4 Jun 2014, Geert Uytterhoeven wrote:

> Hi Julia,
>
> On Wed, Jun 4, 2014 at 1:00 PM, Julia Lawall <julia.lawall@lip6.fr> wrote:
> > OK, thanks.  I was only looking at the C code.
> >
> > But the C code contains a loop that is followed by:
> >
> >         if (!size)
> >                 return result;
> >         tmp = *p;
> >
> > found_first:
> >         tmp |= ~0UL << size;
> >         if (tmp == ~0UL)        /* Are any bits zero? */
> >                 return result + size;   /* Nope. */
> >
> > In the first return, it would seem that result == size.  Could the second
> > one be changed to just return size?  It should not hurt performance.
>
> "size" may have been changed between function entry and this line.
> So you have to store it in a temporary.

Sorry, after reflection it seems that indeed size + result is always the
original size, so it is actually all of the code that uses >= that is
doing something unnecessary.  == for the failure test is fine.

julia