Re: [PATCH 0/10] use safer test on the result of find_first_zero_bit
From: Julia Lawall
Date: Wed Jun 04 2014 - 09:12:43 EST
On Wed, 4 Jun 2014, Geert Uytterhoeven wrote:
> Hi Julia,
> On Wed, Jun 4, 2014 at 1:00 PM, Julia Lawall <julia.lawall@xxxxxxx> 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.
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