Re: [PATCH v4 1/5] lib/bitmap: add bitmap_{set,get}_value()

[Andy Shevchenko]

On Fri, Aug 04, 2023 at 12:55:01PM -0700, Yury Norov wrote:
> On Fri, Aug 04, 2023 at 06:07:00PM +0200, Alexander Potapenko wrote:

> > > > ~BITMAP_FIRST_WORD_MASK(start));
> > >
> > > As I said, ~BITMAP_FIRST_WORD_MASK() is the same as BITMAP_LAST_WORD_MASK()
> > > and vise-versa.
> > 
> > Surprisingly, ~BITMAP_FIRST_WORD_MASK() generates better code than
> > BITMAP_LAST_WORD_MASK().
>  
> Wow... If that's consistent across different compilers/arches, we'd
> just drop the latter. Thanks for pointing that. I'll check.

It might be...

...

> >         map[index] &= (fit ? (~(GENMASK(nbits - 1, 0) << offset)) :
> > ~BITMAP_FIRST_WORD_MASK(start));

...that both parts of ternary are using negation. So compiler may use negation
only once. (Haven't looked at the assembly.)

-- 
With Best Regards,
Andy Shevchenko