Re: [PATCH v3 06/19] range: Introduce range_get_last_bit()

[Cédric Le Goater]

On 4/30/24 11:58, Duan, Zhenzhong wrote:
> > -----Original Message-----
> > From: Cédric Le Goater <clg@redhat.com>
> > Subject: Re: [PATCH v3 06/19] range: Introduce range_get_last_bit()
> >
> > On 4/29/24 08:50, Zhenzhong Duan wrote:
> > > This helper get the highest 1 bit position of the upper bound.
> > >
> > > If the range is empty or upper bound is zero, -1 is returned.
> > >
> > > Suggested-by: Cédric Le Goater <clg@redhat.com>
> > > Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> > > ---
> > >    include/qemu/range.h | 11 +++++++++++
> > >    1 file changed, 11 insertions(+)
> > >
> > > diff --git a/include/qemu/range.h b/include/qemu/range.h
> > > index 205e1da76d..8e05bc1d9f 100644
> > > --- a/include/qemu/range.h
> > > +++ b/include/qemu/range.h
> > > @@ -20,6 +20,8 @@
> > >    #ifndef QEMU_RANGE_H
> > >    #define QEMU_RANGE_H
> > >
> > > +#include "qemu/bitops.h"
> > > +
> > >    /*
> > >     * Operations on 64 bit address ranges.
> > >     * Notes:
> > > @@ -217,6 +219,15 @@ static inline int ranges_overlap(uint64_t first1,
> > uint64_t len1,
> > >        return !(last2 < first1 || last1 < first2);
> > >    }
> > >
> > > +/* Get highest non-zero bit position of a range */
> > > +static inline int range_get_last_bit(Range *range)
> > > +{
> > > +    if (range_is_empty(range) || !range->upb) {
> > > +        return -1;
> > > +    }
> > > +    return find_last_bit(&range->upb, sizeof(range->upb));
> >
> > This breaks builds on 32-bit host systems.
>
> Oh, I missed 32bit build. Thanks, will fix.

This should provide the same result ?

    return 63 - clz64(range->upb);

Thanks,

C.