Re: [PATCH v6 06/19] range: Introduce range_get_last_bit()

[Eric Auger <eric.auger@redhat.com>]

On 6/3/24 08:10, 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>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  include/qemu/range.h | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/include/qemu/range.h b/include/qemu/range.h
> index 205e1da76d..4ce694a398 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)) {
> +        return -1;
> +    }
> +    return 63 - clz64(range->upb);
> +}
> +
>  /*
>   * Return -1 if @a < @b, 1 @a > @b, and 0 if they touch or overlap.
>   * Both @a and @b must not be empty.