[PATCH] x86_64: Add log2 with FMA

[Sunil Pandey]

On Fri, Aug 11, 2023 at 2:26 AM Paul Zimmermann via Libc-alpha <
libc-alpha@sourceware.org> wrote:

>        Hi H.J.,
>
> > On Skylake, it improves log2 bench performance by:
> >
> >         Before       After     Improvement
> > max     208.779      63.827       69%
> > min     9.977        6.55         34%
> > mean    10.366       6.8191       34%
>
> for what concerns accuracy, after a limited search, I get a small
> improvement
> for the largest known error. It was 0.554114 ulp before (obtained for
> x=0x1.0b53197bd66c8p+0), and I find 0.547517 ulp now (obtained for
> x=0x1.140c8ac38f327p+0).
>
> Paul
>

 I would like to backport this patch to release branches.

Any comments or objections?

--Sunil