On Thu, Jul 16, 2020 at 8:28 AM Mateusz Guzik <m...@freebsd.org> wrote:
>
> Author: mjg
> Date: Thu Jul 16 11:28:24 2020
> New Revision: 363242
> URL: https://svnweb.freebsd.org/changeset/base/363242
>
> Log:
> amd64: patch ffsl to use the compiler builtin
>
> This shortens fdalloc by over 60 bytes. Correctness verified by running both
> variants at the same time and comparing the result of each call.
>
> Note someone(tm) should make a pass at converting everything else feasible.
>
I have a local version of such a change. I'll see about getting it up
for review in the next little while.
Mitchell
> Modified:
> head/sys/amd64/include/cpufunc.h
>
> Modified: head/sys/amd64/include/cpufunc.h
> ==============================================================================
> --- head/sys/amd64/include/cpufunc.h Thu Jul 16 10:20:35 2020
> (r363241)
> +++ head/sys/amd64/include/cpufunc.h Thu Jul 16 11:28:24 2020
> (r363242)
> @@ -167,7 +167,8 @@ enable_intr(void)
> static __inline __pure2 int
> ffsl(long mask)
> {
> - return (mask == 0 ? mask : (int)bsfq((u_long)mask) + 1);
> +
> + return (__builtin_ffsl(mask));
> }
>
> #define HAVE_INLINE_FFSLL
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