[PATCH] x86_64: Optimize ffsll function code size.

[Florian Weimer]

* Alexander Monakov:

> On Thu, 27 Jul 2023, Florian Weimer via Libc-alpha wrote:
>
>> * Noah Goldstein via Libc-alpha:
>> 
>> > Likewise for the string/memory library....
>> > Why not just update it w.o cmov? Just seems like a waste not to
>> > address it while we're at it.
>> 
>> Given that it violates the spec, doing it in an inline function seems
>> kind of risky.
>
> Sorry, what inline function? The function seems to modify an implementation
> in ffsll.c, nothing else.

Yeah, sorry, I was confused.  There's a GCC built-in, right?  So the
glibc implementation probably isn't that important on x86.

Thanks,
Florian