[PATCH] x86_64: Optimize ffsll function code size.

[Florian Weimer]

* Sunil Pandey:

> Ffsll is one of the benchmark tests in the phoronix test suite, not
> sure how much it matters to the application. Lots of people involved
> in phoronix benchmark testing/tracking and this kind of random perf
> behavior wastes their time.

That's a good point.  I've seen similar reports before (sadly I don't
recall if they were specifically about ffsll).

Regarding the mechanics of fixing it, if the instruction ordering and
sizing is so sensitive, should this be an assembler implementation
instead?  And will the fix even work for distributions that build with
--enable-cet, considering that there's going to be an additional 4-byte
NOP at the start of the function?

Thanks,
Florian