Re: [PATCH]: x86 gas: allow 'rep' prefix on 'bsf' and 'bsr' instructions

On Fri, Jul 6, 2012 at 2:52 AM, Jan Beulich <JBeulich@...> wrote:
>>>> On 21.06.12 at 23:36, Roland McGrath <mcgrathr@...> wrote:
>> 'rep; bsf ...'/'rep; bsr ...' are encoded the same as 'tzcnt ...'/'lzcnt
>> ...'.
>
> While tzcnt really is an extension of bsf, lzcnt is not one of bsr,
> so I don't really follow why it's useful to allow the prefix there.
>

It can be used to encode lzcnt with the older assembler,
similar to pause.


--
H.J.