svn commit: r363242 - head/sys/amd64/include

[Mateusz Guzik]

Sounds good, albeit true to my commit message, I'm strongly
recommending you run both at the same time. I had ORIG_ and NEW_, with
ffs calling both and comparing the result.

But perhaps more importantly this may be a good time to create a
MI-header for this stuff and do a pass with other archs. We are long
past a point where hand-rolled primitives make sense in the common
case.

On 7/16/20, Mitchell Horne <mhorne at freebsd.org> wrote:
> On Thu, Jul 16, 2020 at 8:28 AM Mateusz Guzik <mjg at 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
>


-- 
Mateusz Guzik <mjguzik gmail.com>