[Mesa-dev] [PATCH 12/29] tnl: Use bitmask/ffs to iterate enabled lights

[Ian Romanick]

On 05/25/2016 12:57 PM, Matt Turner wrote:
> On Wed, May 25, 2016 at 9:17 AM, Ian Romanick <idr at freedesktop.org> wrote:
>> On 05/23/2016 11:42 PM, Mathias.Froehlich at gmx.net wrote:
>>> From: Mathias Fröhlich <mathias.froehlich at web.de>
>>>
>>> Replaces loops that iterate all lights and test
>>> which of them is enabled by a loop only iterating over
>>> the bits set in the enabled bitmask.
>>> ---
>>>  src/mesa/tnl/t_vb_light.c    |  2 +-
>>>  src/mesa/tnl/t_vb_lighttmp.h | 27 ++++++++++++++++++++-------
>>>  2 files changed, 21 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/src/mesa/tnl/t_vb_light.c b/src/mesa/tnl/t_vb_light.c
>>> index 029265a..0cdb925 100644
>>> --- a/src/mesa/tnl/t_vb_light.c
>>> +++ b/src/mesa/tnl/t_vb_light.c
>>> @@ -394,7 +394,7 @@ static void validate_lighting( struct gl_context *ctx,
>>>        tab = _tnl_light_tab;
>>>     }
>>>     else {
>>> -      if (ctx->Light.EnabledList.next == ctx->Light.EnabledList.prev)
>>> +      if (_mesa_bitcount(ctx->Light._EnabledLights) == 1)
>>
>> I think using an is_pow2() predicate here would be better.  It looks
>> like the only one in Mesa is in src/intel/isl/isl_priv.h, but it should
>> be easy enough to add that to somewhere in src/util.
> 
> _mesa_is_pow_two in imports.h.

Ugh.  So... there are three different versions in the code base, and
each spells things completely different.