[Mesa-dev] [PATCH 2/2] gallium/docs: clarify TGSI_SEMANTIC_SAMPLEMASK, again

[Brian Paul]

On 06/12/2017 11:49 AM, Nicolai Hähnle wrote:
> On 12.06.2017 19:37, Brian Paul wrote:
>> I've since discovered the fragment shader sample mask input (which
>> corresponds to gl_SampleMaskIn).
>> ---
>>   src/gallium/docs/source/tgsi.rst | 15 +++++++++++----
>>   1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/src/gallium/docs/source/tgsi.rst
>> b/src/gallium/docs/source/tgsi.rst
>> index 310b49d..7ca07dd 100644
>> --- a/src/gallium/docs/source/tgsi.rst
>> +++ b/src/gallium/docs/source/tgsi.rst
>> @@ -3328,10 +3328,17 @@ the center of the fragment.
>>   TGSI_SEMANTIC_SAMPLEMASK
>>   """"""""""""""""""""""""
>> -For fragment shaders, this semantic label indicates that an output
>> contains
>> -the sample mask used to disable further sample processing.  The output's
>> -type is uint[4] but only the X component is used (i.e.
>> gl_SampleMask[0]).
>> -Each bit corresponds to one sample position (up to 32x MSAA is
>> supported).
>> +For fragment shaders, this semantic label can be applied to either a
>> +shader input or output.
>> +
>> +For an input, the sample mask indicates the set of samples covered by
>> +the current primitive.  If MSAA is not enabled, the value is (~0, ~0,
>> ~0, ~0).
>
> This doesn't match radeonsi behavior. I think you may get (1, ?, ?, ?)
> without MSAA, although I've never tried, and if DX says you get ~0, then
> perhaps that's actually what our hardware does.

DX docs (as usual) don't say.  I'd be ok with (1, undef, undef, undef).

I was just trying to indicate "all samples enabled".

-Brian


>
> But what I'm certain about is that trying to use the yzw components will
> lead to a shader compiler assertion :-)
>
> Cheers,
> Nicolai
>
>
>> +
>> +For an output, the sample mask is used to disable further sample
>> processing.
>> +
>> +For both inputs and outputs, the register type is uint[4] but only the X
>> +component is used (i.e. gl_SampleMask[0]). Each bit corresponds to one
>> +sample position (up to 32x MSAA is supported).
>>   TGSI_SEMANTIC_INVOCATIONID
>>   """"""""""""""""""""""""""
>>
>
>