[Mesa-dev] [PATCH 1/2] radeonsi: simplify gl_FragCoord behavior

[Alex Deucher]

On Tue, Jan 12, 2016 at 1:10 PM, Marek Olšák <maraeo at gmail.com> wrote:
> Hi,
>
> For AMD guys: Is it okay with you to push this patch series?

No objections here.

Alex

>
> Thanks,
>
> Marek
>
> On Fri, Jan 8, 2016 at 2:30 AM, Marek Olšák <maraeo at gmail.com> wrote:
>> From: Marek Olšák <marek.olsak at amd.com>
>>
>> It will become a system value, not an input.
>> ---
>>  src/gallium/drivers/radeonsi/si_state_shaders.c | 45 ++++++++++++-------------
>>  1 file changed, 22 insertions(+), 23 deletions(-)
>>
>> diff --git a/src/gallium/drivers/radeonsi/si_state_shaders.c b/src/gallium/drivers/radeonsi/si_state_shaders.c
>> index 64adf69..460dda5 100644
>> --- a/src/gallium/drivers/radeonsi/si_state_shaders.c
>> +++ b/src/gallium/drivers/radeonsi/si_state_shaders.c
>> @@ -399,30 +399,29 @@ static void si_shader_ps(struct si_shader *shader)
>>         if (!pm4)
>>                 return;
>>
>> -       for (i = 0; i < info->num_inputs; i++) {
>> -               switch (info->input_semantic_name[i]) {
>> -               case TGSI_SEMANTIC_POSITION:
>> -                       /* SPI_BARYC_CNTL.POS_FLOAT_LOCATION
>> -                        * Possible vaules:
>> -                        * 0 -> Position = pixel center (default)
>> -                        * 1 -> Position = pixel centroid
>> -                        * 2 -> Position = at sample position
>> -                        */
>> -                       switch (info->input_interpolate_loc[i]) {
>> -                       case TGSI_INTERPOLATE_LOC_CENTROID:
>> -                               spi_baryc_cntl |= S_0286E0_POS_FLOAT_LOCATION(1);
>> -                               break;
>> -                       case TGSI_INTERPOLATE_LOC_SAMPLE:
>> -                               spi_baryc_cntl |= S_0286E0_POS_FLOAT_LOCATION(2);
>> -                               break;
>> -                       }
>> +       /* SPI_BARYC_CNTL.POS_FLOAT_LOCATION
>> +        * Possible vaules:
>> +        * 0 -> Position = pixel center
>> +        * 1 -> Position = pixel centroid
>> +        * 2 -> Position = at sample position
>> +        *
>> +        * From GLSL 4.5 specification, section 7.1:
>> +        *   "The variable gl_FragCoord is available as an input variable from
>> +        *    within fragment shaders and it holds the window relative coordinates
>> +        *    (x, y, z, 1/w) values for the fragment. If multi-sampling, this
>> +        *    value can be for any location within the pixel, or one of the
>> +        *    fragment samples. The use of centroid does not further restrict
>> +        *    this value to be inside the current primitive."
>> +        *
>> +        * Meaning that centroid has no effect and we can return anything within
>> +        * the pixel. Thus, return the value at sample position, because that's
>> +        * the most accurate one shaders can get.
>> +        */
>> +       spi_baryc_cntl |= S_0286E0_POS_FLOAT_LOCATION(2);
>>
>> -                       if (info->properties[TGSI_PROPERTY_FS_COORD_PIXEL_CENTER] ==
>> -                           TGSI_FS_COORD_PIXEL_CENTER_INTEGER)
>> -                               spi_baryc_cntl |= S_0286E0_POS_FLOAT_ULC(1);
>> -                       break;
>> -               }
>> -       }
>> +       if (info->properties[TGSI_PROPERTY_FS_COORD_PIXEL_CENTER] ==
>> +           TGSI_FS_COORD_PIXEL_CENTER_INTEGER)
>> +               spi_baryc_cntl |= S_0286E0_POS_FLOAT_ULC(1);
>>
>>         /* Find out what SPI_SHADER_COL_FORMAT and CB_SHADER_MASK should be. */
>>         colors_written = info->colors_written;
>> --
>> 2.1.4
>>
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