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

[Marek Olšák]

Hi,

For AMD guys: Is it okay with you to push this patch series?

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
>