[Mesa-dev] [PATCH] radv: try to select better export formats for chips without Rb+

[Bas Nieuwenhuizen]

On Tue, Jan 22, 2019 at 4:32 PM Samuel Pitoiset
<samuel.pitoiset at gmail.com> wrote:
>
> For some R8 formats, it's useless to export two channels
> when no alpha blending is used. I assume the CB should
> automatically clamps its inputs.
>
> 29077 shaders in 15096 tests
> Totals:
> SGPRS: 1321106 -> 1320970 (-0.01 %)
> VGPRS: 935936 -> 935948 (0.00 %)
> Spilled SGPRs: 25186 -> 25204 (0.07 %)
> Code Size: 49813556 -> 49796944 (-0.03 %) bytes
> Max Waves: 242091 -> 242088 (-0.00 %)
>
> Totals from affected shaders:
> SGPRS: 170608 -> 170472 (-0.08 %)
> VGPRS: 99752 -> 99764 (0.01 %)
> Spilled SGPRs: 10377 -> 10395 (0.17 %)
> Code Size: 6332492 -> 6315880 (-0.26 %) bytes
> Max Waves: 12317 -> 12314 (-0.02 %)
>
> This helps some Rise Of Tomb Raider shaders, especially
> when an expcnt instruction is added between two MRT exports.
>
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>  src/amd/vulkan/radv_pipeline.c | 27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
>
> diff --git a/src/amd/vulkan/radv_pipeline.c b/src/amd/vulkan/radv_pipeline.c
> index 138e153f9a4..25281c3c6da 100644
> --- a/src/amd/vulkan/radv_pipeline.c
> +++ b/src/amd/vulkan/radv_pipeline.c
> @@ -372,9 +372,10 @@ static bool is_dual_src(VkBlendFactor factor)
>         }
>  }
>
> -static unsigned si_choose_spi_color_format(VkFormat vk_format,
> -                                           bool blend_enable,
> -                                           bool blend_need_alpha)
> +static unsigned si_choose_spi_color_format(struct radv_device *device,
> +                                          VkFormat vk_format,
> +                                          bool blend_enable,
> +                                          bool blend_need_alpha)
>  {
>         const struct vk_format_description *desc = vk_format_description(vk_format);
>         unsigned format, ntype, swap;
> @@ -486,6 +487,20 @@ static unsigned si_choose_spi_color_format(VkFormat vk_format,
>                 unreachable("unhandled blend format");
>         }
>
> +       if (device && /* NULL for internal meta formats */
> +           !device->physical_device->rbplus_allowed) {
> +               /* Try to select better export formats for chips without Rb+. */
> +               if (desc->nr_channels == 1 &&
> +                   desc->channel[0].size == 8 &&

Why do we only allow this for 8 bit components? Why not also for
16/32-bit components?

> +                   swap == V_028C70_SWAP_STD && /* R */
> +                   !vk_format_is_srgb(vk_format)) {
> +                       /* Do not need to export two channels for some R8
> +                        * formats when alpha blending isn't used.
> +                        */
> +                       blend = normal = V_028714_SPI_SHADER_32_R;
> +               }
> +       }
> +
>         if (blend_enable && blend_need_alpha)
>                 return blend_alpha;
>         else if(blend_need_alpha)
> @@ -516,7 +531,8 @@ radv_pipeline_compute_spi_color_formats(struct radv_pipeline *pipeline,
>                         bool blend_enable =
>                                 blend->blend_enable_4bit & (0xfu << (i * 4));
>
> -                       cf = si_choose_spi_color_format(attachment->format,
> +                       cf = si_choose_spi_color_format(pipeline->device,
> +                                                       attachment->format,
>                                                         blend_enable,
>                                                         blend->need_src_alpha & (1 << i));
>                 }
> @@ -586,7 +602,8 @@ const VkFormat radv_fs_key_format_exemplars[NUM_META_FS_KEYS] = {
>
>  unsigned radv_format_meta_fs_key(VkFormat format)
>  {
> -       unsigned col_format = si_choose_spi_color_format(format, false, false);
> +       unsigned col_format =
> +               si_choose_spi_color_format(NULL, format, false, false);

I think we properly need to plumb through the device here?
>
>         assert(col_format != V_028714_SPI_SHADER_32_AR);
>         if (col_format >= V_028714_SPI_SHADER_32_AR)
> --
> 2.20.1
>
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