[Mesa-dev] [PATCH 4/5] radv/gfx10: do not enable NGG if a pipeline uses XFB

[Bas Nieuwenhuizen]

On Tue, Jul 23, 2019 at 3:21 PM Samuel Pitoiset
<samuel.pitoiset at gmail.com> wrote:
>
> NGG GS for streamout requires a bunch of work, so enable it with
> the legacy path only for now.
>
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>  src/amd/vulkan/radv_pipeline.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
>
> diff --git a/src/amd/vulkan/radv_pipeline.c b/src/amd/vulkan/radv_pipeline.c
> index a7ff0e2d139..0903e5abf37 100644
> --- a/src/amd/vulkan/radv_pipeline.c
> +++ b/src/amd/vulkan/radv_pipeline.c
> @@ -33,6 +33,7 @@
>  #include "radv_shader.h"
>  #include "nir/nir.h"
>  #include "nir/nir_builder.h"
> +#include "nir/nir_xfb_info.h"
>  #include "spirv/nir_spirv.h"
>  #include "vk_util.h"
>
> @@ -2269,6 +2270,16 @@ radv_generate_graphics_pipeline_key(struct radv_pipeline *pipeline,
>         return key;
>  }
>
> +static bool
> +radv_nir_stage_uses_xfb(const nir_shader *nir)
> +{
> +       nir_xfb_info *xfb = nir_gather_xfb_info(nir, NULL);
> +       bool uses_xfb = !!xfb;
> +
> +       ralloc_free(xfb);
> +       return uses_xfb;
> +}
> +
>  static void
>  radv_fill_shader_keys(struct radv_device *device,
>                       struct radv_shader_variant_key *keys,
> @@ -2321,6 +2332,23 @@ radv_fill_shader_keys(struct radv_device *device,
>                          */
>                         keys[MESA_SHADER_TESS_EVAL].vs_common_out.as_ngg = false;
>                 }
> +
> +               /* TODO: Implement streamout support for NGG. */
> +               bool uses_xfb = false;
> +               if ((nir[MESA_SHADER_VERTEX] &&
> +                    radv_nir_stage_uses_xfb(nir[MESA_SHADER_VERTEX])) ||
> +                   (nir[MESA_SHADER_TESS_EVAL] &&
> +                    radv_nir_stage_uses_xfb(nir[MESA_SHADER_TESS_EVAL])) ||
> +                   (nir[MESA_SHADER_GEOMETRY] &&
> +                    radv_nir_stage_uses_xfb(nir[MESA_SHADER_GEOMETRY])))
> +                       uses_xfb = true;

transform feedback can only happen on the last stage before PS right?
Can we first determine what the last shader is and only then check for
xfb? That way we don't have to scan 3 shaders.
> +
> +               if (uses_xfb) {
> +                       if (nir[MESA_SHADER_TESS_CTRL])
> +                               keys[MESA_SHADER_TESS_EVAL].vs_common_out.as_ngg = false;
> +                       else
> +                               keys[MESA_SHADER_VERTEX].vs_common_out.as_ngg = false;
> +               }
>         }
>
>         for(int i = 0; i < MESA_SHADER_STAGES; ++i)
> --
> 2.22.0
>
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