[Mesa-dev] [PATCH 3/4] radv/gfx10: determine correct wave size when lowering subgroups

[Bas Nieuwenhuizen]

So I'm not sure we can actually do this.

AFAIU even though we use a 32-bit wave internally we still have to
expose 64-bit externally, because with
VkPhysicalDeviceSubgroupProperties we say the subgroup size is 64
bits.

So we have to ~emulate a 64-lane wave that always has the upper bits empty.

On Thu, Aug 1, 2019 at 10:40 AM Samuel Pitoiset
<samuel.pitoiset at gmail.com> wrote:
>
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>  src/amd/vulkan/radv_shader.c | 30 +++++++++++++++++-------------
>  1 file changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/src/amd/vulkan/radv_shader.c b/src/amd/vulkan/radv_shader.c
> index 97fa80b348c..f0ab2d5e467 100644
> --- a/src/amd/vulkan/radv_shader.c
> +++ b/src/amd/vulkan/radv_shader.c
> @@ -124,6 +124,17 @@ unsigned shader_io_get_unique_index(gl_varying_slot slot)
>         unreachable("illegal slot in get unique index\n");
>  }
>
> +static uint8_t
> +radv_get_shader_wave_size(const struct radv_physical_device *pdevice,
> +                         gl_shader_stage stage)
> +{
> +       if (stage == MESA_SHADER_COMPUTE)
> +               return pdevice->cs_wave_size;
> +       else if (stage == MESA_SHADER_FRAGMENT)
> +               return pdevice->ps_wave_size;
> +       return pdevice->ge_wave_size;
> +}
> +
>  VkResult radv_CreateShaderModule(
>         VkDevice                                    _device,
>         const VkShaderModuleCreateInfo*             pCreateInfo,
> @@ -422,9 +433,13 @@ radv_shader_compile_to_nir(struct radv_device *device,
>
>         nir_lower_global_vars_to_local(nir);
>         nir_remove_dead_variables(nir, nir_var_function_temp);
> +
> +       uint8_t wave_size = radv_get_shader_wave_size(device->physical_device,
> +                                                     nir->info.stage);
> +
>         nir_lower_subgroups(nir, &(struct nir_lower_subgroups_options) {
> -                       .subgroup_size = 64,
> -                       .ballot_bit_size = 64,
> +                       .subgroup_size = wave_size,
> +                       .ballot_bit_size = wave_size,
>                         .lower_to_scalar = 1,
>                         .lower_subgroup_masks = 1,
>                         .lower_shuffle = 1,
> @@ -667,17 +682,6 @@ radv_get_shader_binary_size(size_t code_size)
>         return code_size + DEBUGGER_NUM_MARKERS * 4;
>  }
>
> -static uint8_t
> -radv_get_shader_wave_size(const struct radv_physical_device *pdevice,
> -                         gl_shader_stage stage)
> -{
> -       if (stage == MESA_SHADER_COMPUTE)
> -               return pdevice->cs_wave_size;
> -       else if (stage == MESA_SHADER_FRAGMENT)
> -               return pdevice->ps_wave_size;
> -       return pdevice->ge_wave_size;
> -}
> -
>  static void radv_postprocess_config(const struct radv_physical_device *pdevice,
>                                     const struct ac_shader_config *config_in,
>                                     const struct radv_shader_variant_info *info,
> --
> 2.22.0
>
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