[Mesa-dev] [PATCH 2/2] nir: add lowering for gl_HelperInvocation

[Jason Ekstrand]

On Wed, Jun 6, 2018 at 7:43 AM, Rob Clark <robdclark at gmail.com> wrote:

> Signed-off-by: Rob Clark <robdclark at gmail.com>
> ---
> I can't say for sure that this will work on all drivers, but it is
> what the blob driver does, and it seems to make deqp happy.  I could
> move this to it's own pass inside ir3, but that seemed like overkill
>
>  src/compiler/nir/nir.h                      | 10 ++++++++++
>  src/compiler/nir/nir_lower_system_values.c  | 17 +++++++++++++++++
>  src/gallium/drivers/freedreno/ir3/ir3_nir.c |  1 +
>  3 files changed, 28 insertions(+)
>
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index 073ab4e82ea..de3d55d83af 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -1963,6 +1963,16 @@ typedef struct nir_shader_compiler_options {
>      */
>     bool lower_base_vertex;
>
> +   /**
> +    * If enabled, gl_HelperInvocation will be lowered as:
> +    *
> +    *   !((1 << gl_SampleID) & gl_SampleMaskIN[0]))
>

This only works for multi-sampling.  What about the single-sampled case?

--Jason



> +    *
> +    * TODO any hw w/ more than 32 samples?  For them (if they
> +    * used this option), a bit more math would be involved.
> +    */
> +   bool lower_helper_invocation;
> +
>     bool lower_cs_local_index_from_id;
>
>     bool lower_device_index_to_zero;
> diff --git a/src/compiler/nir/nir_lower_system_values.c
> b/src/compiler/nir/nir_lower_system_values.c
> index 487da042620..6668cbb5dcd 100644
> --- a/src/compiler/nir/nir_lower_system_values.c
> +++ b/src/compiler/nir/nir_lower_system_values.c
> @@ -136,6 +136,23 @@ convert_block(nir_block *block, nir_builder *b)
>                                nir_load_first_vertex(b));
>           break;
>
> +      case SYSTEM_VALUE_HELPER_INVOCATION:
> +         if (b->shader->options->lower_helper_invocation) {
> +            nir_ssa_def *tmp;
> +
> +            tmp = nir_ushr(b,
> +                           nir_imm_int(b, 1),
> +                           nir_load_sample_id(b));
> +
> +            tmp = nir_iand(b,
> +                           nir_load_sample_mask_in(b),
> +                           tmp);
> +
> +            sysval = nir_inot(b, nir_i2b(b, tmp));
> +         }
> +
> +         break;
> +
>        case SYSTEM_VALUE_INSTANCE_INDEX:
>           sysval = nir_iadd(b,
>                             nir_load_instance_id(b),
> diff --git a/src/gallium/drivers/freedreno/ir3/ir3_nir.c
> b/src/gallium/drivers/freedreno/ir3/ir3_nir.c
> index cd1f9c526f2..341d990b269 100644
> --- a/src/gallium/drivers/freedreno/ir3/ir3_nir.c
> +++ b/src/gallium/drivers/freedreno/ir3/ir3_nir.c
> @@ -51,6 +51,7 @@ static const nir_shader_compiler_options options = {
>                 .lower_extract_byte = true,
>                 .lower_extract_word = true,
>                 .lower_all_io_to_temps = true,
> +               .lower_helper_invocation = true,
>  };
>
>  struct nir_shader *
> --
> 2.17.0
>
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