[Mesa-dev] [PATCH] radv: make use of nir_lower_load_const_to_scalar()

[Bas Nieuwenhuizen]

Reviewed-by: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
On Mon, Sep 24, 2018 at 10:19 AM Timothy Arceri <tarceri at itsqueeze.com> wrote:
>
> This allows NIR to CSE more operations. LLVM does this also so the
> impact is limited, however doing this in NIR allows other opts to
> make progress. For example in radeonsi more loops are unrolled in
> Civilization Beyond Earth.
>
> The actual pipeline-db stats are not overwhelming but even in the
> negatively affected shaders the NIR is clearly better. It just
> happens that the code shuffling and in some cases calls to max
> rather than a flt result in the final output from LLVM not
> giving as good numbers.
>
> However this is an incremental opt that further passes build off
> so the change should be made IMO.
>
> Totals from affected shaders:
> SGPRS: 20192 -> 20184 (-0.04 %)
> VGPRS: 19516 -> 19524 (0.04 %)
> Spilled SGPRs: 437 -> 444 (1.60 %)
> Spilled VGPRs: 0 -> 0 (0.00 %)
> Private memory VGPRs: 0 -> 0 (0.00 %)
> Scratch size: 0 -> 0 (0.00 %) dwords per thread
> Code Size: 1527444 -> 1522276 (-0.34 %) bytes
> LDS: 6 -> 6 (0.00 %) blocks
> Max Waves: 1018 -> 1016 (-0.20 %)
> Wait states: 0 -> 0 (0.00 %)
> ---
>  src/amd/vulkan/radv_shader.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/src/amd/vulkan/radv_shader.c b/src/amd/vulkan/radv_shader.c
> index 9c038a5570d..3e3eb96a531 100644
> --- a/src/amd/vulkan/radv_shader.c
> +++ b/src/amd/vulkan/radv_shader.c
> @@ -316,6 +316,8 @@ radv_shader_compile_to_nir(struct radv_device *device,
>                         .lower_vote_eq_to_ballot = 1,
>                 });
>
> +       nir_lower_load_const_to_scalar(nir);
> +
>         if (!(flags & VK_PIPELINE_CREATE_DISABLE_OPTIMIZATION_BIT))
>                 radv_optimize_nir(nir, false);
>
> --
> 2.17.1
>
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