[Mesa-dev] [PATCH 2/2] radv: call nir_lower_io_to_temporaries for VS, GS, TES and FS

[Timothy Arceri]

 From what I recall with my testing on radeonsi this wasn't really the 
ideal thing to do. Especially when varyings arrays are accessed via and 
indirect index, register use very quickly gets out of control.


On 23/05/18 22:31, Samuel Pitoiset wrote:
> Do not lower FS inputs because this moves all load_var
> instructions at beginning of shaders and because
> interp_var_at_sample (and friends) seem broken. That might
> be eventually enabled later on if we really want to preload
> all FS inputs at beginning.
> 
> Polaris10:
> Totals from affected shaders:
> SGPRS: 54072 -> 54264 (0.36 %)
> VGPRS: 38580 -> 38124 (-1.18 %)
> Spilled SGPRs: 652 -> 652 (0.00 %)
> Spilled VGPRs: 0 -> 0 (0.00 %)
> Code Size: 2128116 -> 2127380 (-0.03 %) bytes
> Max Waves: 8048 -> 8086 (0.47 %)
> 
> Vega10:
> Totals from affected shaders:
> SGPRS: 52616 -> 52656 (0.08 %)
> VGPRS: 37536 -> 37116 (-1.12 %)
> Spilled SGPRs: 828 -> 828 (0.00 %)
> Code Size: 2043756 -> 2042672 (-0.05 %) bytes
> Max Waves: 9176 -> 9254 (0.85 %)
> 
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>   src/amd/vulkan/radv_shader.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/src/amd/vulkan/radv_shader.c b/src/amd/vulkan/radv_shader.c
> index 7ed5d2a421..84ad215ccb 100644
> --- a/src/amd/vulkan/radv_shader.c
> +++ b/src/amd/vulkan/radv_shader.c
> @@ -278,6 +278,16 @@ radv_shader_compile_to_nir(struct radv_device *device,
>   
>   	nir_lower_vars_to_ssa(nir);
>   
> +	if (nir->info.stage == MESA_SHADER_VERTEX ||
> +	    nir->info.stage == MESA_SHADER_GEOMETRY) {
> +		NIR_PASS_V(nir, nir_lower_io_to_temporaries,
> +			   nir_shader_get_entrypoint(nir), true, true);
> +	} else if (nir->info.stage == MESA_SHADER_TESS_EVAL||
> +		   nir->info.stage == MESA_SHADER_FRAGMENT) {
> +		NIR_PASS_V(nir, nir_lower_io_to_temporaries,
> +			   nir_shader_get_entrypoint(nir), true, false);
> +	}
> +
>   	nir_split_var_copies(nir);
>   	nir_lower_var_copies(nir);
>   
>