[Mesa-dev] [PATCH 3/3] amd/common: only load used channels when sampling buffer views

[Nicolai Hähnle]

For the series:

Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>

On 10.01.2018 20:12, Samuel Pitoiset wrote:
> This allows to reduce the number of dwords that are loaded
> with buffer_load_format_xyzw. For example, when the only used
> channel is 1, the driver will emit buffer_load_format_x instead.
> 
> Shader stats for DOW3 (with some local hacky scripts for SPIRV):
> 
> 143 shaders in 143 tests
> Totals:
> SGPRS: 5344 -> 5352 (0.15 %)
> VGPRS: 3476 -> 3452 (-0.69 %)
> Spilled SGPRs: 30 -> 29 (-3.33 %)
> Spilled VGPRs: 0 -> 0 (0.00 %)
> Private memory VGPRs: 0 -> 0 (0.00 %)
> Scratch size: 0 -> 0 (0.00 %) dwords per thread
> Code Size: 269860 -> 269808 (-0.02 %) bytes
> LDS: 0 -> 0 (0.00 %) blocks
> Max Waves: 1267 -> 1272 (0.39 %)
> Wait states: 0 -> 0 (0.00 %)
> 
> The 'const' qualifier has to be removed to avoid a compilation
> warning with nir_ssa_def_components_read().
> 
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>   src/amd/common/ac_nir_to_llvm.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
> index 8f5df12e3d..bafbdbb250 100644
> --- a/src/amd/common/ac_nir_to_llvm.c
> +++ b/src/amd/common/ac_nir_to_llvm.c
> @@ -2242,16 +2242,19 @@ static LLVMValueRef radv_lower_gather4_integer(struct ac_llvm_context *ctx,
>   }
>   
>   static LLVMValueRef build_tex_intrinsic(struct ac_nir_context *ctx,
> -					const nir_tex_instr *instr,
> +					nir_tex_instr *instr,
>   					bool lod_is_zero,
>   					struct ac_image_args *args)
>   {
>   	if (instr->sampler_dim == GLSL_SAMPLER_DIM_BUF) {
> +		unsigned mask = nir_ssa_def_components_read(&instr->dest.ssa);
> +
>   		return ac_build_buffer_load_format(&ctx->ac,
>   						   args->resource,
>   						   args->addr,
>   						   ctx->ac.i32_0,
> -						   4, true);
> +						   util_last_bit(mask),
> +						   true);
>   	}
>   
>   	args->opcode = ac_image_sample;
> 


-- 
Lerne, wie die Welt wirklich ist,
Aber vergiss niemals, wie sie sein sollte.