[Mesa-dev] [PATCH 2/2] ac/nir: don't write tcs outputs to LDS that aren't read back.

Nicolai Hähnle nhaehnle at gmail.com
Wed Nov 15 11:15:10 UTC 2017


On 14.11.2017 06:18, Dave Airlie wrote:
> From: Dave Airlie <airlied at redhat.com>
> 
> If the TCS doesn't read back the outputs, no need to store them
> to LDS in the first place. (except for tess factors).
> 
> This seems to give about 50fps (3290->3330) with tessellation demo.
> 
> I haven't tested if it impacts DoW3 at all.
> 
> Signed-off-by: Dave Airlie <airlied at redhat.com>

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

> ---
>   src/amd/common/ac_nir_to_llvm.c | 17 ++++++++++++++++-
>   1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
> index 3d9f613..e7133ec 100644
> --- a/src/amd/common/ac_nir_to_llvm.c
> +++ b/src/amd/common/ac_nir_to_llvm.c
> @@ -150,6 +150,9 @@ struct nir_to_llvm_context {
>   	unsigned tes_primitive_mode;
>   	uint64_t tess_outputs_written;
>   	uint64_t tess_patch_outputs_written;
> +
> +	uint32_t tcs_patch_outputs_read;
> +	uint64_t tcs_outputs_read;
>   };
>   
>   static inline struct nir_to_llvm_context *
> @@ -2790,7 +2793,15 @@ store_tcs_output(struct nir_to_llvm_context *ctx,
>   	const unsigned comp = instr->variables[0]->var->data.location_frac;
>   	const bool per_vertex = nir_is_per_vertex_io(instr->variables[0]->var, ctx->stage);
>   	const bool is_compact = instr->variables[0]->var->data.compact;
> +	bool store_lds = true;
>   
> +	if (instr->variables[0]->var->data.patch) {
> +		if (!(ctx->tcs_patch_outputs_read & (1U << instr->variables[0]->var->data.location)))
> +			store_lds = false;
> +	} else {
> +		if (!(ctx->tcs_outputs_read & (1ULL << instr->variables[0]->var->data.location)))
> +			store_lds = false;
> +	}
>   	get_deref_offset(ctx->nir, instr->variables[0],
>   			 false, NULL, per_vertex ? &vertex_index : NULL,
>   			 &const_index, &indir_index);
> @@ -2827,7 +2838,8 @@ store_tcs_output(struct nir_to_llvm_context *ctx,
>   			continue;
>   		LLVMValueRef value = llvm_extract_elem(&ctx->ac, src, chan - comp);
>   
> -		ac_lds_store(&ctx->ac, dw_addr, value);
> +		if (store_lds || is_tess_factor)
> +			ac_lds_store(&ctx->ac, dw_addr, value);
>   
>   		if (!is_tess_factor && writemask != 0xF)
>   			ac_build_buffer_store_dword(&ctx->ac, ctx->hs_ring_tess_offchip, value, 1,
> @@ -6550,6 +6562,9 @@ LLVMModuleRef ac_translate_nir_to_llvm(LLVMTargetMachineRef tm,
>   			ctx.gs_next_vertex = ac_build_alloca(&ctx.ac, ctx.ac.i32, "gs_next_vertex");
>   
>   			ctx.gs_max_out_vertices = shaders[i]->info.gs.vertices_out;
> +		} else if (shaders[i]->info.stage == MESA_SHADER_TESS_CTRL) {
> +			ctx.tcs_outputs_read = shaders[i]->info.outputs_read;
> +			ctx.tcs_patch_outputs_read = shaders[i]->info.patch_outputs_read;
>   		} else if (shaders[i]->info.stage == MESA_SHADER_TESS_EVAL) {
>   			ctx.tes_primitive_mode = shaders[i]->info.tess.primitive_mode;
>   		} else if (shaders[i]->info.stage == MESA_SHADER_VERTEX) {
> 


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


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