[Mesa-dev] [PATCH] radeonsi: emit s_waitcnt for shader memory barriers and volatile

[Marek Olšák]

Reviewed-by: Marek Olšák <marek.olsak at amd.com>

Marek

On Mon, Apr 18, 2016 at 12:27 AM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>
> Turns out that this is needed after all to satisfy some strengthened
> coherency tests. Depends on support in LLVM, see
> http://reviews.llvm.org/D19203
> ---
> Note that this patch applies on top of the compute shader series, otherwise
> you'll get a trivial merge conflict.
>
>  src/gallium/drivers/radeonsi/si_shader.c | 32 +++++++++++++++++++-------------
>  1 file changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
> index dcbdde3..0398a28 100644
> --- a/src/gallium/drivers/radeonsi/si_shader.c
> +++ b/src/gallium/drivers/radeonsi/si_shader.c
> @@ -2826,6 +2826,13 @@ static void emit_optimization_barrier(struct si_shader_context *ctx)
>         LLVMBuildCall(builder, inlineasm, NULL, 0, "");
>  }
>
> +static void emit_waitcnt(struct si_shader_context *ctx)
> +{
> +       LLVMBuilderRef builder = ctx->radeon_bld.gallivm.builder;
> +       lp_build_intrinsic(builder, "llvm.amdgcn.s.waitcnt.all",
> +                          ctx->voidt, NULL, 0, LLVMNoUnwindAttribute);
> +}
> +
>  static void membar_emit(
>                 const struct lp_build_tgsi_action *action,
>                 struct lp_build_tgsi_context *bld_base,
> @@ -2833,14 +2840,7 @@ static void membar_emit(
>  {
>         struct si_shader_context *ctx = si_shader_context(bld_base);
>
> -       /* Since memoryBarrier only makes guarantees about atomics and
> -        * coherent image accesses (which bypass TC L1), we do not need to emit
> -        * any special cache handling here.
> -        *
> -        * We do have to prevent LLVM from re-ordering loads across
> -        * the barrier though.
> -        */
> -       emit_optimization_barrier(ctx);
> +       emit_waitcnt(ctx);
>  }
>
>  static LLVMValueRef
> @@ -3200,7 +3200,7 @@ static void load_emit(
>         }
>
>         if (inst->Memory.Qualifier & TGSI_MEMORY_VOLATILE)
> -               emit_optimization_barrier(ctx);
> +               emit_waitcnt(ctx);
>
>         if (inst->Src[0].Register.File == TGSI_FILE_BUFFER) {
>                 load_emit_buffer(ctx, emit_data);
> @@ -3390,6 +3390,7 @@ static void store_emit(
>                 struct lp_build_tgsi_context *bld_base,
>                 struct lp_build_emit_data *emit_data)
>  {
> +       struct si_shader_context *ctx = si_shader_context(bld_base);
>         struct gallivm_state *gallivm = bld_base->base.gallivm;
>         LLVMBuilderRef builder = gallivm->builder;
>         const struct tgsi_full_instruction * inst = emit_data->inst;
> @@ -3397,11 +3398,16 @@ static void store_emit(
>         char intrinsic_name[32];
>         char coords_type[8];
>
> -       if (inst->Dst[0].Register.File == TGSI_FILE_BUFFER) {
> -               store_emit_buffer(si_shader_context(bld_base), emit_data);
> +       if (inst->Dst[0].Register.File == TGSI_FILE_MEMORY) {
> +               store_emit_memory(ctx, emit_data);
>                 return;
> -       } else if (inst->Dst[0].Register.File == TGSI_FILE_MEMORY) {
> -               store_emit_memory(si_shader_context(bld_base), emit_data);
> +       }
> +
> +       if (inst->Memory.Qualifier & TGSI_MEMORY_VOLATILE)
> +               emit_waitcnt(ctx);
> +
> +       if (inst->Dst[0].Register.File == TGSI_FILE_BUFFER) {
> +               store_emit_buffer(ctx, emit_data);
>                 return;
>         }
>
> --
> 2.5.0
>
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