[Mesa-dev] [PATCH] ac/nir: mark some texture intrinsics as convergent

[Marek Olšák]

The first and last hunks look like they shouldn't be there. Other than that:

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

Marek

On Fri, May 31, 2019 at 11:53 AM Rhys Perry <pendingchaos02 at gmail.com>
wrote:

> Otherwise LLVM can sink them and their texture coordinate calculations
> into divergent branches.
>
> v2: simplify the conditions on which the intrinsic is marked as convergent
> v3: only mark as convergent in FS and CS with derivative groups
>
> Cc: <mesa-stable at lists.freedesktop.org>
> Signed-off-by: Rhys Perry <pendingchaos02 at gmail.com>
> ---
>  src/amd/common/ac_nir_to_llvm.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/src/amd/common/ac_nir_to_llvm.c
> b/src/amd/common/ac_nir_to_llvm.c
> index 265e3b636c4..9e9fade7227 100644
> --- a/src/amd/common/ac_nir_to_llvm.c
> +++ b/src/amd/common/ac_nir_to_llvm.c
> @@ -38,6 +38,7 @@ struct ac_nir_context {
>         struct ac_shader_abi *abi;
>
>         gl_shader_stage stage;
> +       shader_info *info;
>
>         LLVMValueRef *ssa_defs;
>
> @@ -1394,6 +1395,22 @@ static LLVMValueRef build_tex_intrinsic(struct
> ac_nir_context *ctx,
>         }
>
>         args->attributes = AC_FUNC_ATTR_READNONE;
> +       bool cs_derivs = ctx->stage == MESA_SHADER_COMPUTE &&
> +                        ctx->info->cs.derivative_group !=
> DERIVATIVE_GROUP_NONE;
> +       if (ctx->stage == MESA_SHADER_FRAGMENT || cs_derivs) {
> +               /* Prevent texture instructions with implicit derivatives
> from being
> +                * sinked into branches. */
> +               switch (instr->op) {
> +               case nir_texop_tex:
> +               case nir_texop_txb:
> +               case nir_texop_lod:
> +                       args->attributes |= AC_FUNC_ATTR_CONVERGENT;
> +                       break;
> +               default:
> +                       break;
> +               }
> +       }
> +
>         return ac_build_image_opcode(&ctx->ac, args);
>  }
>
> @@ -4350,6 +4367,7 @@ void ac_nir_translate(struct ac_llvm_context *ac,
> struct ac_shader_abi *abi,
>         ctx.abi = abi;
>
>         ctx.stage = nir->info.stage;
> +       ctx.info = &nir->info;
>
>         ctx.main_function = LLVMGetBasicBlockParent(LLVMGetInsertBlock(
> ctx.ac.builder));
>
> --
> 2.21.0
>
>
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