[Mesa-dev] [PATCH 17/17] radv/ac: enable EXT_shader_subgroup_ballot and EXT_shader_subgroup_vote

[Bas Nieuwenhuizen]

On Sat, Jun 10, 2017 at 1:50 AM, Connor Abbott
<connora at valvesoftware.com> wrote:
> From: Connor Abbott <cwabbott0 at gmail.com>
>
> Signed-off-by: Connor Abbott <cwabbott0 at gmail.com>
> ---
>  src/amd/common/ac_nir_to_llvm.c | 75 +++++++++++++++++++++++++++++++++++++++++
>  src/amd/vulkan/radv_device.c    |  8 +++++
>  src/amd/vulkan/radv_pipeline.c  |  2 ++
>  3 files changed, 85 insertions(+)
>
> diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
> index 5bbd1c5..111e575 100644
> --- a/src/amd/common/ac_nir_to_llvm.c
> +++ b/src/amd/common/ac_nir_to_llvm.c
> @@ -4069,6 +4069,81 @@ static void visit_intrinsic(struct nir_to_llvm_context *ctx,
>         case nir_intrinsic_load_patch_vertices_in:
>                 result = LLVMConstInt(ctx->i32, ctx->options->key.tcs.input_vertices, false);
>                 break;
> +       case nir_intrinsic_ballot:
> +               result = ac_build_ballot(&ctx->ac, get_src(ctx, instr->src[0]));
> +               break;
> +       case nir_intrinsic_read_first_invocation: {
> +               LLVMValueRef src0 = get_src(ctx, instr->src[0]);
> +               ac_build_optimization_barrier(&ctx->ac, &src0);
> +               LLVMValueRef srcs[1] = { src0 };
> +               result = ac_build_intrinsic(&ctx->ac, "llvm.amdgcn.readfirstlane",
> +                                           ctx->i32, srcs, 1,
> +                                           AC_FUNC_ATTR_NOUNWIND |
> +                                           AC_FUNC_ATTR_READNONE |
> +                                           AC_FUNC_ATTR_CONVERGENT);
> +               break;
> +        }
> +       case nir_intrinsic_read_invocation: {
> +               LLVMValueRef src0 = get_src(ctx, instr->src[0]);
> +               ac_build_optimization_barrier(&ctx->ac, &src0);
> +               LLVMValueRef srcs[2] = { src0, get_src(ctx, instr->src[1]) };
> +               result = ac_build_intrinsic(&ctx->ac, "llvm.amdgcn.readlane",
> +                                           ctx->i32, srcs, 2,
> +                                           AC_FUNC_ATTR_NOUNWIND |
> +                                           AC_FUNC_ATTR_READNONE |
> +                                           AC_FUNC_ATTR_CONVERGENT);
> +               break;
> +        }
> +       case nir_intrinsic_load_subgroup_invocation:
> +               result = ac_get_thread_id(&ctx->ac);
> +               break;
> +       case nir_intrinsic_load_subgroup_size:
> +               result = LLVMConstInt(ctx->i32, 64, 0);
> +               break;
> +       case nir_intrinsic_all_invocations:
> +               result = LLVMBuildSExt(ctx->builder,
> +                                      ac_build_vote_all(&ctx->ac,
> +                                                        get_src(ctx, instr->src[0])),
> +                                      ctx->i32, "");

How well does LLVM optimize this? I've always found the boolean as
int32 with -1 and 0 an awkward mapping to LLVM, and am wondering
whether LLVM is able to optimize the SExt away or if a select might be
better.


> +               break;
> +       case nir_intrinsic_any_invocations:
> +               result = LLVMBuildSExt(ctx->builder,
> +                                      ac_build_vote_any(&ctx->ac,
> +                                                        get_src(ctx, instr->src[0])),
> +                                      ctx->i32, "");
> +               break;
> +       case nir_intrinsic_all_invocations_equal:
> +               result = LLVMBuildSExt(ctx->builder,
> +                                      ac_build_vote_eq(&ctx->ac,
> +                                                        get_src(ctx, instr->src[0])),
> +                                      ctx->i32, "");
> +               break;
> +       case nir_intrinsic_load_subgroup_eq_mask: {
> +               LLVMValueRef id = ac_get_thread_id(&ctx->ac);
> +               id = LLVMBuildZExt(ctx->builder, id, ctx->i64, "");
> +               result = LLVMBuildShl(ctx->builder, LLVMConstInt(ctx->i64, 1, 0), id, "");
> +               break;
> +       }
> +       case nir_intrinsic_load_subgroup_ge_mask:
> +       case nir_intrinsic_load_subgroup_gt_mask:
> +       case nir_intrinsic_load_subgroup_le_mask:
> +       case nir_intrinsic_load_subgroup_lt_mask: {
> +               LLVMValueRef id = ac_get_thread_id(&ctx->ac);
> +               if (instr->intrinsic == nir_intrinsic_load_subgroup_gt_mask ||
> +                   instr->intrinsic == nir_intrinsic_load_subgroup_le_mask) {
> +                       /* All bits set except LSB */
> +                       result = LLVMConstInt(ctx->i64, -2, 0);
> +               } else {
> +                       /* All bits set */
> +                       result = LLVMConstInt(ctx->i64, -1, 0);
> +               }
> +               id = LLVMBuildZExt(ctx->builder, id, ctx->i64, "");
> +               result = LLVMBuildShl(ctx->builder, result, id, "");
> +               if (instr->intrinsic == nir_intrinsic_load_subgroup_le_mask ||
> +                   instr->intrinsic == nir_intrinsic_load_subgroup_lt_mask)
> +                       result = LLVMBuildNot(ctx->builder, result, "");
> +               break;
> +       }
>         default:
>                 fprintf(stderr, "Unknown intrinsic: ");
>                 nir_print_instr(&instr->instr, stderr);
> diff --git a/src/amd/vulkan/radv_device.c b/src/amd/vulkan/radv_device.c
> index e9bf44c..ea50acc 100644
> --- a/src/amd/vulkan/radv_device.c
> +++ b/src/amd/vulkan/radv_device.c
> @@ -127,6 +127,14 @@ static const VkExtensionProperties common_device_extensions[] = {
>                 .extensionName = VK_NV_DEDICATED_ALLOCATION_EXTENSION_NAME,
>                 .specVersion = 1,
>         },
> +       {
> +               .extensionName = VK_EXT_SHADER_SUBGROUP_BALLOT_EXTENSION_NAME,
> +               .specVersion = 1,
> +       },
> +       {
> +               .extensionName = VK_EXT_SHADER_SUBGROUP_VOTE_EXTENSION_NAME,
> +               .specVersion = 1,
> +       },
>  };
>
>  static VkResult
> diff --git a/src/amd/vulkan/radv_pipeline.c b/src/amd/vulkan/radv_pipeline.c
> index 39cbd5a..242890a 100644
> --- a/src/amd/vulkan/radv_pipeline.c
> +++ b/src/amd/vulkan/radv_pipeline.c
> @@ -228,6 +228,8 @@ radv_shader_compile_to_nir(struct radv_device *device,
>                         .image_write_without_format = true,
>                         .tessellation = true,
>                         .int64 = true,
> +                       .shader_ballot = true,
> +                       .shader_group_vote = true,
>                 };
>                 entry_point = spirv_to_nir(spirv, module->size / 4,
>                                            spec_entries, num_spec_entries,
> --
> 2.9.4
>
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