On Wed, Mar 7, 2018 at 6:47 AM, Bas Nieuwenhuizen <b...@basnieuwenhuizen.nl>
wrote:

> The old vote_eq implementation supported only booleans, but now
> we have to support arbitrary values, so use the read_first_invocation
> intrinsic + ballot.
>
> I took this as an opportunity to figure out how easy it was to do this
> in nir instead of in the nir_to_llvm pass, and it actually turned out
> pretty okay IMO. Only creating the pass is some extra code.
>

We have nir_lower_subgroups for exactly this sort of thing.  You might as
well put it in common code in case anyone else wants it.  Also, it means
you can drop the boiler-plate. :-)  Just put it behind a flag
lower_vote_to_cmp or something.


> Reviewed-by: Dave Airlie <airl...@redhat.com>
> ---
>  src/amd/Makefile.sources            |  1 +
>  src/amd/common/ac_lower_subgroups.c | 92 ++++++++++++++++++++++++++++++
> +++++++
>  src/amd/common/ac_nir_to_llvm.c     |  8 ++--
>  src/amd/common/ac_nir_to_llvm.h     |  2 +
>  src/amd/common/meson.build          |  1 +
>  5 files changed, 99 insertions(+), 5 deletions(-)
>  create mode 100644 src/amd/common/ac_lower_subgroups.c
>
> diff --git a/src/amd/Makefile.sources b/src/amd/Makefile.sources
> index 10c4827e19..f57dd403c5 100644
> --- a/src/amd/Makefile.sources
> +++ b/src/amd/Makefile.sources
> @@ -44,6 +44,7 @@ AMD_COMPILER_FILES = \
>         common/ac_llvm_helper.cpp \
>         common/ac_llvm_util.c \
>         common/ac_llvm_util.h \
> +       common/ac_lower_subgroups.c \
>         common/ac_shader_abi.h \
>         common/ac_shader_info.c \
>         common/ac_shader_info.h \
> diff --git a/src/amd/common/ac_lower_subgroups.c
> b/src/amd/common/ac_lower_subgroups.c
> new file mode 100644
> index 0000000000..d0782b481b
> --- /dev/null
> +++ b/src/amd/common/ac_lower_subgroups.c
> @@ -0,0 +1,92 @@
> +/*
> + * Copyright © 2018 Google Inc.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the
> "Software"),
> + * to deal in the Software without restriction, including without
> limitation
> + * the rights to use, copy, modify, merge, publish, distribute,
> sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the
> next
> + * paragraph) shall be included in all copies or substantial portions of
> the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT
> SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
> OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> DEALINGS
> + * IN THE SOFTWARE.
> + */
> +
> +#include "nir/nir.h"
> +#include "nir/nir_builder.h"
> +
> +#include "ac_nir_to_llvm.h"
> +
> +static nir_ssa_def *ac_lower_subgroups_intrin(nir_builder *b,
> nir_intrinsic_instr *intrin)
> +{
> +       switch(intrin->intrinsic) {
> +       case nir_intrinsic_vote_ieq:
> +       case nir_intrinsic_vote_feq: {
> +               nir_intrinsic_instr *rfi =
> +                       nir_intrinsic_instr_create(b->shader,
> nir_intrinsic_read_first_invocation);
> +               nir_ssa_dest_init(&rfi->instr, &rfi->dest,
> +                                 1, intrin->src[0].ssa->bit_size, NULL);
> +               nir_src_copy(&rfi->src[0], &intrin->src[0], rfi);
> +               rfi->num_components = 1;
> +
> +               nir_ssa_def *is_ne;
> +               if (intrin->intrinsic == nir_intrinsic_vote_feq)
> +                       is_ne = nir_fne(b, &rfi->dest.ssa,
> intrin->src[0].ssa);
> +               else
> +                       is_ne = nir_ine(b, &rfi->dest.ssa,
> intrin->src[0].ssa);
> +
> +               nir_intrinsic_instr *ballot =
> +                       nir_intrinsic_instr_create(b->shader,
> nir_intrinsic_ballot);
> +               nir_ssa_dest_init(&ballot->instr, &ballot->dest,
> +                                 1, 64, NULL);
> +               ballot->src[0] = nir_src_for_ssa(is_ne);
> +               ballot->num_components = 1;
> +
> +               return nir_ieq(b, &ballot->dest.ssa, nir_imm_int64(b, 0));
> +       }
> +       default:
> +               return NULL;
> +       }
> +}
> +
> +bool ac_lower_subgroups(struct nir_shader *shader)
> +{
> +       bool progress = false;
> +
> +       nir_foreach_function(function, shader) {
> +               if (!function->impl)
> +                       continue;
> +
> +               nir_builder b;
> +               nir_builder_init(&b, function->impl);
> +
> +               nir_foreach_block(block, function->impl) {
> +                       nir_foreach_instr_safe(instr, block) {
> +                               if (instr->type !=
> nir_instr_type_intrinsic)
> +                                       continue;
> +
> +                               nir_intrinsic_instr *intrin =
> nir_instr_as_intrinsic(instr);
> +                               b.cursor = nir_before_instr(instr);
> +
> +                               nir_ssa_def *lower =
> ac_lower_subgroups_intrin(&b, intrin);
> +                               if (!lower)
> +                                       continue;
> +
> +                               nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
> nir_src_for_ssa(lower));
> +                               nir_instr_remove(instr);
> +                               progress = true;
> +                       }
> +               }
> +       }
> +
> +       return progress;
> +}
> diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_
> llvm.c
> index d2df2837c8..3bf1a4ba3c 100644
> --- a/src/amd/common/ac_nir_to_llvm.c
> +++ b/src/amd/common/ac_nir_to_llvm.c
> @@ -4563,11 +4563,6 @@ static void visit_intrinsic(struct ac_nir_context
> *ctx,
>                 result = LLVMBuildSExt(ctx->ac.builder, tmp, ctx->ac.i32,
> "");
>                 break;
>         }
> -       case nir_intrinsic_vote_eq: {
> -               LLVMValueRef tmp = ac_build_vote_eq(&ctx->ac, get_src(ctx,
> instr->src[0]));
> -               result = LLVMBuildSExt(ctx->ac.builder, tmp, ctx->ac.i32,
> "");
> -               break;
> -       }
>         default:
>                 fprintf(stderr, "Unknown intrinsic: ");
>                 nir_print_instr(&instr->instr, stderr);
> @@ -6737,6 +6732,9 @@ void ac_nir_translate(struct ac_llvm_context *ac,
> struct ac_shader_abi *abi,
>         struct ac_nir_context ctx = {};
>         struct nir_function *func;
>
> +       /* Last minute passes for both radv & radeonsi */
> +       ac_lower_subgroups(nir);
> +
>         ctx.ac = *ac;
>         ctx.abi = abi;
>
> diff --git a/src/amd/common/ac_nir_to_llvm.h b/src/amd/common/ac_nir_to_
> llvm.h
> index eea393a9c2..306039aecf 100644
> --- a/src/amd/common/ac_nir_to_llvm.h
> +++ b/src/amd/common/ac_nir_to_llvm.h
> @@ -234,4 +234,6 @@ void ac_lower_indirect_derefs(struct nir_shader *nir,
> enum chip_class);
>  void ac_nir_translate(struct ac_llvm_context *ac, struct ac_shader_abi
> *abi,
>                       struct nir_shader *nir);
>
> +bool ac_lower_subgroups(struct nir_shader *shader);
> +
>  #endif /* AC_NIR_TO_LLVM_H */
> diff --git a/src/amd/common/meson.build b/src/amd/common/meson.build
> index 22c13b955f..6c5c2f45ac 100644
> --- a/src/amd/common/meson.build
> +++ b/src/amd/common/meson.build
> @@ -35,6 +35,7 @@ amd_common_files = files(
>    'ac_llvm_helper.cpp',
>    'ac_llvm_util.c',
>    'ac_llvm_util.h',
> +  'ac_lower_subgroups.c',
>    'ac_shader_abi.h',
>    'ac_shader_info.c',
>    'ac_shader_info.h',
> --
> 2.16.1
>
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