src/compiler/nir/nir_lower_subgroups.c

   1 /*
   2  * Copyright © 2017 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include "nir.h"
  25 #include "nir_builder.h"
  26
  27 /**
  28  * \file nir_opt_intrinsics.c
  29  */
  30
  31 /* Converts a uint32_t or uint64_t value to uint64_t or uvec4 */
  32 static nir_ssa_def *
  33 uint_to_ballot_type(nir_builder *b, nir_ssa_def *value,
  34                     unsigned num_components, unsigned bit_size)
  35 {
  36    assert(value->num_components == 1);
  37    assert(value->bit_size == 32 || value->bit_size == 64);
  38
  39    nir_ssa_def *zero = nir_imm_int(b, 0);
  40    if (num_components > 1) {
  41       /* SPIR-V uses a uvec4 for ballot values */
  42       assert(num_components == 4);
  43       assert(bit_size == 32);
  44
  45       if (value->bit_size == 32) {
  46          return nir_vec4(b, value, zero, zero, zero);
  47       } else {
  48          assert(value->bit_size == 64);
  49          return nir_vec4(b, nir_unpack_64_2x32_split_x(b, value),
  50                             nir_unpack_64_2x32_split_y(b, value),
  51                             zero, zero);
  52       }
  53    } else {
  54       /* GLSL uses a uint64_t for ballot values */
  55       assert(num_components == 1);
  56       assert(bit_size == 64);
  57
  58       if (value->bit_size == 32) {
  59          return nir_pack_64_2x32_split(b, value, zero);
  60       } else {
  61          assert(value->bit_size == 64);
  62          return value;
  63       }
  64    }
  65 }
  66
  67 static nir_ssa_def *
  68 lower_read_invocation_to_scalar(nir_builder *b, nir_intrinsic_instr *intrin)
  69 {
  70    /* This is safe to call on scalar things but it would be silly */
  71    assert(intrin->dest.ssa.num_components > 1);
  72
  73    nir_ssa_def *value = nir_ssa_for_src(b, intrin->src[0],
  74                                            intrin->num_components);
  75    nir_ssa_def *reads[4];
  76
  77    for (unsigned i = 0; i < intrin->num_components; i++) {
  78       nir_intrinsic_instr *chan_intrin =
  79          nir_intrinsic_instr_create(b->shader, intrin->intrinsic);
  80       nir_ssa_dest_init(&chan_intrin->instr, &chan_intrin->dest,
  81                         1, intrin->dest.ssa.bit_size, NULL);
  82       chan_intrin->num_components = 1;
  83
  84       /* value */
  85       chan_intrin->src[0] = nir_src_for_ssa(nir_channel(b, value, i));
  86       /* invocation */
  87       if (intrin->intrinsic == nir_intrinsic_read_invocation)
  88          nir_src_copy(&chan_intrin->src[1], &intrin->src[1], chan_intrin);
  89
  90       nir_builder_instr_insert(b, &chan_intrin->instr);
  91
  92       reads[i] = &chan_intrin->dest.ssa;
  93    }
  94
  95    return nir_vec(b, reads, intrin->num_components);
  96 }
  97
  98 static nir_ssa_def *
  99 lower_subgroups_intrin(nir_builder *b, nir_intrinsic_instr *intrin,
 100                        const nir_lower_subgroups_options *options)
 101 {
 102    switch (intrin->intrinsic) {
 103    case nir_intrinsic_vote_any:
 104    case nir_intrinsic_vote_all:
 105       if (options->lower_vote_trivial)
 106          return nir_ssa_for_src(b, intrin->src[0], 1);
 107       break;
 108
 109    case nir_intrinsic_vote_eq:
 110       if (options->lower_vote_trivial)
 111          return nir_imm_int(b, NIR_TRUE);
 112       break;
 113
 114    case nir_intrinsic_load_subgroup_size:
 115       if (options->subgroup_size)
 116          return nir_imm_int(b, options->subgroup_size);
 117       break;
 118
 119    case nir_intrinsic_read_invocation:
 120    case nir_intrinsic_read_first_invocation:
 121       if (options->lower_to_scalar && intrin->num_components > 1)
 122          return lower_read_invocation_to_scalar(b, intrin);
 123       break;
 124
 125    case nir_intrinsic_load_subgroup_eq_mask:
 126    case nir_intrinsic_load_subgroup_ge_mask:
 127    case nir_intrinsic_load_subgroup_gt_mask:
 128    case nir_intrinsic_load_subgroup_le_mask:
 129    case nir_intrinsic_load_subgroup_lt_mask: {
 130       if (!options->lower_subgroup_masks)
 131          return NULL;
 132
 133       /* If either the result or the requested bit size is 64-bits then we
 134        * know that we have 64-bit types and using them will probably be more
 135        * efficient than messing around with 32-bit shifts and packing.
 136        */
 137       const unsigned bit_size = MAX2(options->ballot_bit_size,
 138                                      intrin->dest.ssa.bit_size);
 139
 140       assert(options->subgroup_size <= 64);
 141       uint64_t group_mask = ~0ull >> (64 - options->subgroup_size);
 142
 143       nir_ssa_def *count = nir_load_subgroup_invocation(b);
 144       nir_ssa_def *val;
 145       switch (intrin->intrinsic) {
 146       case nir_intrinsic_load_subgroup_eq_mask:
 147          val = nir_ishl(b, nir_imm_intN_t(b, 1ull, bit_size), count);
 148          break;
 149       case nir_intrinsic_load_subgroup_ge_mask:
 150          val = nir_iand(b, nir_ishl(b, nir_imm_intN_t(b, ~0ull, bit_size), count),
 151                            nir_imm_intN_t(b, group_mask, bit_size));
 152          break;
 153       case nir_intrinsic_load_subgroup_gt_mask:
 154          val = nir_iand(b, nir_ishl(b, nir_imm_intN_t(b, ~1ull, bit_size), count),
 155                            nir_imm_intN_t(b, group_mask, bit_size));
 156          break;
 157       case nir_intrinsic_load_subgroup_le_mask:
 158          val = nir_inot(b, nir_ishl(b, nir_imm_intN_t(b, ~1ull, bit_size), count));
 159          break;
 160       case nir_intrinsic_load_subgroup_lt_mask:
 161          val = nir_inot(b, nir_ishl(b, nir_imm_intN_t(b, ~0ull, bit_size), count));
 162          break;
 163       default:
 164          unreachable("you seriously can't tell this is unreachable?");
 165       }
 166
 167       return uint_to_ballot_type(b, val,
 168                                  intrin->dest.ssa.num_components,
 169                                  intrin->dest.ssa.bit_size);
 170    }
 171
 172    case nir_intrinsic_ballot: {
 173       if (intrin->dest.ssa.num_components == 1 &&
 174           intrin->dest.ssa.bit_size == options->ballot_bit_size)
 175          return NULL;
 176
 177       nir_intrinsic_instr *ballot =
 178          nir_intrinsic_instr_create(b->shader, nir_intrinsic_ballot);
 179       ballot->num_components = 1;
 180       nir_ssa_dest_init(&ballot->instr, &ballot->dest,
 181                         1, options->ballot_bit_size, NULL);
 182       nir_src_copy(&ballot->src[0], &intrin->src[0], ballot);
 183       nir_builder_instr_insert(b, &ballot->instr);
 184
 185       return uint_to_ballot_type(b, &ballot->dest.ssa,
 186                                  intrin->dest.ssa.num_components,
 187                                  intrin->dest.ssa.bit_size);
 188    }
 189
 190    default:
 191       break;
 192    }
 193
 194    return NULL;
 195 }
 196
 197 static bool
 198 lower_subgroups_impl(nir_function_impl *impl,
 199                      const nir_lower_subgroups_options *options)
 200 {
 201    nir_builder b;
 202    nir_builder_init(&b, impl);
 203    bool progress = false;
 204
 205    nir_foreach_block(block, impl) {
 206       nir_foreach_instr_safe(instr, block) {
 207          if (instr->type != nir_instr_type_intrinsic)
 208             continue;
 209
 210          nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
 211          b.cursor = nir_before_instr(instr);
 212
 213          nir_ssa_def *lower = lower_subgroups_intrin(&b, intrin, options);
 214          if (!lower)
 215             continue;
 216
 217          nir_ssa_def_rewrite_uses(&intrin->dest.ssa, nir_src_for_ssa(lower));
 218          nir_instr_remove(instr);
 219          progress = true;
 220       }
 221    }
 222
 223    return progress;
 224 }
 225
 226 bool
 227 nir_lower_subgroups(nir_shader *shader,
 228                     const nir_lower_subgroups_options *options)
 229 {
 230    bool progress = false;
 231
 232    nir_foreach_function(function, shader) {
 233       if (!function->impl)
 234          continue;
 235
 236       if (lower_subgroups_impl(function->impl, options)) {
 237          progress = true;
 238          nir_metadata_preserve(function->impl, nir_metadata_block_index |
 239                                                nir_metadata_dominance);
 240       }
 241    }
 242
 243    return progress;
 244 }