src/compiler/nir/nir_lower_to_source_mods.c

   1 /*
   2  * Copyright © 2014 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  * Authors:
  24  *    Jason Ekstrand (jason@jlekstrand.net)
  25  *
  26  */
  27
  28 #include "nir.h"
  29
  30 /*
  31  * This pass lowers the neg, abs, and sat operations to source modifiers on
  32  * ALU operations to make things nicer for the backend.  It's just much
  33  * easier to not have them when we're doing optimizations.
  34  */
  35
  36 static bool
  37 nir_lower_to_source_mods_block(nir_block *block,
  38                                nir_lower_to_source_mods_flags options)
  39 {
  40    bool progress = false;
  41
  42    nir_foreach_instr(instr, block) {
  43       if (instr->type != nir_instr_type_alu)
  44          continue;
  45
  46       nir_alu_instr *alu = nir_instr_as_alu(instr);
  47
  48       bool lower_abs = (nir_op_infos[alu->op].num_inputs < 3) ||
  49             (options & nir_lower_triop_abs);
  50
  51       for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) {
  52          if (!alu->src[i].src.is_ssa)
  53             continue;
  54
  55          if (alu->src[i].src.ssa->parent_instr->type != nir_instr_type_alu)
  56             continue;
  57
  58          nir_alu_instr *parent = nir_instr_as_alu(alu->src[i].src.ssa->parent_instr);
  59
  60          if (parent->dest.saturate)
  61             continue;
  62
  63          switch (nir_alu_type_get_base_type(nir_op_infos[alu->op].input_types[i])) {
  64          case nir_type_float:
  65             if (!(options & nir_lower_float_source_mods))
  66                continue;
  67             if (parent->op != nir_op_fmov)
  68                continue;
  69             break;
  70          case nir_type_int:
  71             if (!(options & nir_lower_int_source_mods))
  72                continue;
  73             if (parent->op != nir_op_imov)
  74                continue;
  75             break;
  76          default:
  77             continue;
  78          }
  79
  80          /* We can only do a rewrite if the source we are copying is SSA.
  81           * Otherwise, moving the read might invalidly reorder reads/writes
  82           * on a register.
  83           */
  84          if (!parent->src[0].src.is_ssa)
  85             continue;
  86
  87          if (!lower_abs && parent->src[0].abs)
  88             continue;
  89
  90          nir_instr_rewrite_src(instr, &alu->src[i].src, parent->src[0].src);
  91          if (alu->src[i].abs) {
  92             /* abs trumps both neg and abs, do nothing */
  93          } else {
  94             alu->src[i].negate = (alu->src[i].negate != parent->src[0].negate);
  95             alu->src[i].abs |= parent->src[0].abs;
  96          }
  97
  98          for (int j = 0; j < 4; ++j) {
  99             if (!nir_alu_instr_channel_used(alu, i, j))
 100                continue;
 101             alu->src[i].swizzle[j] = parent->src[0].swizzle[alu->src[i].swizzle[j]];
 102          }
 103
 104          if (list_empty(&parent->dest.dest.ssa.uses) &&
 105              list_empty(&parent->dest.dest.ssa.if_uses))
 106             nir_instr_remove(&parent->instr);
 107
 108          progress = true;
 109       }
 110
 111       if (options & nir_lower_float_source_mods) {
 112          switch (alu->op) {
 113          case nir_op_fsat:
 114             alu->op = nir_op_fmov;
 115             alu->dest.saturate = true;
 116             break;
 117          case nir_op_fneg:
 118             alu->op = nir_op_fmov;
 119             alu->src[0].negate = !alu->src[0].negate;
 120             break;
 121          case nir_op_fabs:
 122             alu->op = nir_op_fmov;
 123             alu->src[0].abs = true;
 124             alu->src[0].negate = false;
 125             break;
 126          default:
 127             break;
 128          }
 129       }
 130
 131       if (options & nir_lower_int_source_mods) {
 132          switch (alu->op) {
 133          case nir_op_ineg:
 134             alu->op = nir_op_imov;
 135             alu->src[0].negate = !alu->src[0].negate;
 136             break;
 137          case nir_op_iabs:
 138             alu->op = nir_op_imov;
 139             alu->src[0].abs = true;
 140             alu->src[0].negate = false;
 141             break;
 142          default:
 143             break;
 144          }
 145       }
 146       /* We've covered sources.  Now we're going to try and saturate the
 147        * destination if we can.
 148        */
 149
 150       if (!alu->dest.dest.is_ssa)
 151          continue;
 152
 153       /* We can only saturate float destinations */
 154       if (nir_alu_type_get_base_type(nir_op_infos[alu->op].output_type) !=
 155           nir_type_float)
 156          continue;
 157
 158       if (!(options & nir_lower_float_source_mods))
 159          continue;
 160
 161       if (!list_empty(&alu->dest.dest.ssa.if_uses))
 162          continue;
 163
 164       bool all_children_are_sat = true;
 165       nir_foreach_use(child_src, &alu->dest.dest.ssa) {
 166          assert(child_src->is_ssa);
 167          nir_instr *child = child_src->parent_instr;
 168          if (child->type != nir_instr_type_alu) {
 169             all_children_are_sat = false;
 170             continue;
 171          }
 172
 173          nir_alu_instr *child_alu = nir_instr_as_alu(child);
 174          if (child_alu->src[0].negate || child_alu->src[0].abs) {
 175             all_children_are_sat = false;
 176             continue;
 177          }
 178
 179          if (child_alu->op != nir_op_fsat &&
 180              !(child_alu->op == nir_op_fmov && child_alu->dest.saturate)) {
 181             all_children_are_sat = false;
 182             continue;
 183          }
 184       }
 185
 186       if (!all_children_are_sat)
 187          continue;
 188
 189       alu->dest.saturate = true;
 190       progress = true;
 191
 192       nir_foreach_use(child_src, &alu->dest.dest.ssa) {
 193          assert(child_src->is_ssa);
 194          nir_alu_instr *child_alu = nir_instr_as_alu(child_src->parent_instr);
 195
 196          child_alu->op = nir_op_fmov;
 197          child_alu->dest.saturate = false;
 198          /* We could propagate the dest of our instruction to the
 199           * destinations of the uses here.  However, one quick round of
 200           * copy propagation will clean that all up and then we don't have
 201           * the complexity.
 202           */
 203       }
 204    }
 205
 206    return progress;
 207 }
 208
 209 static bool
 210 nir_lower_to_source_mods_impl(nir_function_impl *impl,
 211                               nir_lower_to_source_mods_flags options)
 212 {
 213    bool progress = false;
 214
 215    nir_foreach_block(block, impl) {
 216       progress |= nir_lower_to_source_mods_block(block, options);
 217    }
 218
 219    if (progress)
 220       nir_metadata_preserve(impl, nir_metadata_block_index |
 221                                   nir_metadata_dominance);
 222
 223    return progress;
 224 }
 225
 226 bool
 227 nir_lower_to_source_mods(nir_shader *shader,
 228                          nir_lower_to_source_mods_flags options)
 229 {
 230    bool progress = false;
 231
 232    nir_foreach_function(function, shader) {
 233       if (function->impl) {
 234          progress |= nir_lower_to_source_mods_impl(function->impl, options);
 235       }
 236    }
 237
 238    return progress;
 239 }