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 {
  39    bool progress = false;
  40
  41    nir_foreach_instr(instr, block) {
  42       if (instr->type != nir_instr_type_alu)
  43          continue;
  44
  45       nir_alu_instr *alu = nir_instr_as_alu(instr);
  46
  47       for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) {
  48          if (!alu->src[i].src.is_ssa)
  49             continue;
  50
  51          if (alu->src[i].src.ssa->parent_instr->type != nir_instr_type_alu)
  52             continue;
  53
  54          nir_alu_instr *parent = nir_instr_as_alu(alu->src[i].src.ssa->parent_instr);
  55
  56          if (parent->dest.saturate)
  57             continue;
  58
  59          switch (nir_alu_type_get_base_type(nir_op_infos[alu->op].input_types[i])) {
  60          case nir_type_float:
  61             if (parent->op != nir_op_fmov)
  62                continue;
  63             break;
  64          case nir_type_int:
  65             if (parent->op != nir_op_imov)
  66                continue;
  67             break;
  68          default:
  69             continue;
  70          }
  71
  72          /* We can only do a rewrite if the source we are copying is SSA.
  73           * Otherwise, moving the read might invalidly reorder reads/writes
  74           * on a register.
  75           */
  76          if (!parent->src[0].src.is_ssa)
  77             continue;
  78
  79          nir_instr_rewrite_src(instr, &alu->src[i].src, parent->src[0].src);
  80          if (alu->src[i].abs) {
  81             /* abs trumps both neg and abs, do nothing */
  82          } else {
  83             alu->src[i].negate = (alu->src[i].negate != parent->src[0].negate);
  84             alu->src[i].abs |= parent->src[0].abs;
  85          }
  86
  87          for (int j = 0; j < 4; ++j) {
  88             if (!nir_alu_instr_channel_used(alu, i, j))
  89                continue;
  90             alu->src[i].swizzle[j] = parent->src[0].swizzle[alu->src[i].swizzle[j]];
  91          }
  92
  93          if (list_empty(&parent->dest.dest.ssa.uses) &&
  94              list_empty(&parent->dest.dest.ssa.if_uses))
  95             nir_instr_remove(&parent->instr);
  96
  97          progress = true;
  98       }
  99
 100       switch (alu->op) {
 101       case nir_op_fsat:
 102          alu->op = nir_op_fmov;
 103          alu->dest.saturate = true;
 104          break;
 105       case nir_op_ineg:
 106          alu->op = nir_op_imov;
 107          alu->src[0].negate = !alu->src[0].negate;
 108          break;
 109       case nir_op_fneg:
 110          alu->op = nir_op_fmov;
 111          alu->src[0].negate = !alu->src[0].negate;
 112          break;
 113       case nir_op_iabs:
 114          alu->op = nir_op_imov;
 115          alu->src[0].abs = true;
 116          alu->src[0].negate = false;
 117          break;
 118       case nir_op_fabs:
 119          alu->op = nir_op_fmov;
 120          alu->src[0].abs = true;
 121          alu->src[0].negate = false;
 122          break;
 123       default:
 124          break;
 125       }
 126
 127       /* We've covered sources.  Now we're going to try and saturate the
 128        * destination if we can.
 129        */
 130
 131       if (!alu->dest.dest.is_ssa)
 132          continue;
 133
 134       /* We can only saturate float destinations */
 135       if (nir_alu_type_get_base_type(nir_op_infos[alu->op].output_type) !=
 136           nir_type_float)
 137          continue;
 138
 139       if (!list_empty(&alu->dest.dest.ssa.if_uses))
 140          continue;
 141
 142       bool all_children_are_sat = true;
 143       nir_foreach_use(child_src, &alu->dest.dest.ssa) {
 144          assert(child_src->is_ssa);
 145          nir_instr *child = child_src->parent_instr;
 146          if (child->type != nir_instr_type_alu) {
 147             all_children_are_sat = false;
 148             continue;
 149          }
 150
 151          nir_alu_instr *child_alu = nir_instr_as_alu(child);
 152          if (child_alu->src[0].negate || child_alu->src[0].abs) {
 153             all_children_are_sat = false;
 154             continue;
 155          }
 156
 157          if (child_alu->op != nir_op_fsat &&
 158              !(child_alu->op == nir_op_fmov && child_alu->dest.saturate)) {
 159             all_children_are_sat = false;
 160             continue;
 161          }
 162       }
 163
 164       if (!all_children_are_sat)
 165          continue;
 166
 167       alu->dest.saturate = true;
 168       progress = true;
 169
 170       nir_foreach_use(child_src, &alu->dest.dest.ssa) {
 171          assert(child_src->is_ssa);
 172          nir_alu_instr *child_alu = nir_instr_as_alu(child_src->parent_instr);
 173
 174          child_alu->op = nir_op_fmov;
 175          child_alu->dest.saturate = false;
 176          /* We could propagate the dest of our instruction to the
 177           * destinations of the uses here.  However, one quick round of
 178           * copy propagation will clean that all up and then we don't have
 179           * the complexity.
 180           */
 181       }
 182    }
 183
 184    return progress;
 185 }
 186
 187 static bool
 188 nir_lower_to_source_mods_impl(nir_function_impl *impl)
 189 {
 190    bool progress = false;
 191
 192    nir_foreach_block(block, impl) {
 193       progress |= nir_lower_to_source_mods_block(block);
 194    }
 195
 196    if (progress)
 197       nir_metadata_preserve(impl, nir_metadata_block_index |
 198                                   nir_metadata_dominance);
 199
 200    return progress;
 201 }
 202
 203 bool
 204 nir_lower_to_source_mods(nir_shader *shader)
 205 {
 206    bool progress = false;
 207
 208    nir_foreach_function(function, shader) {
 209       if (function->impl) {
 210          progress |= nir_lower_to_source_mods_impl(function->impl);
 211       }
 212    }
 213
 214    return progress;
 215 }