src/compiler/nir/nir_lower_discard_to_demote.c

   1 /*
   2  * Copyright © 2020 Valve 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
  25 #include "nir.h"
  26
  27 /**
  28  * This pass is intended as workaround for game bugs to force correct
  29  * derivatives after kill. This lowering is not valid in the general case
  30  * as it might change the result of subgroup operations and loop behavior.
  31  *
  32  * discard() will be lowered as demote() and gl_HelperInvocation
  33  * will be lowered as helperInvocationEXT().
  34  */
  35 bool
  36 nir_lower_discard_to_demote(nir_shader *shader)
  37 {
  38    if (shader->info.stage != MESA_SHADER_FRAGMENT)
  39       return false;
  40
  41    bool progress = false;
  42
  43    nir_foreach_function(function, shader) {
  44       nir_foreach_block(block, function->impl) {
  45          nir_foreach_instr(instr, block) {
  46             if (instr->type != nir_instr_type_intrinsic)
  47                continue;
  48
  49             nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
  50             switch (intrin->intrinsic) {
  51             case nir_intrinsic_discard:
  52                intrin->intrinsic = nir_intrinsic_demote;
  53                shader->info.fs.uses_demote = true;
  54                break;
  55             case nir_intrinsic_discard_if:
  56                intrin->intrinsic = nir_intrinsic_demote_if;
  57                shader->info.fs.uses_demote = true;
  58                break;
  59             case nir_intrinsic_load_helper_invocation:
  60                intrin->intrinsic = nir_intrinsic_is_helper_invocation;
  61                break;
  62             default:
  63                continue;
  64             }
  65             progress = true;
  66          }
  67       }
  68    }
  69
  70    return progress;
  71 }