nir: update uses_demote flag in discard_to_demote pass
[mesa.git] / 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 }