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