1/*
2 * Copyright © 2021 Collabora Ltd.
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#include "nir.h"
25#include "nir_builder.h"
26
27/*
28 * spirv_to_nir() creates system values for some builtin inputs, but
29 * backends might want to have those inputs exposed as varyings. This
30 * lowering pass allows backends to convert system values to input
31 * varyings and should be called just after spirv_to_nir() when needed.
32 */
33
34bool
35nir_lower_sysvals_to_varyings(nir_shader *shader,
36                              const struct nir_lower_sysvals_to_varyings_options *options)
37{
38   bool progress = false;
39
40   nir_foreach_variable_with_modes(var, shader, nir_var_system_value) {
41      switch (var->data.location) {
42#define SYSVAL_TO_VARYING(opt, sysval, varying) \
43        case SYSTEM_VALUE_ ## sysval: \
44           if (options->opt) { \
45              var->data.mode = nir_var_shader_in; \
46              var->data.location = VARYING_SLOT_ ## varying; \
47              progress = true; \
48           } \
49           break
50
51      SYSVAL_TO_VARYING(frag_coord, FRAG_COORD, POS);
52      SYSVAL_TO_VARYING(point_coord, POINT_COORD, PNTC);
53      SYSVAL_TO_VARYING(front_face, FRONT_FACE, FACE);
54
55#undef SYSVAL_TO_VARYING
56
57      default:
58         break;
59      }
60   }
61
62   if (progress)
63      nir_fixup_deref_modes(shader);
64
65   /* Nothing this does actually changes anything tracked by metadata.
66    * If we ever made this pass more complicated, we might need to care
67    * more about metadata.
68    */
69   nir_shader_preserve_all_metadata(shader);
70
71   return progress;
72}
73