1/*
2 * Copyright © 2021 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
24#include "nir.h"
25#include "nir_builder.h"
26
27static bool
28lower_single_sampled_instr(nir_builder *b,
29                           nir_instr *instr,
30                           UNUSED void *cb_data)
31{
32   if (instr->type != nir_instr_type_intrinsic)
33      return false;
34
35   nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
36
37   nir_ssa_def *lowered;
38   switch (intrin->intrinsic) {
39   case nir_intrinsic_load_sample_id:
40      b->cursor = nir_before_instr(instr);
41      lowered = nir_imm_int(b, 0);
42      break;
43
44   case nir_intrinsic_load_sample_pos:
45      b->cursor = nir_before_instr(instr);
46      lowered = nir_imm_vec2(b, 0.5, 0.5);
47      break;
48
49   case nir_intrinsic_load_sample_mask_in:
50      /* Don't lower to helper invocations if helper invocations are going
51       * to be lowered right back to sample mask.
52       */
53      if (b->shader->options->lower_helper_invocation)
54         return false;
55
56      b->cursor = nir_before_instr(instr);
57      lowered = nir_b2i32(b, nir_inot(b, nir_load_helper_invocation(b, 1)));
58      break;
59
60   case nir_intrinsic_interp_deref_at_centroid:
61   case nir_intrinsic_interp_deref_at_sample:
62      b->cursor = nir_before_instr(instr);
63      assert(intrin->src[0].is_ssa);
64      lowered = nir_load_deref(b, nir_src_as_deref(intrin->src[0]));
65      break;
66
67   case nir_intrinsic_load_barycentric_centroid:
68   case nir_intrinsic_load_barycentric_sample:
69   case nir_intrinsic_load_barycentric_at_sample:
70      b->cursor = nir_before_instr(instr);
71      lowered = nir_load_barycentric(b, nir_intrinsic_load_barycentric_pixel,
72                                        nir_intrinsic_interp_mode(intrin));
73
74      if (nir_intrinsic_interp_mode(intrin) == INTERP_MODE_NOPERSPECTIVE) {
75         BITSET_SET(b->shader->info.system_values_read,
76                    SYSTEM_VALUE_BARYCENTRIC_LINEAR_PIXEL);
77      } else {
78         BITSET_SET(b->shader->info.system_values_read,
79                    SYSTEM_VALUE_BARYCENTRIC_PERSP_PIXEL);
80      }
81      break;
82
83   default:
84      return false;
85   }
86
87   nir_ssa_def_rewrite_uses(&intrin->dest.ssa, lowered);
88   nir_instr_remove(instr);
89   return true;
90}
91
92/* Assume the fragment shader is single-sampled and lower accordingly
93 *
94 * This drops sample/centroid qualifiers from all input variables, forces
95 * barycentrics to pixel, and constant-folds various built-ins.
96 */
97bool
98nir_lower_single_sampled(nir_shader *shader)
99{
100   assert(shader->info.stage == MESA_SHADER_FRAGMENT);
101
102   bool progress = false;
103   nir_foreach_shader_in_variable(var, shader) {
104      if (var->data.sample) {
105         var->data.sample = false;
106         progress = true;
107      }
108      if (var->data.centroid) {
109         var->data.centroid = false;
110         progress = true;
111      }
112   }
113
114   /* We're going to get rid of any uses of these */
115   BITSET_CLEAR(shader->info.system_values_read,
116                SYSTEM_VALUE_BARYCENTRIC_PERSP_SAMPLE);
117   BITSET_CLEAR(shader->info.system_values_read,
118                SYSTEM_VALUE_BARYCENTRIC_PERSP_CENTROID);
119   BITSET_CLEAR(shader->info.system_values_read,
120                SYSTEM_VALUE_BARYCENTRIC_LINEAR_SAMPLE);
121   BITSET_CLEAR(shader->info.system_values_read,
122                SYSTEM_VALUE_BARYCENTRIC_LINEAR_CENTROID);
123
124   return nir_shader_instructions_pass(shader, lower_single_sampled_instr,
125                                       nir_metadata_block_index |
126                                       nir_metadata_dominance,
127                                       NULL) || progress;
128}
129