1/*
2 * Copyright © 2019 Google, Inc.
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 * This lower pass lowers load_interpolated_input for various interpolation
26 * modes (as configured via nir_lower_interpolation_options bitmask) into
27 * load_attribute_deltas plus alu instructions:
28 *
29 *    vec3 ad = load_attribute_deltas(varying_slot)
30 *    float result = ad.x + ad.y * j + ad.z * i
31 *
32 */
33
34#include "nir.h"
35#include "nir_builder.h"
36
37static bool
38nir_lower_interpolation_block(nir_block *block, nir_builder *b,
39                              nir_lower_interpolation_options options)
40{
41   bool progress = false;
42
43   nir_foreach_instr_safe(instr, block) {
44      if (instr->type != nir_instr_type_intrinsic)
45         continue;
46
47      nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
48
49      if (intr->intrinsic != nir_intrinsic_load_interpolated_input)
50         continue;
51
52      assert(intr->dest.is_ssa);
53      assert(intr->src[0].is_ssa);
54      assert(intr->src[1].is_ssa);
55
56      nir_intrinsic_instr *bary_intrinsic =
57         nir_instr_as_intrinsic(intr->src[0].ssa->parent_instr);
58
59      /* Leave VARYING_SLOT_POS alone */
60      if (nir_intrinsic_base(intr) == VARYING_SLOT_POS)
61         continue;
62
63      const enum glsl_interp_mode interp_mode =
64         nir_intrinsic_interp_mode(bary_intrinsic);
65
66      /* We need actual interpolation modes by the time we get here */
67      assert(interp_mode != INTERP_MODE_NONE);
68
69      /* Only lower for inputs that need interpolation */
70      if (interp_mode != INTERP_MODE_SMOOTH &&
71          interp_mode != INTERP_MODE_NOPERSPECTIVE)
72         continue;
73
74      nir_intrinsic_op op = bary_intrinsic->intrinsic;
75
76      switch (op) {
77      case nir_intrinsic_load_barycentric_at_sample:
78         if (options & nir_lower_interpolation_at_sample)
79            break;
80         continue;
81      case nir_intrinsic_load_barycentric_at_offset:
82         if (options & nir_lower_interpolation_at_offset)
83            break;
84         continue;
85      case nir_intrinsic_load_barycentric_centroid:
86         if (options & nir_lower_interpolation_centroid)
87            break;
88         continue;
89      case nir_intrinsic_load_barycentric_pixel:
90         if (options & nir_lower_interpolation_pixel)
91            break;
92         continue;
93      case nir_intrinsic_load_barycentric_sample:
94         if (options & nir_lower_interpolation_sample)
95            break;
96         continue;
97      default:
98         continue;
99      }
100
101      b->cursor = nir_before_instr(instr);
102
103      nir_ssa_def *comps[NIR_MAX_VEC_COMPONENTS];
104      for (int i = 0; i < intr->num_components; i++) {
105         nir_ssa_def *iid =
106            nir_load_fs_input_interp_deltas(b, 32, intr->src[1].ssa,
107                                            .base = nir_intrinsic_base(intr),
108                                            .component = (nir_intrinsic_component(intr) + i),
109                                            .io_semantics = nir_intrinsic_io_semantics(intr));
110
111         nir_ssa_def *bary = intr->src[0].ssa;
112         nir_ssa_def *val;
113
114         val = nir_ffma(b, nir_channel(b, bary, 1),
115                           nir_channel(b, iid, 1),
116                           nir_channel(b, iid, 0));
117         val = nir_ffma(b, nir_channel(b, bary, 0),
118                           nir_channel(b, iid, 2),
119                           val);
120
121         comps[i] = val;
122      }
123      nir_ssa_def *vec = nir_vec(b, comps, intr->num_components);
124      nir_ssa_def_rewrite_uses(&intr->dest.ssa, vec);
125
126      progress = true;
127   }
128
129   return progress;
130}
131
132static bool
133nir_lower_interpolation_impl(nir_function_impl *impl,
134                             nir_lower_interpolation_options options)
135{
136   bool progress = false;
137   nir_builder builder;
138   nir_builder_init(&builder, impl);
139
140   nir_foreach_block(block, impl) {
141      progress |= nir_lower_interpolation_block(block, &builder, options);
142   }
143
144   nir_metadata_preserve(impl, nir_metadata_block_index |
145                               nir_metadata_dominance);
146   return progress;
147}
148
149bool
150nir_lower_interpolation(nir_shader *shader, nir_lower_interpolation_options options)
151{
152   bool progress = false;
153
154   nir_foreach_function(function, shader) {
155      if (function->impl)
156         progress |= nir_lower_interpolation_impl(function->impl, options);
157   }
158
159   return progress;
160}
161