1 /*
2 * Copyright © 2015 Broadcom
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 "util/macros.h"
25 #include "nir.h"
26 #include "nir_builder.h"
27
28 /** @file nir_lower_load_const_to_scalar.c
29 *
30 * Replaces vector nir_load_const instructions with a series of loads and a
31 * vec[234] to reconstruct the original vector (on the assumption that
32 * nir_lower_alu_to_scalar() will then be used to split it up).
33 *
34 * This gives NIR a chance to CSE more operations on a scalar shader, when the
35 * same value was used in different vector contant loads.
36 */
37
38 static bool
lower_load_const_instr_scalar(nir_load_const_instr * lower)39 lower_load_const_instr_scalar(nir_load_const_instr *lower)
40 {
41 if (lower->def.num_components == 1)
42 return false;
43
44 nir_builder b;
45 nir_builder_init(&b, nir_cf_node_get_function(&lower->instr.block->cf_node));
46 b.cursor = nir_before_instr(&lower->instr);
47
48 /* Emit the individual loads. */
49 nir_ssa_def *loads[NIR_MAX_VEC_COMPONENTS];
50 for (unsigned i = 0; i < lower->def.num_components; i++) {
51 nir_load_const_instr *load_comp =
52 nir_load_const_instr_create(b.shader, 1, lower->def.bit_size);
53 load_comp->value[0] = lower->value[i];
54 nir_builder_instr_insert(&b, &load_comp->instr);
55 loads[i] = &load_comp->def;
56 }
57
58 /* Batch things back together into a vector. */
59 nir_ssa_def *vec = nir_vec(&b, loads, lower->def.num_components);
60
61 /* Replace the old load with a reference to our reconstructed vector. */
62 nir_ssa_def_rewrite_uses(&lower->def, vec);
63 nir_instr_remove(&lower->instr);
64 return true;
65 }
66
67 static bool
nir_lower_load_const_to_scalar_impl(nir_function_impl * impl)68 nir_lower_load_const_to_scalar_impl(nir_function_impl *impl)
69 {
70 bool progress = false;
71
72 nir_foreach_block(block, impl) {
73 nir_foreach_instr_safe(instr, block) {
74 if (instr->type == nir_instr_type_load_const)
75 progress |=
76 lower_load_const_instr_scalar(nir_instr_as_load_const(instr));
77 }
78 }
79
80 if (progress) {
81 nir_metadata_preserve(impl, nir_metadata_block_index |
82 nir_metadata_dominance);
83 } else {
84 nir_metadata_preserve(impl, nir_metadata_all);
85 }
86
87 return progress;
88 }
89
90 bool
nir_lower_load_const_to_scalar(nir_shader * shader)91 nir_lower_load_const_to_scalar(nir_shader *shader)
92 {
93 bool progress = false;
94
95 nir_foreach_function(function, shader) {
96 if (function->impl)
97 progress |= nir_lower_load_const_to_scalar_impl(function->impl);
98 }
99
100 return progress;
101 }
102