1 /*
2 * Copyright (C) 2021 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 FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 * SOFTWARE.
22 */
23
24 #include "ir3_ra.h"
25 #include "ir3_shader.h"
26 #include "ralloc.h"
27
28 /* A note on how phi node uses are handled:
29 *
30 * - Phi node sources are considered to happen after the end of the
31 * predecessor block, so the live_out for that block contains phi sources.
32 * - On the other hand, phi destinations are considered to happen at the start
33 * of the block, so that live_in does *not* contain phi destinations. This
34 * is mainly because phi destinations and live-through values have to be
35 * treated very differently by RA at the beginning of a block.
36 */
37
38 static bool
compute_block_liveness(struct ir3_liveness * live,struct ir3_block * block,BITSET_WORD * tmp_live,unsigned bitset_words)39 compute_block_liveness(struct ir3_liveness *live, struct ir3_block *block,
40 BITSET_WORD *tmp_live, unsigned bitset_words)
41 {
42 memcpy(tmp_live, live->live_out[block->index],
43 bitset_words * sizeof(BITSET_WORD));
44
45 /* Process instructions */
46 foreach_instr_rev (instr, &block->instr_list) {
47 ra_foreach_dst (dst, instr) {
48 if (BITSET_TEST(tmp_live, dst->name))
49 dst->flags &= ~IR3_REG_UNUSED;
50 else
51 dst->flags |= IR3_REG_UNUSED;
52 BITSET_CLEAR(tmp_live, dst->name);
53 }
54
55 /* Phi node uses occur after the predecessor block */
56 if (instr->opc != OPC_META_PHI) {
57 ra_foreach_src (src, instr) {
58 if (BITSET_TEST(tmp_live, src->def->name))
59 src->flags &= ~IR3_REG_KILL;
60 else
61 src->flags |= IR3_REG_KILL;
62 }
63
64 ra_foreach_src (src, instr) {
65 if (BITSET_TEST(tmp_live, src->def->name))
66 src->flags &= ~IR3_REG_FIRST_KILL;
67 else
68 src->flags |= IR3_REG_FIRST_KILL;
69 BITSET_SET(tmp_live, src->def->name);
70 }
71 }
72 }
73
74 memcpy(live->live_in[block->index], tmp_live,
75 bitset_words * sizeof(BITSET_WORD));
76
77 bool progress = false;
78 for (unsigned i = 0; i < block->predecessors_count; i++) {
79 const struct ir3_block *pred = block->predecessors[i];
80 for (unsigned j = 0; j < bitset_words; j++) {
81 if (tmp_live[j] & ~live->live_out[pred->index][j])
82 progress = true;
83 live->live_out[pred->index][j] |= tmp_live[j];
84 }
85
86 /* Process phi sources. */
87 foreach_instr (phi, &block->instr_list) {
88 if (phi->opc != OPC_META_PHI)
89 break;
90 if (!phi->srcs[i]->def)
91 continue;
92 unsigned name = phi->srcs[i]->def->name;
93 if (!BITSET_TEST(live->live_out[pred->index], name)) {
94 progress = true;
95 BITSET_SET(live->live_out[pred->index], name);
96 }
97 }
98 }
99
100 for (unsigned i = 0; i < block->physical_predecessors_count; i++) {
101 const struct ir3_block *pred = block->physical_predecessors[i];
102 unsigned name;
103 BITSET_FOREACH_SET (name, tmp_live, live->definitions_count) {
104 struct ir3_register *reg = live->definitions[name];
105 if (!(reg->flags & IR3_REG_SHARED))
106 continue;
107 if (!BITSET_TEST(live->live_out[pred->index], name)) {
108 progress = true;
109 BITSET_SET(live->live_out[pred->index], name);
110 }
111 }
112 }
113
114 return progress;
115 }
116
117 struct ir3_liveness *
ir3_calc_liveness(void * mem_ctx,struct ir3 * ir)118 ir3_calc_liveness(void *mem_ctx, struct ir3 *ir)
119 {
120 struct ir3_liveness *live = rzalloc(mem_ctx, struct ir3_liveness);
121
122 /* Reserve name 0 to mean "doesn't have a name yet" to make the debug
123 * output nicer.
124 */
125 array_insert(live, live->definitions, NULL);
126
127 /* Build definition <-> name mapping */
128 unsigned block_count = 0;
129 foreach_block (block, &ir->block_list) {
130 block->index = block_count++;
131 foreach_instr (instr, &block->instr_list) {
132 ra_foreach_dst (dst, instr) {
133 dst->name = live->definitions_count;
134 array_insert(live, live->definitions, dst);
135 }
136 }
137 }
138
139 live->block_count = block_count;
140
141 unsigned bitset_words = BITSET_WORDS(live->definitions_count);
142 BITSET_WORD *tmp_live = ralloc_array(live, BITSET_WORD, bitset_words);
143 live->live_in = ralloc_array(live, BITSET_WORD *, block_count);
144 live->live_out = ralloc_array(live, BITSET_WORD *, block_count);
145 unsigned i = 0;
146 foreach_block (block, &ir->block_list) {
147 block->index = i++;
148 live->live_in[block->index] =
149 rzalloc_array(live, BITSET_WORD, bitset_words);
150 live->live_out[block->index] =
151 rzalloc_array(live, BITSET_WORD, bitset_words);
152 }
153
154 bool progress = true;
155 while (progress) {
156 progress = false;
157 foreach_block_rev (block, &ir->block_list) {
158 progress |=
159 compute_block_liveness(live, block, tmp_live, bitset_words);
160 }
161 }
162
163 return live;
164 }
165
166 /* Return true if "def" is live after "instr". It's assumed that "def"
167 * dominates "instr".
168 */
169 bool
ir3_def_live_after(struct ir3_liveness * live,struct ir3_register * def,struct ir3_instruction * instr)170 ir3_def_live_after(struct ir3_liveness *live, struct ir3_register *def,
171 struct ir3_instruction *instr)
172 {
173 /* If it's live out then it's definitely live at the instruction. */
174 if (BITSET_TEST(live->live_out[instr->block->index], def->name))
175 return true;
176
177 /* If it's not live in and not defined in the same block then the live
178 * range can't extend to the instruction.
179 */
180 if (def->instr->block != instr->block &&
181 !BITSET_TEST(live->live_in[instr->block->index], def->name))
182 return false;
183
184 /* Ok, now comes the tricky case, where "def" is killed somewhere in
185 * "instr"'s block and we have to check if it's before or after.
186 */
187 foreach_instr_rev (test_instr, &instr->block->instr_list) {
188 if (test_instr == instr)
189 break;
190
191 for (unsigned i = 0; i < test_instr->srcs_count; i++) {
192 if (test_instr->srcs[i]->def == def)
193 return true;
194 }
195 }
196
197 return false;
198 }
199