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
38static bool
39compute_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
117struct ir3_liveness *
118ir3_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 */
169bool
170ir3_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