1/*
2 * Copyright (C) 2020 Collabora, Ltd.
3 * Copyright (C) 2018-2019 Alyssa Rosenzweig <alyssa@rosenzweig.io>
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice (including the next
13 * paragraph) shall be included in all copies or substantial portions of the
14 * Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25#include "compiler.h"
26#include "util/u_memory.h"
27#include "util/list.h"
28#include "util/set.h"
29
30/* Liveness analysis is a backwards-may dataflow analysis pass. Within a block,
31 * we compute live_out from live_in. The intrablock pass is linear-time. It
32 * returns whether progress was made. */
33
34void
35bi_liveness_ins_update(uint8_t *live, bi_instr *ins, unsigned max)
36{
37        /* live_in[s] = GEN[s] + (live_out[s] - KILL[s]) */
38
39        bi_foreach_dest(ins, d) {
40                unsigned node = bi_get_node(ins->dest[d]);
41
42                if (node < max)
43                        live[node] &= ~bi_writemask(ins, d);
44        }
45
46        bi_foreach_src(ins, src) {
47                unsigned count = bi_count_read_registers(ins, src);
48                unsigned rmask = BITFIELD_MASK(count);
49                uint8_t mask = (rmask << ins->src[src].offset);
50
51                unsigned node = bi_get_node(ins->src[src]);
52                if (node < max)
53                        live[node] |= mask;
54        }
55}
56
57static bool
58liveness_block_update(bi_block *blk, unsigned temp_count)
59{
60        bool progress = false;
61
62        /* live_out[s] = sum { p in succ[s] } ( live_in[p] ) */
63        bi_foreach_successor(blk, succ) {
64                for (unsigned i = 0; i < temp_count; ++i)
65                        blk->live_out[i] |= succ->live_in[i];
66        }
67
68        uint8_t *live = ralloc_array(blk, uint8_t, temp_count);
69        memcpy(live, blk->live_out, temp_count);
70
71        bi_foreach_instr_in_block_rev(blk, ins)
72                bi_liveness_ins_update(live, (bi_instr *) ins, temp_count);
73
74        /* To figure out progress, diff live_in */
75
76        for (unsigned i = 0; (i < temp_count) && !progress; ++i)
77                progress |= (blk->live_in[i] != live[i]);
78
79        ralloc_free(blk->live_in);
80        blk->live_in = live;
81
82        return progress;
83}
84
85/* Globally, liveness analysis uses a fixed-point algorithm based on a
86 * worklist. We initialize a work list with the exit block. We iterate the work
87 * list to compute live_in from live_out for each block on the work list,
88 * adding the predecessors of the block to the work list if we made progress.
89 */
90
91void
92bi_compute_liveness(bi_context *ctx)
93{
94        if (ctx->has_liveness)
95                return;
96
97        unsigned temp_count = bi_max_temp(ctx);
98
99        /* Set of bi_block */
100        struct set *work_list = _mesa_set_create(NULL,
101                        _mesa_hash_pointer,
102                        _mesa_key_pointer_equal);
103
104        struct set *visited = _mesa_set_create(NULL,
105                        _mesa_hash_pointer,
106                        _mesa_key_pointer_equal);
107
108        list_for_each_entry(bi_block, block, &ctx->blocks, link) {
109                if (block->live_in)
110                        ralloc_free(block->live_in);
111
112                if (block->live_out)
113                        ralloc_free(block->live_out);
114
115                block->live_in = rzalloc_array(block, uint8_t, temp_count);
116                block->live_out = rzalloc_array(block, uint8_t, temp_count);
117        }
118
119        /* Initialize the work list with the exit block */
120        struct set_entry *cur;
121
122        cur = _mesa_set_add(work_list, pan_exit_block(&ctx->blocks));
123
124        /* Iterate the work list */
125
126        do {
127                /* Pop off a block */
128                bi_block *blk = (struct bi_block *) cur->key;
129                _mesa_set_remove(work_list, cur);
130
131                /* Update its liveness information */
132                bool progress = liveness_block_update(blk, temp_count);
133
134                /* If we made progress, we need to process the predecessors */
135
136                if (progress || !_mesa_set_search(visited, blk)) {
137                        bi_foreach_predecessor(blk, pred)
138                                _mesa_set_add(work_list, pred);
139                }
140
141                _mesa_set_add(visited, blk);
142        } while((cur = _mesa_set_next_entry(work_list, NULL)) != NULL);
143
144        _mesa_set_destroy(visited, NULL);
145        _mesa_set_destroy(work_list, NULL);
146
147        ctx->has_liveness = true;
148}
149
150/* Once liveness data is no longer valid, call this */
151
152void
153bi_invalidate_liveness(bi_context *ctx)
154{
155        ctx->has_liveness = false;
156}
157