1 /*
2 * Copyright (C) 2020 Collabora, Ltd.
3 * Copyright (C) 2018-2019 Alyssa Rosenzweig <[email protected]>
4 * Copyright © 2014 Intel Corporation
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice (including the next
14 * paragraph) shall be included in all copies or substantial portions of the
15 * Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
23 * SOFTWARE.
24 */
25
26 #include "util/u_memory.h"
27 #include "compiler.h"
28
29 void
bi_liveness_ins_update_ssa(BITSET_WORD * live,const bi_instr * I)30 bi_liveness_ins_update_ssa(BITSET_WORD *live, const bi_instr *I)
31 {
32 bi_foreach_dest(I, d)
33 BITSET_CLEAR(live, I->dest[d].value);
34
35 bi_foreach_ssa_src(I, s)
36 BITSET_SET(live, I->src[s].value);
37 }
38
39 void
bi_compute_liveness_ssa(bi_context * ctx)40 bi_compute_liveness_ssa(bi_context *ctx)
41 {
42 u_worklist worklist;
43 u_worklist_init(&worklist, ctx->num_blocks, NULL);
44
45 /* Free any previous liveness, and allocate */
46 unsigned words = BITSET_WORDS(ctx->ssa_alloc);
47
48 bi_foreach_block(ctx, block) {
49 if (block->ssa_live_in)
50 ralloc_free(block->ssa_live_in);
51
52 if (block->ssa_live_out)
53 ralloc_free(block->ssa_live_out);
54
55 block->ssa_live_in = rzalloc_array(block, BITSET_WORD, words);
56 block->ssa_live_out = rzalloc_array(block, BITSET_WORD, words);
57
58 bi_worklist_push_head(&worklist, block);
59 }
60
61 /* Iterate the work list */
62 while (!u_worklist_is_empty(&worklist)) {
63 /* Pop in reverse order since liveness is a backwards pass */
64 bi_block *blk = bi_worklist_pop_head(&worklist);
65
66 /* Update its liveness information */
67 memcpy(blk->ssa_live_in, blk->ssa_live_out, words * sizeof(BITSET_WORD));
68
69 bi_foreach_instr_in_block_rev(blk, I) {
70 /* Phi nodes are handled separately, so we skip them. As phi nodes are
71 * at the beginning and we're iterating backwards, we stop as soon as
72 * we hit a phi node.
73 */
74 if (I->op == BI_OPCODE_PHI)
75 break;
76
77 bi_liveness_ins_update_ssa(blk->ssa_live_in, I);
78 }
79
80 /* Propagate the live in of the successor (blk) to the live out of
81 * predecessors.
82 *
83 * Phi nodes are logically on the control flow edge and act in parallel.
84 * To handle when propagating, we kill writes from phis and make live the
85 * corresponding sources.
86 */
87 bi_foreach_predecessor(blk, pred) {
88 BITSET_WORD *live = ralloc_array(blk, BITSET_WORD, words);
89 memcpy(live, blk->ssa_live_in, words * sizeof(BITSET_WORD));
90
91 /* Kill write */
92 bi_foreach_instr_in_block(blk, I) {
93 if (I->op != BI_OPCODE_PHI)
94 break;
95
96 BITSET_CLEAR(live, I->dest[0].value);
97 }
98
99 /* Make live the corresponding source */
100 bi_foreach_instr_in_block(blk, I) {
101 if (I->op != BI_OPCODE_PHI)
102 break;
103
104 bi_index operand = I->src[bi_predecessor_index(blk, *pred)];
105 if (bi_is_ssa(operand))
106 BITSET_SET(live, operand.value);
107 }
108
109 BITSET_WORD progress = 0;
110
111 for (unsigned i = 0; i < words; ++i) {
112 progress |= live[i] & ~((*pred)->ssa_live_out[i]);
113 (*pred)->ssa_live_out[i] |= live[i];
114 }
115
116 if (progress != 0)
117 bi_worklist_push_tail(&worklist, *pred);
118 }
119 }
120
121 u_worklist_fini(&worklist);
122 }
123