1 /*
2 * Copyright (C) 2020 Collabora, Ltd.
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 "compiler.h"
25
26 /* The scheduler packs multiple instructions into a clause (grouped as bundle),
27 * and the packing code takes in a clause and emits it to the wire. During
28 * scheduling, we need to lay out the instructions (bundles) and constants
29 * within the clause so constraints can be resolved during scheduling instead
30 * of failing packing. These routines will help building clauses from
31 * instructions so the scheduler can focus on the high-level algorithm, and
32 * manipulating clause layouts.
33 */
34
35 /* Helper to see if a bundle can be inserted. We must satisfy the invariant:
36 *
37 * constant_count + bundle_count <= 13
38 *
39 * ...which is equivalent to the clause ending up with 8 or fewer quardwords.
40 * Inserting a bundle increases bundle_count by one, and if it reads a unique
41 * constant, it increases constant_count by one.
42 */
43
44 bool
bi_can_insert_bundle(bi_clause * clause,bool constant)45 bi_can_insert_bundle(bi_clause *clause, bool constant)
46 {
47 unsigned constant_count = clause->constant_count + (constant ? 1 : 0);
48 unsigned bundle_count = clause->bundle_count + 1;
49
50 return (constant_count + bundle_count) <= 13;
51 }
52
53 /* Helper to calculate the number of quadwords in a clause. This is a function
54 * of the number of instructions and constants; it doesn't require actually
55 * packing, which is useful for branch offsets.
56 *
57 * Table of instruction count to instruction quadwords, per the packing
58 * algorithm, where * indicates a constant is packed for free:
59 *
60 * X | Y
61 * ---|---
62 * 1 | 1
63 * 2 | 2
64 * 3 | 3*
65 * 4 | 3
66 * 5 | 4*
67 * 6 | 5*
68 * 7 | 5
69 * 8 | 6*
70 *
71 * Y = { X if X <= 3
72 * { X - 1 if 4 <= X <= 6
73 * { X - 2 if 7 <= X <= 8
74 *
75 * and there is a constant for free if X is in {3, 5, 6, 8}. The remaining
76 * constants are packed two-by-two as constant quadwords.
77 */
78
79 unsigned
bi_clause_quadwords(bi_clause * clause)80 bi_clause_quadwords(bi_clause *clause)
81 {
82 unsigned X = clause->bundle_count;
83 unsigned Y = X - ((X >= 7) ? 2 : (X >= 4) ? 1 : 0);
84
85 unsigned constants = clause->constant_count;
86
87 if ((X != 4) && (X != 7) && (X >= 3) && constants)
88 constants--;
89
90 return Y + DIV_ROUND_UP(constants, 2);
91 }
92
93 /* Measures the number of quadwords a branch jumps. Bifrost relative offsets
94 * are from the beginning of a clause so to jump forward we count the current
95 * clause length, but to jump backwards we do not. */
96
97 signed
bi_block_offset(bi_context * ctx,bi_clause * start,bi_block * target)98 bi_block_offset(bi_context *ctx, bi_clause *start, bi_block *target)
99 {
100 /* Signed since we might jump backwards */
101 signed ret = 0;
102
103 /* Determine if the block we're branching to is strictly greater in
104 * source order */
105 bool forwards = target->base.name > start->block->base.name;
106
107 if (forwards) {
108 /* We have to jump through this block from the start of this
109 * clause to the end */
110 bi_foreach_clause_in_block_from(start->block, clause, start) {
111 ret += bi_clause_quadwords(clause);
112 }
113
114 /* We then need to jump through every clause of every following
115 * block until the target */
116 bi_foreach_block_from(ctx, start->block, _blk) {
117 bi_block *blk = (bi_block *) _blk;
118
119 /* Don't double-count the first block */
120 if (blk == start->block)
121 continue;
122
123 /* End just before the target */
124 if (blk == target)
125 break;
126
127 /* Count every clause in the block */
128 bi_foreach_clause_in_block(blk, clause) {
129 ret += bi_clause_quadwords(clause);
130 }
131 }
132 } else {
133 /* We start at the beginning of the clause but have to jump
134 * through the clauses before us in the block */
135 bi_foreach_clause_in_block_from_rev(start->block, clause, start) {
136 if (clause == start)
137 continue;
138
139 ret -= bi_clause_quadwords(clause);
140 }
141
142 /* And jump back every clause of preceding blocks up through
143 * and including the target to get to the beginning of the
144 * target */
145 bi_foreach_block_from_rev(ctx, start->block, _blk) {
146 bi_block *blk = (bi_block *) _blk;
147
148 if (blk == start->block)
149 continue;
150
151 bi_foreach_clause_in_block(blk, clause) {
152 ret -= bi_clause_quadwords(clause);
153 }
154
155 /* End just after the target */
156 if (blk == target)
157 break;
158 }
159 }
160
161 return ret;
162 }
163