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 tuple),
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 (tuples) 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 /* Is embedded constant 0 packed for free in a clause with this many tuples? */
36
37 bool
bi_ec0_packed(unsigned tuple_count)38 bi_ec0_packed(unsigned tuple_count)
39 {
40 return (tuple_count == 3) || (tuple_count == 5) || (tuple_count == 6) ||
41 (tuple_count == 8);
42 }
43
44 /* Helper to calculate the number of quadwords in a clause. This is a function
45 * of the number of instructions and constants; it doesn't require actually
46 * packing, which is useful for branch offsets.
47 *
48 * Table of instruction count to instruction quadwords, per the packing
49 * algorithm, where * indicates a constant is packed for free:
50 *
51 * X | Y
52 * ---|---
53 * 1 | 1
54 * 2 | 2
55 * 3 | 3*
56 * 4 | 3
57 * 5 | 4*
58 * 6 | 5*
59 * 7 | 5
60 * 8 | 6*
61 *
62 * Y = { X if X <= 3
63 * { X - 1 if 4 <= X <= 6
64 * { X - 2 if 7 <= X <= 8
65 *
66 * and there is a constant for free if X is in {3, 5, 6, 8}. The remaining
67 * constants are packed two-by-two as constant quadwords.
68 */
69
70 static unsigned
bi_clause_quadwords(bi_clause * clause)71 bi_clause_quadwords(bi_clause *clause)
72 {
73 unsigned X = clause->tuple_count;
74 unsigned Y = X - ((X >= 7) ? 2 : (X >= 4) ? 1 : 0);
75
76 unsigned constants = clause->constant_count;
77
78 if ((X != 4) && (X != 7) && (X >= 3) && constants)
79 constants--;
80
81 return Y + DIV_ROUND_UP(constants, 2);
82 }
83
84 /* Measures the number of quadwords a branch jumps. Bifrost relative offsets
85 * are from the beginning of a clause so to jump forward we count the current
86 * clause length, but to jump backwards we do not. */
87
88 signed
bi_block_offset(bi_context * ctx,bi_clause * start,bi_block * target)89 bi_block_offset(bi_context *ctx, bi_clause *start, bi_block *target)
90 {
91 /* Signed since we might jump backwards */
92 signed ret = 0;
93
94 /* Determine if the block we're branching to is strictly greater in
95 * source order */
96 bool forwards = target->index > start->block->index;
97
98 if (forwards) {
99 /* We have to jump through this block from the start of this
100 * clause to the end */
101 bi_foreach_clause_in_block_from(start->block, clause, start) {
102 ret += bi_clause_quadwords(clause);
103 }
104
105 /* We then need to jump through every clause of every following
106 * block until the target */
107 bi_foreach_block_from(ctx, start->block, blk) {
108 /* Don't double-count the first block */
109 if (blk == start->block)
110 continue;
111
112 /* End just before the target */
113 if (blk == target)
114 break;
115
116 /* Count every clause in the block */
117 bi_foreach_clause_in_block(blk, clause) {
118 ret += bi_clause_quadwords(clause);
119 }
120 }
121 } else {
122 /* We start at the beginning of the clause but have to jump
123 * through the clauses before us in the block */
124 bi_foreach_clause_in_block_from_rev(start->block, clause, start) {
125 if (clause == start)
126 continue;
127
128 ret -= bi_clause_quadwords(clause);
129 }
130
131 /* And jump back every clause of preceding blocks up through
132 * and including the target to get to the beginning of the
133 * target */
134 bi_foreach_block_from_rev(ctx, start->block, blk) {
135 if (blk == start->block)
136 continue;
137
138 bi_foreach_clause_in_block(blk, clause) {
139 ret -= bi_clause_quadwords(clause);
140 }
141
142 /* End just after the target */
143 if (blk == target)
144 break;
145 }
146 }
147
148 return ret;
149 }
150