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) ||
41 (tuple_count == 5) ||
42 (tuple_count == 6) ||
43 (tuple_count == 8);
44 }
45
46 /* Helper to calculate the number of quadwords in a clause. This is a function
47 * of the number of instructions and constants; it doesn't require actually
48 * packing, which is useful for branch offsets.
49 *
50 * Table of instruction count to instruction quadwords, per the packing
51 * algorithm, where * indicates a constant is packed for free:
52 *
53 * X | Y
54 * ---|---
55 * 1 | 1
56 * 2 | 2
57 * 3 | 3*
58 * 4 | 3
59 * 5 | 4*
60 * 6 | 5*
61 * 7 | 5
62 * 8 | 6*
63 *
64 * Y = { X if X <= 3
65 * { X - 1 if 4 <= X <= 6
66 * { X - 2 if 7 <= X <= 8
67 *
68 * and there is a constant for free if X is in {3, 5, 6, 8}. The remaining
69 * constants are packed two-by-two as constant quadwords.
70 */
71
72 static unsigned
bi_clause_quadwords(bi_clause * clause)73 bi_clause_quadwords(bi_clause *clause)
74 {
75 unsigned X = clause->tuple_count;
76 unsigned Y = X - ((X >= 7) ? 2 : (X >= 4) ? 1 : 0);
77
78 unsigned constants = clause->constant_count;
79
80 if ((X != 4) && (X != 7) && (X >= 3) && constants)
81 constants--;
82
83 return Y + DIV_ROUND_UP(constants, 2);
84 }
85
86 /* Measures the number of quadwords a branch jumps. Bifrost relative offsets
87 * are from the beginning of a clause so to jump forward we count the current
88 * clause length, but to jump backwards we do not. */
89
90 signed
bi_block_offset(bi_context * ctx,bi_clause * start,bi_block * target)91 bi_block_offset(bi_context *ctx, bi_clause *start, bi_block *target)
92 {
93 /* Signed since we might jump backwards */
94 signed ret = 0;
95
96 /* Determine if the block we're branching to is strictly greater in
97 * source order */
98 bool forwards = target->name > start->block->name;
99
100 if (forwards) {
101 /* We have to jump through this block from the start of this
102 * clause to the end */
103 bi_foreach_clause_in_block_from(start->block, clause, start) {
104 ret += bi_clause_quadwords(clause);
105 }
106
107 /* We then need to jump through every clause of every following
108 * block until the target */
109 bi_foreach_block_from(ctx, start->block, blk) {
110 /* Don't double-count the first block */
111 if (blk == start->block)
112 continue;
113
114 /* End just before the target */
115 if (blk == target)
116 break;
117
118 /* Count every clause in the block */
119 bi_foreach_clause_in_block(blk, clause) {
120 ret += bi_clause_quadwords(clause);
121 }
122 }
123 } else {
124 /* We start at the beginning of the clause but have to jump
125 * through the clauses before us in the block */
126 bi_foreach_clause_in_block_from_rev(start->block, clause, start) {
127 if (clause == start)
128 continue;
129
130 ret -= bi_clause_quadwords(clause);
131 }
132
133 /* And jump back every clause of preceding blocks up through
134 * and including the target to get to the beginning of the
135 * target */
136 bi_foreach_block_from_rev(ctx, start->block, blk) {
137 if (blk == start->block)
138 continue;
139
140 bi_foreach_clause_in_block(blk, clause) {
141 ret -= bi_clause_quadwords(clause);
142 }
143
144 /* End just after the target */
145 if (blk == target)
146 break;
147 }
148 }
149
150 return ret;
151 }
152