1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
|
/* Source code for RCC-Legacy.
Copyright (C) 2026 Richard Qin
This file is part of RCC.
RCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
RCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with RCC; see the file LICENSE. If not see
<http://www.gnu.org/licenses/>. */
/// @file live.cc
/// @brief Backward dataflow liveness analysis.
///
/// See docs/live.md for architectural notes.
#include "rcc/all.h"
namespace rcc {
void liveon(BSet* v, Blk* b, Blk* s) {
bscopy(v, s->in);
// s's phi-defs.
for (Phi* p = s->phi; p; p = p->link)
if (rtype(p->to) == RTmp)
bsclr(v, p->to.val);
// phi-arg edge check.
for (Phi* p = s->phi; p; p = p->link) {
for (uint n = 0; n < p->narg; n++) {
if (p->blk[n] != b)
continue;
if (rtype(p->arg[n]) != RTmp)
continue;
uint t = p->arg[n].val;
bsset(v, t);
bsset(b->gen, t);
}
}
}
namespace {
/// Add ref (if tmp) to b->gen and b->in; on first entry to b->in, increment live count for its K
/// bucket.
inline void use_ref(Ref r, Blk* b, int nlv[2], Tmp* tmp) {
if (rtype(r) != RTmp)
return;
uint t = r.val;
bsset(b->gen, t);
if (!bshas(b->in, t)) {
nlv[KBASE(tmp[t].cls)]++;
bsset(b->in, t);
}
}
/// Get maximum of two elements.
inline int imax(int a, int b) {
return a > b ? a : b;
}
} // namespace
void filllive(Ctx* ctx, Fn* fn) {
BSet prev_out[1];
BSet edge_set[1];
bsinit(ctx, prev_out, static_cast<uint>(fn->ntmp));
bsinit(ctx, edge_set, static_cast<uint>(fn->ntmp));
// Initialize sets.
for (Blk* b = fn->start; b; b = b->link) {
bsinit(ctx, b->in, static_cast<uint>(fn->ntmp));
bsinit(ctx, b->out, static_cast<uint>(fn->ntmp));
bsinit(ctx, b->gen, static_cast<uint>(fn->ntmp));
}
// Fixpoint loop.
bool changed = true;
while (changed) {
changed = false;
// Reverse rpo scan.
for (int n = static_cast<int>(fn->nblk) - 1; n >= 0; n--) {
Blk* b = fn->rpo[n];
// Merge successors liveon.
bscopy(prev_out, b->out);
if (b->s1) {
liveon(edge_set, b, b->s1);
bsunion(b->out, edge_set);
}
if (b->s2) {
liveon(edge_set, b, b->s2);
bsunion(b->out, edge_set);
}
if (!bsequal(b->out, prev_out))
changed = true;
// Initial in.
int nlv[2] = {0, 0};
b->out->t[0] |= T.rglob;
bscopy(b->in, b->out);
for (int t = 0; bsiter(b->in, &t); t++)
nlv[KBASE(fn->tmp[t].cls)]++;
// Terminal jump args.
if (rtype(b->jmp.arg) == RCall) {
assert(static_cast<int>(bscount(b->in)) == T.nrglob && b->in->t[0] == T.rglob);
b->in->t[0] |= T.retregs(b->jmp.arg, nlv);
} else {
use_ref(b->jmp.arg, b, nlv, fn->tmp);
}
// Fused cmp+jnz check.
use_ref(b->jmp.arg2, b, nlv, fn->tmp);
// Initial nlive.
for (int k = 0; k < 2; k++)
b->nlive[k] = nlv[k];
// Reverse scan instructions.
for (int idx = static_cast<int>(b->nins) - 1; idx >= 0; idx--) {
Ins* i = &b->ins[idx];
// Post-ABI lowering call.
if (i->op == Ocall && rtype(i->arg[1]) == RCall) {
int call_kill[2];
b->in->t[0] &= ~T.retregs(i->arg[1], call_kill);
for (int k = 0; k < 2; k++) {
nlv[k] -= call_kill[k];
// Midpoint call.
nlv[k] += T.nrsave[k];
b->nlive[k] = imax(b->nlive[k], nlv[k]);
}
int call_arg[2];
b->in->t[0] |= T.argregs(i->arg[1], call_arg);
for (int k = 0; k < 2; k++) {
nlv[k] -= T.nrsave[k];
nlv[k] += call_arg[k];
}
}
// def kill.
if (!req(i->to, Ref::none())) {
assert(rtype(i->to) == RTmp);
uint t = i->to.val;
if (bshas(b->in, t))
nlv[KBASE(fn->tmp[t].cls)]--;
bsset(b->gen, t);
bsclr(b->in, t);
}
// args gen.
for (int k = 0; k < 2; k++) {
Ref a = i->arg[k];
if (rtype(a) == RMem) {
Mem* m = &fn->mem[a.val];
use_ref(m->base, b, nlv, fn->tmp);
use_ref(m->index, b, nlv, fn->tmp);
} else {
use_ref(a, b, nlv, fn->tmp);
}
}
// Update peak.
for (int k = 0; k < 2; k++)
b->nlive[k] = imax(b->nlive[k], nlv[k]);
}
}
}
// Debug dump.
if (debug['L']) {
FILE* f = ctx->dbg_buf;
fprintf(f, "\n> Liveness analysis:\n");
for (Blk* b = fn->start; b; b = b->link) {
fprintf(f, "\t%-10sin: ", b->name);
dumpts(b->in, fn->tmp, f);
fprintf(f, "\t out: ");
dumpts(b->out, fn->tmp, f);
fprintf(f, "\t gen: ");
dumpts(b->gen, fn->tmp, f);
fprintf(f, "\t live: %d %d\n", b->nlive[0], b->nlive[1]);
}
}
}
} // namespace rcc
|
