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
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
|
#include "ir.h"
static const uchar loadszcls[] = {
[Oloads1 - Oloads1] = 1|KI4<<4, [Oloadu1 - Oloads1] = 1|KI4<<4,
[Oloads2 - Oloads1] = 2|KI4<<4, [Oloadu2 - Oloads1] = 2|KI4<<4,
[Oloads4 - Oloads1] = 4|KI4<<4, [Oloadu4 - Oloads1] = 4|KI4<<4,
[Oloadi8 - Oloads1] = 8|KI8<<4,
[Oloadf4 - Oloads1] = 4|KF4<<4,
[Oloadf8 - Oloads1] = 8|KF8<<4,
};
static const uchar load2ext[] = {
[Oloads1 - Oloads1] = Oexts1, [Oloadu1 - Oloads1] = Oextu1,
[Oloads2 - Oloads1] = Oexts2, [Oloadu2 - Oloads1] = Oextu2,
[Oloads4 - Oloads1] = Oexts4, [Oloadu4 - Oloads1] = Oextu4,
[Oloadi8 - Oloads1] = Ocopy,
};
#define loadsz(o) (loadszcls[(o) - Oloads1] & 0xF)
#define loadcls(o) (loadszcls[(o) - Oloads1] >> 4)
#define load2ext(o) (load2ext[(o) - Oloads1])
#define storesz(o) (1 << ((o) - Ostore1))
/* Implements algorithm in 'Simple and Efficient Construction of Static Single' (Braun et al) */
struct pendingphi { ushort var, phi; };
struct ssabuilder {
vec_of(struct pendingphi) *pendingphis; /* map of block to list of incomplete phis in block */
imap_of(union ref *) curdefs; /* map of var to (map of block to def of var) */
int lastvisit;
int nblk;
};
static union ref readvar(struct ssabuilder *, int var, enum irclass, struct block *);
static union ref
deltrivialphis(struct ssabuilder *sb, struct block *blk, union ref phiref)
{
union ref **pcurdefs;
int var;
struct use *use, *uend;
union ref *args = phitab.p[instrtab[phiref.i].l.i];
union ref same = {0};
assert(instrtab[phiref.i].op == Ophi);
for (int i = 0; i < blk->npred; ++i) {
if (args[i].bits == same.bits || args[i].bits == phiref.bits)
continue; /* unique value or self-reference */
if (same.bits != 0) {
return phiref; /* non-trivial */
}
same = args[i];
}
if (same.bits == 0)
same = UNDREF; /* the phi is unreachable or in the start block */
/* replace uses */
replcuses(phiref, same);
imap_each(&sb->curdefs, var, pcurdefs) {
(void)var;
if ((*pcurdefs)[blk->id].bits == phiref.bits)
(*pcurdefs)[blk->id] = same;
}
/* stops infinite recursion and marks phi for removal */
instrtab[phiref.i].op = Onop;
/* recursively try to remove all phi users as they might have become trivial */
Redo:
for (use = instruse[phiref.i], uend = use + instrnuse[phiref.i]; use < uend; ++use) {
if (use->u != USERJUMP && instrtab[use->u].op == Ophi && use->u != phiref.i) {
union ref it = mkref(RTMP, use->u);
union ref vphi2 = deltrivialphis(sb, use->blk, it);
if (vphi2.bits != it.bits) {
/* deletion happened so phiref use may have changed */
goto Redo;
}
}
}
return same;
}
static union ref
addphiargs(struct ssabuilder *sb, int var, enum irclass cls, struct block *blk, union ref phiref)
{
union ref *args = phitab.p[instrtab[phiref.i].l.i];
for (int i = 0; i < blk->npred; ++i) {
struct block *pred = blkpred(blk, i);
args[i] = readvar(sb, var, cls, pred);
adduse(blk, phiref.i, args[i]);
}
return deltrivialphis(sb, blk, phiref);
}
static void
writevar(struct ssabuilder *sb, int var, struct block *blk, union ref val)
{
union ref **pcurdefs;
if (!(pcurdefs = imap_get(&sb->curdefs, var))) {
pcurdefs = imap_set(&sb->curdefs, var, xcalloc(sb->nblk * sizeof(union ref)));
}
(*pcurdefs)[blk->id] = val;
}
static union ref
readvarrec(struct ssabuilder *sb, int var, enum irclass cls, struct block *blk)
{
union ref val;
assert(blk->npred > 0);
if (blk->id > sb->lastvisit) { /* unsealed block */
val = insertphi(blk, cls);
vpush(&sb->pendingphis[blk->id], ((struct pendingphi) { var, val.i }));
} else if (blk->npred == 1) {
val = readvar(sb, var, cls, blkpred(blk, 0));
} else {
val = insertphi(blk, cls);
writevar(sb, var, blk, val);
val = addphiargs(sb, var, cls, blk, val);
}
writevar(sb, var, blk, val);
return val;
}
static union ref
readvar(struct ssabuilder *sb, int var, enum irclass cls, struct block *blk)
{
union ref **pcurdefs;
if ((pcurdefs = imap_get(&sb->curdefs, var)) && (*pcurdefs)[blk->id].bits)
return (*pcurdefs)[blk->id];
if (blk->npred == 0) /* entry block, var is read before being written to */
return UNDREF;
return readvarrec(sb, var, cls, blk);
}
/* require use, blkid; keeps use */
void
mem2reg(struct function *fn)
{
struct block *blk = fn->entry;
struct ssabuilder sb = { .nblk = fn->nblk };
sb.pendingphis = xcalloc(fn->nblk * sizeof *sb.pendingphis);
do {
vec_of(struct pendingphi) *pending;
for (int i = 0; i < blk->ins.n; ++i) {
struct use *use, *uend;
enum irclass k = 0;
int sz = 0, ndef = 0;
enum op ext = Ocopy;
int var = blk->ins.p[i];
struct instr *ins = &instrtab[var];
if (!oisalloca(ins->op)) continue;
uend = instruse[var] + instrnuse[var];
for (use = instruse[var]; use < uend; ++use) {
struct instr *m;
if (use->u == USERJUMP) goto Next;
m = &instrtab[use->u];
if (oisload(m->op) && (!sz || sz == loadsz(m->op))) {
sz = loadsz(m->op);
k = loadcls(m->op);
if (sz < 4) ext = load2ext(m->op);
continue;
}
if (oisstore(m->op) && m->l.bits == mkref(RTMP, var).bits
&& (!sz || sz == storesz(m->op))) {
sz = storesz(m->op);
++ndef;
continue;
}
goto Next;
}
if (!ndef) /* slot is read from but never written to */
goto Next;
for (use = instruse[var]; use < uend; ++use) {
struct instr *m = &instrtab[use->u];
if (oisstore(m->op)) {
writevar(&sb, var, use->blk, m->r);
*m = mkinstr(Onop,0,);
} else if (oisload(m->op)) {
union ref val = readvar(&sb, var, k = m->cls, use->blk);
if (!val.bits) { /* var is used uninitialized */
/* TODO emit diagnostic */
/* load some garbage */
*m = mkinstr(kisflt(k) ? Oloadf4 + (k==KF8) : Oloads1+ilog2(sz)*2,
k, mkref(RREG, mctarg->bpr));
} else {
adduse(use->blk, use->u, val);
*m = mkinstr(ext, k, val);
}
}
}
/* remove alloca */
delinstr(blk, i--);
Next:;
}
assert(sb.lastvisit == blk->id);
pending = (void *) &sb.pendingphis[blk->id];
for (int i = 0; i < pending->n; ++i) {
addphiargs(&sb, pending->p[i].var, instrtab[pending->p[i].phi].cls, blk,
mkref(RTMP, pending->p[i].phi));
}
++sb.lastvisit;
vfree(pending);
} while ((blk = blk->lnext) != fn->entry);
do {
/* remove phis marked for deletion */
for (int i = 0; i < blk->phi.n; ++i)
if (instrtab[blk->phi.p[i]].op == Onop)
delphi(blk, i--);
} while ((blk = blk->lnext) != fn->entry);
free(sb.pendingphis);
for (int i = 0; i < sb.curdefs.mb.N; ++i)
if (bstest(sb.curdefs.mb.bs, i))
free(sb.curdefs.v[i]);
imap_free(&sb.curdefs);
if (ccopt.dbg.m) {
efmt("<< After mem2reg >>\n");
irdump(fn);
}
}
/* vim:set ts=3 sw=3 expandtab: */
|
