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
|
/*
* memops - try to combine memory ops.
*
* Copyright (C) 2004 Linus Torvalds
*/
#include <string.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <stddef.h>
#include <assert.h>
#include "parse.h"
#include "expression.h"
#include "linearize.h"
#include "flow.h"
static int find_dominating_parents(pseudo_t pseudo, struct instruction *insn,
struct basic_block *bb, unsigned long generation, struct pseudo_list **dominators,
int local, int loads)
{
struct basic_block *parent;
if (bb_list_size(bb->parents) > 1)
loads = 0;
FOR_EACH_PTR(bb->parents, parent) {
struct instruction *one;
struct instruction *br;
pseudo_t phi;
FOR_EACH_PTR_REVERSE(parent->insns, one) {
int dominance;
if (one == insn)
goto no_dominance;
dominance = dominates(pseudo, insn, one, local);
if (dominance < 0) {
if (one->opcode == OP_LOAD)
continue;
return 0;
}
if (!dominance)
continue;
if (one->opcode == OP_LOAD && !loads)
continue;
goto found_dominator;
} END_FOR_EACH_PTR_REVERSE(one);
no_dominance:
if (parent->generation == generation)
continue;
parent->generation = generation;
if (!find_dominating_parents(pseudo, insn, parent, generation, dominators, local, loads))
return 0;
continue;
found_dominator:
br = delete_last_instruction(&parent->insns);
phi = alloc_phi(parent, one->target, one->size);
phi->ident = phi->ident ? : one->target->ident;
add_instruction(&parent->insns, br);
use_pseudo(insn, phi, add_pseudo(dominators, phi));
} END_FOR_EACH_PTR(parent);
return 1;
}
static int address_taken(pseudo_t pseudo)
{
struct pseudo_user *pu;
FOR_EACH_PTR(pseudo->users, pu) {
struct instruction *insn = pu->insn;
if (insn->bb && (insn->opcode != OP_LOAD || insn->opcode != OP_STORE))
return 1;
} END_FOR_EACH_PTR(pu);
return 0;
}
static int local_pseudo(pseudo_t pseudo)
{
return pseudo->type == PSEUDO_SYM
&& !(pseudo->sym->ctype.modifiers & (MOD_STATIC | MOD_NONLOCAL))
&& !address_taken(pseudo);
}
static void simplify_loads(struct basic_block *bb)
{
struct instruction *insn;
FOR_EACH_PTR_REVERSE(bb->insns, insn) {
if (!insn->bb)
continue;
if (insn->opcode == OP_LOAD) {
struct instruction *dom;
pseudo_t pseudo = insn->src;
int local = local_pseudo(pseudo);
struct pseudo_list *dominators;
unsigned long generation;
/* Check for illegal offsets.. */
check_access(insn);
RECURSE_PTR_REVERSE(insn, dom) {
int dominance;
if (!dom->bb)
continue;
dominance = dominates(pseudo, insn, dom, local);
if (dominance) {
/* possible partial dominance? */
if (dominance < 0) {
if (dom->opcode == OP_LOAD)
continue;
goto next_load;
}
/* Yeehaa! Found one! */
convert_load_instruction(insn, dom->target);
goto next_load;
}
} END_FOR_EACH_PTR_REVERSE(dom);
/* OK, go find the parents */
generation = ++bb_generation;
bb->generation = generation;
dominators = NULL;
if (find_dominating_parents(pseudo, insn, bb, generation, &dominators, local, 1)) {
/* This happens with initial assignments to structures etc.. */
if (!dominators) {
if (local) {
assert(pseudo->type != PSEUDO_ARG);
convert_load_instruction(insn, value_pseudo(0));
}
goto next_load;
}
rewrite_load_instruction(insn, dominators);
}
}
next_load:
/* Do the next one */;
} END_FOR_EACH_PTR_REVERSE(insn);
}
static void kill_store(struct instruction *insn)
{
if (insn) {
insn->bb = NULL;
insn->opcode = OP_SNOP;
kill_use(&insn->target);
}
}
static void kill_dominated_stores(struct basic_block *bb)
{
struct instruction *insn;
FOR_EACH_PTR_REVERSE(bb->insns, insn) {
if (!insn->bb)
continue;
if (insn->opcode == OP_STORE) {
struct instruction *dom;
pseudo_t pseudo = insn->src;
int local = local_pseudo(pseudo);
RECURSE_PTR_REVERSE(insn, dom) {
int dominance;
if (!dom->bb)
continue;
dominance = dominates(pseudo, insn, dom, local);
if (dominance) {
/* possible partial dominance? */
if (dominance < 0)
goto next_store;
if (dom->opcode == OP_LOAD)
goto next_store;
/* Yeehaa! Found one! */
kill_store(dom);
}
} END_FOR_EACH_PTR_REVERSE(dom);
/* OK, we should check the parents now */
}
next_store:
/* Do the next one */;
} END_FOR_EACH_PTR_REVERSE(insn);
}
void simplify_memops(struct entrypoint *ep)
{
struct basic_block *bb;
FOR_EACH_PTR_REVERSE(ep->bbs, bb) {
simplify_loads(bb);
} END_FOR_EACH_PTR_REVERSE(bb);
FOR_EACH_PTR_REVERSE(ep->bbs, bb) {
kill_dominated_stores(bb);
} END_FOR_EACH_PTR_REVERSE(bb);
}
|
