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
|
/*
* Copyright (C) 2015-2017 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "AirEliminateDeadCode.h"
#if ENABLE(B3_JIT)
#include "AirCode.h"
#include "AirInstInlines.h"
#include "AirPhaseScope.h"
#include "AirTmpInlines.h"
#include "AirTmpSet.h"
#include <wtf/IndexSet.h>
namespace JSC { namespace B3 { namespace Air {
bool eliminateDeadCode(Code& code)
{
PhaseScope phaseScope(code, "eliminateDeadCode"_s);
TmpSet liveTmps;
IndexSet<StackSlot*> liveStackSlots;
bool changed { false };
auto isArgLive = [&] (const Arg& arg) -> bool {
switch (arg.kind()) {
case Arg::Tmp:
if (arg.isReg())
return true;
return liveTmps.contains(arg.tmp());
case Arg::Stack:
if (arg.stackSlot()->isLocked())
return true;
return liveStackSlots.contains(arg.stackSlot());
default:
return true;
}
};
auto isInstLive = [&] (Inst& inst) -> bool {
if (inst.hasNonArgEffects())
return true;
// This instruction should be presumed dead, if its Args are all dead.
bool storesToLive = false;
inst.forEachArg(
[&] (Arg& arg, Arg::Role role, Bank, Width) {
if (!Arg::isAnyDef(role))
return;
if (role == Arg::Scratch)
return;
storesToLive |= isArgLive(arg);
});
return storesToLive;
};
// Returns true if it's live.
auto handleInst = [&] (Inst& inst) -> bool {
if (!isInstLive(inst))
return false;
// We get here if the Inst is live. For simplicity we say that a live instruction forces
// liveness upon everything it mentions.
for (Arg& arg : inst.args) {
if (arg.isStack() && !arg.stackSlot()->isLocked())
changed |= liveStackSlots.add(arg.stackSlot());
arg.forEachTmpFast(
[&] (Tmp& tmp) {
if (!tmp.isReg())
changed |= liveTmps.add(tmp);
});
}
return true;
};
Vector<Inst*> possiblyDead;
for (BasicBlock* block : code) {
for (Inst& inst : *block) {
if (!handleInst(inst))
possiblyDead.append(&inst);
}
}
auto runForward = [&] () -> bool {
changed = false;
possiblyDead.removeAllMatching(
[&] (Inst* inst) -> bool {
bool result = handleInst(*inst);
changed |= result;
return result;
});
return changed;
};
auto runBackward = [&] () -> bool {
changed = false;
for (unsigned i = possiblyDead.size(); i--;) {
bool result = handleInst(*possiblyDead[i]);
if (result) {
possiblyDead[i] = possiblyDead.last();
possiblyDead.removeLast();
changed = true;
}
}
return changed;
};
for (;;) {
// Propagating backward is most likely to be profitable.
if (!runBackward())
break;
if (!runBackward())
break;
// Occasionally propagating forward greatly reduces the likelihood of pathologies.
if (!runForward())
break;
}
unsigned removedInstCount = 0;
for (BasicBlock* block : code) {
removedInstCount += block->insts().removeAllMatching(
[&] (Inst& inst) -> bool {
return !isInstLive(inst);
});
}
return !!removedInstCount;
}
} } } // namespace JSC::B3::Air
#endif // ENABLE(B3_JIT)
|
