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
|
/*
* Copyright (C) 2012 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 "DFGConstantFoldingPhase.h"
#if ENABLE(DFG_JIT)
#include "DFGAbstractState.h"
#include "DFGBasicBlock.h"
#include "DFGGraph.h"
#include "DFGInsertionSet.h"
#include "DFGPhase.h"
namespace JSC { namespace DFG {
class ConstantFoldingPhase : public Phase {
public:
ConstantFoldingPhase(Graph& graph)
: Phase(graph, "constant folding")
{
}
bool run()
{
bool changed = false;
AbstractState state(m_graph);
InsertionSet<NodeIndex> insertionSet;
for (BlockIndex blockIndex = 0; blockIndex < m_graph.m_blocks.size(); ++blockIndex) {
BasicBlock* block = m_graph.m_blocks[blockIndex].get();
if (!block)
continue;
if (!block->cfaFoundConstants)
continue;
state.beginBasicBlock(block);
for (unsigned indexInBlock = 0; indexInBlock < block->size(); ++indexInBlock) {
if (!state.isValid())
break;
state.execute(indexInBlock);
NodeIndex nodeIndex = block->at(indexInBlock);
Node& node = m_graph[nodeIndex];
if (!node.shouldGenerate()
|| m_graph.clobbersWorld(node)
|| node.hasConstant())
continue;
JSValue value = state.forNode(nodeIndex).value();
if (!value)
continue;
Node phantom(Phantom, node.codeOrigin);
if (node.op() == GetLocal) {
ASSERT(m_graph[node.child1()].op() == Phi);
ASSERT(!m_graph[node.child1()].hasResult());
NodeIndex previousLocalAccess = NoNode;
if (block->variablesAtHead.operand(node.local()) == nodeIndex) {
// We expect this to be the common case.
ASSERT(block->isInPhis(node.child1().index()));
previousLocalAccess = node.child1().index();
block->variablesAtHead.operand(node.local()) = previousLocalAccess;
} else {
ASSERT(indexInBlock > 0);
// Must search for the previous access to this local.
for (BlockIndex subIndexInBlock = indexInBlock - 1; subIndexInBlock--;) {
NodeIndex subNodeIndex = block->at(subIndexInBlock);
Node& subNode = m_graph[subNodeIndex];
if (!subNode.shouldGenerate())
continue;
if (!subNode.hasVariableAccessData())
continue;
if (subNode.local() != node.local())
continue;
// The two must have been unified.
ASSERT(subNode.variableAccessData() == node.variableAccessData());
// Currently, the previous node must be a flush.
// NOTE: This assertion should be removed if we ever do
// constant folding on captured variables. In particular,
// this code does not require the previous node to be a flush,
// but we are asserting this anyway because it is a constraint
// of the IR and this is as good a place as any to assert it.
ASSERT(subNode.op() == Flush);
previousLocalAccess = subNodeIndex;
break;
}
ASSERT(previousLocalAccess != NoNode);
}
NodeIndex tailNodeIndex = block->variablesAtTail.operand(node.local());
if (tailNodeIndex == nodeIndex)
block->variablesAtTail.operand(node.local()) = previousLocalAccess;
else {
ASSERT(m_graph[tailNodeIndex].op() == Flush
|| m_graph[tailNodeIndex].op() == SetLocal);
}
}
phantom.children = node.children;
phantom.ref();
m_graph.convertToConstant(nodeIndex, value);
NodeIndex phantomNodeIndex = m_graph.size();
m_graph.append(phantom);
insertionSet.append(indexInBlock, phantomNodeIndex);
changed = true;
}
insertionSet.execute(*block);
state.reset();
}
return changed;
}
};
bool performConstantFolding(Graph& graph)
{
return runPhase<ConstantFoldingPhase>(graph);
}
} } // namespace JSC::DFG
#endif // ENABLE(DFG_JIT)
|
