1/*
2 * Copyright (C) 2008-2019 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of Apple Inc. ("Apple") nor the names of
14 * its contributors may be used to endorse or promote products derived
15 * from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#pragma once
30
31#include <wtf/Assertions.h>
32#include <wtf/Vector.h>
33#include <limits.h>
34
35namespace JSC {
36 template<typename Traits>
37 class BytecodeGeneratorBase;
38 struct JSGeneratorTraits;
39
40 template<typename Traits>
41 class GenericLabel;
42
43 template<typename Traits>
44 class GenericBoundLabel {
45 using BytecodeGenerator = BytecodeGeneratorBase<Traits>;
46 using Label = GenericLabel<Traits>;
47
48 public:
49 GenericBoundLabel()
50 : m_type(Offset)
51 , m_generator(nullptr)
52 , m_target(0)
53 { }
54
55 explicit GenericBoundLabel(int target)
56 : m_type(Offset)
57 , m_generator(nullptr)
58 , m_target(target)
59 { }
60
61 GenericBoundLabel(BytecodeGenerator* generator, Label* label)
62 : m_type(GeneratorForward)
63 , m_generator(generator)
64 , m_label(label)
65 { }
66
67 GenericBoundLabel(BytecodeGenerator* generator, int offset)
68 : m_type(GeneratorBackward)
69 , m_generator(generator)
70 , m_target(offset)
71 { }
72
73 int target()
74 {
75 switch (m_type) {
76 case Offset:
77 return m_target;
78 case GeneratorBackward:
79 return m_target - m_generator->m_writer.position();
80 case GeneratorForward:
81 return 0;
82 default:
83 RELEASE_ASSERT_NOT_REACHED();
84 }
85 }
86
87 int saveTarget()
88 {
89 if (m_type == GeneratorForward) {
90 m_savedTarget = m_generator->m_writer.position();
91 return 0;
92 }
93
94 m_savedTarget = target();
95 return m_savedTarget;
96 }
97
98 int commitTarget()
99 {
100 if (m_type == GeneratorForward) {
101 m_label->m_unresolvedJumps.append(m_savedTarget);
102 return 0;
103 }
104
105 return m_savedTarget;
106 }
107
108 operator int() { return target(); }
109
110 private:
111 enum Type : uint8_t {
112 Offset,
113 GeneratorForward,
114 GeneratorBackward,
115 };
116
117 Type m_type;
118 int m_savedTarget { 0 };
119 BytecodeGenerator* m_generator;
120 union {
121 Label* m_label;
122 int m_target;
123 };
124 };
125
126 template<typename Traits>
127 class GenericLabel {
128 WTF_MAKE_NONCOPYABLE(GenericLabel);
129 using BytecodeGenerator = BytecodeGeneratorBase<Traits>;
130 using BoundLabel = GenericBoundLabel<Traits>;
131
132 public:
133 GenericLabel() = default;
134
135 void setLocation(BytecodeGenerator&, unsigned location);
136
137 BoundLabel bind(BytecodeGenerator* generator)
138 {
139 m_bound = true;
140 if (!isForward())
141 return BoundLabel(generator, m_location);
142 return BoundLabel(generator, this);
143 }
144
145 BoundLabel bind(unsigned offset)
146 {
147 m_bound = true;
148 if (!isForward())
149 return BoundLabel(m_location - offset);
150 m_unresolvedJumps.append(offset);
151 return BoundLabel();
152 }
153
154 BoundLabel bind()
155 {
156 ASSERT(!isForward());
157 return bind(0u);
158 }
159
160 void ref() { ++m_refCount; }
161 void deref()
162 {
163 --m_refCount;
164 ASSERT(m_refCount >= 0);
165 }
166 int refCount() const { return m_refCount; }
167 bool hasOneRef() const { return m_refCount == 1; }
168
169 bool isForward() const { return m_location == invalidLocation; }
170
171 bool isBound() const { return m_bound; }
172
173 private:
174 friend BoundLabel;
175
176 typedef Vector<int, 8> JumpVector;
177
178 static constexpr unsigned invalidLocation = UINT_MAX;
179
180 int m_refCount { 0 };
181 unsigned m_location { invalidLocation };
182 mutable bool m_bound { false };
183 mutable JumpVector m_unresolvedJumps;
184 };
185
186 using Label = GenericLabel<JSGeneratorTraits>;
187 using BoundLabel = GenericBoundLabel<JSGeneratorTraits>;
188
189 namespace Wasm {
190 struct GeneratorTraits;
191 using Label = GenericLabel<Wasm::GeneratorTraits>;
192 }
193
194 // This cannot be declared in the Wasm namespace as it conflicts with the
195 // ruby Wasm namespace when referencing it from BytecodeList.rb
196 using WasmBoundLabel = GenericBoundLabel<Wasm::GeneratorTraits>;
197
198} // namespace JSC
199