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
|
// Copyright 2011 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_AST_VARIABLES_H_
#define V8_AST_VARIABLES_H_
#include "src/ast/ast-value-factory.h"
#include "src/globals.h"
#include "src/zone/zone.h"
namespace v8 {
namespace internal {
// The AST refers to variables via VariableProxies - placeholders for the actual
// variables. Variables themselves are never directly referred to from the AST,
// they are maintained by scopes, and referred to from VariableProxies and Slots
// after binding and variable allocation.
class Variable final : public ZoneObject {
public:
Variable(Scope* scope, const AstRawString* name, VariableMode mode,
VariableKind kind, InitializationFlag initialization_flag,
MaybeAssignedFlag maybe_assigned_flag = kNotAssigned);
// The source code for an eval() call may refer to a variable that is
// in an outer scope about which we don't know anything (it may not
// be the script scope). scope() is NULL in that case. Currently the
// scope is only used to follow the context chain length.
Scope* scope() const { return scope_; }
// This is for adjusting the scope of temporaries used when desugaring
// parameter initializers.
void set_scope(Scope* scope) { scope_ = scope; }
Handle<String> name() const { return name_->string(); }
const AstRawString* raw_name() const { return name_; }
VariableMode mode() const { return VariableModeField::decode(bit_field_); }
bool has_forced_context_allocation() const {
return ForceContextAllocationField::decode(bit_field_);
}
void ForceContextAllocation() {
DCHECK(IsUnallocated() || IsContextSlot() ||
location() == VariableLocation::MODULE);
bit_field_ = ForceContextAllocationField::update(bit_field_, true);
}
bool is_used() { return IsUsedField::decode(bit_field_); }
void set_is_used() { bit_field_ = IsUsedField::update(bit_field_, true); }
MaybeAssignedFlag maybe_assigned() const {
return MaybeAssignedFlagField::decode(bit_field_);
}
void set_maybe_assigned() {
bit_field_ = MaybeAssignedFlagField::update(bit_field_, kMaybeAssigned);
}
int initializer_position() { return initializer_position_; }
void set_initializer_position(int pos) { initializer_position_ = pos; }
bool IsUnallocated() const {
return location() == VariableLocation::UNALLOCATED;
}
bool IsParameter() const { return location() == VariableLocation::PARAMETER; }
bool IsStackLocal() const { return location() == VariableLocation::LOCAL; }
bool IsStackAllocated() const { return IsParameter() || IsStackLocal(); }
bool IsContextSlot() const { return location() == VariableLocation::CONTEXT; }
bool IsLookupSlot() const { return location() == VariableLocation::LOOKUP; }
bool IsGlobalObjectProperty() const;
bool is_dynamic() const { return IsDynamicVariableMode(mode()); }
// Returns the InitializationFlag this Variable was created with.
// Scope analysis may allow us to relax this initialization
// requirement, which will be reflected in the return value of
// binding_needs_init().
InitializationFlag initialization_flag() const {
return InitializationFlagField::decode(bit_field_);
}
// Whether this variable needs to be initialized with the hole at
// declaration time. Only returns valid results after scope analysis.
bool binding_needs_init() const {
DCHECK_IMPLIES(initialization_flag() == kNeedsInitialization,
IsLexicalVariableMode(mode()));
DCHECK_IMPLIES(ForceHoleInitializationField::decode(bit_field_),
initialization_flag() == kNeedsInitialization);
// Always initialize if hole initialization was forced during
// scope analysis.
if (ForceHoleInitializationField::decode(bit_field_)) return true;
// If initialization was not forced, no need for initialization
// for stack allocated variables, since UpdateNeedsHoleCheck()
// in scopes.cc has proven that no VariableProxy refers to
// this variable in such a way that a runtime hole check
// would be generated.
if (IsStackAllocated()) return false;
// Otherwise, defer to the flag set when this Variable was constructed.
return initialization_flag() == kNeedsInitialization;
}
// Called during scope analysis when a VariableProxy is found to
// reference this Variable in such a way that a hole check will
// be required at runtime.
void ForceHoleInitialization() {
DCHECK_EQ(kNeedsInitialization, initialization_flag());
DCHECK(IsLexicalVariableMode(mode()));
bit_field_ = ForceHoleInitializationField::update(bit_field_, true);
}
bool throw_on_const_assignment(LanguageMode language_mode) const {
return kind() != SLOPPY_FUNCTION_NAME_VARIABLE || is_strict(language_mode);
}
bool is_function() const { return kind() == FUNCTION_VARIABLE; }
bool is_this() const { return kind() == THIS_VARIABLE; }
bool is_sloppy_function_name() const {
return kind() == SLOPPY_FUNCTION_NAME_VARIABLE;
}
Variable* local_if_not_shadowed() const {
DCHECK(mode() == DYNAMIC_LOCAL && local_if_not_shadowed_ != NULL);
return local_if_not_shadowed_;
}
void set_local_if_not_shadowed(Variable* local) {
local_if_not_shadowed_ = local;
}
VariableLocation location() const {
return LocationField::decode(bit_field_);
}
VariableKind kind() const { return VariableKindField::decode(bit_field_); }
int index() const { return index_; }
bool IsReceiver() const {
DCHECK(IsParameter());
return index_ == -1;
}
bool IsExport() const {
DCHECK_EQ(location(), VariableLocation::MODULE);
DCHECK_NE(index(), 0);
return index() > 0;
}
void AllocateTo(VariableLocation location, int index) {
DCHECK(IsUnallocated() ||
(this->location() == location && this->index() == index));
DCHECK_IMPLIES(location == VariableLocation::MODULE, index != 0);
bit_field_ = LocationField::update(bit_field_, location);
DCHECK_EQ(location, this->location());
index_ = index;
}
static InitializationFlag DefaultInitializationFlag(VariableMode mode) {
DCHECK(IsDeclaredVariableMode(mode));
return mode == VAR ? kCreatedInitialized : kNeedsInitialization;
}
typedef ThreadedList<Variable> List;
private:
Scope* scope_;
const AstRawString* name_;
// If this field is set, this variable references the stored locally bound
// variable, but it might be shadowed by variable bindings introduced by
// sloppy 'eval' calls between the reference scope (inclusive) and the
// binding scope (exclusive).
Variable* local_if_not_shadowed_;
Variable* next_;
int index_;
int initializer_position_;
uint16_t bit_field_;
class VariableModeField : public BitField16<VariableMode, 0, 3> {};
class VariableKindField
: public BitField16<VariableKind, VariableModeField::kNext, 3> {};
class LocationField
: public BitField16<VariableLocation, VariableKindField::kNext, 3> {};
class ForceContextAllocationField
: public BitField16<bool, LocationField::kNext, 1> {};
class IsUsedField
: public BitField16<bool, ForceContextAllocationField::kNext, 1> {};
class InitializationFlagField
: public BitField16<InitializationFlag, IsUsedField::kNext, 1> {};
class ForceHoleInitializationField
: public BitField16<bool, InitializationFlagField::kNext, 1> {};
class MaybeAssignedFlagField
: public BitField16<MaybeAssignedFlag,
ForceHoleInitializationField::kNext, 1> {};
Variable** next() { return &next_; }
friend List;
};
} // namespace internal
} // namespace v8
#endif // V8_AST_VARIABLES_H_
|
