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1 : // Copyright 2011 the V8 project authors. All rights reserved.
2 : // Use of this source code is governed by a BSD-style license that can be
3 : // found in the LICENSE file.
4 :
5 : #ifndef V8_AST_VARIABLES_H_
6 : #define V8_AST_VARIABLES_H_
7 :
8 : #include "src/ast/ast-value-factory.h"
9 : #include "src/globals.h"
10 : #include "src/zone/zone.h"
11 :
12 : namespace v8 {
13 : namespace internal {
14 :
15 : // The AST refers to variables via VariableProxies - placeholders for the actual
16 : // variables. Variables themselves are never directly referred to from the AST,
17 : // they are maintained by scopes, and referred to from VariableProxies and Slots
18 : // after binding and variable allocation.
19 : class Variable final : public ZoneObject {
20 : public:
21 : Variable(Scope* scope, const AstRawString* name, VariableMode mode,
22 : VariableKind kind, InitializationFlag initialization_flag,
23 : MaybeAssignedFlag maybe_assigned_flag = kNotAssigned)
24 : : scope_(scope),
25 : name_(name),
26 : local_if_not_shadowed_(nullptr),
27 : next_(nullptr),
28 : index_(-1),
29 : initializer_position_(kNoSourcePosition),
30 : bit_field_(MaybeAssignedFlagField::encode(maybe_assigned_flag) |
31 : InitializationFlagField::encode(initialization_flag) |
32 : VariableModeField::encode(mode) |
33 : IsUsedField::encode(false) |
34 : ForceContextAllocationField::encode(false) |
35 : ForceHoleInitializationField::encode(false) |
36 : LocationField::encode(VariableLocation::UNALLOCATED) |
37 174439527 : VariableKindField::encode(kind)) {
38 : // Var declared variables never need initialization.
39 : DCHECK(!(mode == VariableMode::kVar &&
40 : initialization_flag == kNeedsInitialization));
41 : }
42 :
43 : explicit Variable(Variable* other);
44 :
45 : // The source code for an eval() call may refer to a variable that is
46 : // in an outer scope about which we don't know anything (it may not
47 : // be the script scope). scope() is nullptr in that case. Currently the
48 : // scope is only used to follow the context chain length.
49 : Scope* scope() const { return scope_; }
50 :
51 : // This is for adjusting the scope of temporaries used when desugaring
52 : // parameter initializers.
53 12 : void set_scope(Scope* scope) { scope_ = scope; }
54 :
55 12672266 : Handle<String> name() const { return name_->string(); }
56 1120 : const AstRawString* raw_name() const { return name_; }
57 : VariableMode mode() const { return VariableModeField::decode(bit_field_); }
58 : bool has_forced_context_allocation() const {
59 : return ForceContextAllocationField::decode(bit_field_);
60 : }
61 : void ForceContextAllocation() {
62 : DCHECK(IsUnallocated() || IsContextSlot() ||
63 : location() == VariableLocation::MODULE);
64 13337389 : bit_field_ = ForceContextAllocationField::update(bit_field_, true);
65 : }
66 : bool is_used() { return IsUsedField::decode(bit_field_); }
67 138050456 : void set_is_used() { bit_field_ = IsUsedField::update(bit_field_, true); }
68 : MaybeAssignedFlag maybe_assigned() const {
69 : return MaybeAssignedFlagField::decode(bit_field_);
70 : }
71 : void set_maybe_assigned() {
72 16663480 : bit_field_ = MaybeAssignedFlagField::update(bit_field_, kMaybeAssigned);
73 : }
74 :
75 : int initializer_position() { return initializer_position_; }
76 12509534 : void set_initializer_position(int pos) { initializer_position_ = pos; }
77 :
78 24064177 : bool IsUnallocated() const {
79 : return location() == VariableLocation::UNALLOCATED;
80 : }
81 : bool IsParameter() const { return location() == VariableLocation::PARAMETER; }
82 35 : bool IsStackLocal() const { return location() == VariableLocation::LOCAL; }
83 2984479 : bool IsStackAllocated() const { return IsParameter() || IsStackLocal(); }
84 212024 : bool IsContextSlot() const { return location() == VariableLocation::CONTEXT; }
85 : bool IsLookupSlot() const { return location() == VariableLocation::LOOKUP; }
86 : bool IsGlobalObjectProperty() const;
87 :
88 15733166 : bool is_dynamic() const { return IsDynamicVariableMode(mode()); }
89 :
90 : // Returns the InitializationFlag this Variable was created with.
91 : // Scope analysis may allow us to relax this initialization
92 : // requirement, which will be reflected in the return value of
93 : // binding_needs_init().
94 : InitializationFlag initialization_flag() const {
95 : return InitializationFlagField::decode(bit_field_);
96 : }
97 :
98 : // Whether this variable needs to be initialized with the hole at
99 : // declaration time. Only returns valid results after scope analysis.
100 3028486 : bool binding_needs_init() const {
101 : DCHECK_IMPLIES(initialization_flag() == kNeedsInitialization,
102 : IsLexicalVariableMode(mode()));
103 : DCHECK_IMPLIES(ForceHoleInitializationField::decode(bit_field_),
104 : initialization_flag() == kNeedsInitialization);
105 :
106 : // Always initialize if hole initialization was forced during
107 : // scope analysis.
108 6056972 : if (ForceHoleInitializationField::decode(bit_field_)) return true;
109 :
110 : // If initialization was not forced, no need for initialization
111 : // for stack allocated variables, since UpdateNeedsHoleCheck()
112 : // in scopes.cc has proven that no VariableProxy refers to
113 : // this variable in such a way that a runtime hole check
114 : // would be generated.
115 2984479 : if (IsStackAllocated()) return false;
116 :
117 : // Otherwise, defer to the flag set when this Variable was constructed.
118 1460272 : return initialization_flag() == kNeedsInitialization;
119 : }
120 :
121 : // Called during scope analysis when a VariableProxy is found to
122 : // reference this Variable in such a way that a hole check will
123 : // be required at runtime.
124 : void ForceHoleInitialization() {
125 : DCHECK_EQ(kNeedsInitialization, initialization_flag());
126 : DCHECK(IsLexicalVariableMode(mode()));
127 5469612 : bit_field_ = ForceHoleInitializationField::update(bit_field_, true);
128 : }
129 :
130 32943 : bool throw_on_const_assignment(LanguageMode language_mode) const {
131 32943 : return kind() != SLOPPY_FUNCTION_NAME_VARIABLE || is_strict(language_mode);
132 : }
133 :
134 32926920 : bool is_this() const { return kind() == THIS_VARIABLE; }
135 : bool is_sloppy_function_name() const {
136 : return kind() == SLOPPY_FUNCTION_NAME_VARIABLE;
137 : }
138 :
139 2396 : bool is_parameter() const { return kind() == PARAMETER_VARIABLE; }
140 :
141 : Variable* local_if_not_shadowed() const {
142 : DCHECK(mode() == VariableMode::kDynamicLocal &&
143 : local_if_not_shadowed_ != nullptr);
144 : return local_if_not_shadowed_;
145 : }
146 :
147 : void set_local_if_not_shadowed(Variable* local) {
148 4618 : local_if_not_shadowed_ = local;
149 : }
150 :
151 : VariableLocation location() const {
152 : return LocationField::decode(bit_field_);
153 : }
154 : VariableKind kind() const { return VariableKindField::decode(bit_field_); }
155 :
156 : int index() const { return index_; }
157 :
158 : bool IsReceiver() const {
159 : DCHECK(IsParameter());
160 :
161 : return index_ == -1;
162 : }
163 :
164 19733 : bool IsExport() const {
165 : DCHECK_EQ(location(), VariableLocation::MODULE);
166 : DCHECK_NE(index(), 0);
167 : return index() > 0;
168 : }
169 :
170 : void AllocateTo(VariableLocation location, int index) {
171 : DCHECK(IsUnallocated() ||
172 : (this->location() == location && this->index() == index));
173 : DCHECK_IMPLIES(location == VariableLocation::MODULE, index != 0);
174 23440983 : bit_field_ = LocationField::update(bit_field_, location);
175 : DCHECK_EQ(location, this->location());
176 12970455 : index_ = index;
177 : }
178 :
179 : static InitializationFlag DefaultInitializationFlag(VariableMode mode) {
180 : DCHECK(IsDeclaredVariableMode(mode));
181 : return mode == VariableMode::kVar ? kCreatedInitialized
182 9372144 : : kNeedsInitialization;
183 : }
184 :
185 : typedef base::ThreadedList<Variable> List;
186 :
187 : private:
188 : Scope* scope_;
189 : const AstRawString* name_;
190 :
191 : // If this field is set, this variable references the stored locally bound
192 : // variable, but it might be shadowed by variable bindings introduced by
193 : // sloppy 'eval' calls between the reference scope (inclusive) and the
194 : // binding scope (exclusive).
195 : Variable* local_if_not_shadowed_;
196 : Variable* next_;
197 : int index_;
198 : int initializer_position_;
199 : uint16_t bit_field_;
200 :
201 : class VariableModeField : public BitField16<VariableMode, 0, 3> {};
202 : class VariableKindField
203 : : public BitField16<VariableKind, VariableModeField::kNext, 2> {};
204 : class LocationField
205 : : public BitField16<VariableLocation, VariableKindField::kNext, 3> {};
206 : class ForceContextAllocationField
207 : : public BitField16<bool, LocationField::kNext, 1> {};
208 : class IsUsedField
209 : : public BitField16<bool, ForceContextAllocationField::kNext, 1> {};
210 : class InitializationFlagField
211 : : public BitField16<InitializationFlag, IsUsedField::kNext, 1> {};
212 : class ForceHoleInitializationField
213 : : public BitField16<bool, InitializationFlagField::kNext, 1> {};
214 : class MaybeAssignedFlagField
215 : : public BitField16<MaybeAssignedFlag,
216 : ForceHoleInitializationField::kNext, 1> {};
217 : Variable** next() { return &next_; }
218 : friend List;
219 : friend base::ThreadedListTraits<Variable>;
220 : };
221 : } // namespace internal
222 : } // namespace v8
223 :
224 : #endif // V8_AST_VARIABLES_H_
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