1// Copyright 2011 the V8 project authors. All rights reserved.
2// Redistribution and use in source and binary forms, with or without
3// modification, are permitted provided that the following conditions are
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15//
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27
28#ifndef V8_VARIABLES_H_
29#define V8_VARIABLES_H_
30
31#include "zone.h"
32#include "interface.h"
33
34namespace v8 {
35namespace internal {
36
37// The AST refers to variables via VariableProxies - placeholders for the actual
38// variables. Variables themselves are never directly referred to from the AST,
39// they are maintained by scopes, and referred to from VariableProxies and Slots
40// after binding and variable allocation.
41
42class Variable: public ZoneObject {
43 public:
44  enum Kind {
45    NORMAL,
46    THIS,
47    ARGUMENTS
48  };
49
50  enum Location {
51    // Before and during variable allocation, a variable whose location is
52    // not yet determined.  After allocation, a variable looked up as a
53    // property on the global object (and possibly absent).  name() is the
54    // variable name, index() is invalid.
55    UNALLOCATED,
56
57    // A slot in the parameter section on the stack.  index() is the
58    // parameter index, counting left-to-right.  The reciever is index -1;
59    // the first parameter is index 0.
60    PARAMETER,
61
62    // A slot in the local section on the stack.  index() is the variable
63    // index in the stack frame, starting at 0.
64    LOCAL,
65
66    // An indexed slot in a heap context.  index() is the variable index in
67    // the context object on the heap, starting at 0.  scope() is the
68    // corresponding scope.
69    CONTEXT,
70
71    // A named slot in a heap context.  name() is the variable name in the
72    // context object on the heap, with lookup starting at the current
73    // context.  index() is invalid.
74    LOOKUP
75  };
76
77  Variable(Scope* scope,
78           Handle<String> name,
79           VariableMode mode,
80           bool is_valid_lhs,
81           Kind kind,
82           InitializationFlag initialization_flag,
83           Interface* interface = Interface::NewValue());
84
85  // Printing support
86  static const char* Mode2String(VariableMode mode);
87
88  bool IsValidLeftHandSide() { return is_valid_LHS_; }
89
90  // The source code for an eval() call may refer to a variable that is
91  // in an outer scope about which we don't know anything (it may not
92  // be the global scope). scope() is NULL in that case. Currently the
93  // scope is only used to follow the context chain length.
94  Scope* scope() const { return scope_; }
95
96  Handle<String> name() const { return name_; }
97  VariableMode mode() const { return mode_; }
98  bool has_forced_context_allocation() const {
99    return force_context_allocation_;
100  }
101  void ForceContextAllocation() {
102    ASSERT(mode_ != TEMPORARY);
103    force_context_allocation_ = true;
104  }
105  bool is_used() { return is_used_; }
106  void set_is_used(bool flag) { is_used_ = flag; }
107
108  int initializer_position() { return initializer_position_; }
109  void set_initializer_position(int pos) { initializer_position_ = pos; }
110
111  bool IsVariable(Handle<String> n) const {
112    return !is_this() && name().is_identical_to(n);
113  }
114
115  bool IsUnallocated() const { return location_ == UNALLOCATED; }
116  bool IsParameter() const { return location_ == PARAMETER; }
117  bool IsStackLocal() const { return location_ == LOCAL; }
118  bool IsStackAllocated() const { return IsParameter() || IsStackLocal(); }
119  bool IsContextSlot() const { return location_ == CONTEXT; }
120  bool IsLookupSlot() const { return location_ == LOOKUP; }
121
122  bool is_dynamic() const {
123    return (mode_ == DYNAMIC ||
124            mode_ == DYNAMIC_GLOBAL ||
125            mode_ == DYNAMIC_LOCAL);
126  }
127  bool is_const_mode() const {
128    return (mode_ == CONST ||
129            mode_ == CONST_HARMONY);
130  }
131  bool binding_needs_init() const {
132    return initialization_flag_ == kNeedsInitialization;
133  }
134
135  bool is_global() const;
136  bool is_this() const { return kind_ == THIS; }
137  bool is_arguments() const { return kind_ == ARGUMENTS; }
138
139  // True if the variable is named eval and not known to be shadowed.
140  bool is_possibly_eval() const {
141    return IsVariable(FACTORY->eval_symbol());
142  }
143
144  Variable* local_if_not_shadowed() const {
145    ASSERT(mode_ == DYNAMIC_LOCAL && local_if_not_shadowed_ != NULL);
146    return local_if_not_shadowed_;
147  }
148
149  void set_local_if_not_shadowed(Variable* local) {
150    local_if_not_shadowed_ = local;
151  }
152
153  Location location() const { return location_; }
154  int index() const { return index_; }
155  InitializationFlag initialization_flag() const {
156    return initialization_flag_;
157  }
158  Interface* interface() const { return interface_; }
159
160  void AllocateTo(Location location, int index) {
161    location_ = location;
162    index_ = index;
163  }
164
165  static int CompareIndex(Variable* const* v, Variable* const* w);
166
167 private:
168  Scope* scope_;
169  Handle<String> name_;
170  VariableMode mode_;
171  Kind kind_;
172  Location location_;
173  int index_;
174  int initializer_position_;
175
176  // If this field is set, this variable references the stored locally bound
177  // variable, but it might be shadowed by variable bindings introduced by
178  // non-strict 'eval' calls between the reference scope (inclusive) and the
179  // binding scope (exclusive).
180  Variable* local_if_not_shadowed_;
181
182  // Valid as a LHS? (const and this are not valid LHS, for example)
183  bool is_valid_LHS_;
184
185  // Usage info.
186  bool force_context_allocation_;  // set by variable resolver
187  bool is_used_;
188  InitializationFlag initialization_flag_;
189
190  // Module type info.
191  Interface* interface_;
192};
193
194
195} }  // namespace v8::internal
196
197#endif  // V8_VARIABLES_H_
198