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_VARIABLES_H_
6#define V8_VARIABLES_H_
7
8#include "src/zone.h"
9#include "src/interface.h"
10
11namespace v8 {
12namespace internal {
13
14// The AST refers to variables via VariableProxies - placeholders for the actual
15// variables. Variables themselves are never directly referred to from the AST,
16// they are maintained by scopes, and referred to from VariableProxies and Slots
17// after binding and variable allocation.
18
19class Variable: public ZoneObject {
20 public:
21  enum Kind {
22    NORMAL,
23    THIS,
24    ARGUMENTS
25  };
26
27  enum Location {
28    // Before and during variable allocation, a variable whose location is
29    // not yet determined.  After allocation, a variable looked up as a
30    // property on the global object (and possibly absent).  name() is the
31    // variable name, index() is invalid.
32    UNALLOCATED,
33
34    // A slot in the parameter section on the stack.  index() is the
35    // parameter index, counting left-to-right.  The receiver is index -1;
36    // the first parameter is index 0.
37    PARAMETER,
38
39    // A slot in the local section on the stack.  index() is the variable
40    // index in the stack frame, starting at 0.
41    LOCAL,
42
43    // An indexed slot in a heap context.  index() is the variable index in
44    // the context object on the heap, starting at 0.  scope() is the
45    // corresponding scope.
46    CONTEXT,
47
48    // A named slot in a heap context.  name() is the variable name in the
49    // context object on the heap, with lookup starting at the current
50    // context.  index() is invalid.
51    LOOKUP
52  };
53
54  Variable(Scope* scope,
55           Handle<String> name,
56           VariableMode mode,
57           bool is_valid_ref,
58           Kind kind,
59           InitializationFlag initialization_flag,
60           Interface* interface = Interface::NewValue());
61
62  // Printing support
63  static const char* Mode2String(VariableMode mode);
64
65  bool IsValidReference() { return is_valid_ref_; }
66
67  // The source code for an eval() call may refer to a variable that is
68  // in an outer scope about which we don't know anything (it may not
69  // be the global scope). scope() is NULL in that case. Currently the
70  // scope is only used to follow the context chain length.
71  Scope* scope() const { return scope_; }
72
73  Handle<String> name() const { return name_; }
74  VariableMode mode() const { return mode_; }
75  bool has_forced_context_allocation() const {
76    return force_context_allocation_;
77  }
78  void ForceContextAllocation() {
79    ASSERT(mode_ != TEMPORARY);
80    force_context_allocation_ = true;
81  }
82  bool is_used() { return is_used_; }
83  void set_is_used(bool flag) { is_used_ = flag; }
84
85  int initializer_position() { return initializer_position_; }
86  void set_initializer_position(int pos) { initializer_position_ = pos; }
87
88  bool IsVariable(Handle<String> n) const {
89    return !is_this() && name().is_identical_to(n);
90  }
91
92  bool IsUnallocated() const { return location_ == UNALLOCATED; }
93  bool IsParameter() const { return location_ == PARAMETER; }
94  bool IsStackLocal() const { return location_ == LOCAL; }
95  bool IsStackAllocated() const { return IsParameter() || IsStackLocal(); }
96  bool IsContextSlot() const { return location_ == CONTEXT; }
97  bool IsLookupSlot() const { return location_ == LOOKUP; }
98  bool IsGlobalObjectProperty() const;
99
100  bool is_dynamic() const { return IsDynamicVariableMode(mode_); }
101  bool is_const_mode() const { return IsImmutableVariableMode(mode_); }
102  bool binding_needs_init() const {
103    return initialization_flag_ == kNeedsInitialization;
104  }
105
106  bool is_this() const { return kind_ == THIS; }
107  bool is_arguments() const { return kind_ == ARGUMENTS; }
108
109  // True if the variable is named eval and not known to be shadowed.
110  bool is_possibly_eval(Isolate* isolate) const {
111    return IsVariable(isolate->factory()->eval_string());
112  }
113
114  Variable* local_if_not_shadowed() const {
115    ASSERT(mode_ == DYNAMIC_LOCAL && local_if_not_shadowed_ != NULL);
116    return local_if_not_shadowed_;
117  }
118
119  void set_local_if_not_shadowed(Variable* local) {
120    local_if_not_shadowed_ = local;
121  }
122
123  Location location() const { return location_; }
124  int index() const { return index_; }
125  InitializationFlag initialization_flag() const {
126    return initialization_flag_;
127  }
128  Interface* interface() const { return interface_; }
129
130  void AllocateTo(Location location, int index) {
131    location_ = location;
132    index_ = index;
133  }
134
135  static int CompareIndex(Variable* const* v, Variable* const* w);
136
137 private:
138  Scope* scope_;
139  Handle<String> name_;
140  VariableMode mode_;
141  Kind kind_;
142  Location location_;
143  int index_;
144  int initializer_position_;
145
146  // If this field is set, this variable references the stored locally bound
147  // variable, but it might be shadowed by variable bindings introduced by
148  // sloppy 'eval' calls between the reference scope (inclusive) and the
149  // binding scope (exclusive).
150  Variable* local_if_not_shadowed_;
151
152  // Valid as a reference? (const and this are not valid, for example)
153  bool is_valid_ref_;
154
155  // Usage info.
156  bool force_context_allocation_;  // set by variable resolver
157  bool is_used_;
158  InitializationFlag initialization_flag_;
159
160  // Module type info.
161  Interface* interface_;
162};
163
164
165} }  // namespace v8::internal
166
167#endif  // V8_VARIABLES_H_
168