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 11 namespace v8 { 12 namespace 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 19 class 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
