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// 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_VARIABLES_H_
#define V8_VARIABLES_H_
#include "src/ast-value-factory.h"
#include "src/interface.h"
#include "src/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: public ZoneObject {
enum Kind {
enum Location {
// Before and during variable allocation, a variable whose location is
// not yet determined. After allocation, a variable looked up as a
// property on the global object (and possibly absent). name() is the
// variable name, index() is invalid.
// A slot in the parameter section on the stack. index() is the
// parameter index, counting left-to-right. The receiver is index -1;
// the first parameter is index 0.
// A slot in the local section on the stack. index() is the variable
// index in the stack frame, starting at 0.
// An indexed slot in a heap context. index() is the variable index in
// the context object on the heap, starting at 0. scope() is the
// corresponding scope.
// A named slot in a heap context. name() is the variable name in the
// context object on the heap, with lookup starting at the current
// context. index() is invalid.
Variable(Scope* scope, const AstRawString* name, VariableMode mode,
bool is_valid_ref, Kind kind, InitializationFlag initialization_flag,
MaybeAssignedFlag maybe_assigned_flag = kNotAssigned,
Interface* interface = Interface::NewValue());
// Printing support
static const char* Mode2String(VariableMode mode);
bool IsValidReference() { return is_valid_ref_; }
// 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_; }
Handle<String> name() const { return name_->string(); }
const AstRawString* raw_name() const { return name_; }
VariableMode mode() const { return mode_; }
bool has_forced_context_allocation() const {
return force_context_allocation_;
void ForceContextAllocation() {
force_context_allocation_ = true;
bool is_used() { return is_used_; }
void set_is_used() { is_used_ = true; }
MaybeAssignedFlag maybe_assigned() const { return maybe_assigned_; }
void set_maybe_assigned() { maybe_assigned_ = kMaybeAssigned; }
int initializer_position() { return initializer_position_; }
void set_initializer_position(int pos) { initializer_position_ = pos; }
bool IsVariable(Handle<String> n) const {
return !is_this() && name().is_identical_to(n);
bool IsUnallocated() const { return location_ == UNALLOCATED; }
bool IsParameter() const { return location_ == PARAMETER; }
bool IsStackLocal() const { return location_ == LOCAL; }
bool IsStackAllocated() const { return IsParameter() || IsStackLocal(); }
bool IsContextSlot() const { return location_ == CONTEXT; }
bool IsLookupSlot() const { return location_ == LOOKUP; }
bool IsGlobalObjectProperty() const;
bool is_dynamic() const { return IsDynamicVariableMode(mode_); }
bool is_const_mode() const { return IsImmutableVariableMode(mode_); }
bool binding_needs_init() const {
return initialization_flag_ == kNeedsInitialization;
bool is_this() const { return kind_ == THIS; }
bool is_arguments() const { return kind_ == ARGUMENTS; }
// True if the variable is named eval and not known to be shadowed.
bool is_possibly_eval(Isolate* isolate) const {
return IsVariable(isolate->factory()->eval_string());
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;
Location location() const { return location_; }
int index() const { return index_; }
InitializationFlag initialization_flag() const {
return initialization_flag_;
Interface* interface() const { return interface_; }
void AllocateTo(Location location, int index) {
location_ = location;
index_ = index;
static int CompareIndex(Variable* const* v, Variable* const* w);
Scope* scope_;
const AstRawString* name_;
VariableMode mode_;
Kind kind_;
Location location_;
int index_;
int initializer_position_;
// 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_;
// Valid as a reference? (const and this are not valid, for example)
bool is_valid_ref_;
// Usage info.
bool force_context_allocation_; // set by variable resolver
bool is_used_;
InitializationFlag initialization_flag_;
MaybeAssignedFlag maybe_assigned_;
// Module type info.
Interface* interface_;
} } // namespace v8::internal
#endif // V8_VARIABLES_H_