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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_AST_VARIABLES_H_
#define V8_AST_VARIABLES_H_
#include "src/ast/ast-value-factory.h"
#include "src/base/threaded-list.h"
#include "src/common/globals.h"
#include "src/zone/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 final : public ZoneObject {
public:
Variable(Scope* scope, const AstRawString* name, VariableMode mode,
VariableKind kind, InitializationFlag initialization_flag,
MaybeAssignedFlag maybe_assigned_flag = kNotAssigned)
: scope_(scope),
name_(name),
local_if_not_shadowed_(nullptr),
next_(nullptr),
index_(-1),
initializer_position_(kNoSourcePosition),
bit_field_(MaybeAssignedFlagField::encode(maybe_assigned_flag) |
InitializationFlagField::encode(initialization_flag) |
VariableModeField::encode(mode) |
IsUsedField::encode(false) |
ForceContextAllocationField::encode(false) |
ForceHoleInitializationField::encode(false) |
LocationField::encode(VariableLocation::UNALLOCATED) |
VariableKindField::encode(kind)) {
// Var declared variables never need initialization.
DCHECK(!(mode == VariableMode::kVar &&
initialization_flag == kNeedsInitialization));
}
explicit Variable(Variable* other);
// 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 nullptr in that case. Currently the
// scope is only used to follow the context chain length.
Scope* scope() const { return scope_; }
// This is for adjusting the scope of temporaries used when desugaring
// parameter initializers.
void set_scope(Scope* scope) { scope_ = scope; }
Handle<String> name() const { return name_->string(); }
const AstRawString* raw_name() const { return name_; }
VariableMode mode() const { return VariableModeField::decode(bit_field_); }
void set_mode(VariableMode mode) {
bit_field_ = VariableModeField::update(bit_field_, mode);
}
bool has_forced_context_allocation() const {
return ForceContextAllocationField::decode(bit_field_);
}
void ForceContextAllocation() {
DCHECK(IsUnallocated() || IsContextSlot() || IsLookupSlot() ||
location() == VariableLocation::MODULE);
bit_field_ = ForceContextAllocationField::update(bit_field_, true);
}
bool is_used() { return IsUsedField::decode(bit_field_); }
void set_is_used() { bit_field_ = IsUsedField::update(bit_field_, true); }
MaybeAssignedFlag maybe_assigned() const {
return MaybeAssignedFlagField::decode(bit_field_);
}
void SetMaybeAssigned() {
// If this variable is dynamically shadowing another variable, then that
// variable could also be assigned (in the non-shadowing case).
if (has_local_if_not_shadowed()) {
// Avoid repeatedly marking the same tree of variables by only recursing
// when this variable's maybe_assigned status actually changes.
if (!maybe_assigned()) {
local_if_not_shadowed()->SetMaybeAssigned();
}
DCHECK(local_if_not_shadowed()->maybe_assigned());
}
set_maybe_assigned();
}
bool requires_brand_check() const {
return IsPrivateMethodOrAccessorVariableMode(mode());
}
int initializer_position() { return initializer_position_; }
void set_initializer_position(int pos) { initializer_position_ = pos; }
bool IsUnallocated() const {
return location() == VariableLocation::UNALLOCATED;
}
bool IsParameter() const { return location() == VariableLocation::PARAMETER; }
bool IsStackLocal() const { return location() == VariableLocation::LOCAL; }
bool IsStackAllocated() const { return IsParameter() || IsStackLocal(); }
bool IsContextSlot() const { return location() == VariableLocation::CONTEXT; }
bool IsLookupSlot() const { return location() == VariableLocation::LOOKUP; }
bool IsGlobalObjectProperty() const;
bool is_dynamic() const { return IsDynamicVariableMode(mode()); }
// Returns the InitializationFlag this Variable was created with.
// Scope analysis may allow us to relax this initialization
// requirement, which will be reflected in the return value of
// binding_needs_init().
InitializationFlag initialization_flag() const {
return InitializationFlagField::decode(bit_field_);
}
// Whether this variable needs to be initialized with the hole at
// declaration time. Only returns valid results after scope analysis.
bool binding_needs_init() const {
DCHECK_IMPLIES(initialization_flag() == kNeedsInitialization,
IsLexicalVariableMode(mode()) ||
IsPrivateMethodOrAccessorVariableMode(mode()));
DCHECK_IMPLIES(ForceHoleInitializationField::decode(bit_field_),
initialization_flag() == kNeedsInitialization);
// Always initialize if hole initialization was forced during
// scope analysis.
if (ForceHoleInitializationField::decode(bit_field_)) return true;
// If initialization was not forced, no need for initialization
// for stack allocated variables, since UpdateNeedsHoleCheck()
// in scopes.cc has proven that no VariableProxy refers to
// this variable in such a way that a runtime hole check
// would be generated.
if (IsStackAllocated()) return false;
// Otherwise, defer to the flag set when this Variable was constructed.
return initialization_flag() == kNeedsInitialization;
}
// Called during scope analysis when a VariableProxy is found to
// reference this Variable in such a way that a hole check will
// be required at runtime.
void ForceHoleInitialization() {
DCHECK_EQ(kNeedsInitialization, initialization_flag());
DCHECK(IsLexicalVariableMode(mode()) ||
IsPrivateMethodOrAccessorVariableMode(mode()));
bit_field_ = ForceHoleInitializationField::update(bit_field_, true);
}
bool throw_on_const_assignment(LanguageMode language_mode) const {
return kind() != SLOPPY_FUNCTION_NAME_VARIABLE || is_strict(language_mode);
}
bool is_this() const { return kind() == THIS_VARIABLE; }
bool is_sloppy_function_name() const {
return kind() == SLOPPY_FUNCTION_NAME_VARIABLE;
}
bool is_parameter() const { return kind() == PARAMETER_VARIABLE; }
bool is_sloppy_block_function() {
return kind() == SLOPPY_BLOCK_FUNCTION_VARIABLE;
}
Variable* local_if_not_shadowed() const {
DCHECK((mode() == VariableMode::kDynamicLocal ||
mode() == VariableMode::kDynamic) &&
has_local_if_not_shadowed());
return local_if_not_shadowed_;
}
bool has_local_if_not_shadowed() const {
return local_if_not_shadowed_ != nullptr;
}
void set_local_if_not_shadowed(Variable* local) {
local_if_not_shadowed_ = local;
}
VariableLocation location() const {
return LocationField::decode(bit_field_);
}
VariableKind kind() const { return VariableKindField::decode(bit_field_); }
int index() const { return index_; }
bool IsReceiver() const {
DCHECK(IsParameter());
return index_ == -1;
}
bool IsExport() const {
DCHECK_EQ(location(), VariableLocation::MODULE);
DCHECK_NE(index(), 0);
return index() > 0;
}
void AllocateTo(VariableLocation location, int index) {
DCHECK(IsUnallocated() ||
(this->location() == location && this->index() == index));
DCHECK_IMPLIES(location == VariableLocation::MODULE, index != 0);
bit_field_ = LocationField::update(bit_field_, location);
DCHECK_EQ(location, this->location());
index_ = index;
}
void MakeParameterNonSimple() {
DCHECK(is_parameter());
bit_field_ = VariableModeField::update(bit_field_, VariableMode::kLet);
bit_field_ =
InitializationFlagField::update(bit_field_, kNeedsInitialization);
}
static InitializationFlag DefaultInitializationFlag(VariableMode mode) {
DCHECK(IsDeclaredVariableMode(mode));
return mode == VariableMode::kVar ? kCreatedInitialized
: kNeedsInitialization;
}
using List = base::ThreadedList<Variable>;
private:
Scope* scope_;
const AstRawString* name_;
// If this field is set, this variable references the stored locally bound
// variable, but it might be shadowed by variable bindings introduced by with
// blocks or sloppy 'eval' calls between the reference scope (inclusive) and
// the binding scope (exclusive).
Variable* local_if_not_shadowed_;
Variable* next_;
int index_;
int initializer_position_;
uint16_t bit_field_;
void set_maybe_assigned() {
bit_field_ = MaybeAssignedFlagField::update(bit_field_, kMaybeAssigned);
}
using VariableModeField = BitField16<VariableMode, 0, 4>;
using VariableKindField =
BitField16<VariableKind, VariableModeField::kNext, 3>;
using LocationField =
BitField16<VariableLocation, VariableKindField::kNext, 3>;
using ForceContextAllocationField = BitField16<bool, LocationField::kNext, 1>;
using IsUsedField = BitField16<bool, ForceContextAllocationField::kNext, 1>;
using InitializationFlagField =
BitField16<InitializationFlag, IsUsedField::kNext, 1>;
using ForceHoleInitializationField =
BitField16<bool, InitializationFlagField::kNext, 1>;
using MaybeAssignedFlagField =
BitField16<MaybeAssignedFlag, ForceHoleInitializationField::kNext, 1>;
Variable** next() { return &next_; }
friend List;
friend base::ThreadedListTraits<Variable>;
};
} // namespace internal
} // namespace v8
#endif // V8_AST_VARIABLES_H_