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// Copyright 2016 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_CONTEXT_SLOT_CACHE_H_
#define V8_AST_CONTEXT_SLOT_CACHE_H_
#include "src/allocation.h"
#include "src/ast/modules.h"
namespace v8 {
namespace internal {
// Cache for mapping (data, property name) into context slot index.
// The cache contains both positive and negative results.
// Slot index equals -1 means the property is absent.
// Cleared at startup and prior to mark sweep collection.
class ContextSlotCache {
public:
// Lookup context slot index for (data, name).
// If absent, kNotFound is returned.
int Lookup(Object* data, String* name, VariableMode* mode,
InitializationFlag* init_flag,
MaybeAssignedFlag* maybe_assigned_flag);
// Update an element in the cache.
void Update(Handle<Object> data, Handle<String> name, VariableMode mode,
InitializationFlag init_flag,
MaybeAssignedFlag maybe_assigned_flag, int slot_index);
// Clear the cache.
void Clear();
static const int kNotFound = -2;
private:
ContextSlotCache() {
for (int i = 0; i < kLength; ++i) {
keys_[i].data = NULL;
keys_[i].name = NULL;
values_[i] = kNotFound;
}
}
inline static int Hash(Object* data, String* name);
#ifdef DEBUG
void ValidateEntry(Handle<Object> data, Handle<String> name,
VariableMode mode, InitializationFlag init_flag,
MaybeAssignedFlag maybe_assigned_flag, int slot_index);
#endif
static const int kLength = 256;
struct Key {
Object* data;
String* name;
};
struct Value {
Value(VariableMode mode, InitializationFlag init_flag,
MaybeAssignedFlag maybe_assigned_flag, int index) {
DCHECK(ModeField::is_valid(mode));
DCHECK(InitField::is_valid(init_flag));
DCHECK(MaybeAssignedField::is_valid(maybe_assigned_flag));
DCHECK(IndexField::is_valid(index));
value_ = ModeField::encode(mode) | IndexField::encode(index) |
InitField::encode(init_flag) |
MaybeAssignedField::encode(maybe_assigned_flag);
DCHECK(mode == this->mode());
DCHECK(init_flag == this->initialization_flag());
DCHECK(maybe_assigned_flag == this->maybe_assigned_flag());
DCHECK(index == this->index());
}
explicit inline Value(uint32_t value) : value_(value) {}
uint32_t raw() { return value_; }
VariableMode mode() { return ModeField::decode(value_); }
InitializationFlag initialization_flag() {
return InitField::decode(value_);
}
MaybeAssignedFlag maybe_assigned_flag() {
return MaybeAssignedField::decode(value_);
}
int index() { return IndexField::decode(value_); }
// Bit fields in value_ (type, shift, size). Must be public so the
// constants can be embedded in generated code.
class ModeField : public BitField<VariableMode, 0, 4> {};
class InitField : public BitField<InitializationFlag, 4, 1> {};
class MaybeAssignedField : public BitField<MaybeAssignedFlag, 5, 1> {};
class IndexField : public BitField<int, 6, 32 - 6> {};
private:
uint32_t value_;
};
Key keys_[kLength];
uint32_t values_[kLength];
friend class Isolate;
DISALLOW_COPY_AND_ASSIGN(ContextSlotCache);
};
} // namespace internal
} // namespace v8
#endif // V8_AST_CONTEXT_SLOT_CACHE_H_
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