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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_LOOKUP_CACHE_H_
#define V8_LOOKUP_CACHE_H_
#include "src/objects.h"
namespace v8 {
namespace internal {
// Cache for mapping (map, property name) into descriptor index.
// The cache contains both positive and negative results.
// Descriptor index equals kNotFound means the property is absent.
// Cleared at startup and prior to any gc.
class DescriptorLookupCache {
public:
// Lookup descriptor index for (map, name).
// If absent, kAbsent is returned.
inline int Lookup(Map* source, Name* name);
// Update an element in the cache.
inline void Update(Map* source, Name* name, int result);
// Clear the cache.
void Clear();
static const int kAbsent = -2;
private:
DescriptorLookupCache() {
for (int i = 0; i < kLength; ++i) {
keys_[i].source = NULL;
keys_[i].name = NULL;
results_[i] = kAbsent;
}
}
static inline int Hash(Object* source, Name* name);
static const int kLength = 64;
struct Key {
Map* source;
Name* name;
};
Key keys_[kLength];
int results_[kLength];
friend class Isolate;
DISALLOW_COPY_AND_ASSIGN(DescriptorLookupCache);
};
// Cache for mapping (map, property name) into field offset.
// Cleared at startup and prior to mark sweep collection.
class KeyedLookupCache {
public:
// Lookup field offset for (map, name). If absent, -1 is returned.
int Lookup(Handle<Map> map, Handle<Name> name);
// Update an element in the cache.
void Update(Handle<Map> map, Handle<Name> name, int field_offset);
// Clear the cache.
void Clear();
static const int kLength = 256;
static const int kCapacityMask = kLength - 1;
static const int kMapHashShift = 5;
static const int kHashMask = -4; // Zero the last two bits.
static const int kEntriesPerBucket = 4;
static const int kEntryLength = 2;
static const int kMapIndex = 0;
static const int kKeyIndex = 1;
static const int kNotFound = -1;
// kEntriesPerBucket should be a power of 2.
STATIC_ASSERT((kEntriesPerBucket & (kEntriesPerBucket - 1)) == 0);
STATIC_ASSERT(kEntriesPerBucket == -kHashMask);
private:
KeyedLookupCache() {
for (int i = 0; i < kLength; ++i) {
keys_[i].map = NULL;
keys_[i].name = NULL;
field_offsets_[i] = kNotFound;
}
}
static inline int Hash(Handle<Map> map, Handle<Name> name);
// Get the address of the keys and field_offsets arrays. Used in
// generated code to perform cache lookups.
Address keys_address() { return reinterpret_cast<Address>(&keys_); }
Address field_offsets_address() {
return reinterpret_cast<Address>(&field_offsets_);
}
struct Key {
Map* map;
Name* name;
};
Key keys_[kLength];
int field_offsets_[kLength];
friend class ExternalReference;
friend class Isolate;
DISALLOW_COPY_AND_ASSIGN(KeyedLookupCache);
};
} // namespace internal
} // namespace v8
#endif // V8_LOOKUP_CACHE_H_
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