1// Copyright 2016 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_LOOKUP_CACHE_H_
6#define V8_LOOKUP_CACHE_H_
7
8#include "src/objects.h"
9
10namespace v8 {
11namespace internal {
12
13// Cache for mapping (map, property name) into descriptor index.
14// The cache contains both positive and negative results.
15// Descriptor index equals kNotFound means the property is absent.
16// Cleared at startup and prior to any gc.
17class DescriptorLookupCache {
18 public:
19  // Lookup descriptor index for (map, name).
20  // If absent, kAbsent is returned.
21  inline int Lookup(Map* source, Name* name);
22
23  // Update an element in the cache.
24  inline void Update(Map* source, Name* name, int result);
25
26  // Clear the cache.
27  void Clear();
28
29  static const int kAbsent = -2;
30
31 private:
32  DescriptorLookupCache() {
33    for (int i = 0; i < kLength; ++i) {
34      keys_[i].source = NULL;
35      keys_[i].name = NULL;
36      results_[i] = kAbsent;
37    }
38  }
39
40  static inline int Hash(Object* source, Name* name);
41
42  static const int kLength = 64;
43  struct Key {
44    Map* source;
45    Name* name;
46  };
47
48  Key keys_[kLength];
49  int results_[kLength];
50
51  friend class Isolate;
52  DISALLOW_COPY_AND_ASSIGN(DescriptorLookupCache);
53};
54
55}  // namespace internal
56}  // namespace v8
57
58#endif  // V8_LOOKUP_CACHE_H_
59