1// Copyright 2014 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_FIELD_INDEX_H_
6#define V8_FIELD_INDEX_H_
7
8#include "src/property-details.h"
9#include "src/utils.h"
10
11namespace v8 {
12namespace internal {
13
14class Map;
15
16// Wrapper class to hold a field index, usually but not necessarily generated
17// from a property index. When available, the wrapper class captures additional
18// information to allow the field index to be translated back into the property
19// index it was originally generated from.
20class FieldIndex FINAL {
21 public:
22  static FieldIndex ForPropertyIndex(Map* map,
23                                     int index,
24                                     bool is_double = false);
25  static FieldIndex ForInObjectOffset(int offset, Map* map = NULL);
26  static FieldIndex ForDescriptor(Map* map, int descriptor_index);
27  static FieldIndex ForLoadByFieldIndex(Map* map, int index);
28  static FieldIndex ForKeyedLookupCacheIndex(Map* map, int index);
29  static FieldIndex FromFieldAccessStubKey(int key);
30
31  int GetLoadByFieldIndex() const;
32
33  bool is_inobject() const {
34    return IsInObjectBits::decode(bit_field_);
35  }
36
37  bool is_double() const {
38    return IsDoubleBits::decode(bit_field_);
39  }
40
41  int offset() const {
42    return index() * kPointerSize;
43  }
44
45  // Zero-indexed from beginning of the object.
46  int index() const {
47    return IndexBits::decode(bit_field_);
48  }
49
50  int outobject_array_index() const {
51    DCHECK(!is_inobject());
52    return index() - first_inobject_property_offset() / kPointerSize;
53  }
54
55  // Zero-based from the first inobject property. Overflows to out-of-object
56  // properties.
57  int property_index() const {
58    DCHECK(!IsHiddenField::decode(bit_field_));
59    int result = index() - first_inobject_property_offset() / kPointerSize;
60    if (!is_inobject()) {
61      result += InObjectPropertyBits::decode(bit_field_);
62    }
63    return result;
64  }
65
66  int GetKeyedLookupCacheIndex() const;
67
68  int GetFieldAccessStubKey() const {
69    return bit_field_ &
70        (IsInObjectBits::kMask | IsDoubleBits::kMask | IndexBits::kMask);
71  }
72
73 private:
74  FieldIndex(bool is_inobject, int local_index, bool is_double,
75             int inobject_properties, int first_inobject_property_offset,
76             bool is_hidden = false) {
77    DCHECK((first_inobject_property_offset & (kPointerSize - 1)) == 0);
78    bit_field_ = IsInObjectBits::encode(is_inobject) |
79      IsDoubleBits::encode(is_double) |
80      FirstInobjectPropertyOffsetBits::encode(first_inobject_property_offset) |
81      IsHiddenField::encode(is_hidden) |
82      IndexBits::encode(local_index) |
83      InObjectPropertyBits::encode(inobject_properties);
84  }
85
86  explicit FieldIndex(int bit_field) : bit_field_(bit_field) {}
87
88  int first_inobject_property_offset() const {
89    DCHECK(!IsHiddenField::decode(bit_field_));
90    return FirstInobjectPropertyOffsetBits::decode(bit_field_);
91  }
92
93  static const int kIndexBitsSize = kDescriptorIndexBitCount + 1;
94
95  // Index from beginning of object.
96  class IndexBits: public BitField<int, 0, kIndexBitsSize> {};
97  class IsInObjectBits: public BitField<bool, IndexBits::kNext, 1> {};
98  class IsDoubleBits: public BitField<bool, IsInObjectBits::kNext, 1> {};
99  // Number of inobject properties.
100  class InObjectPropertyBits
101      : public BitField<int, IsDoubleBits::kNext, kDescriptorIndexBitCount> {};
102  // Offset of first inobject property from beginning of object.
103  class FirstInobjectPropertyOffsetBits
104      : public BitField<int, InObjectPropertyBits::kNext, 7> {};
105  class IsHiddenField
106      : public BitField<bool, FirstInobjectPropertyOffsetBits::kNext, 1> {};
107  STATIC_ASSERT(IsHiddenField::kNext <= 32);
108
109  int bit_field_;
110};
111
112} }  // namespace v8::internal
113
114#endif
115