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/utils.h"
9#include "src/property-details.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 V8_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 ForLookupResult(const LookupResult* result);
27  static FieldIndex ForDescriptor(Map* map, int descriptor_index);
28  static FieldIndex ForLoadByFieldIndex(Map* map, int index);
29  static FieldIndex ForKeyedLookupCacheIndex(Map* map, int index);
30
31  bool is_inobject() const {
32    return IsInObjectBits::decode(bit_field_);
33  }
34
35  bool is_double() const {
36    return IsDoubleBits::decode(bit_field_);
37  }
38
39  int offset() const {
40    return index() * kPointerSize;
41  }
42
43  int index() const {
44    return IndexBits::decode(bit_field_);
45  }
46
47  int outobject_array_index() const {
48    ASSERT(!is_inobject());
49    return index() - first_inobject_property_offset() / kPointerSize;
50  }
51
52  int property_index() const {
53    ASSERT(!IsHiddenField::decode(bit_field_));
54    int result = index() - first_inobject_property_offset() / kPointerSize;
55    if (!is_inobject()) {
56      result += InObjectPropertyBits::decode(bit_field_);
57    }
58    return result;
59  }
60
61  int GetLoadByFieldIndex() const {
62    // For efficiency, the LoadByFieldIndex instruction takes an index that is
63    // optimized for quick access. If the property is inline, the index is
64    // positive. If it's out-of-line, the encoded index is -raw_index - 1 to
65    // disambiguate the zero out-of-line index from the zero inobject case.
66    // The index itself is shifted up by one bit, the lower-most bit
67    // signifying if the field is a mutable double box (1) or not (0).
68    int result = index() - first_inobject_property_offset() / kPointerSize;
69    if (!is_inobject()) {
70      result = -result - 1;
71    }
72    result <<= 1;
73    return is_double() ? (result | 1) : result;
74  }
75
76  int GetKeyedLookupCacheIndex() const;
77
78  int GetLoadFieldStubKey() const {
79    return bit_field_ &
80        (IsInObjectBits::kMask | IsDoubleBits::kMask | IndexBits::kMask);
81  }
82
83 private:
84  FieldIndex(bool is_inobject, int local_index, bool is_double,
85             int inobject_properties, int first_inobject_property_offset,
86             bool is_hidden = false) {
87    ASSERT((first_inobject_property_offset & (kPointerSize - 1)) == 0);
88    bit_field_ = IsInObjectBits::encode(is_inobject) |
89      IsDoubleBits::encode(is_double) |
90      FirstInobjectPropertyOffsetBits::encode(first_inobject_property_offset) |
91      IsHiddenField::encode(is_hidden) |
92      IndexBits::encode(local_index) |
93      InObjectPropertyBits::encode(inobject_properties);
94  }
95
96  int first_inobject_property_offset() const {
97    ASSERT(!IsHiddenField::decode(bit_field_));
98    return FirstInobjectPropertyOffsetBits::decode(bit_field_);
99  }
100
101  static const int kIndexBitsSize = kDescriptorIndexBitCount + 1;
102
103  class IndexBits: public BitField<int, 0, kIndexBitsSize> {};
104  class IsInObjectBits: public BitField<bool, IndexBits::kNext, 1> {};
105  class IsDoubleBits: public BitField<bool, IsInObjectBits::kNext, 1> {};
106  class InObjectPropertyBits: public BitField<int, IsDoubleBits::kNext,
107                                              kDescriptorIndexBitCount> {};
108  class FirstInobjectPropertyOffsetBits:
109      public BitField<int, InObjectPropertyBits::kNext, 7> {};
110  class IsHiddenField:
111      public BitField<bool, FirstInobjectPropertyOffsetBits::kNext, 1> {};
112  STATIC_ASSERT(IsHiddenField::kNext <= 32);
113
114  int bit_field_;
115};
116
117} }  // namespace v8::internal
118
119#endif
120