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 
11 namespace v8 {
12 namespace internal {
13 
14 class 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.
20 class 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 
is_inobject()33   bool is_inobject() const {
34     return IsInObjectBits::decode(bit_field_);
35   }
36 
is_double()37   bool is_double() const {
38     return IsDoubleBits::decode(bit_field_);
39   }
40 
offset()41   int offset() const {
42     return index() * kPointerSize;
43   }
44 
45   // Zero-indexed from beginning of the object.
index()46   int index() const {
47     return IndexBits::decode(bit_field_);
48   }
49 
outobject_array_index()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.
property_index()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 
GetFieldAccessStubKey()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 
FieldIndex(int bit_field)86   explicit FieldIndex(int bit_field) : bit_field_(bit_field) {}
87 
first_inobject_property_offset()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