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: FieldIndex()22 FieldIndex() : bit_field_(0) {} 23 24 static FieldIndex ForPropertyIndex(Map* map, 25 int index, 26 bool is_double = false); 27 static FieldIndex ForInObjectOffset(int offset, Map* map = NULL); 28 static FieldIndex ForDescriptor(Map* map, int descriptor_index); 29 static FieldIndex ForLoadByFieldIndex(Map* map, int index); 30 static FieldIndex FromFieldAccessStubKey(int key); 31 32 int GetLoadByFieldIndex() const; 33 is_inobject()34 bool is_inobject() const { 35 return IsInObjectBits::decode(bit_field_); 36 } 37 is_hidden_field()38 bool is_hidden_field() const { return IsHiddenField::decode(bit_field_); } 39 is_double()40 bool is_double() const { 41 return IsDoubleBits::decode(bit_field_); 42 } 43 offset()44 int offset() const { 45 return index() * kPointerSize; 46 } 47 48 // Zero-indexed from beginning of the object. index()49 int index() const { 50 return IndexBits::decode(bit_field_); 51 } 52 outobject_array_index()53 int outobject_array_index() const { 54 DCHECK(!is_inobject()); 55 return index() - first_inobject_property_offset() / kPointerSize; 56 } 57 58 // Zero-based from the first inobject property. Overflows to out-of-object 59 // properties. property_index()60 int property_index() const { 61 DCHECK(!is_hidden_field()); 62 int result = index() - first_inobject_property_offset() / kPointerSize; 63 if (!is_inobject()) { 64 result += InObjectPropertyBits::decode(bit_field_); 65 } 66 return result; 67 } 68 GetFieldAccessStubKey()69 int GetFieldAccessStubKey() const { 70 return bit_field_ & 71 (IsInObjectBits::kMask | IsDoubleBits::kMask | IndexBits::kMask); 72 } 73 74 bool operator==(FieldIndex const& other) const { 75 return bit_field_ == other.bit_field_; 76 } 77 bool operator!=(FieldIndex const& other) const { return !(*this == other); } 78 79 private: 80 FieldIndex(bool is_inobject, int local_index, bool is_double, 81 int inobject_properties, int first_inobject_property_offset, 82 bool is_hidden = false) { 83 DCHECK((first_inobject_property_offset & (kPointerSize - 1)) == 0); 84 bit_field_ = IsInObjectBits::encode(is_inobject) | 85 IsDoubleBits::encode(is_double) | 86 FirstInobjectPropertyOffsetBits::encode(first_inobject_property_offset) | 87 IsHiddenField::encode(is_hidden) | 88 IndexBits::encode(local_index) | 89 InObjectPropertyBits::encode(inobject_properties); 90 } 91 FieldIndex(int bit_field)92 explicit FieldIndex(int bit_field) : bit_field_(bit_field) {} 93 first_inobject_property_offset()94 int first_inobject_property_offset() const { 95 DCHECK(!is_hidden_field()); 96 return FirstInobjectPropertyOffsetBits::decode(bit_field_); 97 } 98 99 static const int kIndexBitsSize = kDescriptorIndexBitCount + 1; 100 101 // Index from beginning of object. 102 class IndexBits: public BitField<int, 0, kIndexBitsSize> {}; 103 class IsInObjectBits: public BitField<bool, IndexBits::kNext, 1> {}; 104 class IsDoubleBits: public BitField<bool, IsInObjectBits::kNext, 1> {}; 105 // Number of inobject properties. 106 class InObjectPropertyBits 107 : public BitField<int, IsDoubleBits::kNext, kDescriptorIndexBitCount> {}; 108 // Offset of first inobject property from beginning of object. 109 class FirstInobjectPropertyOffsetBits 110 : public BitField<int, InObjectPropertyBits::kNext, 7> {}; 111 class IsHiddenField 112 : public BitField<bool, FirstInobjectPropertyOffsetBits::kNext, 1> {}; 113 STATIC_ASSERT(IsHiddenField::kNext <= 32); 114 115 int bit_field_; 116 }; 117 118 } // namespace internal 119 } // namespace v8 120 121 #endif 122