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