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      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 
     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