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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_INL_H_
      6 #define V8_FIELD_INDEX_INL_H_
      7 
      8 #include "src/field-index.h"
      9 #include "src/objects-inl.h"
     10 #include "src/objects/descriptor-array.h"
     11 
     12 namespace v8 {
     13 namespace internal {
     14 
     15 inline FieldIndex FieldIndex::ForInObjectOffset(int offset, Encoding encoding,
     16                                                 const Map* map) {
     17   DCHECK(map == nullptr || offset < map->instance_size());
     18   DCHECK(encoding == kWord32 ? (offset % kInt32Size) == 0
     19                              : (offset % kPointerSize) == 0);
     20   return FieldIndex(true, offset, encoding, 0, 0);
     21 }
     22 
     23 inline FieldIndex FieldIndex::ForPropertyIndex(const Map* map,
     24                                                int property_index,
     25                                                Representation representation) {
     26   DCHECK(map->instance_type() >= FIRST_NONSTRING_TYPE);
     27   int inobject_properties = map->GetInObjectProperties();
     28   bool is_inobject = property_index < inobject_properties;
     29   int first_inobject_offset;
     30   int offset;
     31   if (is_inobject) {
     32     first_inobject_offset = map->GetInObjectPropertyOffset(0);
     33     offset = map->GetInObjectPropertyOffset(property_index);
     34   } else {
     35     first_inobject_offset = FixedArray::kHeaderSize;
     36     property_index -= inobject_properties;
     37     offset = FixedArray::kHeaderSize + property_index * kPointerSize;
     38   }
     39   Encoding encoding = FieldEncoding(representation);
     40   return FieldIndex(is_inobject, offset, encoding, inobject_properties,
     41                     first_inobject_offset);
     42 }
     43 
     44 // Returns the index format accepted by the HLoadFieldByIndex instruction.
     45 // (In-object: zero-based from (object start + JSObject::kHeaderSize),
     46 // out-of-object: zero-based from FixedArray::kHeaderSize.)
     47 inline int FieldIndex::GetLoadByFieldIndex() const {
     48   // For efficiency, the LoadByFieldIndex instruction takes an index that is
     49   // optimized for quick access. If the property is inline, the index is
     50   // positive. If it's out-of-line, the encoded index is -raw_index - 1 to
     51   // disambiguate the zero out-of-line index from the zero inobject case.
     52   // The index itself is shifted up by one bit, the lower-most bit
     53   // signifying if the field is a mutable double box (1) or not (0).
     54   int result = index();
     55   if (is_inobject()) {
     56     result -= JSObject::kHeaderSize / kPointerSize;
     57   } else {
     58     result -= FixedArray::kHeaderSize / kPointerSize;
     59     result = -result - 1;
     60   }
     61   result <<= 1;
     62   return is_double() ? (result | 1) : result;
     63 }
     64 
     65 inline FieldIndex FieldIndex::ForDescriptor(const Map* map,
     66                                             int descriptor_index) {
     67   PropertyDetails details =
     68       map->instance_descriptors()->GetDetails(descriptor_index);
     69   int field_index = details.field_index();
     70   return ForPropertyIndex(map, field_index, details.representation());
     71 }
     72 
     73 }  // namespace internal
     74 }  // namespace v8
     75 
     76 #endif  // V8_FIELD_INDEX_INL_H_
     77