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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 
ForInObjectOffset(int offset,Encoding encoding,const Map * map)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 
ForPropertyIndex(const Map * map,int property_index,Representation representation)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.)
GetLoadByFieldIndex()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 
ForDescriptor(const Map * map,int descriptor_index)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