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// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_OBJECTS_FIELD_INDEX_H_
#define V8_OBJECTS_FIELD_INDEX_H_
#include "src/objects/property-details.h"
#include "src/utils/utils.h"
namespace v8 {
namespace internal {
class Map;
// Wrapper class to hold a field index, usually but not necessarily generated
// from a property index. When available, the wrapper class captures additional
// information to allow the field index to be translated back into the property
// index it was originally generated from.
class FieldIndex final {
public:
enum Encoding { kTagged, kDouble, kWord32 };
FieldIndex() : bit_field_(0) {}
static inline FieldIndex ForPropertyIndex(
Map map, int index,
Representation representation = Representation::Tagged());
static inline FieldIndex ForInObjectOffset(int offset, Encoding encoding);
static inline FieldIndex ForDescriptor(Map map, int descriptor_index);
static inline FieldIndex ForDescriptor(Isolate* isolate, Map map,
int descriptor_index);
inline int GetLoadByFieldIndex() const;
bool is_inobject() const { return IsInObjectBits::decode(bit_field_); }
bool is_double() const { return EncodingBits::decode(bit_field_) == kDouble; }
int offset() const { return OffsetBits::decode(bit_field_); }
// Zero-indexed from beginning of the object.
int index() const {
DCHECK(IsAligned(offset(), kTaggedSize));
return offset() / kTaggedSize;
}
int outobject_array_index() const {
DCHECK(!is_inobject());
return index() - first_inobject_property_offset() / kTaggedSize;
}
// Zero-based from the first inobject property. Overflows to out-of-object
// properties.
int property_index() const {
int result = index() - first_inobject_property_offset() / kTaggedSize;
if (!is_inobject()) {
result += InObjectPropertyBits::decode(bit_field_);
}
return result;
}
int GetFieldAccessStubKey() const {
return bit_field_ &
(IsInObjectBits::kMask | EncodingBits::kMask | OffsetBits::kMask);
}
bool operator==(FieldIndex const& other) const {
return bit_field_ == other.bit_field_;
}
bool operator!=(FieldIndex const& other) const { return !(*this == other); }
private:
FieldIndex(bool is_inobject, int offset, Encoding encoding,
int inobject_properties, int first_inobject_property_offset) {
DCHECK(IsAligned(first_inobject_property_offset, kTaggedSize));
bit_field_ = IsInObjectBits::encode(is_inobject) |
EncodingBits::encode(encoding) |
FirstInobjectPropertyOffsetBits::encode(
first_inobject_property_offset) |
OffsetBits::encode(offset) |
InObjectPropertyBits::encode(inobject_properties);
}
static Encoding FieldEncoding(Representation representation) {
switch (representation.kind()) {
case Representation::kNone:
case Representation::kSmi:
case Representation::kHeapObject:
case Representation::kTagged:
return kTagged;
case Representation::kDouble:
return kDouble;
default:
break;
}
PrintF("%s\n", representation.Mnemonic());
UNREACHABLE();
return kTagged;
}
int first_inobject_property_offset() const {
return FirstInobjectPropertyOffsetBits::decode(bit_field_);
}
static const int kOffsetBitsSize =
(kDescriptorIndexBitCount + 1 + kTaggedSizeLog2);
// Index from beginning of object.
using OffsetBits = BitField64<int, 0, kOffsetBitsSize>;
using IsInObjectBits = OffsetBits::Next<bool, 1>;
using EncodingBits = IsInObjectBits::Next<Encoding, 2>;
// Number of inobject properties.
using InObjectPropertyBits =
EncodingBits::Next<int, kDescriptorIndexBitCount>;
// Offset of first inobject property from beginning of object.
using FirstInobjectPropertyOffsetBits =
InObjectPropertyBits::Next<int, kFirstInobjectPropertyOffsetBitCount>;
STATIC_ASSERT(FirstInobjectPropertyOffsetBits::kLastUsedBit < 64);
uint64_t bit_field_;
};
} // namespace internal
} // namespace v8
#endif // V8_OBJECTS_FIELD_INDEX_H_