// Copyright 2014 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_FIELD_INDEX_H_
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#define V8_FIELD_INDEX_H_
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#include "src/property-details.h"
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#include "src/utils.h"
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namespace v8 {
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namespace internal {
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class Map;
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// Wrapper class to hold a field index, usually but not necessarily generated
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// from a property index. When available, the wrapper class captures additional
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// information to allow the field index to be translated back into the property
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// index it was originally generated from.
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class FieldIndex final {
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public:
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enum Encoding { kTagged, kDouble, kWord32 };
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FieldIndex() : bit_field_(0) {}
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static FieldIndex ForPropertyIndex(
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const Map* map, int index,
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Representation representation = Representation::Tagged());
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static FieldIndex ForInObjectOffset(int offset, Encoding encoding,
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const Map* map = nullptr);
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static FieldIndex ForDescriptor(const Map* map, int descriptor_index);
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int GetLoadByFieldIndex() const;
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bool is_inobject() const {
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return IsInObjectBits::decode(bit_field_);
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}
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bool is_hidden_field() const { return IsHiddenField::decode(bit_field_); }
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bool is_double() const { return EncodingBits::decode(bit_field_) == kDouble; }
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int offset() const { return OffsetBits::decode(bit_field_); }
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// Zero-indexed from beginning of the object.
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int index() const {
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DCHECK_EQ(0, offset() % kPointerSize);
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return offset() / kPointerSize;
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}
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int outobject_array_index() const {
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DCHECK(!is_inobject());
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return index() - first_inobject_property_offset() / kPointerSize;
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}
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// Zero-based from the first inobject property. Overflows to out-of-object
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// properties.
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int property_index() const {
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DCHECK(!is_hidden_field());
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int result = index() - first_inobject_property_offset() / kPointerSize;
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if (!is_inobject()) {
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result += InObjectPropertyBits::decode(bit_field_);
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}
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return result;
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}
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int GetFieldAccessStubKey() const {
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return bit_field_ &
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(IsInObjectBits::kMask | EncodingBits::kMask | OffsetBits::kMask);
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}
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bool operator==(FieldIndex const& other) const {
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return bit_field_ == other.bit_field_;
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}
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bool operator!=(FieldIndex const& other) const { return !(*this == other); }
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private:
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FieldIndex(bool is_inobject, int offset, Encoding encoding,
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int inobject_properties, int first_inobject_property_offset,
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bool is_hidden = false) {
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DCHECK_EQ(first_inobject_property_offset & (kPointerSize - 1), 0);
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bit_field_ = IsInObjectBits::encode(is_inobject) |
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EncodingBits::encode(encoding) |
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FirstInobjectPropertyOffsetBits::encode(
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first_inobject_property_offset) |
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IsHiddenField::encode(is_hidden) | OffsetBits::encode(offset) |
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InObjectPropertyBits::encode(inobject_properties);
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}
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static Encoding FieldEncoding(Representation representation) {
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switch (representation.kind()) {
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case Representation::kNone:
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case Representation::kSmi:
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case Representation::kHeapObject:
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case Representation::kTagged:
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return kTagged;
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case Representation::kDouble:
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return kDouble;
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default:
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break;
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}
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PrintF("%s\n", representation.Mnemonic());
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UNREACHABLE();
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return kTagged;
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}
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int first_inobject_property_offset() const {
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DCHECK(!is_hidden_field());
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return FirstInobjectPropertyOffsetBits::decode(bit_field_);
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}
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static const int kOffsetBitsSize =
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(kDescriptorIndexBitCount + 1 + kPointerSizeLog2);
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// Index from beginning of object.
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class OffsetBits : public BitField64<int, 0, kOffsetBitsSize> {};
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class IsInObjectBits : public BitField64<bool, OffsetBits::kNext, 1> {};
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class EncodingBits : public BitField64<Encoding, IsInObjectBits::kNext, 2> {};
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// Number of inobject properties.
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class InObjectPropertyBits
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: public BitField64<int, EncodingBits::kNext, kDescriptorIndexBitCount> {
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};
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// Offset of first inobject property from beginning of object.
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class FirstInobjectPropertyOffsetBits
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: public BitField64<int, InObjectPropertyBits::kNext,
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kFirstInobjectPropertyOffsetBitCount> {};
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class IsHiddenField
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: public BitField64<bool, FirstInobjectPropertyOffsetBits::kNext, 1> {};
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STATIC_ASSERT(IsHiddenField::kNext <= 64);
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uint64_t bit_field_;
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};
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} // namespace internal
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} // namespace v8
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#endif // V8_FIELD_INDEX_H_
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