chromium/v8/src/heap/slot-set.h

// Copyright 2016 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_HEAP_SLOT_SET_H_
#define V8_HEAP_SLOT_SET_H_

#include <map>
#include <memory>
#include <stack>
#include <vector>

#include "src/base/bit-field.h"
#include "src/heap/base/basic-slot-set.h"
#include "src/objects/compressed-slots.h"
#include "src/objects/slots.h"
#include "src/utils/allocation.h"
#include "src/utils/utils.h"
#include "testing/gtest/include/gtest/gtest_prod.h"  // nogncheck

namespace v8 {
namespace internal {

KEEP_SLOT;
REMOVE_SLOT;
SlotCallbackResult;

// Possibly empty buckets (buckets that do not contain any slots) are discovered
// by the scavenger. Buckets might become non-empty when promoting objects later
// or in another thread, so all those buckets need to be revisited.
// Track possibly empty buckets within a SlotSet in this data structure. The
// class contains a word-sized bitmap, in case more bits are needed the bitmap
// is replaced with a pointer to a malloc-allocated bitmap.
class PossiblyEmptyBuckets { … };

static_assert(std::is_standard_layout<PossiblyEmptyBuckets>::value);
static_assert …;

class SlotSet final : public ::heap::base::BasicSlotSet<kTaggedSize> { … };

static_assert(std::is_standard_layout<SlotSet>::value);
static_assert(std::is_standard_layout<SlotSet::Bucket>::value);

enum class SlotType : uint8_t { … };

// Data structure for maintaining a list of typed slots in a page.
// Typed slots can only appear in Code objects, so
// the maximum possible offset is limited by the
// LargePageMetadata::kMaxCodePageSize. The implementation is a chain of chunks,
// where each chunk is an array of encoded (slot type, slot offset) pairs. There
// is no duplicate detection and we do not expect many duplicates because typed
// slots contain V8 internal pointers that are not directly exposed to JS.
class V8_EXPORT_PRIVATE TypedSlots { … };

// A multiset of per-page typed slots that allows concurrent iteration
// clearing of invalid slots.
class V8_EXPORT_PRIVATE TypedSlotSet : public TypedSlots { … };

}  // namespace internal
}  // namespace v8

#endif  // V8_HEAP_SLOT_SET_H_