caged-heap-local-data.h

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// Copyright 2020 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 INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_
#define INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_
 
#include <array>
 
#include "cppgc/internal/api-constants.h"
#include "cppgc/internal/logging.h"
#include "cppgc/platform.h"
#include "v8config.h"              // NOLINT(build/include_directory)
 
namespace cppgc {
namespace internal {
 
class HeapBase;
 
#if defined(CPPGC_YOUNG_GENERATION)
 
// AgeTable contains entries that correspond to 4KB memory regions. Each entry
// can be in one of three states: kOld, kYoung or kUnknown.
class AgeTable final {
  static constexpr size_t kGranularityBits = 12;  // 4KiB per byte.
 
 public:
  enum class Age : uint8_t { kOld, kYoung, kUnknown };
 
  static constexpr size_t kEntrySizeInBytes = 1 << kGranularityBits;
 
  Age& operator[](uintptr_t offset) { return table_[entry(offset)]; }
  Age operator[](uintptr_t offset) const { return table_[entry(offset)]; }
 
  void Reset(PageAllocator* allocator);
 
 private:
  static constexpr size_t kAgeTableSize =
      api_constants::kCagedHeapReservationSize >> kGranularityBits;
 
  size_t entry(uintptr_t offset) const {
    const size_t entry = offset >> kGranularityBits;
    CPPGC_DCHECK(table_.size() > entry);
    return entry;
  }
 
  std::array<Age, kAgeTableSize> table_;
};
 
static_assert(sizeof(AgeTable) == 1 * api_constants::kMB,
              "Size of AgeTable is 1MB");
 
#endif  // CPPGC_YOUNG_GENERATION
 
struct CagedHeapLocalData final {
  explicit CagedHeapLocalData(HeapBase* heap_base) : heap_base(heap_base) {}
 
  bool is_incremental_marking_in_progress = false;
  HeapBase* heap_base = nullptr;
#if defined(CPPGC_YOUNG_GENERATION)
  AgeTable age_table;
#endif
};
 
}  // namespace internal
}  // namespace cppgc
 
#endif  // INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_