File Explorer

1// Copyright 2020 the V8 project authors. All rights reserved.2// Use of this source code is governed by a BSD-style license that can be3// found in the LICENSE file.4 5#ifndef INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_6#define INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_7 8#include <array>9#include <cstddef>10#include <cstdint>11 12#include "cppgc/internal/api-constants.h"13#include "cppgc/internal/caged-heap.h"14#include "cppgc/internal/logging.h"15#include "cppgc/platform.h"16#include "v8config.h"  // NOLINT(build/include_directory)17 18#if __cpp_lib_bitopts19#include <bit>20#endif  // __cpp_lib_bitopts21 22#if defined(CPPGC_CAGED_HEAP)23 24namespace cppgc {25namespace internal {26 27class HeapBase;28class HeapBaseHandle;29 30#if defined(CPPGC_YOUNG_GENERATION)31 32// AgeTable is the bytemap needed for the fast generation check in the write33// barrier. AgeTable contains entries that correspond to 4096 bytes memory34// regions (cards). Each entry in the table represents generation of the objects35// that reside on the corresponding card (young, old or mixed).36class V8_EXPORT AgeTable final {37  static constexpr size_t kRequiredSize = 1 * api_constants::kMB;38  static constexpr size_t kAllocationGranularity =39      api_constants::kAllocationGranularity;40 41 public:42  // Represents age of the objects living on a single card.43  enum class Age : uint8_t { kOld, kYoung, kMixed };44  // When setting age for a range, consider or ignore ages of the adjacent45  // cards.46  enum class AdjacentCardsPolicy : uint8_t { kConsider, kIgnore };47 48  static constexpr size_t kCardSizeInBytes =49      api_constants::kCagedHeapDefaultReservationSize / kRequiredSize;50 51  static constexpr size_t CalculateAgeTableSizeForHeapSize(size_t heap_size) {52    return heap_size / kCardSizeInBytes;53  }54 55  void SetAge(uintptr_t cage_offset, Age age) {56    table_[card(cage_offset)] = age;57  }58 59  V8_INLINE Age GetAge(uintptr_t cage_offset) const {60    return table_[card(cage_offset)];61  }62 63  void SetAgeForRange(uintptr_t cage_offset_begin, uintptr_t cage_offset_end,64                      Age age, AdjacentCardsPolicy adjacent_cards_policy);65 66  Age GetAgeForRange(uintptr_t cage_offset_begin,67                     uintptr_t cage_offset_end) const;68 69  void ResetForTesting();70 71 private:72  V8_INLINE size_t card(uintptr_t offset) const {73    constexpr size_t kGranularityBits =74#if __cpp_lib_bitopts75        std::countr_zero(static_cast<uint32_t>(kCardSizeInBytes));76#elif V8_HAS_BUILTIN_CTZ77        __builtin_ctz(static_cast<uint32_t>(kCardSizeInBytes));78#else   //! V8_HAS_BUILTIN_CTZ79        // Hardcode and check with assert.80        12;81#endif  // !V8_HAS_BUILTIN_CTZ82    static_assert((1 << kGranularityBits) == kCardSizeInBytes);83    const size_t entry = offset >> kGranularityBits;84    CPPGC_DCHECK(CagedHeapBase::GetAgeTableSize() > entry);85    return entry;86  }87 88#if defined(V8_CC_GNU)89  // gcc disallows flexible arrays in otherwise empty classes.90  Age table_[0];91#else   // !defined(V8_CC_GNU)92  Age table_[];93#endif  // !defined(V8_CC_GNU)94};95 96#endif  // CPPGC_YOUNG_GENERATION97 98struct CagedHeapLocalData final {99  V8_INLINE static CagedHeapLocalData& Get() {100    return *reinterpret_cast<CagedHeapLocalData*>(CagedHeapBase::GetBase());101  }102 103  static constexpr size_t CalculateLocalDataSizeForHeapSize(size_t heap_size) {104    return AgeTable::CalculateAgeTableSizeForHeapSize(heap_size);105  }106 107#if defined(CPPGC_YOUNG_GENERATION)108  AgeTable age_table;109#endif110};111 112}  // namespace internal113}  // namespace cppgc114 115#endif  // defined(CPPGC_CAGED_HEAP)116 117#endif  // INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_LOCAL_DATA_H_118