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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 V8_HEAP_CPPGC_GLOBALS_H_
#define V8_HEAP_CPPGC_GLOBALS_H_
#include <stddef.h>
#include <stdint.h>
#include "include/cppgc/internal/gc-info.h"
#include "src/base/build_config.h"
namespace cppgc {
namespace internal {
using Address = uint8_t*;
using ConstAddress = const uint8_t*;
constexpr size_t kKB = 1024;
constexpr size_t kMB = kKB * 1024;
constexpr size_t kGB = kMB * 1024;
// AccessMode used for choosing between atomic and non-atomic accesses.
enum class AccessMode : uint8_t { kNonAtomic, kAtomic };
// See 6.7.6 (http://eel.is/c++draft/basic.align) for alignment restrictions. We
// do not fully support all alignment restrictions (following
// alignof(std::max_align_t)) but limit to alignof(double).
//
// This means that any scalar type with stricter alignment requirements (in
// practice: long double) cannot be used unrestricted in garbage-collected
// objects.
#if defined(V8_TARGET_ARCH_64_BIT)
constexpr size_t kAllocationGranularity = 8;
#else // !V8_TARGET_ARCH_64_BIT
constexpr size_t kAllocationGranularity = 4;
#endif // !V8_TARGET_ARCH_64_BIT
constexpr size_t kAllocationMask = kAllocationGranularity - 1;
constexpr size_t kPageSizeLog2 = 17;
constexpr size_t kPageSize = 1 << kPageSizeLog2;
constexpr size_t kPageOffsetMask = kPageSize - 1;
constexpr size_t kPageBaseMask = ~kPageOffsetMask;
#if defined(V8_TARGET_ARCH_ARM64) && defined(V8_OS_DARWIN)
// No guard pages on ARM64 macOS. This target has 16 kiB pages, meaning that
// the guard pages do not protect anything, since there is no inaccessible
// region surrounding the allocation.
//
// However, with a 4k guard page size (as below), we avoid putting any data
// inside the "guard pages" region. Effectively, this wastes 2 * 4kiB of memory
// for each 128kiB page, since this is memory we pay for (since accounting as at
// the OS page level), but never use.
//
// The layout of pages is broadly:
// | guard page | header | payload | guard page |
// <--- 4k ---> <--- 4k --->
// <------------------ 128k -------------------->
//
// Since this is aligned on an OS page boundary (16k), the guard pages are part
// of the first and last OS page, respectively. So they are really private dirty
// memory which we never use.
constexpr size_t kGuardPageSize = 0;
#else
// Guard pages are always put into memory. Whether they are actually protected
// depends on the allocator provided to the garbage collector.
constexpr size_t kGuardPageSize = 4096;
#endif
constexpr size_t kLargeObjectSizeThreshold = kPageSize / 2;
constexpr GCInfoIndex kFreeListGCInfoIndex = 0;
constexpr size_t kFreeListEntrySize = 2 * sizeof(uintptr_t);
#if defined(CPPGC_2GB_CAGE)
constexpr size_t kCagedHeapReservationSize = static_cast<size_t>(2) * kGB;
#else // !defined(CPPGC_2GB_CAGE)
constexpr size_t kCagedHeapReservationSize = static_cast<size_t>(4) * kGB;
#endif // !defined(CPPGC_2GB_CAGE)
constexpr size_t kCagedHeapReservationAlignment = kCagedHeapReservationSize;
#if defined(CPPGC_POINTER_COMPRESSION)
constexpr size_t kSlotSize = sizeof(uint32_t);
#else // !defined(CPPGC_POINTER_COMPRESSION)
constexpr size_t kSlotSize = sizeof(uintptr_t);
#endif // !defined(CPPGC_POINTER_COMPRESSION)
} // namespace internal
} // namespace cppgc
#endif // V8_HEAP_CPPGC_GLOBALS_H_
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