cppgc/internal/api-constants.h

0001 // Copyright 2020 the V8 project authors. All rights reserved.
0002 // Use of this source code is governed by a BSD-style license that can be
0003 // found in the LICENSE file.
0004
0005 #ifndef INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_
0006 #define INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_
0007
0008 #include <cstddef>
0009 #include <cstdint>
0010
0011 #include "v8config.h"  // NOLINT(build/include_directory)
0012
0013 namespace cppgc {
0014 namespace internal {
0015
0016 // Embedders should not rely on this code!
0017
0018 // Internal constants to avoid exposing internal types on the API surface.
0019 namespace api_constants {
0020
0021 constexpr size_t kKB = 1024;
0022 constexpr size_t kMB = kKB * 1024;
0023 constexpr size_t kGB = kMB * 1024;
0024
0025 // Offset of the uint16_t bitfield from the payload contaning the
0026 // in-construction bit. This is subtracted from the payload pointer to get
0027 // to the right bitfield.
0028 static constexpr size_t kFullyConstructedBitFieldOffsetFromPayload =
0029     2 * sizeof(uint16_t);
0030 // Mask for in-construction bit.
0031 static constexpr uint16_t kFullyConstructedBitMask = uint16_t{1};
0032
0033 static constexpr size_t kPageSize = size_t{1} << 17;
0034
0035 #if defined(V8_HOST_ARCH_ARM64) && defined(V8_OS_DARWIN)
0036 constexpr size_t kGuardPageSize = 0;
0037 #else
0038 constexpr size_t kGuardPageSize = 4096;
0039 #endif
0040
0041 static constexpr size_t kLargeObjectSizeThreshold = kPageSize / 2;
0042
0043 #if defined(CPPGC_POINTER_COMPRESSION)
0044 #if defined(CPPGC_ENABLE_LARGER_CAGE)
0045 constexpr unsigned kPointerCompressionShift = 3;
0046 #else   // !defined(CPPGC_ENABLE_LARGER_CAGE)
0047 constexpr unsigned kPointerCompressionShift = 1;
0048 #endif  // !defined(CPPGC_ENABLE_LARGER_CAGE)
0049 #endif  // !defined(CPPGC_POINTER_COMPRESSION)
0050
0051 #if defined(CPPGC_CAGED_HEAP)
0052 #if defined(CPPGC_2GB_CAGE)
0053 constexpr size_t kCagedHeapDefaultReservationSize =
0054     static_cast<size_t>(2) * kGB;
0055 constexpr size_t kCagedHeapMaxReservationSize =
0056     kCagedHeapDefaultReservationSize;
0057 #else  // !defined(CPPGC_2GB_CAGE)
0058 constexpr size_t kCagedHeapDefaultReservationSize =
0059     static_cast<size_t>(4) * kGB;
0060 #if defined(CPPGC_POINTER_COMPRESSION)
0061 constexpr size_t kCagedHeapMaxReservationSize =
0062     size_t{1} << (31 + kPointerCompressionShift);
0063 #else   // !defined(CPPGC_POINTER_COMPRESSION)
0064 constexpr size_t kCagedHeapMaxReservationSize =
0065     kCagedHeapDefaultReservationSize;
0066 #endif  // !defined(CPPGC_POINTER_COMPRESSION)
0067 #endif  // !defined(CPPGC_2GB_CAGE)
0068 constexpr size_t kCagedHeapReservationAlignment = kCagedHeapMaxReservationSize;
0069 #endif  // defined(CPPGC_CAGED_HEAP)
0070
0071 static constexpr size_t kDefaultAlignment = sizeof(void*);
0072
0073 // Maximum support alignment for a type as in `alignof(T)`.
0074 static constexpr size_t kMaxSupportedAlignment = 2 * kDefaultAlignment;
0075
0076 // Granularity of heap allocations.
0077 constexpr size_t kAllocationGranularity = sizeof(void*);
0078
0079 // Default cacheline size.
0080 constexpr size_t kCachelineSize = 64;
0081
0082 }  // namespace api_constants
0083
0084 }  // namespace internal
0085 }  // namespace cppgc
0086
0087 #endif  // INCLUDE_CPPGC_INTERNAL_API_CONSTANTS_H_