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globals.h
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globals.h
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// Copyright 2012 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_COMMON_GLOBALS_H_
#define V8_COMMON_GLOBALS_H_
#include <stddef.h>
#include <stdint.h>
#include <limits>
#include <ostream>
#include "include/v8-internal.h"
#include "src/base/atomic-utils.h"
#include "src/base/build_config.h"
#include "src/base/enum-set.h"
#include "src/base/flags.h"
#include "src/base/logging.h"
#include "src/base/macros.h"
#define V8_INFINITY std::numeric_limits<double>::infinity()
namespace v8 {
namespace base {
class Mutex;
class RecursiveMutex;
} // namespace base
namespace internal {
constexpr int KB = 1024;
constexpr int MB = KB * 1024;
constexpr int GB = MB * 1024;
constexpr int64_t TB = static_cast<int64_t>(GB) * 1024;
// Determine whether we are running in a simulated environment.
// Setting USE_SIMULATOR explicitly from the build script will force
// the use of a simulated environment.
#if !defined(USE_SIMULATOR)
#if (V8_TARGET_ARCH_ARM64 && !V8_HOST_ARCH_ARM64)
#define USE_SIMULATOR 1
#endif
#if (V8_TARGET_ARCH_ARM && !V8_HOST_ARCH_ARM)
#define USE_SIMULATOR 1
#endif
#if (V8_TARGET_ARCH_PPC && !V8_HOST_ARCH_PPC)
#define USE_SIMULATOR 1
#endif
#if (V8_TARGET_ARCH_PPC64 && !V8_HOST_ARCH_PPC64)
#define USE_SIMULATOR 1
#endif
#if (V8_TARGET_ARCH_MIPS && !V8_HOST_ARCH_MIPS)
#define USE_SIMULATOR 1
#endif
#if (V8_TARGET_ARCH_MIPS64 && !V8_HOST_ARCH_MIPS64)
#define USE_SIMULATOR 1
#endif
#if (V8_TARGET_ARCH_S390 && !V8_HOST_ARCH_S390)
#define USE_SIMULATOR 1
#endif
#if (V8_TARGET_ARCH_RISCV64 && !V8_HOST_ARCH_RISCV64)
#define USE_SIMULATOR 1
#endif
#if (V8_TARGET_ARCH_LOONG64 && !V8_HOST_ARCH_LOONG64)
#define USE_SIMULATOR 1
#endif
#endif
// Determine whether the architecture uses an embedded constant pool
// (contiguous constant pool embedded in code object).
#if V8_TARGET_ARCH_PPC || V8_TARGET_ARCH_PPC64
#define V8_EMBEDDED_CONSTANT_POOL true
#else
#define V8_EMBEDDED_CONSTANT_POOL false
#endif
#if V8_TARGET_ARCH_ARM || V8_TARGET_ARCH_ARM64
// Set stack limit lower for ARM and ARM64 than for other architectures because:
// - on Arm stack allocating MacroAssembler takes 120K bytes.
// See issue crbug.com/405338
// - on Arm64 when running in single-process mode for Android WebView, when
// initializing V8 we already have a large stack and so have to set the
// limit lower. See issue crbug.com/v8/10575
#define V8_DEFAULT_STACK_SIZE_KB 864
#else
// Slightly less than 1MB, since Windows' default stack size for
// the main execution thread is 1MB for both 32 and 64-bit.
#define V8_DEFAULT_STACK_SIZE_KB 984
#endif
// Minimum stack size in KB required by compilers.
constexpr int kStackSpaceRequiredForCompilation = 40;
// In order to emit more efficient stack checks in optimized code,
// deoptimization may implicitly exceed the V8 stack limit by this many bytes.
// Stack checks in functions with `difference between optimized and unoptimized
// stack frame sizes <= slack` can simply emit the simple stack check.
constexpr int kStackLimitSlackForDeoptimizationInBytes = 256;
// Sanity-check, assuming that we aim for a real OS stack size of at least 1MB.
STATIC_ASSERT(V8_DEFAULT_STACK_SIZE_KB* KB +
kStackLimitSlackForDeoptimizationInBytes <=
MB);
#if defined(V8_SHORT_BUILTIN_CALLS) && \
(!defined(V8_COMPRESS_POINTERS) || defined(V8_EXTERNAL_CODE_SPACE))
#define V8_ENABLE_NEAR_CODE_RANGE_BOOL true
#else
#define V8_ENABLE_NEAR_CODE_RANGE_BOOL false
#endif
// This constant is used for detecting whether the machine has >= 4GB of
// physical memory by checking the max old space size.
const size_t kShortBuiltinCallsOldSpaceSizeThreshold = size_t{2} * GB;
// This constant is used for detecting whether code range could be
// allocated within the +/- 2GB boundary to builtins' embedded blob
// to use short builtin calls.
const size_t kShortBuiltinCallsBoundary = size_t{2} * GB;
// Determine whether dict mode prototypes feature is enabled.
#ifdef V8_ENABLE_SWISS_NAME_DICTIONARY
#define V8_ENABLE_SWISS_NAME_DICTIONARY_BOOL true
#else
#define V8_ENABLE_SWISS_NAME_DICTIONARY_BOOL false
#endif
// Determine whether dict property constness tracking feature is enabled.
#ifdef V8_DICT_PROPERTY_CONST_TRACKING
#define V8_DICT_PROPERTY_CONST_TRACKING_BOOL true
#else
#define V8_DICT_PROPERTY_CONST_TRACKING_BOOL false
#endif
#ifdef V8_EXTERNAL_CODE_SPACE
#define V8_EXTERNAL_CODE_SPACE_BOOL true
class CodeDataContainer;
using CodeT = CodeDataContainer;
#else
#define V8_EXTERNAL_CODE_SPACE_BOOL false
class Code;
using CodeT = Code;
#endif
// Determine whether tagged pointers are 8 bytes (used in Torque layouts for
// choosing where to insert padding).
#if V8_TARGET_ARCH_64_BIT && !defined(V8_COMPRESS_POINTERS)
#define TAGGED_SIZE_8_BYTES true
#else
#define TAGGED_SIZE_8_BYTES false
#endif
// Some types of tracing require the SFI to store a unique ID.
#if defined(V8_TRACE_MAPS) || defined(V8_TRACE_UNOPTIMIZED)
#define V8_SFI_HAS_UNIQUE_ID true
#else
#define V8_SFI_HAS_UNIQUE_ID false
#endif
#if defined(V8_OS_WIN) && defined(V8_TARGET_ARCH_X64)
#define V8_OS_WIN_X64 true
#endif
#if defined(V8_OS_WIN) && defined(V8_TARGET_ARCH_ARM64)
#define V8_OS_WIN_ARM64 true
#endif
#if defined(V8_OS_WIN_X64) || defined(V8_OS_WIN_ARM64)
#define V8_OS_WIN64 true
#endif
// Superclass for classes only using static method functions.
// The subclass of AllStatic cannot be instantiated at all.
class AllStatic {
#ifdef DEBUG
public:
AllStatic() = delete;
#endif
};
using byte = uint8_t;
// -----------------------------------------------------------------------------
// Constants
constexpr int kMaxInt = 0x7FFFFFFF;
constexpr int kMinInt = -kMaxInt - 1;
constexpr int kMaxInt8 = (1 << 7) - 1;
constexpr int kMinInt8 = -(1 << 7);
constexpr int kMaxUInt8 = (1 << 8) - 1;
constexpr int kMinUInt8 = 0;
constexpr int kMaxInt16 = (1 << 15) - 1;
constexpr int kMinInt16 = -(1 << 15);
constexpr int kMaxUInt16 = (1 << 16) - 1;
constexpr int kMinUInt16 = 0;
constexpr int kMaxInt31 = kMaxInt / 2;
constexpr int kMinInt31 = kMinInt / 2;
constexpr uint32_t kMaxUInt32 = 0xFFFFFFFFu;
constexpr int kMinUInt32 = 0;
constexpr int kInt8Size = sizeof(int8_t);
constexpr int kUInt8Size = sizeof(uint8_t);
constexpr int kByteSize = sizeof(byte);
constexpr int kCharSize = sizeof(char);
constexpr int kShortSize = sizeof(short); // NOLINT
constexpr int kInt16Size = sizeof(int16_t);
constexpr int kUInt16Size = sizeof(uint16_t);
constexpr int kIntSize = sizeof(int);
constexpr int kInt32Size = sizeof(int32_t);
constexpr int kInt64Size = sizeof(int64_t);
constexpr int kUInt32Size = sizeof(uint32_t);
constexpr int kSizetSize = sizeof(size_t);
constexpr int kFloatSize = sizeof(float);
constexpr int kDoubleSize = sizeof(double);
constexpr int kIntptrSize = sizeof(intptr_t);
constexpr int kUIntptrSize = sizeof(uintptr_t);
constexpr int kSystemPointerSize = sizeof(void*);
constexpr int kSystemPointerHexDigits = kSystemPointerSize == 4 ? 8 : 12;
constexpr int kPCOnStackSize = kSystemPointerSize;
constexpr int kFPOnStackSize = kSystemPointerSize;
#if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_IA32
constexpr int kElidedFrameSlots = kPCOnStackSize / kSystemPointerSize;
#else
constexpr int kElidedFrameSlots = 0;
#endif
constexpr int kDoubleSizeLog2 = 3;
// The maximal length of the string representation for a double value
// (e.g. "-2.2250738585072020E-308"). It is composed as follows:
// - 17 decimal digits, see base::kBase10MaximalLength (dtoa.h)
// - 1 sign
// - 1 decimal point
// - 1 E or e
// - 1 exponent sign
// - 3 exponent
constexpr int kMaxDoubleStringLength = 24;
// Total wasm code space per engine (i.e. per process) is limited to make
// certain attacks that rely on heap spraying harder.
// Just below 4GB, such that {kMaxWasmCodeMemory} fits in a 32-bit size_t.
constexpr size_t kMaxWasmCodeMB = 4095;
constexpr size_t kMaxWasmCodeMemory = kMaxWasmCodeMB * MB;
#if V8_HOST_ARCH_64_BIT
constexpr int kSystemPointerSizeLog2 = 3;
constexpr intptr_t kIntptrSignBit =
static_cast<intptr_t>(uintptr_t{0x8000000000000000});
constexpr bool kPlatformRequiresCodeRange = true;
#if (V8_HOST_ARCH_PPC || V8_HOST_ARCH_PPC64) && \
(V8_TARGET_ARCH_PPC || V8_TARGET_ARCH_PPC64) && V8_OS_LINUX
constexpr size_t kMaximalCodeRangeSize = 512 * MB;
constexpr size_t kMinExpectedOSPageSize = 64 * KB; // OS page on PPC Linux
#elif V8_TARGET_ARCH_ARM64
constexpr size_t kMaximalCodeRangeSize = 128 * MB;
constexpr size_t kMinExpectedOSPageSize = 4 * KB; // OS page.
#else
constexpr size_t kMaximalCodeRangeSize = 128 * MB;
constexpr size_t kMinExpectedOSPageSize = 4 * KB; // OS page.
#endif
#if V8_OS_WIN
constexpr size_t kMinimumCodeRangeSize = 4 * MB;
constexpr size_t kReservedCodeRangePages = 1;
#else
constexpr size_t kMinimumCodeRangeSize = 3 * MB;
constexpr size_t kReservedCodeRangePages = 0;
#endif
#else
constexpr int kSystemPointerSizeLog2 = 2;
constexpr intptr_t kIntptrSignBit = 0x80000000;
#if (V8_HOST_ARCH_PPC || V8_HOST_ARCH_PPC64) && \
(V8_TARGET_ARCH_PPC || V8_TARGET_ARCH_PPC64) && V8_OS_LINUX
constexpr bool kPlatformRequiresCodeRange = false;
constexpr size_t kMaximalCodeRangeSize = 0 * MB;
constexpr size_t kMinimumCodeRangeSize = 0 * MB;
constexpr size_t kMinExpectedOSPageSize = 64 * KB; // OS page on PPC Linux
#elif V8_TARGET_ARCH_MIPS
constexpr bool kPlatformRequiresCodeRange = false;
constexpr size_t kMaximalCodeRangeSize = 2048LL * MB;
constexpr size_t kMinimumCodeRangeSize = 0 * MB;
constexpr size_t kMinExpectedOSPageSize = 4 * KB; // OS page.
#else
constexpr bool kPlatformRequiresCodeRange = false;
constexpr size_t kMaximalCodeRangeSize = 0 * MB;
constexpr size_t kMinimumCodeRangeSize = 0 * MB;
constexpr size_t kMinExpectedOSPageSize = 4 * KB; // OS page.
#endif
constexpr size_t kReservedCodeRangePages = 0;
#endif
STATIC_ASSERT(kSystemPointerSize == (1 << kSystemPointerSizeLog2));
#ifdef V8_COMPRESS_ZONES
#define COMPRESS_ZONES_BOOL true
#else
#define COMPRESS_ZONES_BOOL false
#endif // V8_COMPRESS_ZONES
// The flag controls whether zones pointer compression should be enabled for
// TurboFan graphs or not.
static constexpr bool kCompressGraphZone = COMPRESS_ZONES_BOOL;
#ifdef V8_COMPRESS_POINTERS
static_assert(
kSystemPointerSize == kInt64Size,
"Pointer compression can be enabled only for 64-bit architectures");
constexpr int kTaggedSize = kInt32Size;
constexpr int kTaggedSizeLog2 = 2;
// These types define raw and atomic storage types for tagged values stored
// on V8 heap.
using Tagged_t = uint32_t;
using AtomicTagged_t = base::Atomic32;
#else
constexpr int kTaggedSize = kSystemPointerSize;
constexpr int kTaggedSizeLog2 = kSystemPointerSizeLog2;
// These types define raw and atomic storage types for tagged values stored
// on V8 heap.
using Tagged_t = Address;
using AtomicTagged_t = base::AtomicWord;
#endif // V8_COMPRESS_POINTERS
STATIC_ASSERT(kTaggedSize == (1 << kTaggedSizeLog2));
STATIC_ASSERT((kTaggedSize == 8) == TAGGED_SIZE_8_BYTES);
using AsAtomicTagged = base::AsAtomicPointerImpl<AtomicTagged_t>;
STATIC_ASSERT(sizeof(Tagged_t) == kTaggedSize);
STATIC_ASSERT(sizeof(AtomicTagged_t) == kTaggedSize);
STATIC_ASSERT(kTaggedSize == kApiTaggedSize);
// TODO(ishell): use kTaggedSize or kSystemPointerSize instead.
#ifndef V8_COMPRESS_POINTERS
constexpr int kPointerSize = kSystemPointerSize;
constexpr int kPointerSizeLog2 = kSystemPointerSizeLog2;
STATIC_ASSERT(kPointerSize == (1 << kPointerSizeLog2));
#endif
// This type defines raw storage type for external (or off-V8 heap) pointers
// stored on V8 heap.
constexpr int kExternalPointerSize = sizeof(ExternalPointer_t);
constexpr int kEmbedderDataSlotSize = kSystemPointerSize;
constexpr int kEmbedderDataSlotSizeInTaggedSlots =
kEmbedderDataSlotSize / kTaggedSize;
STATIC_ASSERT(kEmbedderDataSlotSize >= kSystemPointerSize);
constexpr int kExternalAllocationSoftLimit =
internal::Internals::kExternalAllocationSoftLimit;
// Maximum object size that gets allocated into regular pages. Objects larger
// than that size are allocated in large object space and are never moved in
// memory. This also applies to new space allocation, since objects are never
// migrated from new space to large object space. Takes double alignment into
// account.
//
// Current value: half of the page size.
constexpr int kMaxRegularHeapObjectSize = (1 << (kPageSizeBits - 1));
constexpr int kBitsPerByte = 8;
constexpr int kBitsPerByteLog2 = 3;
constexpr int kBitsPerSystemPointer = kSystemPointerSize * kBitsPerByte;
constexpr int kBitsPerSystemPointerLog2 =
kSystemPointerSizeLog2 + kBitsPerByteLog2;
constexpr int kBitsPerInt = kIntSize * kBitsPerByte;
// IEEE 754 single precision floating point number bit layout.
constexpr uint32_t kBinary32SignMask = 0x80000000u;
constexpr uint32_t kBinary32ExponentMask = 0x7f800000u;
constexpr uint32_t kBinary32MantissaMask = 0x007fffffu;
constexpr int kBinary32ExponentBias = 127;
constexpr int kBinary32MaxExponent = 0xFE;
constexpr int kBinary32MinExponent = 0x01;
constexpr int kBinary32MantissaBits = 23;
constexpr int kBinary32ExponentShift = 23;
// Quiet NaNs have bits 51 to 62 set, possibly the sign bit, and no
// other bits set.
constexpr uint64_t kQuietNaNMask = static_cast<uint64_t>(0xfff) << 51;
constexpr int kOneByteSize = kCharSize;
// 128 bit SIMD value size.
constexpr int kSimd128Size = 16;
// Maximum ordinal used for tracking asynchronous module evaluation order.
constexpr unsigned kMaxModuleAsyncEvaluatingOrdinal = (1 << 30) - 1;
// FUNCTION_ADDR(f) gets the address of a C function f.
#define FUNCTION_ADDR(f) (reinterpret_cast<v8::internal::Address>(f))
// FUNCTION_CAST<F>(addr) casts an address into a function
// of type F. Used to invoke generated code from within C.
template <typename F>
F FUNCTION_CAST(byte* addr) {
return reinterpret_cast<F>(reinterpret_cast<Address>(addr));
}
template <typename F>
F FUNCTION_CAST(Address addr) {
return reinterpret_cast<F>(addr);
}
// Determine whether the architecture uses function descriptors
// which provide a level of indirection between the function pointer
// and the function entrypoint.
#if (V8_HOST_ARCH_PPC || V8_HOST_ARCH_PPC64) && \
(V8_OS_AIX || (V8_TARGET_ARCH_PPC64 && V8_TARGET_BIG_ENDIAN && \
(!defined(_CALL_ELF) || _CALL_ELF == 1)))
#define USES_FUNCTION_DESCRIPTORS 1
#define FUNCTION_ENTRYPOINT_ADDRESS(f) \
(reinterpret_cast<v8::internal::Address*>( \
&(reinterpret_cast<intptr_t*>(f)[0])))
#else
#define USES_FUNCTION_DESCRIPTORS 0
#endif
// -----------------------------------------------------------------------------
// Declarations for use in both the preparser and the rest of V8.
// The Strict Mode (ECMA-262 5th edition, 4.2.2).
enum class LanguageMode : bool { kSloppy, kStrict };
static const size_t LanguageModeSize = 2;
inline size_t hash_value(LanguageMode mode) {
return static_cast<size_t>(mode);
}
inline const char* LanguageMode2String(LanguageMode mode) {
switch (mode) {
case LanguageMode::kSloppy:
return "sloppy";
case LanguageMode::kStrict:
return "strict";
}
UNREACHABLE();
}
inline std::ostream& operator<<(std::ostream& os, LanguageMode mode) {
return os << LanguageMode2String(mode);
}
inline bool is_sloppy(LanguageMode language_mode) {
return language_mode == LanguageMode::kSloppy;
}
inline bool is_strict(LanguageMode language_mode) {
return language_mode != LanguageMode::kSloppy;
}
inline bool is_valid_language_mode(int language_mode) {
return language_mode == static_cast<int>(LanguageMode::kSloppy) ||
language_mode == static_cast<int>(LanguageMode::kStrict);
}
inline LanguageMode construct_language_mode(bool strict_bit) {
return static_cast<LanguageMode>(strict_bit);
}
// Return kStrict if either of the language modes is kStrict, or kSloppy
// otherwise.
inline LanguageMode stricter_language_mode(LanguageMode mode1,
LanguageMode mode2) {
STATIC_ASSERT(LanguageModeSize == 2);
return static_cast<LanguageMode>(static_cast<int>(mode1) |
static_cast<int>(mode2));
}
// A non-keyed store is of the form a.x = foo or a["x"] = foo whereas
// a keyed store is of the form a[expression] = foo.
enum class StoreOrigin { kMaybeKeyed, kNamed };
enum class TypeofMode { kInside, kNotInside };
// Use by RecordWrite stubs.
enum class RememberedSetAction { kOmit, kEmit };
// Enums used by CEntry.
enum class SaveFPRegsMode { kIgnore, kSave };
enum class ArgvMode { kStack, kRegister };
// This constant is used as an undefined value when passing source positions.
constexpr int kNoSourcePosition = -1;
// This constant is used to signal the function entry implicit stack check
// bytecode offset.
constexpr int kFunctionEntryBytecodeOffset = -1;
// This constant is used to signal the function exit interrupt budget handling
// bytecode offset.
constexpr int kFunctionExitBytecodeOffset = -1;
// This constant is used to indicate missing deoptimization information.
constexpr int kNoDeoptimizationId = -1;
// Deoptimize bailout kind:
// - Eager: a check failed in the optimized code and deoptimization happens
// immediately.
// - Lazy: the code has been marked as dependent on some assumption which
// is checked elsewhere and can trigger deoptimization the next time the
// code is executed.
// - Soft: similar to lazy deoptimization, but does not contribute to the
// total deopt count which can lead to disabling optimization for a function.
// - Bailout: a check failed in the optimized code but we don't
// deoptimize the code, but try to heal the feedback and try to rerun
// the optimized code again.
// - EagerWithResume: a check failed in the optimized code, but we can execute
// a more expensive check in a builtin that might either result in us resuming
// execution in the optimized code, or deoptimizing immediately.
enum class DeoptimizeKind : uint8_t {
kEager,
kSoft,
kBailout,
kLazy,
kEagerWithResume,
};
constexpr DeoptimizeKind kFirstDeoptimizeKind = DeoptimizeKind::kEager;
constexpr DeoptimizeKind kLastDeoptimizeKind = DeoptimizeKind::kEagerWithResume;
STATIC_ASSERT(static_cast<int>(kFirstDeoptimizeKind) == 0);
constexpr int kDeoptimizeKindCount = static_cast<int>(kLastDeoptimizeKind) + 1;
inline size_t hash_value(DeoptimizeKind kind) {
return static_cast<size_t>(kind);
}
inline std::ostream& operator<<(std::ostream& os, DeoptimizeKind kind) {
switch (kind) {
case DeoptimizeKind::kEager:
return os << "Eager";
case DeoptimizeKind::kSoft:
return os << "Soft";
case DeoptimizeKind::kLazy:
return os << "Lazy";
case DeoptimizeKind::kBailout:
return os << "Bailout";
case DeoptimizeKind::kEagerWithResume:
return os << "EagerMaybeResume";
}
}
// Indicates whether the lookup is related to sloppy-mode block-scoped
// function hoisting, and is a synthetic assignment for that.
enum class LookupHoistingMode { kNormal, kLegacySloppy };
inline std::ostream& operator<<(std::ostream& os,
const LookupHoistingMode& mode) {
switch (mode) {
case LookupHoistingMode::kNormal:
return os << "normal hoisting";
case LookupHoistingMode::kLegacySloppy:
return os << "legacy sloppy hoisting";
}
UNREACHABLE();
}
static_assert(kSmiValueSize <= 32, "Unsupported Smi tagging scheme");
// Smi sign bit position must be 32-bit aligned so we can use sign extension
// instructions on 64-bit architectures without additional shifts.
static_assert((kSmiValueSize + kSmiShiftSize + kSmiTagSize) % 32 == 0,
"Unsupported Smi tagging scheme");
constexpr bool kIsSmiValueInUpper32Bits =
(kSmiValueSize + kSmiShiftSize + kSmiTagSize) == 64;
constexpr bool kIsSmiValueInLower32Bits =
(kSmiValueSize + kSmiShiftSize + kSmiTagSize) == 32;
static_assert(!SmiValuesAre32Bits() == SmiValuesAre31Bits(),
"Unsupported Smi tagging scheme");
static_assert(SmiValuesAre32Bits() == kIsSmiValueInUpper32Bits,
"Unsupported Smi tagging scheme");
static_assert(SmiValuesAre31Bits() == kIsSmiValueInLower32Bits,
"Unsupported Smi tagging scheme");
// Mask for the sign bit in a smi.
constexpr intptr_t kSmiSignMask = static_cast<intptr_t>(
uintptr_t{1} << (kSmiValueSize + kSmiShiftSize + kSmiTagSize - 1));
// Desired alignment for tagged pointers.
constexpr int kObjectAlignmentBits = kTaggedSizeLog2;
constexpr intptr_t kObjectAlignment = 1 << kObjectAlignmentBits;
constexpr intptr_t kObjectAlignmentMask = kObjectAlignment - 1;
// Desired alignment for system pointers.
constexpr intptr_t kPointerAlignment = (1 << kSystemPointerSizeLog2);
constexpr intptr_t kPointerAlignmentMask = kPointerAlignment - 1;
// Desired alignment for double values.
constexpr intptr_t kDoubleAlignment = 8;
constexpr intptr_t kDoubleAlignmentMask = kDoubleAlignment - 1;
// Desired alignment for generated code is 64 bytes on x64 (to allow 64-bytes
// loop header alignment) and 32 bytes (to improve cache line utilization) on
// other architectures.
#if V8_TARGET_ARCH_X64
constexpr int kCodeAlignmentBits = 6;
#else
constexpr int kCodeAlignmentBits = 5;
#endif
constexpr intptr_t kCodeAlignment = 1 << kCodeAlignmentBits;
constexpr intptr_t kCodeAlignmentMask = kCodeAlignment - 1;
const Address kWeakHeapObjectMask = 1 << 1;
// The lower 32 bits of the cleared weak reference value is always equal to
// the |kClearedWeakHeapObjectLower32| constant but on 64-bit architectures
// the value of the upper 32 bits part may be
// 1) zero when pointer compression is disabled,
// 2) upper 32 bits of the isolate root value when pointer compression is
// enabled.
// This is necessary to make pointer decompression computation also suitable
// for cleared weak reference.
// Note, that real heap objects can't have lower 32 bits equal to 3 because
// this offset belongs to page header. So, in either case it's enough to
// compare only the lower 32 bits of a MaybeObject value in order to figure
// out if it's a cleared reference or not.
const uint32_t kClearedWeakHeapObjectLower32 = 3;
// Zap-value: The value used for zapping dead objects.
// Should be a recognizable hex value tagged as a failure.
#ifdef V8_HOST_ARCH_64_BIT
constexpr uint64_t kClearedFreeMemoryValue = 0;
constexpr uint64_t kZapValue = uint64_t{0xdeadbeedbeadbeef};
constexpr uint64_t kHandleZapValue = uint64_t{0x1baddead0baddeaf};
constexpr uint64_t kGlobalHandleZapValue = uint64_t{0x1baffed00baffedf};
constexpr uint64_t kFromSpaceZapValue = uint64_t{0x1beefdad0beefdaf};
constexpr uint64_t kDebugZapValue = uint64_t{0xbadbaddbbadbaddb};
constexpr uint64_t kSlotsZapValue = uint64_t{0xbeefdeadbeefdeef};
constexpr uint64_t kFreeListZapValue = 0xfeed1eaffeed1eaf;
#else
constexpr uint32_t kClearedFreeMemoryValue = 0;
constexpr uint32_t kZapValue = 0xdeadbeef;
constexpr uint32_t kHandleZapValue = 0xbaddeaf;
constexpr uint32_t kGlobalHandleZapValue = 0xbaffedf;
constexpr uint32_t kFromSpaceZapValue = 0xbeefdaf;
constexpr uint32_t kSlotsZapValue = 0xbeefdeef;
constexpr uint32_t kDebugZapValue = 0xbadbaddb;
constexpr uint32_t kFreeListZapValue = 0xfeed1eaf;
#endif
constexpr int kCodeZapValue = 0xbadc0de;
constexpr uint32_t kPhantomReferenceZap = 0xca11bac;
// Page constants.
static const intptr_t kPageAlignmentMask = (intptr_t{1} << kPageSizeBits) - 1;
// On Intel architecture, cache line size is 64 bytes.
// On ARM it may be less (32 bytes), but as far this constant is
// used for aligning data, it doesn't hurt to align on a greater value.
#define PROCESSOR_CACHE_LINE_SIZE 64
// Constants relevant to double precision floating point numbers.
// If looking only at the top 32 bits, the QNaN mask is bits 19 to 30.
constexpr uint32_t kQuietNaNHighBitsMask = 0xfff << (51 - 32);
enum class HeapObjectReferenceType {
WEAK,
STRONG,
};
enum class ArgumentsType {
kRuntime,
kJS,
};
// -----------------------------------------------------------------------------
// Forward declarations for frequently used classes
class AccessorInfo;
template <ArgumentsType>
class Arguments;
using RuntimeArguments = Arguments<ArgumentsType::kRuntime>;
using JavaScriptArguments = Arguments<ArgumentsType::kJS>;
class Assembler;
class ClassScope;
class Code;
class CodeDataContainer;
class CodeSpace;
class Context;
class DeclarationScope;
class Debug;
class DebugInfo;
class Descriptor;
class DescriptorArray;
class TransitionArray;
class ExternalReference;
class FeedbackVector;
class FixedArray;
class Foreign;
class FreeStoreAllocationPolicy;
class FunctionTemplateInfo;
class GlobalDictionary;
template <typename T>
class Handle;
class Heap;
class HeapObject;
class HeapObjectReference;
class IC;
class InterceptorInfo;
class Isolate;
class JSReceiver;
class JSArray;
class JSFunction;
class JSObject;
class LocalIsolate;
class MacroAssembler;
class Map;
class MapSpace;
class MarkCompactCollector;
template <typename T>
class MaybeHandle;
class MaybeObject;
class MemoryChunk;
class MessageLocation;
class ModuleScope;
class Name;
class NameDictionary;
class NativeContext;
class NewSpace;
class NewLargeObjectSpace;
class NumberDictionary;
class Object;
class OldLargeObjectSpace;
template <HeapObjectReferenceType kRefType, typename StorageType>
class TaggedImpl;
class StrongTaggedValue;
class TaggedValue;
class CompressedObjectSlot;
class CompressedMaybeObjectSlot;
class CompressedMapWordSlot;
class CompressedHeapObjectSlot;
class OffHeapCompressedObjectSlot;
class FullObjectSlot;
class FullMaybeObjectSlot;
class FullHeapObjectSlot;
class OffHeapFullObjectSlot;
class OldSpace;
class ReadOnlySpace;
class RelocInfo;
class Scope;
class ScopeInfo;
class Script;
class SimpleNumberDictionary;
class Smi;
template <typename Config, class Allocator = FreeStoreAllocationPolicy>
class SplayTree;
class String;
class StringStream;
class Struct;
class Symbol;
class Variable;
// Slots are either full-pointer slots or compressed slots depending on whether
// pointer compression is enabled or not.
struct SlotTraits {
#ifdef V8_COMPRESS_POINTERS
using TObjectSlot = CompressedObjectSlot;
using TMaybeObjectSlot = CompressedMaybeObjectSlot;
using THeapObjectSlot = CompressedHeapObjectSlot;
using TOffHeapObjectSlot = OffHeapCompressedObjectSlot;
using TCodeObjectSlot = OffHeapCompressedObjectSlot;
#else
using TObjectSlot = FullObjectSlot;
using TMaybeObjectSlot = FullMaybeObjectSlot;
using THeapObjectSlot = FullHeapObjectSlot;
using TOffHeapObjectSlot = OffHeapFullObjectSlot;
using TCodeObjectSlot = OffHeapFullObjectSlot;
#endif
};
// An ObjectSlot instance describes a kTaggedSize-sized on-heap field ("slot")
// holding an Object value (smi or strong heap object).
using ObjectSlot = SlotTraits::TObjectSlot;
// A MaybeObjectSlot instance describes a kTaggedSize-sized on-heap field
// ("slot") holding MaybeObject (smi or weak heap object or strong heap object).
using MaybeObjectSlot = SlotTraits::TMaybeObjectSlot;
// A HeapObjectSlot instance describes a kTaggedSize-sized field ("slot")
// holding a weak or strong pointer to a heap object (think:
// HeapObjectReference).
using HeapObjectSlot = SlotTraits::THeapObjectSlot;
// An OffHeapObjectSlot instance describes a kTaggedSize-sized field ("slot")
// holding an Object value (smi or strong heap object), whose slot location is
// off-heap.
using OffHeapObjectSlot = SlotTraits::TOffHeapObjectSlot;
// A CodeObjectSlot instance describes a kTaggedSize-sized field ("slot")
// holding a strong pointer to a Code object. The Code object slots might be
// compressed and since code space might be allocated off the main heap
// the load operations require explicit cage base value for code space.
using CodeObjectSlot = SlotTraits::TCodeObjectSlot;
using WeakSlotCallback = bool (*)(FullObjectSlot pointer);
using WeakSlotCallbackWithHeap = bool (*)(Heap* heap, FullObjectSlot pointer);
// -----------------------------------------------------------------------------
// Miscellaneous
// NOTE: SpaceIterator depends on AllocationSpace enumeration values being
// consecutive.
enum AllocationSpace {
RO_SPACE, // Immortal, immovable and immutable objects,
OLD_SPACE, // Old generation regular object space.
CODE_SPACE, // Old generation code object space, marked executable.
MAP_SPACE, // Old generation map object space, non-movable.
LO_SPACE, // Old generation large object space.
CODE_LO_SPACE, // Old generation large code object space.
NEW_LO_SPACE, // Young generation large object space.
NEW_SPACE, // Young generation semispaces for regular objects collected with
// Scavenger.
FIRST_SPACE = RO_SPACE,
LAST_SPACE = NEW_SPACE,
FIRST_MUTABLE_SPACE = OLD_SPACE,
LAST_MUTABLE_SPACE = NEW_SPACE,
FIRST_GROWABLE_PAGED_SPACE = OLD_SPACE,
LAST_GROWABLE_PAGED_SPACE = MAP_SPACE
};
constexpr int kSpaceTagSize = 4;
STATIC_ASSERT(FIRST_SPACE == 0);
enum class AllocationType : uint8_t {
kYoung, // Regular object allocated in NEW_SPACE or NEW_LO_SPACE
kOld, // Regular object allocated in OLD_SPACE or LO_SPACE
kCode, // Code object allocated in CODE_SPACE or CODE_LO_SPACE
kMap, // Map object allocated in MAP_SPACE
kReadOnly, // Object allocated in RO_SPACE
kSharedOld, // Regular object allocated in OLD_SPACE in the shared heap
kSharedMap, // Map object in MAP_SPACE in the shared heap
};
inline size_t hash_value(AllocationType kind) {
return static_cast<uint8_t>(kind);
}
inline std::ostream& operator<<(std::ostream& os, AllocationType kind) {
switch (kind) {
case AllocationType::kYoung:
return os << "Young";
case AllocationType::kOld:
return os << "Old";
case AllocationType::kCode:
return os << "Code";
case AllocationType::kMap:
return os << "Map";
case AllocationType::kReadOnly:
return os << "ReadOnly";
case AllocationType::kSharedOld:
return os << "SharedOld";
case AllocationType::kSharedMap:
return os << "SharedMap";
}
UNREACHABLE();
}
inline constexpr bool IsSharedAllocationType(AllocationType kind) {
return kind == AllocationType::kSharedOld ||
kind == AllocationType::kSharedMap;
}
// TODO(ishell): review and rename kWordAligned to kTaggedAligned.
enum AllocationAlignment { kWordAligned, kDoubleAligned, kDoubleUnaligned };
enum class AccessMode { ATOMIC, NON_ATOMIC };
enum class AllowLargeObjects { kFalse, kTrue };
enum MinimumCapacity {
USE_DEFAULT_MINIMUM_CAPACITY,
USE_CUSTOM_MINIMUM_CAPACITY
};
enum class GarbageCollector { SCAVENGER, MARK_COMPACTOR, MINOR_MARK_COMPACTOR };
enum class CompactionSpaceKind {
kNone,
kCompactionSpaceForScavenge,
kCompactionSpaceForMarkCompact,
kCompactionSpaceForMinorMarkCompact,
};
enum Executability { NOT_EXECUTABLE, EXECUTABLE };
enum class CodeFlushMode {
kFlushBytecode,
kFlushBaselineCode,
kStressFlushCode,
};
bool inline IsBaselineCodeFlushingEnabled(base::EnumSet<CodeFlushMode> mode) {
return mode.contains(CodeFlushMode::kFlushBaselineCode);
}
bool inline IsByteCodeFlushingEnabled(base::EnumSet<CodeFlushMode> mode) {
return mode.contains(CodeFlushMode::kFlushBytecode);
}
bool inline IsStressFlushingEnabled(base::EnumSet<CodeFlushMode> mode) {
return mode.contains(CodeFlushMode::kStressFlushCode);
}
bool inline IsFlushingDisabled(base::EnumSet<CodeFlushMode> mode) {
return mode.empty();
}
// Indicates whether a script should be parsed and compiled in REPL mode.
enum class REPLMode {
kYes,
kNo,
};
inline REPLMode construct_repl_mode(bool is_repl_mode) {
return is_repl_mode ? REPLMode::kYes : REPLMode::kNo;
}
// Flag indicating whether code is built into the VM (one of the natives files).
enum NativesFlag { NOT_NATIVES_CODE, EXTENSION_CODE, INSPECTOR_CODE };
// ParseRestriction is used to restrict the set of valid statements in a
// unit of compilation. Restriction violations cause a syntax error.
enum ParseRestriction : bool {
NO_PARSE_RESTRICTION, // All expressions are allowed.
ONLY_SINGLE_FUNCTION_LITERAL // Only a single FunctionLiteral expression.
};
// State for inline cache call sites. Aliased as IC::State.
enum InlineCacheState {
// No feedback will be collected.
NO_FEEDBACK,
// Has never been executed.
UNINITIALIZED,
// Has been executed and only one receiver type has been seen.
MONOMORPHIC,
// Check failed due to prototype (or map deprecation).
RECOMPUTE_HANDLER,
// Multiple receiver types have been seen.
POLYMORPHIC,
// Many DOM receiver types have been seen for the same accessor.
MEGADOM,
// Many receiver types have been seen.
MEGAMORPHIC,
// A generic handler is installed and no extra typefeedback is recorded.
GENERIC,
};
// Printing support.
inline const char* InlineCacheState2String(InlineCacheState state) {
switch (state) {
case NO_FEEDBACK:
return "NOFEEDBACK";
case UNINITIALIZED:
return "UNINITIALIZED";
case MONOMORPHIC:
return "MONOMORPHIC";
case RECOMPUTE_HANDLER:
return "RECOMPUTE_HANDLER";
case POLYMORPHIC:
return "POLYMORPHIC";
case MEGAMORPHIC:
return "MEGAMORPHIC";
case MEGADOM:
return "MEGADOM";
case GENERIC:
return "GENERIC";
}
UNREACHABLE();
}
enum WhereToStart { kStartAtReceiver, kStartAtPrototype };
enum ResultSentinel { kNotFound = -1, kUnsupported = -2 };
enum ShouldThrow {
kThrowOnError = Internals::kThrowOnError,
kDontThrow = Internals::kDontThrow
};
enum class ThreadKind { kMain, kBackground };
// Union used for customized checking of the IEEE double types
// inlined within v8 runtime, rather than going to the underlying
// platform headers and libraries
union IeeeDoubleLittleEndianArchType {
double d;
struct {
unsigned int man_low : 32;
unsigned int man_high : 20;
unsigned int exp : 11;
unsigned int sign : 1;
} bits;
};