src/utils/utils.h

// 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_UTILS_UTILS_H_
#define V8_UTILS_UTILS_H_

#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <cmath>
#include <string>
#include <type_traits>

#include "src/base/bits.h"
#include "src/base/compiler-specific.h"
#include "src/base/logging.h"
#include "src/base/macros.h"
#include "src/base/platform/platform.h"
#include "src/base/v8-fallthrough.h"
#include "src/common/globals.h"
#include "src/utils/allocation.h"
#include "src/utils/vector.h"

#if defined(V8_USE_SIPHASH)
#include "src/third_party/siphash/halfsiphash.h"
#endif

#if defined(V8_OS_AIX)
#include <fenv.h>  // NOLINT(build/c++11)
#endif

namespace v8 {
namespace internal {

// ----------------------------------------------------------------------------
// General helper functions

// Returns the value (0 .. 15) of a hexadecimal character c.
// If c is not a legal hexadecimal character, returns a value < 0.
inline int HexValue(uc32 c) {
  c -= '0';
  if (static_cast<unsigned>(c) <= 9) return c;
  c = (c | 0x20) - ('a' - '0');  // detect 0x11..0x16 and 0x31..0x36.
  if (static_cast<unsigned>(c) <= 5) return c + 10;
  return -1;
}

inline char HexCharOfValue(int value) {
  DCHECK(0 <= value && value <= 16);
  if (value < 10) return value + '0';
  return value - 10 + 'A';
}

template <typename T>
static T ArithmeticShiftRight(T x, int shift) {
  DCHECK_LE(0, shift);
  if (x < 0) {
    // Right shift of signed values is implementation defined. Simulate a
    // true arithmetic right shift by adding leading sign bits.
    using UnsignedT = typename std::make_unsigned<T>::type;
    UnsignedT mask = ~(static_cast<UnsignedT>(~0) >> shift);
    return (static_cast<UnsignedT>(x) >> shift) | mask;
  } else {
    return x >> shift;
  }
}

// Returns the maximum of the two parameters.
template <typename T>
constexpr T Max(T a, T b) {
  return a < b ? b : a;
}

// Returns the minimum of the two parameters.
template <typename T>
constexpr T Min(T a, T b) {
  return a < b ? a : b;
}

// Returns the maximum of the two parameters according to JavaScript semantics.
template <typename T>
T JSMax(T x, T y) {
  if (std::isnan(x)) return x;
  if (std::isnan(y)) return y;
  if (std::signbit(x) < std::signbit(y)) return x;
  return x > y ? x : y;
}

// Returns the maximum of the two parameters according to JavaScript semantics.
template <typename T>
T JSMin(T x, T y) {
  if (std::isnan(x)) return x;
  if (std::isnan(y)) return y;
  if (std::signbit(x) < std::signbit(y)) return y;
  return x > y ? y : x;
}

// Returns the absolute value of its argument.
template <typename T,
          typename = typename std::enable_if<std::is_signed<T>::value>::type>
typename std::make_unsigned<T>::type Abs(T a) {
  // This is a branch-free implementation of the absolute value function and is
  // described in Warren's "Hacker's Delight", chapter 2. It avoids undefined
  // behavior with the arithmetic negation operation on signed values as well.
  using unsignedT = typename std::make_unsigned<T>::type;
  unsignedT x = static_cast<unsignedT>(a);
  unsignedT y = static_cast<unsignedT>(a >> (sizeof(T) * 8 - 1));
  return (x ^ y) - y;
}

inline double Modulo(double x, double y) {
#if defined(V8_OS_WIN)
  // Workaround MS fmod bugs. ECMA-262 says:
  // dividend is finite and divisor is an infinity => result equals dividend
  // dividend is a zero and divisor is nonzero finite => result equals dividend
  if (!(std::isfinite(x) && (!std::isfinite(y) && !std::isnan(y))) &&
      !(x == 0 && (y != 0 && std::isfinite(y)))) {
    double result = fmod(x, y);
    // Workaround MS bug in VS CRT in some OS versions, https://crbug.com/915045
    // fmod(-17, +/-1) should equal -0.0 but now returns 0.0.
    if (x < 0 && result == 0) result = -0.0;
    x = result;
  }
  return x;
#elif defined(V8_OS_AIX)
  // AIX raises an underflow exception for (Number.MIN_VALUE % Number.MAX_VALUE)
  feclearexcept(FE_ALL_EXCEPT);
  double result = std::fmod(x, y);
  int exception = fetestexcept(FE_UNDERFLOW);
  return (exception ? x : result);
#else
  return std::fmod(x, y);
#endif
}

template <typename T>
T SaturateAdd(T a, T b) {
  if (std::is_signed<T>::value) {
    if (a > 0 && b > 0) {
      if (a > std::numeric_limits<T>::max() - b) {
        return std::numeric_limits<T>::max();
      }
    } else if (a < 0 && b < 0) {
      if (a < std::numeric_limits<T>::min() - b) {
        return std::numeric_limits<T>::min();
      }
    }
  } else {
    CHECK(std::is_unsigned<T>::value);
    if (a > std::numeric_limits<T>::max() - b) {
      return std::numeric_limits<T>::max();
    }
  }
  return a + b;
}

template <typename T>
T SaturateSub(T a, T b) {
  if (std::is_signed<T>::value) {
    if (a >= 0 && b < 0) {
      if (a > std::numeric_limits<T>::max() + b) {
        return std::numeric_limits<T>::max();
      }
    } else if (a < 0 && b > 0) {
      if (a < std::numeric_limits<T>::min() + b) {
        return std::numeric_limits<T>::min();
      }
    }
  } else {
    CHECK(std::is_unsigned<T>::value);
    if (a < b) {
      return static_cast<T>(0);
    }
  }
  return a - b;
}

// Helper macros for defining a contiguous sequence of field offset constants.
// Example: (backslashes at the ends of respective lines of this multi-line
// macro definition are omitted here to please the compiler)
//
// #define MAP_FIELDS(V)
//   V(kField1Offset, kTaggedSize)
//   V(kField2Offset, kIntSize)
//   V(kField3Offset, kIntSize)
//   V(kField4Offset, kSystemPointerSize)
//   V(kSize, 0)
//
// DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize, MAP_FIELDS)
//
#define DEFINE_ONE_FIELD_OFFSET(Name, Size) Name, Name##End = Name + (Size)-1,

#define DEFINE_FIELD_OFFSET_CONSTANTS(StartOffset, LIST_MACRO) \
  enum {                                                       \
    LIST_MACRO##_StartOffset = StartOffset - 1,                \
    LIST_MACRO(DEFINE_ONE_FIELD_OFFSET)                        \
  };

// Size of the field defined by DEFINE_FIELD_OFFSET_CONSTANTS
#define FIELD_SIZE(Name) (Name##End + 1 - Name)

// Compare two offsets with static cast
#define STATIC_ASSERT_FIELD_OFFSETS_EQUAL(Offset1, Offset2) \
  STATIC_ASSERT(static_cast<int>(Offset1) == Offset2)
// ----------------------------------------------------------------------------
// Hash function.

static const uint64_t kZeroHashSeed = 0;

// Thomas Wang, Integer Hash Functions.
// http://www.concentric.net/~Ttwang/tech/inthash.htm`
inline uint32_t ComputeUnseededHash(uint32_t key) {
  uint32_t hash = key;
  hash = ~hash + (hash << 15);  // hash = (hash << 15) - hash - 1;
  hash = hash ^ (hash >> 12);
  hash = hash + (hash << 2);
  hash = hash ^ (hash >> 4);
  hash = hash * 2057;  // hash = (hash + (hash << 3)) + (hash << 11);
  hash = hash ^ (hash >> 16);
  return hash & 0x3fffffff;
}

inline uint32_t ComputeLongHash(uint64_t key) {
  uint64_t hash = key;
  hash = ~hash + (hash << 18);  // hash = (hash << 18) - hash - 1;
  hash = hash ^ (hash >> 31);
  hash = hash * 21;  // hash = (hash + (hash << 2)) + (hash << 4);
  hash = hash ^ (hash >> 11);
  hash = hash + (hash << 6);
  hash = hash ^ (hash >> 22);
  return static_cast<uint32_t>(hash & 0x3fffffff);
}

inline uint32_t ComputeSeededHash(uint32_t key, uint64_t seed) {
#ifdef V8_USE_SIPHASH
  return halfsiphash(key, seed);
#else
  return ComputeLongHash(static_cast<uint64_t>(key) ^ seed);
#endif  // V8_USE_SIPHASH
}

inline uint32_t ComputePointerHash(void* ptr) {
  return ComputeUnseededHash(
      static_cast<uint32_t>(reinterpret_cast<intptr_t>(ptr)));
}

inline uint32_t ComputeAddressHash(Address address) {
  return ComputeUnseededHash(static_cast<uint32_t>(address & 0xFFFFFFFFul));
}

// ----------------------------------------------------------------------------
// Miscellaneous

// Memory offset for lower and higher bits in a 64 bit integer.
#if defined(V8_TARGET_LITTLE_ENDIAN)
static const int kInt64LowerHalfMemoryOffset = 0;
static const int kInt64UpperHalfMemoryOffset = 4;
#elif defined(V8_TARGET_BIG_ENDIAN)
static const int kInt64LowerHalfMemoryOffset = 4;
static const int kInt64UpperHalfMemoryOffset = 0;
#endif  // V8_TARGET_LITTLE_ENDIAN

// A pointer that can only be set once and doesn't allow NULL values.
template <typename T>
class SetOncePointer {
 public:
  SetOncePointer() = default;

  bool is_set() const { return pointer_ != nullptr; }

  T* get() const {
    DCHECK_NOT_NULL(pointer_);
    return pointer_;
  }

  void set(T* value) {
    DCHECK(pointer_ == nullptr && value != nullptr);
    pointer_ = value;
  }

  SetOncePointer& operator=(T* value) {
    set(value);
    return *this;
  }

  bool operator==(std::nullptr_t) const { return pointer_ == nullptr; }
  bool operator!=(std::nullptr_t) const { return pointer_ != nullptr; }

 private:
  T* pointer_ = nullptr;
};

// Compare 8bit/16bit chars to 8bit/16bit chars.
template <typename lchar, typename rchar>
inline int CompareCharsUnsigned(const lchar* lhs, const rchar* rhs,
                                size_t chars) {
  const lchar* limit = lhs + chars;
  if (sizeof(*lhs) == sizeof(char) && sizeof(*rhs) == sizeof(char)) {
    // memcmp compares byte-by-byte, yielding wrong results for two-byte
    // strings on little-endian systems.
    return memcmp(lhs, rhs, chars);
  }
  while (lhs < limit) {
    int r = static_cast<int>(*lhs) - static_cast<int>(*rhs);
    if (r != 0) return r;
    ++lhs;
    ++rhs;
  }
  return 0;
}

template <typename lchar, typename rchar>
inline int CompareChars(const lchar* lhs, const rchar* rhs, size_t chars) {
  DCHECK_LE(sizeof(lchar), 2);
  DCHECK_LE(sizeof(rchar), 2);
  if (sizeof(lchar) == 1) {
    if (sizeof(rchar) == 1) {
      return CompareCharsUnsigned(reinterpret_cast<const uint8_t*>(lhs),
                                  reinterpret_cast<const uint8_t*>(rhs), chars);
    } else {
      return CompareCharsUnsigned(reinterpret_cast<const uint8_t*>(lhs),
                                  reinterpret_cast<const uint16_t*>(rhs),
                                  chars);
    }
  } else {
    if (sizeof(rchar) == 1) {
      return CompareCharsUnsigned(reinterpret_cast<const uint16_t*>(lhs),
                                  reinterpret_cast<const uint8_t*>(rhs), chars);
    } else {
      return CompareCharsUnsigned(reinterpret_cast<const uint16_t*>(lhs),
                                  reinterpret_cast<const uint16_t*>(rhs),
                                  chars);
    }
  }
}

// Calculate 10^exponent.
inline int TenToThe(int exponent) {
  DCHECK_LE(exponent, 9);
  DCHECK_GE(exponent, 1);
  int answer = 10;
  for (int i = 1; i < exponent; i++) answer *= 10;
  return answer;
}

// Helper class for building result strings in a character buffer. The
// purpose of the class is to use safe operations that checks the
// buffer bounds on all operations in debug mode.
// This simple base class does not allow formatted output.
class SimpleStringBuilder {
 public:
  // Create a string builder with a buffer of the given size. The
  // buffer is allocated through NewArray<char> and must be
  // deallocated by the caller of Finalize().
  explicit SimpleStringBuilder(int size);

  SimpleStringBuilder(char* buffer, int size)
      : buffer_(buffer, size), position_(0) {}

  ~SimpleStringBuilder() {
    if (!is_finalized()) Finalize();
  }

  int size() const { return buffer_.length(); }

  // Get the current position in the builder.
  int position() const {
    DCHECK(!is_finalized());
    return position_;
  }

  // Reset the position.
  void Reset() { position_ = 0; }

  // Add a single character to the builder. It is not allowed to add
  // 0-characters; use the Finalize() method to terminate the string
  // instead.
  void AddCharacter(char c) {
    DCHECK_NE(c, '\0');
    DCHECK(!is_finalized() && position_ < buffer_.length());
    buffer_[position_++] = c;
  }

  // Add an entire string to the builder. Uses strlen() internally to
  // compute the length of the input string.
  void AddString(const char* s);

  // Add the first 'n' characters of the given 0-terminated string 's' to the
  // builder. The input string must have enough characters.
  void AddSubstring(const char* s, int n);

  // Add character padding to the builder. If count is non-positive,
  // nothing is added to the builder.
  void AddPadding(char c, int count);

  // Add the decimal representation of the value.
  void AddDecimalInteger(int value);

  // Finalize the string by 0-terminating it and returning the buffer.
  char* Finalize();

 protected:
  Vector<char> buffer_;
  int position_;

  bool is_finalized() const { return position_ < 0; }

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(SimpleStringBuilder);
};

// Bit field extraction.
inline uint32_t unsigned_bitextract_32(int msb, int lsb, uint32_t x) {
  return (x >> lsb) & ((1 << (1 + msb - lsb)) - 1);
}

inline uint64_t unsigned_bitextract_64(int msb, int lsb, uint64_t x) {
  return (x >> lsb) & ((static_cast<uint64_t>(1) << (1 + msb - lsb)) - 1);
}

inline int32_t signed_bitextract_32(int msb, int lsb, uint32_t x) {
  return static_cast<int32_t>(x << (31 - msb)) >> (lsb + 31 - msb);
}

// Check number width.
inline bool is_intn(int64_t x, unsigned n) {
  DCHECK((0 < n) && (n < 64));
  int64_t limit = static_cast<int64_t>(1) << (n - 1);
  return (-limit <= x) && (x < limit);
}

inline bool is_uintn(int64_t x, unsigned n) {
  DCHECK((0 < n) && (n < (sizeof(x) * kBitsPerByte)));
  return !(x >> n);
}

template <class T>
inline T truncate_to_intn(T x, unsigned n) {
  DCHECK((0 < n) && (n < (sizeof(x) * kBitsPerByte)));
  return (x & ((static_cast<T>(1) << n) - 1));
}

// clang-format off
#define INT_1_TO_63_LIST(V)                                   \
  V(1) V(2) V(3) V(4) V(5) V(6) V(7) V(8) V(9) V(10)          \
  V(11) V(12) V(13) V(14) V(15) V(16) V(17) V(18) V(19) V(20) \
  V(21) V(22) V(23) V(24) V(25) V(26) V(27) V(28) V(29) V(30) \
  V(31) V(32) V(33) V(34) V(35) V(36) V(37) V(38) V(39) V(40) \
  V(41) V(42) V(43) V(44) V(45) V(46) V(47) V(48) V(49) V(50) \
  V(51) V(52) V(53) V(54) V(55) V(56) V(57) V(58) V(59) V(60) \
  V(61) V(62) V(63)
// clang-format on

#define DECLARE_IS_INT_N(N) \
  inline bool is_int##N(int64_t x) { return is_intn(x, N); }
#define DECLARE_IS_UINT_N(N)    \
  template <class T>            \
  inline bool is_uint##N(T x) { \
    return is_uintn(x, N);      \
  }
#define DECLARE_TRUNCATE_TO_INT_N(N) \
  template <class T>                 \
  inline T truncate_to_int##N(T x) { \
    return truncate_to_intn(x, N);   \
  }
INT_1_TO_63_LIST(DECLARE_IS_INT_N)
INT_1_TO_63_LIST(DECLARE_IS_UINT_N)
INT_1_TO_63_LIST(DECLARE_TRUNCATE_TO_INT_N)
#undef DECLARE_IS_INT_N
#undef DECLARE_IS_UINT_N
#undef DECLARE_TRUNCATE_TO_INT_N

// clang-format off
#define INT_0_TO_127_LIST(V)                                          \
V(0)   V(1)   V(2)   V(3)   V(4)   V(5)   V(6)   V(7)   V(8)   V(9)   \
V(10)  V(11)  V(12)  V(13)  V(14)  V(15)  V(16)  V(17)  V(18)  V(19)  \
V(20)  V(21)  V(22)  V(23)  V(24)  V(25)  V(26)  V(27)  V(28)  V(29)  \
V(30)  V(31)  V(32)  V(33)  V(34)  V(35)  V(36)  V(37)  V(38)  V(39)  \
V(40)  V(41)  V(42)  V(43)  V(44)  V(45)  V(46)  V(47)  V(48)  V(49)  \
V(50)  V(51)  V(52)  V(53)  V(54)  V(55)  V(56)  V(57)  V(58)  V(59)  \
V(60)  V(61)  V(62)  V(63)  V(64)  V(65)  V(66)  V(67)  V(68)  V(69)  \
V(70)  V(71)  V(72)  V(73)  V(74)  V(75)  V(76)  V(77)  V(78)  V(79)  \
V(80)  V(81)  V(82)  V(83)  V(84)  V(85)  V(86)  V(87)  V(88)  V(89)  \
V(90)  V(91)  V(92)  V(93)  V(94)  V(95)  V(96)  V(97)  V(98)  V(99)  \
V(100) V(101) V(102) V(103) V(104) V(105) V(106) V(107) V(108) V(109) \
V(110) V(111) V(112) V(113) V(114) V(115) V(116) V(117) V(118) V(119) \
V(120) V(121) V(122) V(123) V(124) V(125) V(126) V(127)
// clang-format on

class FeedbackSlot {
 public:
  FeedbackSlot() : id_(kInvalidSlot) {}
  explicit FeedbackSlot(int id) : id_(id) {}

  int ToInt() const { return id_; }

  static FeedbackSlot Invalid() { return FeedbackSlot(); }
  bool IsInvalid() const { return id_ == kInvalidSlot; }

  bool operator==(FeedbackSlot that) const { return this->id_ == that.id_; }
  bool operator!=(FeedbackSlot that) const { return !(*this == that); }

  friend size_t hash_value(FeedbackSlot slot) { return slot.ToInt(); }
  V8_EXPORT_PRIVATE friend std::ostream& operator<<(std::ostream& os,
                                                    FeedbackSlot);

  FeedbackSlot WithOffset(int offset) const {
    return FeedbackSlot(id_ + offset);
  }

 private:
  static const int kInvalidSlot = -1;

  int id_;
};

V8_EXPORT_PRIVATE std::ostream& operator<<(std::ostream& os, FeedbackSlot);

class BailoutId {
 public:
  explicit BailoutId(int id) : id_(id) {}
  int ToInt() const { return id_; }

  static BailoutId None() { return BailoutId(kNoneId); }

  // Special bailout id support for deopting into the {JSConstructStub} stub.
  // The following hard-coded deoptimization points are supported by the stub:
  //  - {ConstructStubCreate} maps to {construct_stub_create_deopt_pc_offset}.
  //  - {ConstructStubInvoke} maps to {construct_stub_invoke_deopt_pc_offset}.
  static BailoutId ConstructStubCreate() { return BailoutId(1); }
  static BailoutId ConstructStubInvoke() { return BailoutId(2); }
  bool IsValidForConstructStub() const {
    return id_ == ConstructStubCreate().ToInt() ||
           id_ == ConstructStubInvoke().ToInt();
  }

  bool IsNone() const { return id_ == kNoneId; }
  bool operator==(const BailoutId& other) const { return id_ == other.id_; }
  bool operator!=(const BailoutId& other) const { return id_ != other.id_; }
  friend size_t hash_value(BailoutId);
  V8_EXPORT_PRIVATE friend std::ostream& operator<<(std::ostream&, BailoutId);

 private:
  friend class Builtins;

  static const int kNoneId = -1;

  // Using 0 could disguise errors.
  // Builtin continuations bailout ids start here. If you need to add a
  // non-builtin BailoutId, add it before this id so that this Id has the
  // highest number.
  static const int kFirstBuiltinContinuationId = 1;

  int id_;
};

// ----------------------------------------------------------------------------
// I/O support.

// Our version of printf().
V8_EXPORT_PRIVATE void PRINTF_FORMAT(1, 2) PrintF(const char* format, ...);
V8_EXPORT_PRIVATE void PRINTF_FORMAT(2, 3)
    PrintF(FILE* out, const char* format, ...);

// Prepends the current process ID to the output.
void PRINTF_FORMAT(1, 2) PrintPID(const char* format, ...);

// Prepends the current process ID and given isolate pointer to the output.
void PRINTF_FORMAT(2, 3) PrintIsolate(void* isolate, const char* format, ...);

// Safe formatting print. Ensures that str is always null-terminated.
// Returns the number of chars written, or -1 if output was truncated.
V8_EXPORT_PRIVATE int PRINTF_FORMAT(2, 3)
    SNPrintF(Vector<char> str, const char* format, ...);
V8_EXPORT_PRIVATE int PRINTF_FORMAT(2, 0)
    VSNPrintF(Vector<char> str, const char* format, va_list args);

void StrNCpy(Vector<char> dest, const char* src, size_t n);

// Read a line of characters after printing the prompt to stdout. The resulting
// char* needs to be disposed off with DeleteArray by the caller.
char* ReadLine(const char* prompt);

// Write size chars from str to the file given by filename.
// The file is overwritten. Returns the number of chars written.
int WriteChars(const char* filename, const char* str, int size,
               bool verbose = true);

// Write size bytes to the file given by filename.
// The file is overwritten. Returns the number of bytes written.
int WriteBytes(const char* filename, const byte* bytes, int size,
               bool verbose = true);

// Simple support to read a file into std::string.
// On return, *exits tells whether the file existed.
V8_EXPORT_PRIVATE std::string ReadFile(const char* filename, bool* exists,
                                       bool verbose = true);
V8_EXPORT_PRIVATE std::string ReadFile(FILE* file, bool* exists,
                                       bool verbose = true);

class StringBuilder : public SimpleStringBuilder {
 public:
  explicit StringBuilder(int size) : SimpleStringBuilder(size) {}
  StringBuilder(char* buffer, int size) : SimpleStringBuilder(buffer, size) {}

  // Add formatted contents to the builder just like printf().
  void PRINTF_FORMAT(2, 3) AddFormatted(const char* format, ...);

  // Add formatted contents like printf based on a va_list.
  void PRINTF_FORMAT(2, 0) AddFormattedList(const char* format, va_list list);

 private:
  DISALLOW_IMPLICIT_CONSTRUCTORS(StringBuilder);
};

bool DoubleToBoolean(double d);

template <typename Char>
bool TryAddIndexChar(uint32_t* index, Char c);

enum ToIndexMode { kToArrayIndex, kToIntegerIndex };

// {index_t} is meant to be {uint32_t} or {size_t}.
template <typename Stream, typename index_t,
          enum ToIndexMode mode = kToArrayIndex>
bool StringToIndex(Stream* stream, index_t* index);

// Returns the current stack top. Works correctly with ASAN and SafeStack.
// GetCurrentStackPosition() should not be inlined, because it works on stack
// frames if it were inlined into a function with a huge stack frame it would
// return an address significantly above the actual current stack position.
V8_EXPORT_PRIVATE V8_NOINLINE uintptr_t GetCurrentStackPosition();

static inline uint16_t ByteReverse16(uint16_t value) {
#if V8_HAS_BUILTIN_BSWAP16
  return __builtin_bswap16(value);
#else
  return value << 8 | (value >> 8 & 0x00FF);
#endif
}

static inline uint32_t ByteReverse32(uint32_t value) {
#if V8_HAS_BUILTIN_BSWAP32
  return __builtin_bswap32(value);
#else
  return value << 24 | ((value << 8) & 0x00FF0000) |
         ((value >> 8) & 0x0000FF00) | ((value >> 24) & 0x00000FF);
#endif
}

static inline uint64_t ByteReverse64(uint64_t value) {
#if V8_HAS_BUILTIN_BSWAP64
  return __builtin_bswap64(value);
#else
  size_t bits_of_v = sizeof(value) * kBitsPerByte;
  return value << (bits_of_v - 8) |
         ((value << (bits_of_v - 24)) & 0x00FF000000000000) |
         ((value << (bits_of_v - 40)) & 0x0000FF0000000000) |
         ((value << (bits_of_v - 56)) & 0x000000FF00000000) |
         ((value >> (bits_of_v - 56)) & 0x00000000FF000000) |
         ((value >> (bits_of_v - 40)) & 0x0000000000FF0000) |
         ((value >> (bits_of_v - 24)) & 0x000000000000FF00) |
         ((value >> (bits_of_v - 8)) & 0x00000000000000FF);
#endif
}

template <typename V>
static inline V ByteReverse(V value) {
  size_t size_of_v = sizeof(value);
  switch (size_of_v) {
    case 1:
      return value;
    case 2:
      return static_cast<V>(ByteReverse16(static_cast<uint16_t>(value)));
    case 4:
      return static_cast<V>(ByteReverse32(static_cast<uint32_t>(value)));
    case 8:
      return static_cast<V>(ByteReverse64(static_cast<uint64_t>(value)));
    default:
      UNREACHABLE();
  }
}

V8_EXPORT_PRIVATE bool PassesFilter(Vector<const char> name,
                                    Vector<const char> filter);

// Zap the specified area with a specific byte pattern. This currently defaults
// to int3 on x64 and ia32. On other architectures this will produce unspecified
// instruction sequences.
// TODO(jgruber): Better support for other architectures.
V8_INLINE void ZapCode(Address addr, size_t size_in_bytes) {
  static constexpr int kZapByte = 0xCC;
  std::memset(reinterpret_cast<void*>(addr), kZapByte, size_in_bytes);
}

}  // namespace internal
}  // namespace v8

#endif  // V8_UTILS_UTILS_H_