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Cleanups: Follow Standard order for byteswap in <bit> #3543

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merged 2 commits into from
Mar 7, 2023
Merged

Cleanups: Follow Standard order for byteswap in <bit> #3543

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afb5aec
Coalesce `_Byteswap_meow` and `byteswap`, follow Standard order.
StephanTLavavej Mar 6, 2023
99d3a17
Merge branch 'main' into stl-cleanups-byteswap
StephanTLavavej Mar 7, 2023
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88 changes: 43 additions & 45 deletions stl/inc/bit
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,49 @@ _NODISCARD constexpr _To bit_cast(const _From& _Val) noexcept {
return __builtin_bit_cast(_To, _Val);
}

#if _HAS_CXX23
_NODISCARD constexpr unsigned short _Byteswap_ushort(const unsigned short _Val) noexcept {
if (_STD is_constant_evaluated()) {
return static_cast<unsigned short>((_Val << 8) | (_Val >> 8));
} else {
return _byteswap_ushort(_Val);
}
}

_NODISCARD constexpr unsigned long _Byteswap_ulong(const unsigned long _Val) noexcept {
if (_STD is_constant_evaluated()) {
return (_Val << 24) | ((_Val << 8) & 0x00FF'0000) | ((_Val >> 8) & 0x0000'FF00) | (_Val >> 24);
} else {
return _byteswap_ulong(_Val);
}
}

_NODISCARD constexpr unsigned long long _Byteswap_uint64(const unsigned long long _Val) noexcept {
if (_STD is_constant_evaluated()) {
return (_Val << 56) | ((_Val << 40) & 0x00FF'0000'0000'0000) | ((_Val << 24) & 0x0000'FF00'0000'0000)
| ((_Val << 8) & 0x0000'00FF'0000'0000) | ((_Val >> 8) & 0x0000'0000'FF00'0000)
| ((_Val >> 24) & 0x0000'0000'00FF'0000) | ((_Val >> 40) & 0x0000'0000'0000'FF00) | (_Val >> 56);
} else {
return _byteswap_uint64(_Val);
}
}

_EXPORT_STD template <class _Ty, enable_if_t<is_integral_v<_Ty>, int> = 0>
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_NODISCARD constexpr _Ty byteswap(const _Ty _Val) noexcept {
if constexpr (sizeof(_Ty) == 1) {
return _Val;
} else if constexpr (sizeof(_Ty) == 2) {
return static_cast<_Ty>(_Byteswap_ushort(static_cast<unsigned short>(_Val)));
} else if constexpr (sizeof(_Ty) == 4) {
return static_cast<_Ty>(_Byteswap_ulong(static_cast<unsigned long>(_Val)));
} else if constexpr (sizeof(_Ty) == 8) {
return static_cast<_Ty>(_Byteswap_uint64(static_cast<unsigned long long>(_Val)));
} else {
static_assert(_Always_false<_Ty>, "Unexpected integer size");
}
}
#endif // _HAS_CXX23

_EXPORT_STD template <class _Ty, enable_if_t<_Is_standard_unsigned_integer<_Ty>, int> = 0>
_NODISCARD constexpr int countl_zero(_Ty _Val) noexcept;

Expand Down Expand Up @@ -261,34 +304,6 @@ _NODISCARD int _Checked_arm_arm64_countl_zero(const _Ty _Val) noexcept {
}
#endif // defined(_M_ARM) || defined(_M_ARM64)

#if _HAS_CXX23
_NODISCARD constexpr unsigned short _Byteswap_ushort(const unsigned short _Val) noexcept {
if (_STD is_constant_evaluated()) {
return static_cast<unsigned short>((_Val << 8) | (_Val >> 8));
} else {
return _byteswap_ushort(_Val);
}
}

_NODISCARD constexpr unsigned long _Byteswap_ulong(const unsigned long _Val) noexcept {
if (_STD is_constant_evaluated()) {
return (_Val << 24) | ((_Val << 8) & 0x00FF'0000) | ((_Val >> 8) & 0x0000'FF00) | (_Val >> 24);
} else {
return _byteswap_ulong(_Val);
}
}

_NODISCARD constexpr unsigned long long _Byteswap_uint64(const unsigned long long _Val) noexcept {
if (_STD is_constant_evaluated()) {
return (_Val << 56) | ((_Val << 40) & 0x00FF'0000'0000'0000) | ((_Val << 24) & 0x0000'FF00'0000'0000)
| ((_Val << 8) & 0x0000'00FF'0000'0000) | ((_Val >> 8) & 0x0000'0000'FF00'0000)
| ((_Val >> 24) & 0x0000'0000'00FF'0000) | ((_Val >> 40) & 0x0000'0000'0000'FF00) | (_Val >> 56);
} else {
return _byteswap_uint64(_Val);
}
}
#endif // _HAS_CXX23

_EXPORT_STD template <class _Ty, enable_if_t<_Is_standard_unsigned_integer<_Ty>, int> /* = 0 */>
_NODISCARD constexpr int countl_zero(const _Ty _Val) noexcept {
#if defined(_M_IX86) || (defined(_M_X64) && !defined(_M_ARM64EC))
Expand Down Expand Up @@ -324,23 +339,6 @@ _NODISCARD constexpr int popcount(const _Ty _Val) noexcept {
return _Popcount(_Val);
}

#if _HAS_CXX23
_EXPORT_STD template <class _Ty, enable_if_t<is_integral_v<_Ty>, int> = 0>
_NODISCARD constexpr _Ty byteswap(const _Ty _Val) noexcept {
if constexpr (sizeof(_Ty) == 1) {
return _Val;
} else if constexpr (sizeof(_Ty) == 2) {
return static_cast<_Ty>(_Byteswap_ushort(static_cast<unsigned short>(_Val)));
} else if constexpr (sizeof(_Ty) == 4) {
return static_cast<_Ty>(_Byteswap_ulong(static_cast<unsigned long>(_Val)));
} else if constexpr (sizeof(_Ty) == 8) {
return static_cast<_Ty>(_Byteswap_uint64(static_cast<unsigned long long>(_Val)));
} else {
static_assert(_Always_false<_Ty>, "Unexpected integer size");
}
}
#endif // _HAS_CXX23

_EXPORT_STD enum class endian { little = 0, big = 1, native = little };

_STD_END
Expand Down