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Prefer xor to sub for counting bits #4693

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AZero13 (AZero13) wants to merge 1 commit into from
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Prefer xor to sub for counting bits #4693

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2 changes: 1 addition & 1 deletion stl/inc/__msvc_bit_utils.hpp
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Expand Up @@ -107,7 +107,7 @@ _NODISCARD int _Countl_zero_bsr(const _Ty _Val) noexcept {
#ifdef _M_IX86
const unsigned int _High = _Val >> 32;
if (_BitScanReverse(&_Result, _High)) {
return static_cast<int>(31 - _Result);
return static_cast<int>(31 ^ _Result);
}

const auto _Low = static_cast<unsigned int>(_Val);
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2 changes: 1 addition & 1 deletion stl/inc/charconv
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Expand Up @@ -746,7 +746,7 @@ _NODISCARD inline bool _Multiply_by_power_of_ten(_Big_integer_flt& _Xval, const
// Computes the number of zeroes higher than the most significant set bit in _Ux
_NODISCARD inline uint32_t _Count_sequential_high_zeroes(const uint32_t _Ux) noexcept {
unsigned long _Index; // Intentionally uninitialized for better codegen
return _BitScanReverse(&_Index, _Ux) ? 31 - _Index : 32;
return _BitScanReverse(&_Index, _Ux) ? 31 ^ _Index : 32;
}

// This high-precision integer division implementation was translated from the implementation of
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