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Use __builtin_ctz

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This commit is contained in:
Peter Dimov
2020-12-29 01:56:34 +02:00
parent c838ebc003
commit 8bd2239b0b
1 changed files with 42 additions and 0 deletions
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42
include/boost/core/bit.hpp
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@ -190,6 +190,46 @@ BOOST_CONSTEXPR int countl_one( T x ) BOOST_NOEXCEPT
// countr
#if defined(__GNUC__) || defined(__clang__)
namespace detail
{
BOOST_CONSTEXPR inline int countr_impl( unsigned char x ) BOOST_NOEXCEPT
{
return x? __builtin_ctz( x ): std::numeric_limits<unsigned char>::digits;
}
BOOST_CONSTEXPR inline int countr_impl( unsigned short x ) BOOST_NOEXCEPT
{
return x? __builtin_ctz( x ): std::numeric_limits<unsigned short>::digits;
}
BOOST_CONSTEXPR inline int countr_impl( unsigned int x ) BOOST_NOEXCEPT
{
return x? __builtin_ctz( x ): std::numeric_limits<unsigned int>::digits;
}
BOOST_CONSTEXPR inline int countr_impl( unsigned long x ) BOOST_NOEXCEPT
{
return x? __builtin_ctzl( x ): std::numeric_limits<unsigned long>::digits;
}
BOOST_CONSTEXPR inline int countr_impl( unsigned long long x ) BOOST_NOEXCEPT
{
return x? __builtin_ctzll( x ): std::numeric_limits<unsigned long long>::digits;
}
} // namespace detail
template<class T>
BOOST_CONSTEXPR int countr_zero( T x ) BOOST_NOEXCEPT
{
return boost::core::detail::countr_impl( x );
}
#else // defined(__GNUC__) || defined(__clang__)
namespace detail
{
@ -241,6 +281,8 @@ int countr_zero( T x ) BOOST_NOEXCEPT
}
}
#endif // defined(__GNUC__) || defined(__clang__)
template<class T>
BOOST_CONSTEXPR int countr_one( T x ) BOOST_NOEXCEPT
{