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Use MS _byteswap intrinsics

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This commit is contained in:
Peter Dimov
2023-05-30 21:12:25 +03:00
parent b7f7eb4f90
commit 06fef712c9
1 changed files with 42 additions and 0 deletions
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42
include/boost/core/bit.hpp
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@@ -20,6 +20,7 @@
#include <boost/cstdint.hpp>
#include <limits>
#include <cstring>
#include <cstdlib>
#if defined(_MSC_VER)
@@ -819,6 +820,47 @@ BOOST_CXX14_CONSTEXPR inline boost::uint64_t byteswap_impl( boost::uint64_t x )
return __builtin_bswap64( x );
}
#elif defined(_MSC_VER) && defined(BOOST_CORE_HAS_BUILTIN_ISCONSTEVAL)
BOOST_CXX14_CONSTEXPR inline boost::uint32_t byteswap_impl( boost::uint32_t x ) BOOST_NOEXCEPT
{
if( __builtin_is_constant_evaluated() )
{
boost::uint32_t step16 = x << 16 | x >> 16;
return ((step16 << 8) & 0xff00ff00) | ((step16 >> 8) & 0x00ff00ff);
}
else
{
return _byteswap_ulong( x );
}
}
BOOST_CXX14_CONSTEXPR inline boost::uint64_t byteswap_impl( boost::uint64_t x ) BOOST_NOEXCEPT
{
if( __builtin_is_constant_evaluated() )
{
boost::uint64_t step32 = x << 32 | x >> 32;
boost::uint64_t step16 = (step32 & 0x0000FFFF0000FFFFULL) << 16 | (step32 & 0xFFFF0000FFFF0000ULL) >> 16;
return (step16 & 0x00FF00FF00FF00FFULL) << 8 | (step16 & 0xFF00FF00FF00FF00ULL) >> 8;
}
else
{
return _byteswap_uint64( x );
}
}
#elif defined(_MSC_VER)
inline boost::uint32_t byteswap_impl( boost::uint32_t x ) BOOST_NOEXCEPT
{
return _byteswap_ulong( x );
}
inline boost::uint64_t byteswap_impl( boost::uint64_t x ) BOOST_NOEXCEPT
{
return _byteswap_uint64( x );
}
#else
BOOST_CXX14_CONSTEXPR inline boost::uint32_t byteswap_impl( boost::uint32_t x ) BOOST_NOEXCEPT