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added Peter Dimov's portable implementation of get_remainder

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joaquintides
2022-06-25 17:35:43 +02:00
parent d49eda63f8
commit 2670bb149d
1 changed files with 13 additions and 11 deletions
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24
include/boost/unordered/detail/fca.hpp
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@ -150,8 +150,7 @@ namespace boost {
#endif
#endif
#if !defined(BOOST_NO_INT64_T) && \
(defined(BOOST_HAS_INT128) || (defined(_MSC_VER) && defined(_M_X64)))
#if !defined(BOOST_NO_INT64_T)
#define BOOST_UNORDERED_FCA_FASTMOD_SUPPORT
#endif
@ -203,20 +202,23 @@ namespace boost {
// modulo) exploiting how compilers transform division
//
#if defined(_MSC_VER)
static inline uint64_t get_remainder(uint64_t fractional, uint32_t d)
{
// use fancy msvc instrinsic when available instead of using `>> 64`
//
#if defined(_MSC_VER) && defined(_WIN64)
// use MSVC instrinsic when available to avoid promotion to 128 bits
return __umulh(fractional, d);
}
#elif defined(BOOST_HAS_INT128)
return static_cast<uint64_t>(((boost::uint128_type)fractional * d) >> 64);
#else
static inline uint64_t get_remainder(uint64_t fractional, uint32_t d)
{
__extension__ typedef unsigned __int128 uint128;
return static_cast<uint64_t>(((uint128)fractional * d) >> 64);
}
// portable implementation in the absence of boost::uint128_type
uint64_t r1 = (fractional & UINT32_MAX) * d;
uint64_t r2 = (fractional >> 32 ) * d;
r2 += r1 >> 32;
return r2 >> 32;
#endif /* defined(_MSC_VER) */
}
static inline uint32_t fast_modulo(uint32_t a, uint64_t M, uint32_t d)
{