bitscan.hpp
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///////////////////////////////////////////////////////////////
// Copyright 2013 John Maddock. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
//
// Comparison operators for cpp_int_backend:
//
#ifndef BOOST_MP_DETAIL_BITSCAN_HPP
#define BOOST_MP_DETAIL_BITSCAN_HPP
#include <cstdint>
#include <climits>
#include <type_traits>
#include <boost/multiprecision/detail/endian.hpp>
#include <boost/multiprecision/detail/standalone_config.hpp>
#if (defined(BOOST_MSVC) || (defined(__clang__) && defined(__c2__)) || (defined(BOOST_INTEL) && defined(_MSC_VER))) && (defined(_M_IX86) || defined(_M_X64))
#include <intrin.h>
#endif
namespace boost { namespace multiprecision { namespace detail {
template <class Unsigned>
inline BOOST_MP_CXX14_CONSTEXPR std::size_t find_lsb_default(Unsigned mask)
{
std::size_t result = 0;
while (!(mask & 1u))
{
mask >>= 1;
++result;
}
return result;
}
template <class Unsigned>
inline BOOST_MP_CXX14_CONSTEXPR std::size_t find_msb_default(Unsigned mask)
{
std::size_t index = 0;
while (mask)
{
++index;
mask >>= 1;
}
return --index;
}
template <class Unsigned>
inline BOOST_MP_CXX14_CONSTEXPR std::size_t find_lsb(Unsigned mask, const std::integral_constant<int, 0>&)
{
return find_lsb_default(mask);
}
template <class Unsigned>
inline BOOST_MP_CXX14_CONSTEXPR std::size_t find_msb(Unsigned mask, const std::integral_constant<int, 0>&)
{
return find_msb_default(mask);
}
#if (defined(BOOST_MSVC) || (defined(__clang__) && defined(__c2__)) || (defined(BOOST_INTEL) && defined(_MSC_VER))) && (defined(_M_IX86) || defined(_M_X64))
#pragma intrinsic(_BitScanForward, _BitScanReverse)
BOOST_FORCEINLINE std::size_t find_lsb(unsigned long mask, const std::integral_constant<int, 1>&)
{
unsigned long result;
_BitScanForward(&result, mask);
return result;
}
BOOST_FORCEINLINE std::size_t find_msb(unsigned long mask, const std::integral_constant<int, 1>&)
{
unsigned long result;
_BitScanReverse(&result, mask);
return result;
}
#ifdef _M_X64
#pragma intrinsic(_BitScanForward64, _BitScanReverse64)
BOOST_FORCEINLINE std::size_t find_lsb(unsigned __int64 mask, const std::integral_constant<int, 2>&)
{
unsigned long result;
_BitScanForward64(&result, mask);
return result;
}
template <class Unsigned>
BOOST_FORCEINLINE std::size_t find_msb(Unsigned mask, const std::integral_constant<int, 2>&)
{
unsigned long result;
_BitScanReverse64(&result, mask);
return result;
}
#endif
template <class Unsigned>
BOOST_FORCEINLINE BOOST_MP_CXX14_CONSTEXPR std::size_t find_lsb(Unsigned mask)
{
using ui_type = typename boost::multiprecision::detail::make_unsigned<Unsigned>::type;
using tag_type = typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned long),
std::integral_constant<int, 1>,
#ifdef _M_X64
typename std::conditional<
sizeof(Unsigned) <= sizeof(__int64),
std::integral_constant<int, 2>,
std::integral_constant<int, 0> >::type
#else
std::integral_constant<int, 0>
#endif
>::type;
#ifndef BOOST_MP_NO_CONSTEXPR_DETECTION
if (BOOST_MP_IS_CONST_EVALUATED(mask))
{
return find_lsb_default(mask);
}
else
#endif
return find_lsb(static_cast<ui_type>(mask), tag_type());
}
template <class Unsigned>
BOOST_FORCEINLINE BOOST_MP_CXX14_CONSTEXPR std::size_t find_msb(Unsigned mask)
{
using ui_type = typename boost::multiprecision::detail::make_unsigned<Unsigned>::type;
using tag_type = typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned long),
std::integral_constant<int, 1>,
#ifdef _M_X64
typename std::conditional<
sizeof(Unsigned) <= sizeof(__int64),
std::integral_constant<int, 2>,
std::integral_constant<int, 0> >::type
#else
std::integral_constant<int, 0>
#endif
>::type;
#ifndef BOOST_MP_NO_CONSTEXPR_DETECTION
if (BOOST_MP_IS_CONST_EVALUATED(mask))
{
return find_msb_default(mask);
}
else
#endif
return find_msb(static_cast<ui_type>(mask), tag_type());
}
#elif defined(BOOST_GCC) || defined(__clang__) || (defined(BOOST_INTEL) && defined(__GNUC__))
BOOST_FORCEINLINE std::size_t find_lsb(std::size_t mask, std::integral_constant<int, 1> const&)
{
return static_cast<std::size_t>(__builtin_ctz(static_cast<unsigned int>(mask)));
}
BOOST_FORCEINLINE std::size_t find_lsb(unsigned long mask, std::integral_constant<int, 2> const&)
{
return static_cast<std::size_t>(__builtin_ctzl(static_cast<unsigned long>(mask)));
}
BOOST_FORCEINLINE std::size_t find_lsb(unsigned long long mask, std::integral_constant<int, 3> const&)
{
return static_cast<std::size_t>(__builtin_ctzll(static_cast<unsigned long long>(mask)));
}
BOOST_FORCEINLINE std::size_t find_msb(std::size_t mask, std::integral_constant<int, 1> const&)
{
return static_cast<std::size_t>(static_cast<std::size_t>(sizeof(unsigned) * static_cast<std::size_t>(CHAR_BIT) - 1u) - static_cast<std::size_t>(__builtin_clz(static_cast<unsigned int>(mask))));
}
BOOST_FORCEINLINE std::size_t find_msb(unsigned long mask, std::integral_constant<int, 2> const&)
{
return static_cast<std::size_t>(static_cast<std::size_t>(sizeof(unsigned long) * static_cast<std::size_t>(CHAR_BIT) - 1u) - static_cast<std::size_t>(__builtin_clzl(static_cast<unsigned long>(mask))));
}
BOOST_FORCEINLINE std::size_t find_msb(unsigned long long mask, std::integral_constant<int, 3> const&)
{
return static_cast<std::size_t>(static_cast<std::size_t>(sizeof(unsigned long long) * static_cast<std::size_t>(CHAR_BIT) - 1u) - static_cast<std::size_t>(__builtin_clzll(static_cast<unsigned long long>(mask))));
}
#ifdef BOOST_HAS_INT128
BOOST_FORCEINLINE std::size_t find_msb(uint128_type mask, std::integral_constant<int, 0> const&)
{
union
{
uint128_type v;
std::uint64_t sv[2];
} val;
val.v = mask;
#if BOOST_MP_ENDIAN_LITTLE_BYTE
if (val.sv[1])
return find_msb(val.sv[1], std::integral_constant<int, 3>()) + 64;
return find_msb(val.sv[0], std::integral_constant<int, 3>());
#else
if (val.sv[0])
return find_msb(val.sv[0], std::integral_constant<int, 3>()) + 64;
return find_msb(val.sv[1], std::integral_constant<int, 3>());
#endif
}
BOOST_FORCEINLINE std::size_t find_lsb(uint128_type mask, std::integral_constant<int, 0> const&)
{
union
{
uint128_type v;
std::uint64_t sv[2];
} val;
val.v = mask;
#if BOOST_MP_ENDIAN_LITTLE_BYTE
if (val.sv[0] == 0)
return find_lsb(val.sv[1], std::integral_constant<int, 3>()) + 64;
return find_lsb(val.sv[0], std::integral_constant<int, 3>());
#else
if (val.sv[1] == 0)
return find_lsb(val.sv[0], std::integral_constant<int, 3>()) + 64;
return find_lsb(val.sv[1], std::integral_constant<int, 3>());
#endif
}
#endif
template <class Unsigned>
BOOST_FORCEINLINE BOOST_MP_CXX14_CONSTEXPR std::size_t find_lsb(Unsigned mask)
{
using ui_type = typename boost::multiprecision::detail::make_unsigned<Unsigned>::type;
using tag_type = typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned),
std::integral_constant<int, 1>,
typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned long),
std::integral_constant<int, 2>,
typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned long long),
std::integral_constant<int, 3>,
std::integral_constant<int, 0> >::type>::type>::type;
#ifndef BOOST_MP_NO_CONSTEXPR_DETECTION
if (BOOST_MP_IS_CONST_EVALUATED(mask))
{
return find_lsb_default(mask);
}
else
#endif
return find_lsb(static_cast<ui_type>(mask), tag_type());
}
template <class Unsigned>
BOOST_FORCEINLINE BOOST_MP_CXX14_CONSTEXPR std::size_t find_msb(Unsigned mask)
{
using ui_type = typename boost::multiprecision::detail::make_unsigned<Unsigned>::type;
using tag_type = typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned),
std::integral_constant<int, 1>,
typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned long),
std::integral_constant<int, 2>,
typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned long long),
std::integral_constant<int, 3>,
std::integral_constant<int, 0> >::type>::type>::type;
#ifndef BOOST_MP_NO_CONSTEXPR_DETECTION
if (BOOST_MP_IS_CONST_EVALUATED(mask))
{
return find_msb_default(mask);
}
else
#endif
return find_msb(static_cast<ui_type>(mask), tag_type());
}
#elif defined(BOOST_INTEL)
BOOST_FORCEINLINE std::size_t find_lsb(std::size_t mask, std::integral_constant<int, 1> const&)
{
return _bit_scan_forward(mask);
}
BOOST_FORCEINLINE std::size_t find_msb(std::size_t mask, std::integral_constant<int, 1> const&)
{
return _bit_scan_reverse(mask);
}
template <class Unsigned>
BOOST_FORCEINLINE BOOST_MP_CXX14_CONSTEXPR std::size_t find_lsb(Unsigned mask)
{
using ui_type = typename boost::multiprecision::detail::make_unsigned<Unsigned>::type;
using tag_type = typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned),
std::integral_constant<int, 1>,
std::integral_constant<int, 0> >::type;
#ifndef BOOST_MP_NO_CONSTEXPR_DETECTION
if (BOOST_MP_IS_CONST_EVALUATED(mask))
{
return find_lsb_default(mask);
}
else
#endif
return find_lsb(static_cast<ui_type>(mask), tag_type());
}
template <class Unsigned>
BOOST_FORCEINLINE BOOST_MP_CXX14_CONSTEXPR std::size_t find_msb(Unsigned mask)
{
using ui_type = typename boost::multiprecision::detail::make_unsigned<Unsigned>::type;
using tag_type = typename std::conditional<
sizeof(Unsigned) <= sizeof(unsigned),
std::integral_constant<int, 1>,
std::integral_constant<int, 0> >::type;
#ifndef BOOST_MP_NO_CONSTEXPR_DETECTION
if (BOOST_MP_IS_CONST_EVALUATED(mask))
{
return find_msb_default(mask);
}
else
#endif
return find_msb(static_cast<ui_type>(mask), tag_type());
}
#else
template <class Unsigned>
BOOST_FORCEINLINE BOOST_MP_CXX14_CONSTEXPR std::size_t find_lsb(Unsigned mask)
{
return find_lsb(mask, std::integral_constant<int, 0>());
}
template <class Unsigned>
BOOST_FORCEINLINE BOOST_MP_CXX14_CONSTEXPR std::size_t find_msb(Unsigned mask)
{
return find_msb(mask, std::integral_constant<int, 0>());
}
#endif
}}} // namespace boost::multiprecision::detail
#endif