[thirdparty/gcc.git] / libstdc++-v3 / include / std / bit

// <bit> -*- C++ -*-

// Copyright (C) 2018-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file include/bit
 *  This is a Standard C++ Library header.
 */

#ifndef _GLIBCXX_BIT
#define _GLIBCXX_BIT 1

#pragma GCC system_header

#if __cplusplus >= 201402L

#include <type_traits>

#if _GLIBCXX_HOSTED
# include <ext/numeric_traits.h>
#else
# include <limits>
/// @cond undocumented
namespace __gnu_cxx
{
  template<typename _Tp>
    struct __int_traits
    {
      static constexpr int __digits = std::numeric_limits<_Tp>::digits;
      static constexpr _Tp __max = std::numeric_limits<_Tp>::max();
    };
}
/// @endcond
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  /**
   * @defgroup bit_manip Bit manipulation
   * @ingroup numerics
   *
   * Utilities for examining and manipulating individual bits.
   *
   * @{
   */

#if __cplusplus > 201703l && __has_builtin(__builtin_bit_cast)
#define __cpp_lib_bit_cast 201806L

  /// Create a value of type `To` from the bits of `from`.
  template<typename _To, typename _From>
    [[nodiscard]]
    constexpr _To
    bit_cast(const _From& __from) noexcept
    {
      return __builtin_bit_cast(_To, __from);
    }
#endif

  /// @cond undoc

  template<typename _Tp>
    constexpr _Tp
    __rotl(_Tp __x, int __s) noexcept
    {
      constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
      if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0)
	{
	  // Variant for power of two _Nd which the compiler can
	  // easily pattern match.
	  constexpr unsigned __uNd = _Nd;
	  const unsigned __r = __s;
	  return (__x << (__r % __uNd)) | (__x >> ((-__r) % __uNd));
	}
      const int __r = __s % _Nd;
      if (__r == 0)
	return __x;
      else if (__r > 0)
	return (__x << __r) | (__x >> ((_Nd - __r) % _Nd));
      else
	return (__x >> -__r) | (__x << ((_Nd + __r) % _Nd)); // rotr(x, -r)
    }

  template<typename _Tp>
    constexpr _Tp
    __rotr(_Tp __x, int __s) noexcept
    {
      constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
      if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0)
	{
	  // Variant for power of two _Nd which the compiler can
	  // easily pattern match.
	  constexpr unsigned __uNd = _Nd;
	  const unsigned __r = __s;
	  return (__x >> (__r % __uNd)) | (__x << ((-__r) % __uNd));
	}
      const int __r = __s % _Nd;
      if (__r == 0)
	return __x;
      else if (__r > 0)
	return (__x >> __r) | (__x << ((_Nd - __r) % _Nd));
      else
	return (__x << -__r) | (__x >> ((_Nd + __r) % _Nd)); // rotl(x, -r)
    }

  template<typename _Tp>
    constexpr int
    __countl_zero(_Tp __x) noexcept
    {
      using __gnu_cxx::__int_traits;
      constexpr auto _Nd = __int_traits<_Tp>::__digits;

      if (__x == 0)
        return _Nd;

      constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
      constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
      constexpr auto _Nd_u = __int_traits<unsigned>::__digits;

      if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
	{
	  constexpr int __diff = _Nd_u - _Nd;
	  return __builtin_clz(__x) - __diff;
	}
      else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
	{
	  constexpr int __diff = _Nd_ul - _Nd;
	  return __builtin_clzl(__x) - __diff;
	}
      else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
	{
	  constexpr int __diff = _Nd_ull - _Nd;
	  return __builtin_clzll(__x) - __diff;
	}
      else // (_Nd > _Nd_ull)
	{
	  static_assert(_Nd <= (2 * _Nd_ull),
			"Maximum supported integer size is 128-bit");

	  unsigned long long __high = __x >> _Nd_ull;
	  if (__high != 0)
	    {
	      constexpr int __diff = (2 * _Nd_ull) - _Nd;
	      return __builtin_clzll(__high) - __diff;
	    }
	  constexpr auto __max_ull = __int_traits<unsigned long long>::__max;
	  unsigned long long __low = __x & __max_ull;
	  return (_Nd - _Nd_ull) + __builtin_clzll(__low);
	}
    }

  template<typename _Tp>
    constexpr int
    __countl_one(_Tp __x) noexcept
    {
      return std::__countl_zero<_Tp>((_Tp)~__x);
    }

  template<typename _Tp>
    constexpr int
    __countr_zero(_Tp __x) noexcept
    {
      using __gnu_cxx::__int_traits;
      constexpr auto _Nd = __int_traits<_Tp>::__digits;

      if (__x == 0)
        return _Nd;

      constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
      constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
      constexpr auto _Nd_u = __int_traits<unsigned>::__digits;

      if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
	return __builtin_ctz(__x);
      else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
	return __builtin_ctzl(__x);
      else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
	return __builtin_ctzll(__x);
      else // (_Nd > _Nd_ull)
	{
	  static_assert(_Nd <= (2 * _Nd_ull),
			"Maximum supported integer size is 128-bit");

	  constexpr auto __max_ull = __int_traits<unsigned long long>::__max;
	  unsigned long long __low = __x & __max_ull;
	  if (__low != 0)
	    return __builtin_ctzll(__low);
	  unsigned long long __high = __x >> _Nd_ull;
	  return __builtin_ctzll(__high) + _Nd_ull;
	}
    }

  template<typename _Tp>
    constexpr int
    __countr_one(_Tp __x) noexcept
    {
      return std::__countr_zero((_Tp)~__x);
    }

  template<typename _Tp>
    constexpr int
    __popcount(_Tp __x) noexcept
    {
      using __gnu_cxx::__int_traits;
      constexpr auto _Nd = __int_traits<_Tp>::__digits;

      constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
      constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
      constexpr auto _Nd_u = __int_traits<unsigned>::__digits;

      if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
	return __builtin_popcount(__x);
      else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
	return __builtin_popcountl(__x);
      else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
	return __builtin_popcountll(__x);
      else // (_Nd > _Nd_ull)
	{
	  static_assert(_Nd <= (2 * _Nd_ull),
			"Maximum supported integer size is 128-bit");

	  constexpr auto __max_ull = __int_traits<unsigned long long>::__max;
	  unsigned long long __low = __x & __max_ull;
	  unsigned long long __high = __x >> _Nd_ull;
	  return __builtin_popcountll(__low) + __builtin_popcountll(__high);
	}
    }

  template<typename _Tp>
    constexpr bool
    __has_single_bit(_Tp __x) noexcept
    { return std::__popcount(__x) == 1; }

  template<typename _Tp>
    constexpr _Tp
    __bit_ceil(_Tp __x) noexcept
    {
      using __gnu_cxx::__int_traits;
      constexpr auto _Nd = __int_traits<_Tp>::__digits;
      if (__x == 0 || __x == 1)
        return 1;
      auto __shift_exponent = _Nd - std::__countl_zero((_Tp)(__x - 1u));
      // If the shift exponent equals _Nd then the correct result is not
      // representable as a value of _Tp, and so the result is undefined.
      // Want that undefined behaviour to be detected in constant expressions,
      // by UBSan, and by debug assertions.
#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
      if (!__builtin_is_constant_evaluated())
	{
	  __glibcxx_assert( __shift_exponent != __int_traits<_Tp>::__digits );
	}
#endif
      using __promoted_type = decltype(__x << 1);
      if _GLIBCXX17_CONSTEXPR (!is_same<__promoted_type, _Tp>::value)
	{
	  // If __x undergoes integral promotion then shifting by _Nd is
	  // not undefined. In order to make the shift undefined, so that
	  // it is diagnosed in constant expressions and by UBsan, we also
	  // need to "promote" the shift exponent to be too large for the
	  // promoted type.
	  const int __extra_exp = sizeof(__promoted_type) / sizeof(_Tp) / 2;
	  __shift_exponent |= (__shift_exponent & _Nd) << __extra_exp;
	}
      return (_Tp)1u << __shift_exponent;
    }

  template<typename _Tp>
    constexpr _Tp
    __bit_floor(_Tp __x) noexcept
    {
      constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
      if (__x == 0)
        return 0;
      return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x >> 1)));
    }

  template<typename _Tp>
    constexpr _Tp
    __bit_width(_Tp __x) noexcept
    {
      constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
      return _Nd - std::__countl_zero(__x);
    }

  /// @endcond

#if __cplusplus > 201703L

#define __cpp_lib_bitops 201907L

  /// @cond undoc
  template<typename _Tp, typename _Up = _Tp>
    using _If_is_unsigned_integer
      = enable_if_t<__is_unsigned_integer<_Tp>::value, _Up>;
  /// @endcond

  // [bit.rot], rotating

  /// Rotate `x` to the left by `s` bits.
  template<typename _Tp>
    [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
    rotl(_Tp __x, int __s) noexcept
    { return std::__rotl(__x, __s); }

  /// Rotate `x` to the right by `s` bits.
  template<typename _Tp>
    [[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
    rotr(_Tp __x, int __s) noexcept
    { return std::__rotr(__x, __s); }

  // [bit.count], counting

  /// The number of contiguous zero bits, starting from the highest bit.
  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    countl_zero(_Tp __x) noexcept
    { return std::__countl_zero(__x); }

  /// The number of contiguous one bits, starting from the highest bit.
  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    countl_one(_Tp __x) noexcept
    { return std::__countl_one(__x); }

  /// The number of contiguous zero bits, starting from the lowest bit.
  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    countr_zero(_Tp __x) noexcept
    { return std::__countr_zero(__x); }

  /// The number of contiguous one bits, starting from the lowest bit.
  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    countr_one(_Tp __x) noexcept
    { return std::__countr_one(__x); }

  /// The number of bits set in `x`.
  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, int>
    popcount(_Tp __x) noexcept
    { return std::__popcount(__x); }

  // [bit.pow.two], integral powers of 2

#define __cpp_lib_int_pow2 202002L

  /// True if `x` is a power of two, false otherwise.
  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp, bool>
    has_single_bit(_Tp __x) noexcept
    { return std::__has_single_bit(__x); }

  /// The smallest power-of-two not less than `x`.
  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp>
    bit_ceil(_Tp __x) noexcept
    { return std::__bit_ceil(__x); }

  /// The largest power-of-two not greater than `x`.
  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp>
    bit_floor(_Tp __x) noexcept
    { return std::__bit_floor(__x); }

  /// The smallest integer greater than the base-2 logarithm of `x`.
  template<typename _Tp>
    constexpr _If_is_unsigned_integer<_Tp>
    bit_width(_Tp __x) noexcept
    { return std::__bit_width(__x); }

#define __cpp_lib_endian 201907L

  /// Byte order
  enum class endian
  {
    little = __ORDER_LITTLE_ENDIAN__,
    big    = __ORDER_BIG_ENDIAN__,
    native = __BYTE_ORDER__
  };
#endif // C++2a

  /// @}

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif // C++14
#endif // _GLIBCXX_BIT
Commit	Line	Data
f3e91052 JW	1	// <bit> -- C++ --
f3e91052 JW	2
99dee823	3	// Copyright (C) 2018-2021 Free Software Foundation, Inc.
f3e91052 JW	4	//
	5	// This file is part of the GNU ISO C++ Library. This library is free
	6	// software; you can redistribute it and/or modify it under the
	7	// terms of the GNU General Public License as published by the
	8	// Free Software Foundation; either version 3, or (at your option)
	9	// any later version.
	10
	11	// This library is distributed in the hope that it will be useful,
	12	// but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	// GNU General Public License for more details.
	15
	16	// Under Section 7 of GPL version 3, you are granted additional
	17	// permissions described in the GCC Runtime Library Exception, version
	18	// 3.1, as published by the Free Software Foundation.
	19
	20	// You should have received a copy of the GNU General Public License and
	21	// a copy of the GCC Runtime Library Exception along with this program;
	22	// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
	23	// <http://www.gnu.org/licenses/>.
	24
	25	/** @file include/bit
	26	* This is a Standard C++ Library header.
	27	*/
	28
	29	#ifndef _GLIBCXX_BIT
	30	#define _GLIBCXX_BIT 1
	31
	32	#pragma GCC system_header
	33
	34	#if __cplusplus >= 201402L
	35
	36	#include <type_traits>
474cb5a0 JW	37
	38	#if _GLIBCXX_HOSTED
	39	# include <ext/numeric_traits.h>
	40	#else
	41	# include <limits>
	42	/// @cond undocumented
	43	namespace __gnu_cxx
	44	{
	45	template<typename _Tp>
	46	struct __int_traits
	47	{
	48	static constexpr int __digits = std::numeric_limits<_Tp>::digits;
	49	static constexpr _Tp __max = std::numeric_limits<_Tp>::max();
	50	};
	51	}
	52	/// @endcond
	53	#endif
f3e91052 JW	54
	55	namespace std _GLIBCXX_VISIBILITY(default)
	56	{
	57	_GLIBCXX_BEGIN_NAMESPACE_VERSION
	58
27e6c1f4 JW	59	/**
	60	* @defgroup bit_manip Bit manipulation
	61	* @ingroup numerics
	62	*
	63	* Utilities for examining and manipulating individual bits.
	64	*
	65	* @{
	66	*/
	67
9e433b34 JW	68	#if __cplusplus > 201703l && __has_builtin(__builtin_bit_cast)
	69	#define __cpp_lib_bit_cast 201806L
	70
	71	/// Create a value of type `To` from the bits of `from`.
	72	template<typename _To, typename _From>
406f58e1	73	[[nodiscard]]
9e433b34 JW	74	constexpr _To
	75	bit_cast(const _From& __from) noexcept
	76	{
	77	return __builtin_bit_cast(_To, __from);
	78	}
	79	#endif
	80
27e6c1f4 JW	81	/// @cond undoc
27e6c1f4 JW	82
f3e91052 JW	83	template<typename _Tp>
f3e91052 JW	84	constexpr _Tp
f35da524	85	__rotl(_Tp __x, int __s) noexcept
f3e91052	86	{
eb04805b	87	constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
84185598 JJ	88	if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0)
	89	{
	90	// Variant for power of two _Nd which the compiler can
	91	// easily pattern match.
	92	constexpr unsigned __uNd = _Nd;
	93	const unsigned __r = __s;
	94	return (__x << (__r % __uNd)) \| (__x >> ((-__r) % __uNd));
	95	}
f35da524 JW	96	const int __r = __s % _Nd;
	97	if (__r == 0)
	98	return __x;
	99	else if (__r > 0)
	100	return (__x << __r) \| (__x >> ((_Nd - __r) % _Nd));
	101	else
	102	return (__x >> -__r) \| (__x << ((_Nd + __r) % _Nd)); // rotr(x, -r)
f3e91052 JW	103	}
	104
	105	template<typename _Tp>
	106	constexpr _Tp
f35da524	107	__rotr(_Tp __x, int __s) noexcept
f3e91052	108	{
eb04805b	109	constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
84185598 JJ	110	if _GLIBCXX17_CONSTEXPR ((_Nd & (_Nd - 1)) == 0)
	111	{
	112	// Variant for power of two _Nd which the compiler can
	113	// easily pattern match.
	114	constexpr unsigned __uNd = _Nd;
	115	const unsigned __r = __s;
	116	return (__x >> (__r % __uNd)) \| (__x << ((-__r) % __uNd));
	117	}
f35da524 JW	118	const int __r = __s % _Nd;
	119	if (__r == 0)
	120	return __x;
	121	else if (__r > 0)
	122	return (__x >> __r) \| (__x << ((_Nd - __r) % _Nd));
	123	else
	124	return (__x << -__r) \| (__x >> ((_Nd + __r) % _Nd)); // rotl(x, -r)
f3e91052 JW	125	}
	126
	127	template<typename _Tp>
	128	constexpr int
	129	__countl_zero(_Tp __x) noexcept
	130	{
eb04805b JW	131	using __gnu_cxx::__int_traits;
eb04805b JW	132	constexpr auto _Nd = __int_traits<_Tp>::__digits;
f3e91052 JW	133
f3e91052 JW	134	if (__x == 0)
337dc307	135	return _Nd;
f3e91052	136
eb04805b JW	137	constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
	138	constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
	139	constexpr auto _Nd_u = __int_traits<unsigned>::__digits;
f3e91052	140
337dc307	141	if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
f3e91052	142	{
337dc307	143	constexpr int __diff = _Nd_u - _Nd;
f3e91052 JW	144	return __builtin_clz(__x) - __diff;
f3e91052 JW	145	}
337dc307	146	else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
f3e91052	147	{
337dc307	148	constexpr int __diff = _Nd_ul - _Nd;
f3e91052 JW	149	return __builtin_clzl(__x) - __diff;
f3e91052 JW	150	}
337dc307	151	else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
f3e91052	152	{
337dc307	153	constexpr int __diff = _Nd_ull - _Nd;
f3e91052 JW	154	return __builtin_clzll(__x) - __diff;
f3e91052 JW	155	}
337dc307	156	else // (_Nd > _Nd_ull)
f3e91052	157	{
337dc307	158	static_assert(_Nd <= (2 * _Nd_ull),
f3e91052 JW	159	"Maximum supported integer size is 128-bit");
f3e91052 JW	160
337dc307	161	unsigned long long __high = __x >> _Nd_ull;
f3e91052 JW	162	if (__high != 0)
f3e91052 JW	163	{
337dc307	164	constexpr int __diff = (2 * _Nd_ull) - _Nd;
f3e91052 JW	165	return __builtin_clzll(__high) - __diff;
f3e91052 JW	166	}
eb04805b	167	constexpr auto __max_ull = __int_traits<unsigned long long>::__max;
337dc307 JW	168	unsigned long long __low = __x & __max_ull;
337dc307 JW	169	return (_Nd - _Nd_ull) + __builtin_clzll(__low);
f3e91052 JW	170	}
	171	}
	172
	173	template<typename _Tp>
	174	constexpr int
	175	__countl_one(_Tp __x) noexcept
	176	{
f3e91052 JW	177	return std::__countl_zero<_Tp>((_Tp)~__x);
	178	}
	179
	180	template<typename _Tp>
	181	constexpr int
	182	__countr_zero(_Tp __x) noexcept
	183	{
eb04805b JW	184	using __gnu_cxx::__int_traits;
eb04805b JW	185	constexpr auto _Nd = __int_traits<_Tp>::__digits;
f3e91052 JW	186
f3e91052 JW	187	if (__x == 0)
337dc307	188	return _Nd;
f3e91052	189
eb04805b JW	190	constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
	191	constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
	192	constexpr auto _Nd_u = __int_traits<unsigned>::__digits;
f3e91052	193
337dc307	194	if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
f3e91052	195	return __builtin_ctz(__x);
337dc307	196	else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
f3e91052	197	return __builtin_ctzl(__x);
337dc307	198	else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
f3e91052	199	return __builtin_ctzll(__x);
337dc307	200	else // (_Nd > _Nd_ull)
f3e91052	201	{
337dc307	202	static_assert(_Nd <= (2 * _Nd_ull),
f3e91052 JW	203	"Maximum supported integer size is 128-bit");
f3e91052 JW	204
eb04805b	205	constexpr auto __max_ull = __int_traits<unsigned long long>::__max;
337dc307	206	unsigned long long __low = __x & __max_ull;
f3e91052 JW	207	if (__low != 0)
f3e91052 JW	208	return __builtin_ctzll(__low);
337dc307 JW	209	unsigned long long __high = __x >> _Nd_ull;
337dc307 JW	210	return __builtin_ctzll(__high) + _Nd_ull;
f3e91052 JW	211	}
	212	}
	213
	214	template<typename _Tp>
	215	constexpr int
	216	__countr_one(_Tp __x) noexcept
	217	{
f3e91052 JW	218	return std::__countr_zero((_Tp)~__x);
	219	}
	220
	221	template<typename _Tp>
	222	constexpr int
	223	__popcount(_Tp __x) noexcept
	224	{
eb04805b JW	225	using __gnu_cxx::__int_traits;
eb04805b JW	226	constexpr auto _Nd = __int_traits<_Tp>::__digits;
f3e91052	227
eb04805b JW	228	constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
	229	constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
	230	constexpr auto _Nd_u = __int_traits<unsigned>::__digits;
f3e91052	231
337dc307	232	if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_u)
f3e91052	233	return __builtin_popcount(__x);
337dc307	234	else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ul)
f3e91052	235	return __builtin_popcountl(__x);
337dc307	236	else if _GLIBCXX17_CONSTEXPR (_Nd <= _Nd_ull)
f3e91052	237	return __builtin_popcountll(__x);
337dc307	238	else // (_Nd > _Nd_ull)
f3e91052	239	{
337dc307	240	static_assert(_Nd <= (2 * _Nd_ull),
f3e91052 JW	241	"Maximum supported integer size is 128-bit");
f3e91052 JW	242
eb04805b	243	constexpr auto __max_ull = __int_traits<unsigned long long>::__max;
337dc307 JW	244	unsigned long long __low = __x & __max_ull;
337dc307 JW	245	unsigned long long __high = __x >> _Nd_ull;
f3e91052 JW	246	return __builtin_popcountll(__low) + __builtin_popcountll(__high);
	247	}
	248	}
	249
	250	template<typename _Tp>
	251	constexpr bool
9866abe3	252	__has_single_bit(_Tp __x) noexcept
f3e91052 JW	253	{ return std::__popcount(__x) == 1; }
	254
	255	template<typename _Tp>
	256	constexpr _Tp
9866abe3	257	__bit_ceil(_Tp __x) noexcept
f3e91052	258	{
eb04805b JW	259	using __gnu_cxx::__int_traits;
eb04805b JW	260	constexpr auto _Nd = __int_traits<_Tp>::__digits;
2fb17d2d	261	if (__x == 0 \|\| __x == 1)
f3e91052	262	return 1;
281ab2fb JW	263	auto __shift_exponent = _Nd - std::__countl_zero((_Tp)(__x - 1u));
	264	// If the shift exponent equals _Nd then the correct result is not
	265	// representable as a value of _Tp, and so the result is undefined.
	266	// Want that undefined behaviour to be detected in constant expressions,
	267	// by UBSan, and by debug assertions.
	268	#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
	269	if (!__builtin_is_constant_evaluated())
3b39526e	270	{
eb04805b	271	__glibcxx_assert( __shift_exponent != __int_traits<_Tp>::__digits );
3b39526e	272	}
281ab2fb JW	273	#endif
	274	using __promoted_type = decltype(__x << 1);
	275	if _GLIBCXX17_CONSTEXPR (!is_same<__promoted_type, _Tp>::value)
	276	{
	277	// If __x undergoes integral promotion then shifting by _Nd is
	278	// not undefined. In order to make the shift undefined, so that
	279	// it is diagnosed in constant expressions and by UBsan, we also
	280	// need to "promote" the shift exponent to be too large for the
	281	// promoted type.
	282	const int __extra_exp = sizeof(__promoted_type) / sizeof(_Tp) / 2;
	283	__shift_exponent \|= (__shift_exponent & _Nd) << __extra_exp;
	284	}
	285	return (_Tp)1u << __shift_exponent;
f3e91052 JW	286	}
	287
	288	template<typename _Tp>
	289	constexpr _Tp
9866abe3	290	__bit_floor(_Tp __x) noexcept
f3e91052	291	{
eb04805b	292	constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
f3e91052 JW	293	if (__x == 0)
	294	return 0;
	295	return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x >> 1)));
	296	}
	297
	298	template<typename _Tp>
	299	constexpr _Tp
9866abe3	300	__bit_width(_Tp __x) noexcept
f3e91052	301	{
eb04805b	302	constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
f3e91052 JW	303	return _Nd - std::__countl_zero(__x);
	304	}
	305
27e6c1f4 JW	306	/// @endcond
27e6c1f4 JW	307
f3e91052 JW	308	#if __cplusplus > 201703L
f3e91052 JW	309
0d58d88d JW	310	#define __cpp_lib_bitops 201907L
0d58d88d JW	311
27e6c1f4	312	/// @cond undoc
f3e91052 JW	313	template<typename _Tp, typename _Up = _Tp>
f3e91052 JW	314	using _If_is_unsigned_integer
47f79054	315	= enable_if_t<__is_unsigned_integer<_Tp>::value, _Up>;
27e6c1f4	316	/// @endcond
f3e91052	317
f35da524	318	// [bit.rot], rotating
f3e91052	319
27e6c1f4	320	/// Rotate `x` to the left by `s` bits.
f3e91052	321	template<typename _Tp>
f35da524 JW	322	[[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
f35da524 JW	323	rotl(_Tp __x, int __s) noexcept
f3e91052 JW	324	{ return std::__rotl(__x, __s); }
f3e91052 JW	325
27e6c1f4	326	/// Rotate `x` to the right by `s` bits.
f3e91052	327	template<typename _Tp>
f35da524 JW	328	[[nodiscard]] constexpr _If_is_unsigned_integer<_Tp>
f35da524 JW	329	rotr(_Tp __x, int __s) noexcept
f3e91052 JW	330	{ return std::__rotr(__x, __s); }
f3e91052 JW	331
f35da524	332	// [bit.count], counting
f3e91052	333
27e6c1f4	334	/// The number of contiguous zero bits, starting from the highest bit.
f3e91052 JW	335	template<typename _Tp>
	336	constexpr _If_is_unsigned_integer<_Tp, int>
	337	countl_zero(_Tp __x) noexcept
	338	{ return std::__countl_zero(__x); }
	339
27e6c1f4	340	/// The number of contiguous one bits, starting from the highest bit.
f3e91052 JW	341	template<typename _Tp>
	342	constexpr _If_is_unsigned_integer<_Tp, int>
	343	countl_one(_Tp __x) noexcept
	344	{ return std::__countl_one(__x); }
	345
27e6c1f4	346	/// The number of contiguous zero bits, starting from the lowest bit.
f3e91052 JW	347	template<typename _Tp>
	348	constexpr _If_is_unsigned_integer<_Tp, int>
	349	countr_zero(_Tp __x) noexcept
	350	{ return std::__countr_zero(__x); }
	351
27e6c1f4	352	/// The number of contiguous one bits, starting from the lowest bit.
f3e91052 JW	353	template<typename _Tp>
	354	constexpr _If_is_unsigned_integer<_Tp, int>
	355	countr_one(_Tp __x) noexcept
	356	{ return std::__countr_one(__x); }
	357
27e6c1f4	358	/// The number of bits set in `x`.
f3e91052 JW	359	template<typename _Tp>
	360	constexpr _If_is_unsigned_integer<_Tp, int>
	361	popcount(_Tp __x) noexcept
	362	{ return std::__popcount(__x); }
f3e91052	363
f35da524	364	// [bit.pow.two], integral powers of 2
f3e91052	365
9866abe3 JW	366	#define __cpp_lib_int_pow2 202002L
9866abe3 JW	367
27e6c1f4	368	/// True if `x` is a power of two, false otherwise.
f3e91052 JW	369	template<typename _Tp>
f3e91052 JW	370	constexpr _If_is_unsigned_integer<_Tp, bool>
9866abe3 JW	371	has_single_bit(_Tp __x) noexcept
9866abe3 JW	372	{ return std::__has_single_bit(__x); }
f3e91052	373
27e6c1f4	374	/// The smallest power-of-two not less than `x`.
f3e91052 JW	375	template<typename _Tp>
f3e91052 JW	376	constexpr _If_is_unsigned_integer<_Tp>
9866abe3 JW	377	bit_ceil(_Tp __x) noexcept
9866abe3 JW	378	{ return std::__bit_ceil(__x); }
f3e91052	379
27e6c1f4	380	/// The largest power-of-two not greater than `x`.
f3e91052 JW	381	template<typename _Tp>
f3e91052 JW	382	constexpr _If_is_unsigned_integer<_Tp>
9866abe3 JW	383	bit_floor(_Tp __x) noexcept
9866abe3 JW	384	{ return std::__bit_floor(__x); }
f3e91052	385
27e6c1f4	386	/// The smallest integer greater than the base-2 logarithm of `x`.
f3e91052 JW	387	template<typename _Tp>
f3e91052 JW	388	constexpr _If_is_unsigned_integer<_Tp>
9866abe3 JW	389	bit_width(_Tp __x) noexcept
9866abe3 JW	390	{ return std::__bit_width(__x); }
f3e91052	391
a5378f9b JW	392	#define __cpp_lib_endian 201907L
a5378f9b JW	393
45c7215c JW	394	/// Byte order
	395	enum class endian
	396	{
	397	little = __ORDER_LITTLE_ENDIAN__,
	398	big = __ORDER_BIG_ENDIAN__,
	399	native = __BYTE_ORDER__
	400	};
f3e91052 JW	401	#endif // C++2a
f3e91052 JW	402
27e6c1f4 JW	403	/// @}
27e6c1f4 JW	404
f3e91052 JW	405	_GLIBCXX_END_NAMESPACE_VERSION
	406	} // namespace std
	407
	408	#endif // C++14
	409	#endif // _GLIBCXX_BIT