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

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

// Copyright (C) 2018-2025 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

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#if __cplusplus >= 201402L

#include <concepts> // for std::integral
#include <type_traits>

#if _GLIBCXX_HOSTED || __has_include(<ext/numeric_traits.h>)
# 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

#define __glibcxx_want_bit_cast
#define __glibcxx_want_byteswap
#define __glibcxx_want_bitops
#define __glibcxx_want_int_pow2
#define __glibcxx_want_endian
#include <bits/version.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

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

#ifdef __cpp_lib_bit_cast // C++ >= 20

  /// Create a value of type `To` from the bits of `from`.
  /**
   * @tparam _To   A trivially-copyable type.
   * @param __from A trivially-copyable object of the same size as `_To`.
   * @return       An object of type `_To`.
   * @since C++20
   */
  template<typename _To, typename _From>
    [[nodiscard]]
    constexpr _To
    bit_cast(const _From& __from) noexcept
#ifdef __cpp_concepts
    requires (sizeof(_To) == sizeof(_From))
      && is_trivially_copyable_v<_To> && is_trivially_copyable_v<_From>
#endif
    {
      return __builtin_bit_cast(_To, __from);
    }
#endif // __cpp_lib_bit_cast

#ifdef __cpp_lib_byteswap // C++ >= 23

  /// Reverse order of bytes in the object representation of `value`.
  /**
   * @tparam _Tp     An integral type.
   * @param __value  An object of integer type.
   * @return         An object of the same type, with the bytes reversed.
   * @since C++23
   */
  template<integral _Tp>
    [[nodiscard]]
    constexpr _Tp
    byteswap(_Tp __value) noexcept
    {
      if constexpr (sizeof(_Tp) == 1)
	return __value;
#if __cpp_if_consteval >= 202106L && __CHAR_BIT__ == 8
      if !consteval
	{
	  if constexpr (sizeof(_Tp) == 2)
	    return __builtin_bswap16(__value);
	  if constexpr (sizeof(_Tp) == 4)
	    return __builtin_bswap32(__value);
	  if constexpr (sizeof(_Tp) == 8)
	    return __builtin_bswap64(__value);
	  if constexpr (sizeof(_Tp) == 16)
#if __has_builtin(__builtin_bswap128)
	    return __builtin_bswap128(__value);
#else
	    return (__builtin_bswap64(__value >> 64)
		    | (static_cast<_Tp>(__builtin_bswap64(__value)) << 64));
#endif
	}
#endif

      // Fallback implementation that handles even __int24 etc.
      using _Up = typename __make_unsigned<__remove_cv_t<_Tp>>::__type;
      size_t __diff = __CHAR_BIT__ * (sizeof(_Tp) - 1);
      _Up __mask1 = static_cast<unsigned char>(~0);
      _Up __mask2 = __mask1 << __diff;
      _Up __val = __value;
      for (size_t __i = 0; __i < sizeof(_Tp) / 2; ++__i)
	{
	  _Up __byte1 = __val & __mask1;
	  _Up __byte2 = __val & __mask2;
	  __val = (__val ^ __byte1 ^ __byte2
		   ^ (__byte1 << __diff) ^ (__byte2 >> __diff));
	  __mask1 <<= __CHAR_BIT__;
	  __mask2 >>= __CHAR_BIT__;
	  __diff -= 2 * __CHAR_BIT__;
	}
      return __val;
    }
#endif // __cpp_lib_byteswap

  /// @cond undocumented
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr

  template<typename _Tp>
    constexpr _Tp
    __rotl(_Tp __x, int __s) noexcept
    {
      constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
      if constexpr ((_Nd & (_Nd - 1)) == 0)
	{
	  // Variant for power of two _Nd which the compiler can
	  // easily pattern match.
	  constexpr unsigned __uNd = _Nd;
	  const auto __r = static_cast<unsigned>(__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 constexpr ((_Nd & (_Nd - 1)) == 0)
	{
	  // Variant for power of two _Nd which the compiler can
	  // easily pattern match.
	  constexpr unsigned __uNd = _Nd;
	  const auto __r = static_cast<unsigned>(__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 _GLIBCXX_USE_BUILTIN_TRAIT(__builtin_clzg)
      return __builtin_clzg(__x, _Nd);
#else
      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 constexpr (_Nd <= _Nd_u)
	{
	  constexpr int __diff = _Nd_u - _Nd;
	  return __builtin_clz(__x) - __diff;
	}
      else if constexpr (_Nd <= _Nd_ul)
	{
	  constexpr int __diff = _Nd_ul - _Nd;
	  return __builtin_clzl(__x) - __diff;
	}
      else if 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);
	}
#endif
    }

  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 _GLIBCXX_USE_BUILTIN_TRAIT(__builtin_ctzg)
      return __builtin_ctzg(__x, _Nd);
#else
      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 constexpr (_Nd <= _Nd_u)
	return __builtin_ctz(__x);
      else if constexpr (_Nd <= _Nd_ul)
	return __builtin_ctzl(__x);
      else if 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;
	}
#endif
    }

  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
    {
#if _GLIBCXX_USE_BUILTIN_TRAIT(__builtin_popcountg)
      return __builtin_popcountg(__x);
#else
      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 constexpr (_Nd <= _Nd_u)
	return __builtin_popcount(__x);
      else if constexpr (_Nd <= _Nd_ul)
	return __builtin_popcountl(__x);
      else if 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);
	}
#endif
    }

  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.
      if (!std::__is_constant_evaluated())
	{
	  __glibcxx_assert( __shift_exponent != __int_traits<_Tp>::__digits );
	}

      using __promoted_type = decltype(__x << 1);
      if 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 int
    __bit_width(_Tp __x) noexcept
    {
      constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
      return _Nd - std::__countl_zero(__x);
    }

#pragma GCC diagnostic pop
  /// @endcond

#ifdef __cpp_lib_bitops // C++ >= 20

  /// @cond undocumented
  template<typename _Tp>
    concept __unsigned_integer = __is_unsigned_integer<_Tp>::value;
  /// @endcond

  // [bit.rot], rotating

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

  /// Rotate `x` to the right by `s` bits.
  template<__unsigned_integer _Tp>
    [[nodiscard]] constexpr _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<__unsigned_integer _Tp>
    constexpr int
    countl_zero(_Tp __x) noexcept
    { return std::__countl_zero(__x); }

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

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

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

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

#ifdef __cpp_lib_int_pow2 // C++ >= 20
  // [bit.pow.two], integral powers of 2

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

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

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

  // _GLIBCXX_RESOLVE_LIB_DEFECTS
  // 3656. Inconsistent bit operations returning a count
  /// The smallest integer greater than the base-2 logarithm of `x`.
  template<__unsigned_integer _Tp>
    constexpr int
    bit_width(_Tp __x) noexcept
    { return std::__bit_width(__x); }
#endif // defined (__cpp_lib_int_pow2)

#ifdef __cpp_lib_endian // C++ >= 20

  /// Byte order constants
  /**
   * The platform endianness can be checked by comparing `std::endian::native`
   * to one of `std::endian::big` or `std::endian::little`.
   *
   * @since C++20
   */
  enum class endian
  {
    little = __ORDER_LITTLE_ENDIAN__,
    big    = __ORDER_BIG_ENDIAN__,
    native = __BYTE_ORDER__
  };
#endif // __cpp_lib_endian

  /// @}

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif // C++14
#endif // _GLIBCXX_BIT
Commit	Line	Data
f3e91052 JW	1	// <bit> -- C++ --
f3e91052 JW	2
6441eb6d	3	// Copyright (C) 2018-2025 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
63a598de	32	#ifdef _GLIBCXX_SYSHDR
f3e91052	33	#pragma GCC system_header
63a598de	34	#endif
f3e91052 JW	35
	36	#if __cplusplus >= 201402L
	37
fd5a858e	38	#include <concepts> // for std::integral
f3e91052	39	#include <type_traits>
474cb5a0	40
cf0fded5	41	#if _GLIBCXX_HOSTED \|\| __has_include(<ext/numeric_traits.h>)
474cb5a0 JW	42	# include <ext/numeric_traits.h>
	43	#else
	44	# include <limits>
	45	/// @cond undocumented
	46	namespace __gnu_cxx
	47	{
	48	template<typename _Tp>
	49	struct __int_traits
	50	{
	51	static constexpr int __digits = std::numeric_limits<_Tp>::digits;
	52	static constexpr _Tp __max = std::numeric_limits<_Tp>::max();
	53	};
	54	}
	55	/// @endcond
	56	#endif
f3e91052	57
083b7f28 AA	58	#define __glibcxx_want_bit_cast
	59	#define __glibcxx_want_byteswap
	60	#define __glibcxx_want_bitops
	61	#define __glibcxx_want_int_pow2
	62	#define __glibcxx_want_endian
	63	#include <bits/version.h>
	64
f3e91052 JW	65	namespace std _GLIBCXX_VISIBILITY(default)
	66	{
	67	_GLIBCXX_BEGIN_NAMESPACE_VERSION
	68
27e6c1f4 JW	69	/**
	70	* @defgroup bit_manip Bit manipulation
	71	* @ingroup numerics
	72	*
	73	* Utilities for examining and manipulating individual bits.
	74	*
	75	* @{
	76	*/
	77
083b7f28	78	#ifdef __cpp_lib_bit_cast // C++ >= 20
9e433b34 JW	79
9e433b34 JW	80	/// Create a value of type `To` from the bits of `from`.
674ec679 JW	81	/**
	82	* @tparam _To A trivially-copyable type.
	83	* @param __from A trivially-copyable object of the same size as `_To`.
	84	* @return An object of type `_To`.
	85	* @since C++20
	86	*/
9e433b34	87	template<typename _To, typename _From>
406f58e1	88	[[nodiscard]]
9e433b34 JW	89	constexpr _To
9e433b34 JW	90	bit_cast(const _From& __from) noexcept
4894d69a JW	91	#ifdef __cpp_concepts
4894d69a JW	92	requires (sizeof(_To) == sizeof(_From))
c3f281a0	93	&& is_trivially_copyable_v<_To> && is_trivially_copyable_v<_From>
4894d69a	94	#endif
9e433b34 JW	95	{
	96	return __builtin_bit_cast(_To, __from);
	97	}
083b7f28	98	#endif // __cpp_lib_bit_cast
9e433b34	99
083b7f28	100	#ifdef __cpp_lib_byteswap // C++ >= 23
7393fa8b JJ	101
7393fa8b JJ	102	/// Reverse order of bytes in the object representation of `value`.
674ec679 JW	103	/**
	104	* @tparam _Tp An integral type.
	105	* @param __value An object of integer type.
	106	* @return An object of the same type, with the bytes reversed.
	107	* @since C++23
	108	*/
fd5a858e	109	template<integral _Tp>
92084a6d	110	[[nodiscard]]
fd5a858e	111	constexpr _Tp
7393fa8b JJ	112	byteswap(_Tp __value) noexcept
	113	{
	114	if constexpr (sizeof(_Tp) == 1)
	115	return __value;
	116	#if __cpp_if_consteval >= 202106L && __CHAR_BIT__ == 8
	117	if !consteval
	118	{
	119	if constexpr (sizeof(_Tp) == 2)
	120	return __builtin_bswap16(__value);
	121	if constexpr (sizeof(_Tp) == 4)
	122	return __builtin_bswap32(__value);
	123	if constexpr (sizeof(_Tp) == 8)
	124	return __builtin_bswap64(__value);
	125	if constexpr (sizeof(_Tp) == 16)
	126	#if __has_builtin(__builtin_bswap128)
	127	return __builtin_bswap128(__value);
	128	#else
	129	return (__builtin_bswap64(__value >> 64)
	130	\| (static_cast<_Tp>(__builtin_bswap64(__value)) << 64));
	131	#endif
	132	}
	133	#endif
	134
	135	// Fallback implementation that handles even __int24 etc.
	136	using _Up = typename __make_unsigned<__remove_cv_t<_Tp>>::__type;
	137	size_t __diff = __CHAR_BIT__ * (sizeof(_Tp) - 1);
	138	_Up __mask1 = static_cast<unsigned char>(~0);
	139	_Up __mask2 = __mask1 << __diff;
	140	_Up __val = __value;
	141	for (size_t __i = 0; __i < sizeof(_Tp) / 2; ++__i)
	142	{
	143	_Up __byte1 = __val & __mask1;
	144	_Up __byte2 = __val & __mask2;
	145	__val = (__val ^ __byte1 ^ __byte2
	146	^ (__byte1 << __diff) ^ (__byte2 >> __diff));
	147	__mask1 <<= __CHAR_BIT__;
	148	__mask2 >>= __CHAR_BIT__;
	149	__diff -= 2 * __CHAR_BIT__;
	150	}
	151	return __val;
	152	}
083b7f28	153	#endif // __cpp_lib_byteswap
7393fa8b	154
30f6aace	155	/// @cond undocumented
77687bc0 JW	156	#pragma GCC diagnostic push
77687bc0 JW	157	#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
27e6c1f4	158
f3e91052 JW	159	template<typename _Tp>
f3e91052 JW	160	constexpr _Tp
f35da524	161	__rotl(_Tp __x, int __s) noexcept
f3e91052	162	{
eb04805b	163	constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
77687bc0	164	if constexpr ((_Nd & (_Nd - 1)) == 0)
84185598 JJ	165	{
	166	// Variant for power of two _Nd which the compiler can
	167	// easily pattern match.
	168	constexpr unsigned __uNd = _Nd;
f12151e5	169	const auto __r = static_cast<unsigned>(__s);
84185598 JJ	170	return (__x << (__r % __uNd)) \| (__x >> ((-__r) % __uNd));
84185598 JJ	171	}
f35da524 JW	172	const int __r = __s % _Nd;
	173	if (__r == 0)
	174	return __x;
	175	else if (__r > 0)
	176	return (__x << __r) \| (__x >> ((_Nd - __r) % _Nd));
	177	else
	178	return (__x >> -__r) \| (__x << ((_Nd + __r) % _Nd)); // rotr(x, -r)
f3e91052 JW	179	}
	180
	181	template<typename _Tp>
	182	constexpr _Tp
f35da524	183	__rotr(_Tp __x, int __s) noexcept
f3e91052	184	{
eb04805b	185	constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
77687bc0	186	if constexpr ((_Nd & (_Nd - 1)) == 0)
84185598 JJ	187	{
	188	// Variant for power of two _Nd which the compiler can
	189	// easily pattern match.
	190	constexpr unsigned __uNd = _Nd;
f12151e5	191	const auto __r = static_cast<unsigned>(__s);
84185598 JJ	192	return (__x >> (__r % __uNd)) \| (__x << ((-__r) % __uNd));
84185598 JJ	193	}
f35da524 JW	194	const int __r = __s % _Nd;
	195	if (__r == 0)
	196	return __x;
	197	else if (__r > 0)
	198	return (__x >> __r) \| (__x << ((_Nd - __r) % _Nd));
	199	else
	200	return (__x << -__r) \| (__x >> ((_Nd + __r) % _Nd)); // rotl(x, -r)
f3e91052 JW	201	}
	202
	203	template<typename _Tp>
	204	constexpr int
	205	__countl_zero(_Tp __x) noexcept
	206	{
eb04805b JW	207	using __gnu_cxx::__int_traits;
eb04805b JW	208	constexpr auto _Nd = __int_traits<_Tp>::__digits;
f3e91052	209
e8ad697a JW	210	#if _GLIBCXX_USE_BUILTIN_TRAIT(__builtin_clzg)
	211	return __builtin_clzg(__x, _Nd);
	212	#else
f3e91052	213	if (__x == 0)
337dc307	214	return _Nd;
f3e91052	215
eb04805b JW	216	constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
	217	constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
	218	constexpr auto _Nd_u = __int_traits<unsigned>::__digits;
f3e91052	219
77687bc0	220	if constexpr (_Nd <= _Nd_u)
f3e91052	221	{
337dc307	222	constexpr int __diff = _Nd_u - _Nd;
f3e91052 JW	223	return __builtin_clz(__x) - __diff;
f3e91052 JW	224	}
77687bc0	225	else if constexpr (_Nd <= _Nd_ul)
f3e91052	226	{
337dc307	227	constexpr int __diff = _Nd_ul - _Nd;
f3e91052 JW	228	return __builtin_clzl(__x) - __diff;
f3e91052 JW	229	}
77687bc0	230	else if constexpr (_Nd <= _Nd_ull)
f3e91052	231	{
337dc307	232	constexpr int __diff = _Nd_ull - _Nd;
f3e91052 JW	233	return __builtin_clzll(__x) - __diff;
f3e91052 JW	234	}
337dc307	235	else // (_Nd > _Nd_ull)
f3e91052	236	{
337dc307	237	static_assert(_Nd <= (2 * _Nd_ull),
f3e91052 JW	238	"Maximum supported integer size is 128-bit");
f3e91052 JW	239
337dc307	240	unsigned long long __high = __x >> _Nd_ull;
f3e91052 JW	241	if (__high != 0)
f3e91052 JW	242	{
337dc307	243	constexpr int __diff = (2 * _Nd_ull) - _Nd;
f3e91052 JW	244	return __builtin_clzll(__high) - __diff;
f3e91052 JW	245	}
eb04805b	246	constexpr auto __max_ull = __int_traits<unsigned long long>::__max;
337dc307 JW	247	unsigned long long __low = __x & __max_ull;
337dc307 JW	248	return (_Nd - _Nd_ull) + __builtin_clzll(__low);
f3e91052	249	}
e8ad697a	250	#endif
f3e91052 JW	251	}
	252
	253	template<typename _Tp>
	254	constexpr int
	255	__countl_one(_Tp __x) noexcept
	256	{
f3e91052 JW	257	return std::__countl_zero<_Tp>((_Tp)~__x);
	258	}
	259
	260	template<typename _Tp>
	261	constexpr int
	262	__countr_zero(_Tp __x) noexcept
	263	{
eb04805b JW	264	using __gnu_cxx::__int_traits;
eb04805b JW	265	constexpr auto _Nd = __int_traits<_Tp>::__digits;
f3e91052	266
e8ad697a JW	267	#if _GLIBCXX_USE_BUILTIN_TRAIT(__builtin_ctzg)
	268	return __builtin_ctzg(__x, _Nd);
	269	#else
f3e91052	270	if (__x == 0)
337dc307	271	return _Nd;
f3e91052	272
eb04805b JW	273	constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
	274	constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
	275	constexpr auto _Nd_u = __int_traits<unsigned>::__digits;
f3e91052	276
77687bc0	277	if constexpr (_Nd <= _Nd_u)
f3e91052	278	return __builtin_ctz(__x);
77687bc0	279	else if constexpr (_Nd <= _Nd_ul)
f3e91052	280	return __builtin_ctzl(__x);
77687bc0	281	else if constexpr (_Nd <= _Nd_ull)
f3e91052	282	return __builtin_ctzll(__x);
337dc307	283	else // (_Nd > _Nd_ull)
f3e91052	284	{
337dc307	285	static_assert(_Nd <= (2 * _Nd_ull),
f3e91052 JW	286	"Maximum supported integer size is 128-bit");
f3e91052 JW	287
eb04805b	288	constexpr auto __max_ull = __int_traits<unsigned long long>::__max;
337dc307	289	unsigned long long __low = __x & __max_ull;
f3e91052 JW	290	if (__low != 0)
f3e91052 JW	291	return __builtin_ctzll(__low);
337dc307 JW	292	unsigned long long __high = __x >> _Nd_ull;
337dc307 JW	293	return __builtin_ctzll(__high) + _Nd_ull;
f3e91052	294	}
e8ad697a	295	#endif
f3e91052 JW	296	}
	297
	298	template<typename _Tp>
	299	constexpr int
	300	__countr_one(_Tp __x) noexcept
	301	{
f3e91052 JW	302	return std::__countr_zero((_Tp)~__x);
	303	}
	304
	305	template<typename _Tp>
	306	constexpr int
	307	__popcount(_Tp __x) noexcept
	308	{
e8ad697a JW	309	#if _GLIBCXX_USE_BUILTIN_TRAIT(__builtin_popcountg)
	310	return __builtin_popcountg(__x);
	311	#else
eb04805b JW	312	using __gnu_cxx::__int_traits;
eb04805b JW	313	constexpr auto _Nd = __int_traits<_Tp>::__digits;
f3e91052	314
eb04805b JW	315	constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
	316	constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
	317	constexpr auto _Nd_u = __int_traits<unsigned>::__digits;
f3e91052	318
77687bc0	319	if constexpr (_Nd <= _Nd_u)
f3e91052	320	return __builtin_popcount(__x);
77687bc0	321	else if constexpr (_Nd <= _Nd_ul)
f3e91052	322	return __builtin_popcountl(__x);
77687bc0	323	else if constexpr (_Nd <= _Nd_ull)
f3e91052	324	return __builtin_popcountll(__x);
337dc307	325	else // (_Nd > _Nd_ull)
f3e91052	326	{
337dc307	327	static_assert(_Nd <= (2 * _Nd_ull),
f3e91052 JW	328	"Maximum supported integer size is 128-bit");
f3e91052 JW	329
eb04805b	330	constexpr auto __max_ull = __int_traits<unsigned long long>::__max;
337dc307 JW	331	unsigned long long __low = __x & __max_ull;
337dc307 JW	332	unsigned long long __high = __x >> _Nd_ull;
f3e91052 JW	333	return __builtin_popcountll(__low) + __builtin_popcountll(__high);
f3e91052 JW	334	}
e8ad697a	335	#endif
f3e91052 JW	336	}
	337
	338	template<typename _Tp>
	339	constexpr bool
9866abe3	340	__has_single_bit(_Tp __x) noexcept
f3e91052 JW	341	{ return std::__popcount(__x) == 1; }
	342
	343	template<typename _Tp>
	344	constexpr _Tp
9866abe3	345	__bit_ceil(_Tp __x) noexcept
f3e91052	346	{
eb04805b JW	347	using __gnu_cxx::__int_traits;
eb04805b JW	348	constexpr auto _Nd = __int_traits<_Tp>::__digits;
2fb17d2d	349	if (__x == 0 \|\| __x == 1)
f3e91052	350	return 1;
281ab2fb JW	351	auto __shift_exponent = _Nd - std::__countl_zero((_Tp)(__x - 1u));
	352	// If the shift exponent equals _Nd then the correct result is not
	353	// representable as a value of _Tp, and so the result is undefined.
	354	// Want that undefined behaviour to be detected in constant expressions,
	355	// by UBSan, and by debug assertions.
74d14778	356	if (!std::__is_constant_evaluated())
3b39526e	357	{
eb04805b	358	__glibcxx_assert( __shift_exponent != __int_traits<_Tp>::__digits );
3b39526e	359	}
74d14778	360
281ab2fb	361	using __promoted_type = decltype(__x << 1);
77687bc0	362	if constexpr (!is_same<__promoted_type, _Tp>::value)
281ab2fb JW	363	{
	364	// If __x undergoes integral promotion then shifting by _Nd is
	365	// not undefined. In order to make the shift undefined, so that
	366	// it is diagnosed in constant expressions and by UBsan, we also
	367	// need to "promote" the shift exponent to be too large for the
	368	// promoted type.
	369	const int __extra_exp = sizeof(__promoted_type) / sizeof(_Tp) / 2;
	370	__shift_exponent \|= (__shift_exponent & _Nd) << __extra_exp;
	371	}
	372	return (_Tp)1u << __shift_exponent;
f3e91052 JW	373	}
	374
	375	template<typename _Tp>
	376	constexpr _Tp
9866abe3	377	__bit_floor(_Tp __x) noexcept
f3e91052	378	{
eb04805b	379	constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
f3e91052 JW	380	if (__x == 0)
	381	return 0;
	382	return (_Tp)1u << (_Nd - std::__countl_zero((_Tp)(__x >> 1)));
	383	}
	384
	385	template<typename _Tp>
45813280	386	constexpr int
9866abe3	387	__bit_width(_Tp __x) noexcept
f3e91052	388	{
eb04805b	389	constexpr auto _Nd = __gnu_cxx::__int_traits<_Tp>::__digits;
f3e91052 JW	390	return _Nd - std::__countl_zero(__x);
	391	}
	392
77687bc0	393	#pragma GCC diagnostic pop
27e6c1f4 JW	394	/// @endcond
27e6c1f4 JW	395
083b7f28	396	#ifdef __cpp_lib_bitops // C++ >= 20
0d58d88d	397
30f6aace	398	/// @cond undocumented
fd5a858e PP	399	template<typename _Tp>
fd5a858e PP	400	concept __unsigned_integer = __is_unsigned_integer<_Tp>::value;
27e6c1f4	401	/// @endcond
f3e91052	402
f35da524	403	// [bit.rot], rotating
f3e91052	404
27e6c1f4	405	/// Rotate `x` to the left by `s` bits.
fd5a858e PP	406	template<__unsigned_integer _Tp>
fd5a858e PP	407	[[nodiscard]] constexpr _Tp
f35da524	408	rotl(_Tp __x, int __s) noexcept
f3e91052 JW	409	{ return std::__rotl(__x, __s); }
f3e91052 JW	410
27e6c1f4	411	/// Rotate `x` to the right by `s` bits.
fd5a858e PP	412	template<__unsigned_integer _Tp>
fd5a858e PP	413	[[nodiscard]] constexpr _Tp
f35da524	414	rotr(_Tp __x, int __s) noexcept
f3e91052 JW	415	{ return std::__rotr(__x, __s); }
f3e91052 JW	416
f35da524	417	// [bit.count], counting
f3e91052	418
27e6c1f4	419	/// The number of contiguous zero bits, starting from the highest bit.
fd5a858e PP	420	template<__unsigned_integer _Tp>
fd5a858e PP	421	constexpr int
f3e91052 JW	422	countl_zero(_Tp __x) noexcept
	423	{ return std::__countl_zero(__x); }
	424
27e6c1f4	425	/// The number of contiguous one bits, starting from the highest bit.
fd5a858e PP	426	template<__unsigned_integer _Tp>
fd5a858e PP	427	constexpr int
f3e91052 JW	428	countl_one(_Tp __x) noexcept
	429	{ return std::__countl_one(__x); }
	430
27e6c1f4	431	/// The number of contiguous zero bits, starting from the lowest bit.
fd5a858e PP	432	template<__unsigned_integer _Tp>
fd5a858e PP	433	constexpr int
f3e91052 JW	434	countr_zero(_Tp __x) noexcept
	435	{ return std::__countr_zero(__x); }
	436
27e6c1f4	437	/// The number of contiguous one bits, starting from the lowest bit.
fd5a858e PP	438	template<__unsigned_integer _Tp>
fd5a858e PP	439	constexpr int
f3e91052 JW	440	countr_one(_Tp __x) noexcept
	441	{ return std::__countr_one(__x); }
	442
27e6c1f4	443	/// The number of bits set in `x`.
fd5a858e PP	444	template<__unsigned_integer _Tp>
fd5a858e PP	445	constexpr int
f3e91052 JW	446	popcount(_Tp __x) noexcept
f3e91052 JW	447	{ return std::__popcount(__x); }
083b7f28	448	#endif // __cpp_lib_bitops
f3e91052	449
083b7f28	450	#ifdef __cpp_lib_int_pow2 // C++ >= 20
f35da524	451	// [bit.pow.two], integral powers of 2
f3e91052	452
27e6c1f4	453	/// True if `x` is a power of two, false otherwise.
fd5a858e PP	454	template<__unsigned_integer _Tp>
fd5a858e PP	455	constexpr bool
9866abe3 JW	456	has_single_bit(_Tp __x) noexcept
9866abe3 JW	457	{ return std::__has_single_bit(__x); }
f3e91052	458
27e6c1f4	459	/// The smallest power-of-two not less than `x`.
fd5a858e PP	460	template<__unsigned_integer _Tp>
fd5a858e PP	461	constexpr _Tp
9866abe3 JW	462	bit_ceil(_Tp __x) noexcept
9866abe3 JW	463	{ return std::__bit_ceil(__x); }
f3e91052	464
27e6c1f4	465	/// The largest power-of-two not greater than `x`.
fd5a858e PP	466	template<__unsigned_integer _Tp>
fd5a858e PP	467	constexpr _Tp
9866abe3 JW	468	bit_floor(_Tp __x) noexcept
9866abe3 JW	469	{ return std::__bit_floor(__x); }
f3e91052	470
45813280 JW	471	// _GLIBCXX_RESOLVE_LIB_DEFECTS
45813280 JW	472	// 3656. Inconsistent bit operations returning a count
27e6c1f4	473	/// The smallest integer greater than the base-2 logarithm of `x`.
fd5a858e PP	474	template<__unsigned_integer _Tp>
fd5a858e PP	475	constexpr int
9866abe3 JW	476	bit_width(_Tp __x) noexcept
9866abe3 JW	477	{ return std::__bit_width(__x); }
083b7f28	478	#endif // defined (__cpp_lib_int_pow2)
f3e91052	479
083b7f28	480	#ifdef __cpp_lib_endian // C++ >= 20
a5378f9b	481
674ec679 JW	482	/// Byte order constants
	483	/**
	484	* The platform endianness can be checked by comparing `std::endian::native`
	485	* to one of `std::endian::big` or `std::endian::little`.
	486	*
	487	* @since C++20
	488	*/
45c7215c JW	489	enum class endian
	490	{
	491	little = __ORDER_LITTLE_ENDIAN__,
	492	big = __ORDER_BIG_ENDIAN__,
	493	native = __BYTE_ORDER__
	494	};
083b7f28	495	#endif // __cpp_lib_endian
f3e91052	496
27e6c1f4 JW	497	/// @}
27e6c1f4 JW	498
f3e91052 JW	499	_GLIBCXX_END_NAMESPACE_VERSION
	500	} // namespace std
	501
	502	#endif // C++14
	503	#endif // _GLIBCXX_BIT