path: root/libcxx/include/bit

// -*- C++ -*-
//===------------------------------ bit ----------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===---------------------------------------------------------------------===//

#ifndef _LIBCPP_BIT
#define _LIBCPP_BIT

/*
    bit synopsis

namespace std {

  template <class T>
    constexpr bool ispow2(T x) noexcept; // C++20
  template <class T>
    constexpr T ceil2(T x);              // C++20
  template <class T>
    constexpr T floor2(T x) noexcept;    // C++20
  template <class T>
    constexpr T log2p1(T x) noexcept;    // C++20

  // 23.20.2, rotating
  template<class T>
    constexpr T rotl(T x, unsigned int s) noexcept; // C++20
  template<class T>
    constexpr T rotr(T x, unsigned int s) noexcept; // C++20

  // 23.20.3, counting
  template<class T>
    constexpr int countl_zero(T x) noexcept;  // C++20
  template<class T>
    constexpr int countl_one(T x) noexcept;   // C++20
  template<class T>
    constexpr int countr_zero(T x) noexcept;  // C++20
  template<class T>
    constexpr int countr_one(T x) noexcept;   // C++20
  template<class T>
    constexpr int popcount(T x) noexcept;     // C++20

} // namespace std

*/

#include <__config>
#include <limits>
#include <type_traits>
#include <version>
#include <__debug>

#if defined(__IBMCPP__)
#include "support/ibm/support.h"
#endif
#if defined(_LIBCPP_COMPILER_MSVC)
#include <intrin.h>
#endif

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

#ifndef _LIBCPP_COMPILER_MSVC

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __ctz(unsigned __x)           _NOEXCEPT { return __builtin_ctz(__x); }

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __ctz(unsigned long __x)      _NOEXCEPT { return __builtin_ctzl(__x); }

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __ctz(unsigned long long __x) _NOEXCEPT { return __builtin_ctzll(__x); }


inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __clz(unsigned __x)           _NOEXCEPT { return __builtin_clz(__x); }

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __clz(unsigned long __x)      _NOEXCEPT { return __builtin_clzl(__x); }

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __clz(unsigned long long __x) _NOEXCEPT { return __builtin_clzll(__x); }


inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __popcount(unsigned __x)           _NOEXCEPT { return __builtin_popcount(__x); }

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __popcount(unsigned long __x)      _NOEXCEPT { return __builtin_popcountl(__x); }

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __popcount(unsigned long long __x) _NOEXCEPT { return __builtin_popcountll(__x); }

#else  // _LIBCPP_COMPILER_MSVC

// Precondition:  __x != 0
inline _LIBCPP_INLINE_VISIBILITY
int __ctz(unsigned __x) {
  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
  static_assert(sizeof(unsigned long) == 4, "");
  unsigned long __where;
  if (_BitScanForward(&__where, __x))
    return static_cast<int>(__where);
  return 32;
}

inline _LIBCPP_INLINE_VISIBILITY
int __ctz(unsigned long __x) {
    static_assert(sizeof(unsigned long) == sizeof(unsigned), "");
    return __ctz(static_cast<unsigned>(__x));
}

inline _LIBCPP_INLINE_VISIBILITY
int __ctz(unsigned long long __x) {
    unsigned long __where;
#if defined(_LIBCPP_HAS_BITSCAN64)
    (defined(_M_AMD64) || defined(__x86_64__))
  if (_BitScanForward64(&__where, __x))
    return static_cast<int>(__where);
#else
  // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls.
  if (_BitScanForward(&__where, static_cast<unsigned long>(__x)))
    return static_cast<int>(__where);
  if (_BitScanForward(&__where, static_cast<unsigned long>(__x >> 32)))
    return static_cast<int>(__where + 32);
#endif
  return 64;
}

// Precondition:  __x != 0
inline _LIBCPP_INLINE_VISIBILITY
int __clz(unsigned __x) {
  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
  static_assert(sizeof(unsigned long) == 4, "");
  unsigned long __where;
  if (_BitScanReverse(&__where, __x))
    return static_cast<int>(31 - __where);
  return 32; // Undefined Behavior.
}

inline _LIBCPP_INLINE_VISIBILITY
int __clz(unsigned long __x) {
    static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
    return __clz(static_cast<unsigned>(__x));
}

inline _LIBCPP_INLINE_VISIBILITY
int __clz(unsigned long long __x) {
  unsigned long __where;
#if defined(_LIBCPP_HAS_BITSCAN64)
  if (_BitScanReverse64(&__where, __x))
    return static_cast<int>(63 - __where);
#else
  // Win32 doesn't have _BitScanReverse64 so emulate it with two 32 bit calls.
  if (_BitScanReverse(&__where, static_cast<unsigned long>(__x >> 32)))
    return static_cast<int>(63 - (__where + 32));
  if (_BitScanReverse(&__where, static_cast<unsigned long>(__x)))
    return static_cast<int>(63 - __where);
#endif
  return 64; // Undefined Behavior.
}

inline _LIBCPP_INLINE_VISIBILITY int __popcount(unsigned __x) {
  static_assert(sizeof(unsigned) == 4, "");
  return __popcnt(__x);
}

inline _LIBCPP_INLINE_VISIBILITY int __popcount(unsigned long __x) {
  static_assert(sizeof(unsigned long) == 4, "");
  return __popcnt(__x);
}

inline _LIBCPP_INLINE_VISIBILITY int __popcount(unsigned long long __x) {
  static_assert(sizeof(unsigned long long) == 8, "");
  return __popcnt64(__x);
}

#endif // _LIBCPP_COMPILER_MSVC

#if _LIBCPP_STD_VER > 17

template <class _Tp>
using __bitop_unsigned_integer _LIBCPP_NODEBUG_TYPE = integral_constant<bool,
         is_integral_v<_Tp> &&
         is_unsigned_v<_Tp> &&
        _IsNotSame<remove_cv_t<_Tp>, bool>::value &&
        _IsNotSame<remove_cv_t<_Tp>, signed char>::value &&
        _IsNotSame<remove_cv_t<_Tp>, wchar_t>::value &&
        _IsNotSame<remove_cv_t<_Tp>, char16_t>::value &&
        _IsNotSame<remove_cv_t<_Tp>, char32_t>::value
    >;


// rotl
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
rotl(_Tp __t, unsigned int __cnt) noexcept
{
    const unsigned int __dig = numeric_limits<_Tp>::digits;
    if ((__cnt % __dig) == 0)
        return __t;
    return (__t << (__cnt % __dig)) | (__t >> (__dig - (__cnt % __dig)));
}


// rotr
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
rotr(_Tp __t, unsigned int __cnt) noexcept
{
    const unsigned int __dig = numeric_limits<_Tp>::digits;
    if ((__cnt % __dig) == 0)
        return __t;
    return (__t >> (__cnt % __dig)) | (__t << (__dig - (__cnt % __dig)));
}


// countl_zero
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
countl_zero(_Tp __t) noexcept
{
    if (__t == 0)
        return numeric_limits<_Tp>::digits;

    if      constexpr (sizeof(_Tp) <= sizeof(unsigned int))
        return __clz(static_cast<unsigned int>(__t))
              - (numeric_limits<unsigned int>::digits - numeric_limits<_Tp>::digits);
    else if constexpr (sizeof(_Tp) <= sizeof(unsigned long))
        return __clz(static_cast<unsigned long>(__t))
              - (numeric_limits<unsigned long>::digits - numeric_limits<_Tp>::digits);
    else if constexpr (sizeof(_Tp) <= sizeof(unsigned long long))
        return __clz(static_cast<unsigned long long>(__t))
              - (numeric_limits<unsigned long long>::digits - numeric_limits<_Tp>::digits);
    else
    {
        int __ret = 0;
        int __iter = 0;
        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
        while (true) {
            __t = rotr(__t, __ulldigits);
            if ((__iter = countl_zero(static_cast<unsigned long long>(__t))) != __ulldigits)
                break;
            __ret += __iter;
            }
        return __ret + __iter;
    }
}


// countl_one
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
countl_one(_Tp __t) noexcept
{
    return __t != numeric_limits<_Tp>::max()
        ? countl_zero(static_cast<_Tp>(~__t))
        : numeric_limits<_Tp>::digits;
}


// countr_zero
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
countr_zero(_Tp __t) noexcept
{
    if (__t == 0)
        return numeric_limits<_Tp>::digits;

    if      constexpr (sizeof(_Tp) <= sizeof(unsigned int))
        return __ctz(static_cast<unsigned int>(__t));
    else if constexpr (sizeof(_Tp) <= sizeof(unsigned long))
        return __ctz(static_cast<unsigned long>(__t));
    else if constexpr (sizeof(_Tp) <= sizeof(unsigned long long))
        return __ctz(static_cast<unsigned long long>(__t));
    else
    {
        int __ret = 0;
        int __iter = 0;
        const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
        while ((__iter = countr_zero(static_cast<unsigned long long>(__t))) == __ulldigits)
        {
            __ret += __iter;
            __t >>= __ulldigits;
        }
        return __ret + __iter;
    }
}


// countr_one
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
countr_one(_Tp __t) noexcept
{
    return __t != numeric_limits<_Tp>::max()
        ? countr_zero(static_cast<_Tp>(~__t))
        : numeric_limits<_Tp>::digits;
}


// popcount
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, int>
popcount(_Tp __t) noexcept
{
    if      constexpr (sizeof(_Tp) <= sizeof(unsigned int))
        return __popcount(static_cast<unsigned int>(__t));
    else if constexpr (sizeof(_Tp) <= sizeof(unsigned long))
        return __popcount(static_cast<unsigned long>(__t));
    else if constexpr (sizeof(_Tp) <= sizeof(unsigned long long))
        return __popcount(static_cast<unsigned long long>(__t));
    else
    {
        int __ret = 0;
        while (__t != 0)
        {
            __ret += __popcount(static_cast<unsigned long long>(__t));
            __t >>= numeric_limits<unsigned long long>::digits;
        }
        return __ret;
    }
}


// integral log base 2
template<class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
unsigned __bit_log2(_Tp __t) noexcept
{ return std::numeric_limits<_Tp>::digits - 1 - countl_zero(__t); }


template <class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, bool>
ispow2(_Tp __t) noexcept { return popcount(__t) == 1; }

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
floor2(_Tp __t) noexcept { return __t == 0 ? 0 : _Tp{1} << __bit_log2(__t); }

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
ceil2(_Tp __t) noexcept
{
    if (__t < 2) return 1;
    const unsigned __n = numeric_limits<_Tp>::digits - countl_zero((_Tp)(__t - 1u));
    _LIBCPP_DEBUG_ASSERT(__libcpp_is_constant_evaluated() || __n != numeric_limits<_Tp>::digits, "Bad input to ceil2");

    if constexpr (sizeof(_Tp) >= sizeof(unsigned))
        return _Tp{1} << __n;
    else
    {
        const unsigned __extra = numeric_limits<unsigned>::digits  - numeric_limits<_Tp>::digits;
        const unsigned __retVal = 1u << (__n + __extra);
        return (_Tp) (__retVal >> __extra);
    }
}

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY constexpr
enable_if_t<__bitop_unsigned_integer<_Tp>::value, _Tp>
log2p1(_Tp __t) noexcept
{ return __t == 0 ? 0 : __bit_log2(__t) + 1; }

#endif // _LIBCPP_STD_VER > 17

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP_BIT