libcxx/include/__bits

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// 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___BITS
#define _LIBCPP___BITS

#include <__config>

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

_LIBCPP_PUSH_MACROS
#include <__undef_macros>


_LIBCPP_BEGIN_NAMESPACE_STD

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

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

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


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

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

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

#  ifndef _LIBCPP_HAS_NO_INT128
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
int __libcpp_clz(__uint128_t __x) _NOEXCEPT {
  // The function is written in this form due to C++ constexpr limitations.
  // The algorithm:
  // - Test whether any bit in the high 64-bits is set
  // - No bits set:
  //   - The high 64-bits contain 64 leading zeros,
  //   - Add the result of the low 64-bits.
  // - Any bits set:
  //   - The number of leading zeros of the input is the number of leading
  //     zeros in the high 64-bits.
  return ((__x >> 64) == 0)
           ? (64 + __builtin_clzll(static_cast<unsigned long long>(__x)))
           : __builtin_clzll(static_cast<unsigned long long>(__x >> 64));
}
#  endif

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

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

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

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unsigned __libcpp_blsr(unsigned __x) _NOEXCEPT {
  return __x ^ (__x & -__x);
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unsigned long __libcpp_blsr(unsigned long __x) _NOEXCEPT {
  return __x ^ (__x & -__x);
}

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unsigned long long __libcpp_blsr(unsigned long long __x) _NOEXCEPT {
  return __x ^ (__x & -__x);
}

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___BITS