1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef _LIBCPP___BIT_COUNTR_H
10#define _LIBCPP___BIT_COUNTR_H
11
12#include <__config>
13#include <__type_traits/integer_traits.h>
14#include <limits>
15
16#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
17# pragma GCC system_header
18#endif
19
20_LIBCPP_PUSH_MACROS
21#include <__undef_macros>
22
23_LIBCPP_BEGIN_NAMESPACE_STD
24
25template <class _Tp>
26[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __countr_zero(_Tp __t) _NOEXCEPT {
27 static_assert(__is_unsigned_integer_v<_Tp>, "__countr_zero only works with unsigned types");
28 return __builtin_ctzg(__t, numeric_limits<_Tp>::digits);
29}
30
31#if _LIBCPP_STD_VER >= 20
32
33template <__unsigned_integer _Tp>
34[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr int countr_zero(_Tp __t) noexcept {
35 return std::__countr_zero(__t);
36}
37
38template <__unsigned_integer _Tp>
39[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr int countr_one(_Tp __t) noexcept {
40 return __t != numeric_limits<_Tp>::max() ? std::countr_zero(static_cast<_Tp>(~__t)) : numeric_limits<_Tp>::digits;
41}
42
43#endif // _LIBCPP_STD_VER >= 20
44
45_LIBCPP_END_NAMESPACE_STD
46
47_LIBCPP_POP_MACROS
48
49#endif // _LIBCPP___BIT_COUNTR_H
50