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// TODO: __builtin_ctzg is available since Clang 19 and GCC 14. When support for older versions is dropped, we can
10// refactor this code to exclusively use __builtin_ctzg.
11
12#ifndef _LIBCPP___BIT_COUNTR_H
13#define _LIBCPP___BIT_COUNTR_H
14
15#include <__bit/rotate.h>
16#include <__concepts/arithmetic.h>
17#include <__config>
18#include <limits>
19
20#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21# pragma GCC system_header
22#endif
23
24_LIBCPP_PUSH_MACROS
25#include <__undef_macros>
26
27_LIBCPP_BEGIN_NAMESPACE_STD
28
29_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_ctz(unsigned __x) _NOEXCEPT {
30 return __builtin_ctz(__x);
31}
32
33_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_ctz(unsigned long __x) _NOEXCEPT {
34 return __builtin_ctzl(__x);
35}
36
37_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_ctz(unsigned long long __x) _NOEXCEPT {
38 return __builtin_ctzll(__x);
39}
40
41template <class _Tp>
42_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int __countr_zero(_Tp __t) _NOEXCEPT {
43#if __has_builtin(__builtin_ctzg)
44 return __builtin_ctzg(__t, numeric_limits<_Tp>::digits);
45#else // __has_builtin(__builtin_ctzg)
46 if (__t == 0)
47 return numeric_limits<_Tp>::digits;
48 if (sizeof(_Tp) <= sizeof(unsigned int))
49 return std::__libcpp_ctz(static_cast<unsigned int>(__t));
50 else if (sizeof(_Tp) <= sizeof(unsigned long))
51 return std::__libcpp_ctz(static_cast<unsigned long>(__t));
52 else if (sizeof(_Tp) <= sizeof(unsigned long long))
53 return std::__libcpp_ctz(static_cast<unsigned long long>(__t));
54 else {
55 int __ret = 0;
56 const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
57 while (static_cast<unsigned long long>(__t) == 0uLL) {
58 __ret += __ulldigits;
59 __t >>= __ulldigits;
60 }
61 return __ret + std::__libcpp_ctz(static_cast<unsigned long long>(__t));
62 }
63#endif // __has_builtin(__builtin_ctzg)
64}
65
66#if _LIBCPP_STD_VER >= 20
67
68template <__libcpp_unsigned_integer _Tp>
69[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr int countr_zero(_Tp __t) noexcept {
70 return std::__countr_zero(__t);
71}
72
73template <__libcpp_unsigned_integer _Tp>
74[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr int countr_one(_Tp __t) noexcept {
75 return __t != numeric_limits<_Tp>::max() ? std::countr_zero(static_cast<_Tp>(~__t)) : numeric_limits<_Tp>::digits;
76}
77
78#endif // _LIBCPP_STD_VER >= 20
79
80_LIBCPP_END_NAMESPACE_STD
81
82_LIBCPP_POP_MACROS
83
84#endif // _LIBCPP___BIT_COUNTR_H
85