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 <__bit/rotate.h>
13 #include <__concepts/arithmetic.h>
14 #include <__config>
15 #include <limits>
16 
17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
18 #  pragma GCC system_header
19 #endif
20 
21 _LIBCPP_PUSH_MACROS
22 #include <__undef_macros>
23 
24 _LIBCPP_BEGIN_NAMESPACE_STD
25 
26 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
27 int __libcpp_ctz(unsigned __x)           _NOEXCEPT { return __builtin_ctz(__x); }
28 
29 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
30 int __libcpp_ctz(unsigned long __x)      _NOEXCEPT { return __builtin_ctzl(__x); }
31 
32 _LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
33 int __libcpp_ctz(unsigned long long __x) _NOEXCEPT { return __builtin_ctzll(__x); }
34 
35 #if _LIBCPP_STD_VER >= 20
36 
37 template <__libcpp_unsigned_integer _Tp>
38 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr int countr_zero(_Tp __t) noexcept {
39   if (__t == 0)
40     return numeric_limits<_Tp>::digits;
41 
42   if (sizeof(_Tp) <= sizeof(unsigned int))
43     return std::__libcpp_ctz(static_cast<unsigned int>(__t));
44   else if (sizeof(_Tp) <= sizeof(unsigned long))
45     return std::__libcpp_ctz(static_cast<unsigned long>(__t));
46   else if (sizeof(_Tp) <= sizeof(unsigned long long))
47     return std::__libcpp_ctz(static_cast<unsigned long long>(__t));
48   else {
49     int __ret = 0;
50     const unsigned int __ulldigits = numeric_limits<unsigned long long>::digits;
51     while (static_cast<unsigned long long>(__t) == 0uLL) {
52       __ret += __ulldigits;
53       __t >>= __ulldigits;
54     }
55     return __ret + std::__libcpp_ctz(static_cast<unsigned long long>(__t));
56   }
57 }
58 
59 template <__libcpp_unsigned_integer _Tp>
60 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr int countr_one(_Tp __t) noexcept {
61   return __t != numeric_limits<_Tp>::max() ? std::countr_zero(static_cast<_Tp>(~__t)) : numeric_limits<_Tp>::digits;
62 }
63 
64 #endif // _LIBCPP_STD_VER >= 20
65 
66 _LIBCPP_END_NAMESPACE_STD
67 
68 _LIBCPP_POP_MACROS
69 
70 #endif // _LIBCPP___BIT_COUNTR_H
71