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_POPCOUNT_H
10 #define _LIBCPP___BIT_POPCOUNT_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 
__libcpp_popcount(unsigned __x)26 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_popcount(unsigned __x) _NOEXCEPT {
27   return __builtin_popcount(__x);
28 }
29 
__libcpp_popcount(unsigned long __x)30 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_popcount(unsigned long __x) _NOEXCEPT {
31   return __builtin_popcountl(__x);
32 }
33 
__libcpp_popcount(unsigned long long __x)34 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int __libcpp_popcount(unsigned long long __x) _NOEXCEPT {
35   return __builtin_popcountll(__x);
36 }
37 
38 #if _LIBCPP_STD_VER >= 20
39 
40 template <__libcpp_unsigned_integer _Tp>
popcount(_Tp __t)41 _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr int popcount(_Tp __t) noexcept {
42   if (sizeof(_Tp) <= sizeof(unsigned int))
43     return std::__libcpp_popcount(static_cast<unsigned int>(__t));
44   else if (sizeof(_Tp) <= sizeof(unsigned long))
45     return std::__libcpp_popcount(static_cast<unsigned long>(__t));
46   else if (sizeof(_Tp) <= sizeof(unsigned long long))
47     return std::__libcpp_popcount(static_cast<unsigned long long>(__t));
48   else {
49     int __ret = 0;
50     while (__t != 0) {
51       __ret += std::__libcpp_popcount(static_cast<unsigned long long>(__t));
52       __t >>= numeric_limits<unsigned long long>::digits;
53     }
54     return __ret;
55   }
56 }
57 
58 #endif // _LIBCPP_STD_VER >= 20
59 
60 _LIBCPP_END_NAMESPACE_STD
61 
62 _LIBCPP_POP_MACROS
63 
64 #endif // _LIBCPP___BIT_POPCOUNT_H
65