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