libcxx/include/__bit/popcount.h

   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_NODISCARD_EXT _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