The popcount built-ins work fine for zero, so there's no need to check
for it.
libstdc++-v3/ChangeLog:
* include/std/bit (__popcount): Remove redundant check for zero.
using __gnu_cxx::__int_traits;
constexpr auto _Nd = __int_traits<_Tp>::__digits;
- if (__x == 0)
- return 0;
-
constexpr auto _Nd_ull = __int_traits<unsigned long long>::__digits;
constexpr auto _Nd_ul = __int_traits<unsigned long>::__digits;
constexpr auto _Nd_u = __int_traits<unsigned>::__digits;