Which isn't super helpful, because there is [a GCC `__builtin_popcount`](https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html), a POPCNT intrinsic if you're developing for SSE4, and [existing implementations](https://en.wikipedia.org/wiki/Hamming_weight#Efficient_imple...) you can look up at any time if you don't want to reinvent the wheel.