> because 64-bit ARMv8.0 lacks a POPCNT instruction It does have this: https://developer.arm.com/documentation/ddi0596/2021-09/SIMD-FP-Instructions/CNT--Popula

> because 64-bit ARMv8.0 lacks a POPCNT instruction It does have this: https://developer.arm.com/documentation/ddi0596/2021-09/SIMD-FP-Instructions/CNT--Population-Count-per-byte- https://developer.arm.com/documentation/ddi0596/2021-09/SIMD... And GCC happily uses it https://godbolt.org/z/dTW46f9Kf https://godbolt.org/z/dTW46f9Kf