Function safe_arch::population_count_i64

#[must_use]pub fn population_count_i64(a: i64) -> i32

This is supported with target feature popcnt only.

Count the number of bits set within an i64

assert_eq!(population_count_i64(0), 0);
assert_eq!(population_count_i64(0b1), 1);
assert_eq!(population_count_i64(0b1001), 2);