Function _mm512_mask_popcnt_epi8 

pub fn _mm512_mask_popcnt_epi8(
    src: __m512i,
    k: __mmask64,
    a: __m512i,
) -> __m512i

Available on x86 and target feature avx512bitalg only.

For each packed 8-bit integer maps the value to the number of logical 1 bits.

Uses the writemask in k - elements are copied from src if the corresponding mask bit is not set. Otherwise the computation result is written into the result.

Intel’s documentation