Function _mm_mask_popcnt_epi16 

pub fn _mm_mask_popcnt_epi16(src: __m128i, k: __mmask8, a: __m128i) -> __m128i

Available on x86-64 and target feature avx512bitalg and target feature avx512vl only.

For each packed 16-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