Function _mm512_mask2_permutex2var_epi64

#[target_feature(enable = "avx512f")]
pub fn _mm512_mask2_permutex2var_epi64(a: __m512i, idx: __m512i, k: __mmask8, b: __m512i) -> __m512i

Shuffle 64-bit integers in a and b across lanes using the corresponding selector and index in idx, and store the results in dst using writemask k (elements are copied from idx when the corresponding mask bit is not set).

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