Function _mm512_mask_bitshuffle_epi64_mask

Considers the input b as packed 64-bit integers and c as packed 8-bit integers. Then groups 8 8-bit values from cas indices into the bits of the corresponding 64-bit integer. It then selects these bits and packs them into the output.

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

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