Available on

**x86-64 and target feature**only.`avx512bitalg,avx512vl`

## Expand description

Considers the input `b`

as packed 64-bit integers and `c`

as packed 8-bit integers.
Then groups 8 8-bit values from `c`

as indices into the 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.