Function _mm256_mask_expand_pd 

pub fn _mm256_mask_expand_pd(src: __m256d, k: __mmask8, a: __m256d) -> __m256d

Available on x86-64 and target feature avx512f and target feature avx512vl only.

Load contiguous active double-precision (64-bit) floating-point elements from a (those with their respective bit set in mask k), and store the results in dst using writemask k (elements are copied from src when the corresponding mask bit is not set).

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