Function _mm256_cmp_pd_mask 

pub fn _mm256_cmp_pd_mask(a: __m256d, b: __m256d, const IMM8: i32) -> __mmask8

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

Compare packed double-precision (64-bit) floating-point elements in a and b based on the comparison operand specified by imm8, and store the results in mask vector k.

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