Function _mm512_castsi256_si512 

pub fn _mm512_castsi256_si512(a: __m256i) -> __m512i

Available on x86 and target feature avx512f only.

Cast vector of type __m256i to type __m512i; the upper 256 bits of the result are indeterminate.

In the Intel documentation, the upper bits are declared to be “undefined”. This is not equivalent to mem::MaybeUninit; instead, these bits are non-deterministically set to some valid value. In practice, this is typically equivalent to mem::zeroed.

This intrinsic is only used for compilation and does not generate any instructions, thus it has zero latency.

Intel’s documentation