Function _mm_undefined_si128
#[target_feature(enable = "sse2")]
pub const fn _mm_undefined_si128() -> __m128iReturns vector of type __m128i with indeterminate elements.with indetermination elements.
Despite using the word "undefined" (following Intel's naming scheme), this non-deterministically
picks some valid value and is not equivalent to mem::MaybeUninit.
In practice, this is typically equivalent to mem::zeroed.