Function safe_arch::load_m128d_splat_m256d

#[must_use]pub fn load_m128d_splat_m256d(a: &m128d) -> m256d

This is supported with target feature avx only.

Load an m128d and splat it to the lower and upper half of an m256d

let a = m128d::from_array([0.0, 1.0]);
let b = load_m128d_splat_m256d(&a).to_array();
assert_eq!(b, [0.0, 1.0, 0.0, 1.0]);