Function safe_arch::load_f64_splat_m256d

#[must_use]pub fn load_f64_splat_m256d(a: &f64) -> m256d

This is supported with target feature avx only.

Load an f64 and splat it to all lanes of an m256d

let a = 1.0;
let b = load_f64_splat_m256d(&a).to_array();
assert_eq!(b, [1.0, 1.0, 1.0, 1.0]);