Function safe_arch::set_splat_m128d

#[must_use]pub fn set_splat_m128d(a: f64) -> m128d

This is supported with target feature sse2 only.

Splats the args into both lanes of the m128d.

let a = m128d::from_array([1.0, 1.0]);
let b = set_splat_m128d(1.0);
assert_eq!(a.to_array(), b.to_array());