Function safe_arch::cast_to_m128d_from_m128i

#[must_use]pub fn cast_to_m128d_from_m128i(a: m128i) -> m128d

This is supported with target feature sse2 only.

Bit-preserving cast to m128d from m128i

let a = m128i::from([1, 2, 3, 4]);
let c: [u64; 2] = cast_to_m128d_from_m128i(a).to_bits();
assert_eq!(c, [0x200000001, 0x400000003]);