Function safe_arch::add_horizontal_i16_m128i

#[must_use]pub fn add_horizontal_i16_m128i(a: m128i, b: m128i) -> m128i

This is supported with target feature ssse3 only.

Add horizontal pairs of i16 values, pack the outputs as a then b.

let a = m128i::from([1_i16, 2, 3, 4, -1, -2, -3, -4]);
let b = m128i::from([5_i16, 6, 7, 8, -15, -26, -37, 48]);
let c: [i16; 8] = add_horizontal_i16_m128i(a, b).into();
assert_eq!(c, [3, 7, -3, -7, 11, 15, -41, 11]);