Function safe_arch::floor_m128d

#[must_use]pub fn floor_m128d(a: m128d) -> m128d

This is supported with target feature sse4.1 only.

Round each lane to a whole number, towards negative infinity

let a = m128d::from_array([-0.1, 1.8]);
assert_eq!(floor_m128d(a).to_array(), [-1.0, 1.0]);