SIMD in Rust is kinda gross.

gross.rs

// Type your code here, or load an example.
#[cfg(target_arch = "x86")]
use std::arch::x86::__m128;
#[cfg(target_arch = "x86_64")]
use std::arch::x86_64::__m128;

#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "sse2"))]
pub struct Ray {
    pub pt: __m128,
    pub dir: __m128,
}

#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "sse2"))]
pub struct Aabb {
    pub min: __m128,
    pub max: __m128,
}

macro_rules! _mm_shuffle {
    ($w:expr, $z:expr, $y:expr, $x:expr) => (
        ($w << 6) | ($z << 4) | ($y << 2) | $x
    )
}

#[cfg(all(any(target_arch = "x86", target_arch = "x86_64"), target_feature = "sse2"))]
pub fn hit(aabb: &Aabb, r: &Ray, t_min: f32, t_max: f32) -> bool {
    #[cfg(target_arch = "x86")]
    use std::arch::x86::*;
    #[cfg(target_arch = "x86_64")]
    use std::arch::x86_64::*;

    unsafe {
        let inv_d =  _mm_div_ps(_mm_set1_ps(1.), r.dir);
        let t0 = _mm_mul_ps(_mm_sub_ps(aabb.min, r.pt), inv_d);
        let t1 = _mm_mul_ps(_mm_sub_ps(aabb.max, r.pt), inv_d);
        // swap
        let nm = _mm_cmplt_ps(inv_d, _mm_setzero_ps());
        let (t0, t1) = (_mm_or_ps(_mm_and_ps(t1, nm), _mm_andnot_ps(nm, t0)),
                        _mm_or_ps(_mm_and_ps(t0, nm), _mm_andnot_ps(nm, t1)));
        let t_min = _mm_move_ss(_mm_shuffle_ps(t0, t0, _mm_shuffle!(2, 1, 0, 0)), _mm_set_ss(t_min));
        let t_max = _mm_move_ss(_mm_shuffle_ps(t1, t1, _mm_shuffle!(2, 1, 0, 0)), _mm_set_ss(t_max));
        let t_min = {
            let v = _mm_max_ps(t_min, _mm_shuffle_ps(t_min, t_min, _mm_shuffle!(0, 0, 3, 2)));
            let v = _mm_max_ps(v, _mm_shuffle_ps(v, v, _mm_shuffle!(0, 0, 0, 1)));
            _mm_cvtss_f32(v)
        };
        let t_max =  { 
            let v = _mm_min_ps(t_max, _mm_shuffle_ps(t_max, t_max, _mm_shuffle!(0, 0, 3, 2)));
            let v = _mm_min_ps(v, _mm_shuffle_ps(v, v, _mm_shuffle!(0, 0, 0, 1)));
            _mm_cvtss_f32(v)
        };

        t_min < t_max
    }
}