Rollup merge of rust-lang#130991 - LaihoE:vectorized_slice_contains, …

…r=Noratrieb

Vectorized SliceContains

Godbolt for the u32 case: https://rust.godbolt.org/z/exT9xYWGs

Unsure about:
- Should align_to be used? It didn't seem to matter in my benchmark but maybe I was lucky with alignment?
- Should u8/i8 also be implemented? Currently uses memchr (SWAR)

Some benchmarks on x86 (contains called on an array with no matches, worst case may be slightly worse):

## Large N
![large_n_contains](/~https://github.com/user-attachments/assets/5be79072-970b-44be-a56c-16dc677dee46)

## Small N
![small_n_contains](/~https://github.com/user-attachments/assets/b8a33790-c176-459f-84f4-05feee893cd0)

core/src/slice/cmp.rs

@@ -257,3 +257,29 @@ impl SliceContains for i8 {
         memchr::memchr(byte, bytes).is_some()
     }
 }
+
+macro_rules! impl_slice_contains {
+    ($($t:ty),*) => {
+        $(
+            impl SliceContains for $t {
+                #[inline]
+                fn slice_contains(&self, arr: &[$t]) -> bool {
+                    // Make our LANE_COUNT 4x the normal lane count (aiming for 128 bit vectors).
+                    // The compiler will nicely unroll it.
+                    const LANE_COUNT: usize = 4 * (128 / (mem::size_of::<$t>() * 8));
+                    // SIMD
+                    let mut chunks = arr.chunks_exact(LANE_COUNT);
+                    for chunk in &mut chunks {
+                        if chunk.iter().fold(false, |acc, x| acc | (*x == *self)) {
+                            return true;
+                        }
+                    }
+                    // Scalar remainder
+                    return chunks.remainder().iter().any(|x| *x == *self);
+                }
+            }
+        )*
+    };
+}
+
+impl_slice_contains!(u16, u32, u64, i16, i32, i64, f32, f64, usize, isize);