Test core::simd works

These tests just verify some basic APIs of core::simd function, and
guarantees that attempting to access the wrong things doesn't work.
The majority of tests are stochastic, and so remain upstream, but
a few deterministic tests arrive in the subtree as doc tests.

Author: workingjubilee

core/tests/lib.rs

@@ -62,6 +62,7 @@
 #![feature(unwrap_infallible)]
 #![feature(option_result_unwrap_unchecked)]
 #![feature(result_into_ok_or_err)]
+#![cfg_attr(not(bootstrap), feature(portable_simd))]
 #![feature(ptr_metadata)]
 #![feature(once_cell)]
 #![feature(unsized_tuple_coercion)]
@@ -104,6 +105,8 @@ mod pattern;
 mod pin;
 mod ptr;
 mod result;
+#[cfg(not(bootstrap))]
+mod simd;
 mod slice;
 mod str;
 mod str_lossy;

core/tests/simd.rs

@@ -0,0 +1,13 @@
+use core::simd::f32x4;
+
+#[test]
+fn testing() {
+    let x = f32x4::from_array([1.0, 1.0, 1.0, 1.0]);
+    let y = -x;
+
+    let h = x * 0.5;
+
+    let r = y.abs();
+    assert_eq!(x, r);
+    assert_eq!(h, f32x4::splat(0.5));
+}