Add autovectorization codegen test

Co-authored-by: Scott McMurray <scottmcm@users.noreply.github.com>

src/test/codegen/autovectorize-f32x4.rs

@@ -0,0 +1,31 @@
+// compile-flags: -C opt-level=3
+// only-x86_64
+#![crate_type = "lib"]
+
+// CHECK-LABEL: @auto_vectorize_direct
+#[no_mangle]
+pub fn auto_vectorize_direct(a: [f32; 4], b: [f32; 4]) -> [f32; 4] {
+// CHECK: load <4 x float>
+// CHECK: load <4 x float>
+// CHECK: fadd <4 x float>
+// CHECK: store <4 x float>
+    [
+        a[0] + b[0],
+        a[1] + b[1],
+        a[2] + b[2],
+        a[3] + b[3],
+    ]
+}
+
+// CHECK-LABEL: @auto_vectorize_loop
+pub fn auto_vectorize_loop(a: [f32; 4], b: [f32; 4]) -> [f32; 4] {
+// CHECK: load <4 x float>
+// CHECK: load <4 x float>
+// CHECK: fadd <4 x float>
+// CHECK: store <4 x float>
+    let mut c = [0.0; 4];
+    for i in 0..4 {
+        c[i] = a[i] + b[i];
+    }
+    c
+}