Add ptr argument check

Author: calebzulawski

tests/codegen/simd/repr-packed.rs

@@ -26,6 +26,7 @@ fn load<T, const N: usize>(v: Simd<T, N>) -> FullSimd<T, N> {
 // CHECK-LABEL: @square_packed
 #[no_mangle]
 pub fn square_packed(x: Simd<f32, 3>) -> FullSimd<f32, 3> {
+    // CHECK: align 4 dereferenceable(12) %x
     // CHECK: load <3 x float>, ptr %x, align 4
     let x = load(x);
     unsafe { simd_mul(x, x) }