Only check for successful vectorization on wider_reduce_into_iter

Different vectorization results are due to different LLVM versions.

Author: dianqk

tests/codegen/simd/simd-wide-sum.rs

@@ -52,8 +52,6 @@ pub fn wider_reduce_iter(x: Simd<u8, N>) -> u16 {
 #[no_mangle]
 // CHECK-LABEL: @wider_reduce_into_iter
 pub fn wider_reduce_into_iter(x: Simd<u8, N>) -> u16 {
-    // CHECK: zext <16 x i8>
-    // CHECK-SAME: to <16 x i16>
-    // CHECK: call i16 @llvm.vector.reduce.add.v16i16(<16 x i16>
+    // CHECK: call i16 @llvm.vector.reduce.add
     x.to_array().into_iter().map(u16::from).sum()
 }