Fortify test.

tests/codegen/overaligned-constant.rs

@@ -1,15 +1,23 @@
 // GVN may create indirect constants with higher alignment than their type requires. Verify that we
 // do not ICE during codegen, and that the LLVM constant has the higher alignment.
 //
-// compile-flags: -O -Zmir-enable-passes=+GVN -Cdebuginfo=2
+// compile-flags: -Zmir-opt-level=0 -Zmir-enable-passes=+GVN
 // compile-flags: -Cno-prepopulate-passes
 // only-64bit
 
 struct S(i32);
 
 struct SmallStruct(f32, Option<S>, &'static [f32]);
 
+// CHECK: @0 = private unnamed_addr constant
+// CHECK-SAME: , align 8
+
 fn main() {
+    // CHECK-LABEL: @_ZN20overaligned_constant4main
+    // CHECK: [[full:%_.*]] = alloca %SmallStruct, align 8
+    // CHECK: call void @llvm.memcpy.p0.p0.i64(ptr align 8 [[full]], ptr align 8 @0, i64 32, i1 false)
+    // CHECK: %b.0 = load i32, ptr @0, align 4,
+    // CHECK: %b.1 = load i32, ptr getelementptr inbounds ({ i32, i32 }, ptr @0, i32 0, i32 1), align 4
     let mut s = S(1);
 
     s.0 = 3;
@@ -26,6 +34,3 @@ fn main() {
     // alignment 8, but only use the `Option<S>` field, at offset 0 with alignment 4.
     let SmallStruct(a, b, c) = SMALL_VAL;
 }
-
-// CHECK: @0 = private unnamed_addr constant
-// CHECK-SAME: , align 8