FileCheck mutable_variable.

Author: cjgillot

tests/mir-opt/const_prop/mutable_variable.rs

@@ -1,8 +1,13 @@
-// skip-filecheck
 // unit-test: ConstProp
 
 // EMIT_MIR mutable_variable.main.ConstProp.diff
 fn main() {
+    // CHECK-LABEL: fn main(
+    // CHECK: debug x => [[x:_.*]];
+    // CHECK: debug y => [[y:_.*]];
+    // CHECK: [[x]] = const 42_i32;
+    // CHECK: [[x]] = const 99_i32;
+    // CHECK: [[y]] = const 99_i32;
     let mut x = 42;
     x = 99;
     let y = x;