It seem it's possible to canonicalize Class.getClass() intrinsic method when the receiver is type of InstanceConstant:

e.g. case#1

  B b = B.default;
  Class s = b.getClass(); // canonicalize to constant

case#2
   public static B foo(){
        return B.default;
    }

    public static boolean test1() {
        B b = foo();
        Class s = b.getClass();
        return true;
    }