AArch64 String.compareTo() may return incorrect result in some corner
cases. This issue can be reproduced in below program by constructing two
strings from the same byte array but with different encoding options.

import java.lang.reflect.Constructor;

public class Test {
  public static void main(String[] args) throws Exception {
    Constructor<String> c = String.class.getDeclaredConstructor(byte[].class, byte.class);
    c.setAccessible(true);

    byte[] bytes = new byte[] {
      'Y', 'm', '_', 'l', 'V', 'n', 'W', 'S', 'w', 'm', 'W', 'S'
    };

    String s1 = c.newInstance(bytes, (byte) 0);
    String s2 = c.newInstance(bytes, (byte) 1);
    System.out.println(s1.compareTo(s2));
  }
}

// $ java -Xint Test
// -27904
// $ java -Xcomp -XX:-TieredCompilation Test
// 6