From some tests, we find System.arraycopy() call with negated small length does not work on AArch64 CPUs with SVE. Below simple Java program can reproduce this issue.

public class Test {
  static char[] src = {'A', 'A', 'A', 'A', 'A'};
  static char[] dst = {'B', 'B', 'B', 'B', 'B'};

  static void copy(int nlen) {
    System.arraycopy(src, 0, dst, 0, -nlen);
  }

  public static void main(String[] args) {
    for (int i = 0; i < 25000; i++) {
      copy(0);
    }
    copy(-5);
    for (char c : dst) {
      if (c != 'A') {
        throw new RuntimeException("Wrong value!");
      }
    }
    System.out.println("PASS");
  }
}

/*
$ java -Xint Test
PASS
$ java -Xbatch Test
Exception in thread "main" java.lang.RuntimeException: Wrong value!
        at Test.main(Test.java:16)
*/

Investigation shows this issue is caused by a new AArch64 matching rule vmask_gen_sub introduced in JDK-8293198. We should fix it ASAP.