static int lastIndexOfIgnoreCase_manual(S a, S b) {
  int la = strL(a), lb = strL(b);
  if (la < lb) ret -1;
  int n = la-lb;
  
  loop: for (int i = n; i >= 0; i--) {
    for (int j = 0; j < lb; j++) {
      char c1 = a.charAt(i+j), c2 = b.charAt(j);
      if (!eqic(c1, c2))
        continue loop;
    }
    ret i;
  }
  ret -1;
}

Began life as a copy of #1013296