code: public void resetLabels() {
          AbstractInsnNode insn = first;
          while (insn != null) {
              if (insn instanceof LabelNode) {
                  ((LabelNode) insn).resetLabel();
              }
              insn = insn.next;
          }
      }
docs: Reset all labels in the instruction list. This method should be called
  before reusing same instructions list between several
  <code>ClassWriter</code>s.