docs: public void dup() {
          ClassNode type = getTopOperand();
          stack.add(type);
          MethodVisitor mv = controller.getMethodVisitor();
          if (type == ClassHelper.double_TYPE || type == ClassHelper.long_TYPE) {
              mv.visitInsn(DUP2);
          } else {
              mv.visitInsn(DUP);
          }
      }