vivado错误请教

本人用Vivado2014.2例化了一个Ethernet 1000base-x pcs/pma的IP， 运行的时候一直报这个错误：

[Opt 31-67] Problem: A LUT2cell in the design is missing a connection on input pin I0, which is used bythe LUT equation. This pin has either been left unconnected in the design orthe connection was removed due to the trimming of unused logic. The LUT cellname

我看有个资料见附近里面描述了一种可能出现ERROR:[Opt 31-67]Problem: A LUT2 cell in the design is missing a connection on input pin I0,
which is used by the LUT equation.的情况，但是我还是不清楚如何约束

查一下是否把未使用的IO给固定了?

   并没有，但是把两个引脚的线引到顶层文件之后就编译通过了。也不知道为啥 但是这样不能解决问题啊 我顶层肯定不可能给他送信号的