求synplify综合报告某警告的含义

becoll

用synplify综合时产生了如下警告： @W: FX474 |User specified initial value found in some of the sequential elements in the design. Applying an initial value to a register may not deliver the best synthesis results. For example, registers with initial values may be preserved and retiming/pipelining may not be performed. To improve synthesis results you may want to remove the register initialization from the RTL code
          没太看明白，请高手指点下：User specified initial value found in some of the sequential elements in the design是个什么情况？可否举个例说明一下？谢谢