一个深度不大于16位的移位寄存器, ISE综合时就会用一个LUT来替代它？

Most synthesis tools (e. g. Synplify Pro, Xilinx XST) are able to infer LUT based shift register (SRL16E) from your source code. Even for depth greater than 16, the tool is smart enough to infer multiple SRL16E to realize the shift register. Another way to utilize this feature is to instantiate an SRL16E in the source code. You can refer to the Library Guide in the Xilinx ISE software package for more details. （参考译文：大多数综合工具, 例如Synplify Pro和Xilinx XST, 都能根据源代码中的移位寄存器SRL16E来推断 LUT. 即使是深度大于16的情况, 此类工具也能够推断出多SRL16E, 从而实现移位寄存器. 利用此功能的另一种途径是在原代码中例示一个SRL16E. 详细说明可以参考Xilinx ISE软件包中的库指南. ）