General Description: MAP may convert XC5200 Logiblox adder CY_MUX's to FG muxes.
There is currently a known problem with Map converting CY_MUX's to FG muxes. This occurs after the CY_MUX used for carry chain initialization has been optimized away.
解决方案
A solution is currently under investigation.
As a work-around, you may use a similar component from the Xilinx Unified Library instead.