COMPXLIB is a tool for compiling the Xilinx HDL-based simulation libraries with the tools provided by simulator vendors. Libraries are generally compiled or recompiled anytime a new version of a simulator is installed, a new ISE version is installed, a new service pack is installed, or when a new IP Update is installed.
Before starting the functional simulation of your design, you must compile the Xilinx simulation libraries for the target vendor simulator. For this purpose, Xilinx provides COMPXLIB.
Note: Do NOT use with ModelSim XE (Xilinx Edition) or ISE Simulator. These simulators come with precompiled Xilinx libraries.