In the 6.1i version of COMPXLIB, you can add additional compile options by modifying the configuration file. The configuration file is located in the directory in which you ran COMPXLIB, and it will be named "compxlib.cfg". Open this file and add +v2k to the VCS line as illustrated below:
OPTION:vcs:verilog: -Mupdate +v2k
Once this modification is complete, re-run COMPXLIB from the directory containing the configuration file; COMPXLIB will use the new option.
In the 5.1i/5.2i software, COMPXLIB cannot be modified to add the +v2k switch. You must manually compile the files for CORE Generator.