To compile Xilinx libraries in ModelSim

To compile libraries manually, example compile commands would be:
vlib
vmap unisim /unisim

vcom -work unisim $XILINX_ENV/vhdl/src/unisims/unisim_vomp.vhd
Information can also be got on the website
park8817.com.ne.kr/modelsim_fpga.pdf