There are mainly two methods to realize this function:
(1) use the tools which can conduct the mix-hdl simulation such as Modelsim and so on
(2) For VCS that is unable to implement this function, then you should follow the process below:
a. create a directory named worklib
b. under this dirctory use the vhdlan commands to map the vhdl source file into the dirctory-- vhdlan -work worklib m1.vhd
c. in the environment, instantiate the vhdl module as m1 m1_ins();
d. in the VCS options: -mhdl \
+ vhdllib+worklib.m1