I somehow solved this issue by myself. The point is, if you open the 'si.env' file in the simulation directory, you should see "veriloga" in the simViewList line,like this:
simViewList = '("spectre" "cmos_sch" "cmos.sch" "schematic" "veriloga")
But the thing is it is useless to edit this file -- if you do (e.g. add "veriloga" into the parentheses), it will change back before it starts netlisting. So you have to run the simulation in a specific directory, although I am not sure of a general way to locate that directory...