The usual way to invoke Vmgen is as follows:
vmgen inputfile
Here inputfile is the VM instruction description file, which usually ends in .vmg. The output filenames are made by taking the basename of inputfile (i.e., the output files will be created in the current working directory) and replacing .vmg with -vm.i, -disasm.i, -gen.i, -labels.i, -profile.i, and -peephole.i. E.g., vmgen hack/foo.vmg will create foo-vm.i, foo-disasm.i, foo-gen.i, foo-labels.i, foo-profile.i and foo-peephole.i.