We don't currently have the information needed to correctly provide the
base typespec, but in the next() and prev() methods I need to know if
the enumeration is two or four state. This patch sets the base typespec
for four state enumerations to vpiReg and to vpiBitVar for two state
enumerations. This provide enough information to get next() and prev()
working correctly.
Create the v2009.vpi module to include SystemVerilog core
functions, and start out with some of the enum methods.
Add to vvp support for creating enum types, including some
vpi access methods.