public boolean isRegister() {
		int type = AddressSpace.ID_TYPE_MASK & spaceID;
		return (type == AddressSpace.TYPE_REGISTER);
	}
@return true if this varnode exists in a Register type space.
If false is returned, keep in mind this varnode may still correspond to a 
defined register within a memory space.  Memory-based registers may be indirectly 
addressed which leads to the distinction with registers within the register space.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/Varnode.java