public static AddressXML restoreXml(XmlElement el, CompilerSpec cspec)
			throws XmlParseException {
		AddressXML result;
		if (el.getName().equals("register")) {
			String regName = el.getAttribute("name");
			if (regName == null) {
				throw new XmlParseException("Missing pentry register name");
			}
			Register register = cspec.getLanguage().getRegister(regName);
			if (register == null) {
				throw new XmlParseException("Unknown pentry register: " + regName);
			}
			result = new AddressXML(register.getAddressSpace(), register.getOffset(),
				register.getMinimumByteSize());
		}
		else {
			result = new AddressXML();
			result.size = 0;
			String spaceName = el.getAttribute("space");
			result.space = cspec.getAddressSpace(spaceName);
			if (result.space == null) {
				throw new XmlParseException("Unknown address space: " + spaceName);
			}
			if (result.space.getType() == AddressSpace.TYPE_JOIN) {
				result.readJoinXML(el, cspec);
			}
			else {
				result.offset = SpecXmlUtils.decodeLong(el.getAttribute("offset"));
			}
			String sizeString = el.getAttribute("size");
			if (sizeString != null) {
				result.size = SpecXmlUtils.decodeInt(sizeString);
			}
		}
		return result;
	}
Restore an Address (as an AddressSpace and an offset) and an optional size from XML tag.
The tag can have any name, but it must either have:
   - A "name" attribute, indicating a register name  OR
   - A "space" and "offset" attribute, indicating the address space and offset
   
If a register name is given, size is obtained from the register.  If an offset is
given, the size can optionally be specified using a "size" attribute.
If not explicitly described, the size is set to zero.

This method supports the "join" address space attached to the compiler specification
@param el is the XML tag
@param cspec is the compiler spec for looking up registers
@return an AddressXML object containing the recovered space,offset,size
@throws XmlParseException for problems parsing
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/AddressXML.java