private void buildVarnodeRefs() {
		refmap = new HashMap<>((int) (1.5 * vbank.size()));
		Iterator<?> iter = vbank.locRange();			// Iterate over all varnodes
		while (iter.hasNext()) {
			VarnodeAST vn = (VarnodeAST) iter.next();
			refmap.put(vn.getUniqueId(), vn);
		}
	}
return all PcodeOps associated with a particular instruction Address
@param addr -- Address of instruction generating PcodeOps
@return -- Iterator to PcodeOps
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/PcodeSyntaxTree.java