protected T evaluateBranch(Program program, Varnode vn, Map<Varnode, T> already) {
		PcodeOp def = vn.getDef();
		if (def == null || def.getOutput() != vn) {
			throw new PcodeExecutionException("No defining p-code op for " + vn);
		}
		return evaluateOp(program, def, already);
	}
Evaluate the given varnode's defining p-code op

@param program the program defining the static context
@param vn the varnode
@param already a cache of already-evaluated varnodes and their values
@return the value
Ghidra/Debug/ProposedUtils/src/main/java/ghidra/pcode/eval/AbstractVarnodeEvaluator.java