protected int getIntConst(Varnode vn) {
		if (!vn.isConstant()) {
			throw new IllegalArgumentException(vn + " is not a constant");
		}
		return (int) vn.getAddress().getOffset();
	}
Assert that a varnode is constant and get its value as an integer.

<p>
Here "constant" means a literal or immediate value. It does not read from the state.

@param vn the varnode
@return the value
Ghidra/Debug/ProposedUtils/src/main/java/ghidra/pcode/eval/AbstractVarnodeEvaluator.java