Convert multiple supported forms of stack pointer representations into stack offsets.

    :param sp:  A stack pointer representation.
    :return:    A stack pointer offset.
    :rtype:     int

def parse_stack_pointer(sp):
    """
    Convert multiple supported forms of stack pointer representations into stack offsets.

    :param sp:  A stack pointer representation.
    :return:    A stack pointer offset.
    :rtype:     int
    """
    if isinstance(sp, int):
        return sp

    if isinstance(sp, StackBaseOffset):
        return sp.offset

    if isinstance(sp, BinaryOp):
        op0, op1 = sp.operands
        off0 = parse_stack_pointer(op0)
        off1 = parse_stack_pointer(op1)
        if sp.op == "Sub":
            return off0 - off1
        elif sp.op == "Add":
            return off0 + off1

    raise NotImplementedError("Unsupported stack pointer representation type %s." % type(sp))