def all_solidity_variables_used_as_args(self):
        """
            Return the Soldiity variables directly used in a call

            Use of the IR to filter index access
            Used to catch check(msg.sender)
        """
        if self._all_solidity_variables_used_as_args is None:
            self._all_solidity_variables_used_as_args = self._explore_functions(
                lambda x: self._explore_func_nodes(x, self._solidity_variable_in_internal_calls))
        return self._all_solidity_variables_used_as_args