Allocating stack before calling function in arc_em assembly

[amgross]

In multiple places I see in arc_em assembly you are allocating 16 bytes on the stack before calling c function, for example at: https://github.com/azure-rtos/threadx/blob/b216ceb25e2b6ae1ea83c1ae91d114a6fc2fc4ec/ports/arc_em/metaware/src/tx_thread_schedule.s#L137-L139 https://github.com/azure-rtos/threadx/blob/b216ceb25e2b6ae1ea83c1ae91d114a6fc2fc4ec/ports/arc_em/metaware/src/tx_timer_interrupt.s#L195-L197 what is the reason for it?