Why are OMAPL138 Starterware ARM isr examples not declared as interrupt functions

The EVM examples do not use the ARM compiler interrupt keyword, they are simply declared as below:

static void TimerIsr(void)

void edma3CCComplIsr()

How are register values etc. preserved?

I have added the interrupt keyword to one of my interrupt functions which calls another function and the code now crashes. Can someone please explain the correct usage.