The disable of the interrupts is needed in ALL cases if you have higher priority interrupts enabled. The use of R0 or R1 as suggested by San would make that register unusable for main code. However, if this interrupt is high priority or all interrupts are low priority, you may skip the disable. Now, as far as I'm concerned, any interrupt that need to know where the main program is is an indication of bad design. I would like for once to be disproven on that one.

Have fun,

Erik