Hi,
You can use the same routine both in interrupt and the main program, only if this routine contains no local variables and parameters.
The feature that you are talking about, informing compiler that there is no reentrancy, is currently not supported by the mikroC PRO for PIC,
It is a very interesting suggestion, and our developers will consider it and eventually add it, but I can't promise you anything.
Thank you for your feedback, and please feel free to inform us about any other problem or suggestion you might have.
I apologize for the inconvenience.
Regards,
Filip.