stack pointer access?

I am have a bug that I'm trying to track down. I need to know the PC value at the point when an interrupt occurs. In the interrupt routine I need to get the return PC from the stack correct? I'm looking through the documentation and having trouble figuring out how to access the stack pointer to retrieve and send the interrupted PC value. I am using the IAR ARM C compiler, and the LM3s618. How do I get access to the stack pointer? Which offset from the SP will the PC address be?

thanks,

Brian