Tweaking a C Function I wrote

I wanted to see if I could squeeze any more performance out of a C set
returning function I wrote.  As such, I looked to a profiler.  Is it
possible to get profile information on the function I wrote?  I've got
postmaster and my function compiled with profiling support, and can find
the gmon.out files... can I actually look at the call tree that occurs
when my function is being executed or will I be limited to viewing calls
to functions in the postmaster binary?

-Adam