add comment on profiler

agb/src/interrupt.rs

@@ -362,6 +362,14 @@ mod tests {
 }
 
 #[must_use]
+/// The behaviour of this function is undefined in the sense that it will output
+/// some information in some way that can be interpreted in a way to give some
+/// profiling information. What it outputs, how it outputs it, and how to
+/// interpret it are all subject to change at any time.
+///
+/// With that out of the way, the current version will, in mgba, output the
+/// program counter at regular intervals. This can be used to see hot functions
+/// using, for example, addr2line.
 pub fn profiler(timer: &mut crate::timer::Timer, period: u16) -> InterruptHandler {
     timer.set_interrupt(true);
     timer.set_overflow_amount(period);