Profile guided and string routines?

Does anyone have any experience of what can be profiled in the profiled guided optimisations?

One of the problems with some of the string routines is that you can write pretty neat fast routines that work well for long strings - but most of the calls actually pass short strings and the overhead of the fast routine means that for most cases you are slower than you would have been with a simple routine.

If Profile Guiding could spot that a particular callsite to say strlen() was often associated with strings of at least 'n' characters we could call a different implementation.

Dave