Optimization beyond the Module Border

[Simon Peyton-Jones]

| I have noticed that there is a great difference between optimizing
| modules separately and all at once, e.g., with -fforce-recomp. I have
| had examples factors up to 15 in run time (and even different behavior
| in context with unsafePerformIO).

GHC does a lot of cross-module inlining already, and *does* write stuff into interface files, provided you use -O.

I'm always interested in performance differences of a factor of 15 though!  Can you supply an example (as small as poss) for us to look at?

Thanks

Simon