Ok, we made some progress on performance last week, but there's still plenty to do. Here's a summary: - Simon PJ found an O(n^2) case in the simplifier that appears to be the cause of most, if not all, of the cases of GHC going out to lunch when compiling certain modules. However, while testing the fix we discovered that it caused worse code to be generated for some programs, so we're still looking into this. - I added a hack in GHC's back end to do some lightweight buffering of the