I am wondering whether there is a particular reason why the optimiser doesn't pull the

(1) a = NO_CCS PArray! [wild1 mba#];

and the

(2) case w of wild3 { I# e# ->

I checked with the before-ghci-branch compiler, and it pulls out (1) but not (2). Simon did a fair amount of work on improving the compilation of IO-ish code and code with lots of newtypes in it after we noticed some problems like the ones you point out above. We'll need to investigate whether the case can be pulled out of the loop too, though. Cheers, Simon