Simon, Sorry for the delay on responding.
I'm using 6.6, so I'll upgrade to 6.6.1 and retest. Preusmably you're only interested if this behaviour persists in 6.6.1. I'll check both cases and make a test cases for them if necessary.
I've upgraded to 6.6.1 and am pleased to report that there appears to be no difference between seq and bang-patterns in the simplifier output. As for the other case (where a function results in two functions in the simplifier output, which appear to be some sort of worker-wrapper pair), a module is attached which gives this behaviour. I compiled it with: ghc -c UTF8.hs -O2 -prof -auto -ddump-simpl Look for $s$wfromUTF8Ptr and $wfromUTF8Ptr. I also notice that with -auto-all, the function readUTF8Char appears in the simplifier output, but with -auto it is inlined into fromUTF8Ptr, and so vanishes from the simplifier output. Running my test case compiled with -auto seems to gives run times at about 70-80% of -auto-all, and allocation is 40% (!) of -auto-all; that's a significant difference. Alistair