As I describe in #9617, GHC's CSE in 7.9 seems to be good enough to let Int and Integer use quot x y = fst (x `quotRem` y) rem x y = snd (x `quotRem` y) And actually get good results in code that uses both the quotient and the remainder. I believe the only thing left to be able to actually implement this is a simple rule to turn a match on quotRemInt# into one on quotInt# or remInt# if only the quotient or only the remainder is used. My question is where I could stick such a rule. Can anyone advise me? All I know is that it has to happen after CSE.