If you remove everything but the quotInteger test from integerConstantFolding and compile with -ddump-rule-rewrites then you'll see that the eqInteger rule fires before quotInteger. This is presumably comparing against 0, as the definition of quot for Integer (in GHC.Real) is _ `quot` 0 = divZeroError n `quot` d = n `quotInteger` d Yes, I noticed these two rules firing together - perhaps that's the explanation why. I created a small program for testing:
main = print quotInt quotInt :: Integer quotInt = 100063 `quot` 156 I noticed that when I define eqInteger wrapper to be NOINLINE, the call to quot is translated to Core as: Main.quotInt = GHC.Real.$fIntegralInteger_$cquot (__integer 100063) (__integer 156) but when I change the wrapper to INLINE I get: Main.quotInt = GHC.Real.$fNumRatio_$cquot <-------- NumRatio instead of IntegralInteger (__integer 100063) (__integer 156) All rule firing happens later (I used -ddump-simpl-iterations -ddump-rule-firings), except that for $fNumRatio_$cquot the quot rules don't fire.
Do you also still have eqInteger wired in? It sounds like you might have given them both the same unique? No, they didn't have the same unique. I modified the existing rules to work on the new primops and ignore their wrappers. At the moment I reverted these changes so that I can make progress and leave this problem for later.
Janek