Same happens in HEAD, so nothing to do with your changes. I didn't notice that, I was comparing against 7.6.2 :/
Better define mkFloatingRelOpRule instead, which doesn't have the equal-args thing. That's what I did initially, but I wasn't sure if that's acceptable because some optimisations will be gone, e.g. ==# 3.0 3.0 will not rewrite to #1 (perhaps this isn't that bad, because comparing floating point numbers for equality isn't a good idea anyway).
Janek
Simon
| -----Original Message----- | From: ghc-devs-bounces@haskell.org [mailto:ghc-devs-bounces@haskell.org] | On Behalf Of Jan Stolarek | Sent: 22 April 2013 13:48 | To: ghc-devs@haskell.org | Subject: Handling of NaN | | I need some help with my work on ticket #6135. Consider this program: | | {-# LANGUAGE BangPatterns, MagicHash #-} module Main where | | import GHC.Exts | | main = print $ nan## ==## nan## | where !(D# nan##) = 0.0 / 0.0 | | This prints False, which is a correct implementation of IEEE754 | standard. However when I compile this with my modified compiler that | uses new comparison primops (they return Int# instead of | Bool) I get True, whcih obviously is incorrect. I belive that the | problem lies in this piece of code from prelude/PrelRules.hs: | | mkRelOpRule :: Name -> (forall a . Ord a => a -> a -> Bool) | -> [RuleM CoreExpr] -> Maybe CoreRule mkRelOpRule nm cmp | extra | = mkPrimOpRule nm 2 $ rules ++ extra | where | rules = [ binaryLit (\_ -> cmpOp cmp) | , equalArgs >> | -- x `cmp` x does not depend on x, so | -- compute it for the arbitrary value 'True' | -- and use that result | return (if cmp True True | then trueVal | else falseVal) ] | | It looks that equalArgs suddenly started to return True, whereas it | previously returned False. On the other hand in GHCi I get correct | result (False). Can anyone give me a hint why is this happening? | | Janek | | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs