[Haskell-cafe] GHC optimizations and unsafePerformIO - Was: Data.Typeable TypeRep Ord instance.

Thinking about this there might be one problem: Without having looked further into this I think perfomance might not be as expected. Using unsafePerformIO affects ghc's optimzations, doesn't it? So I wonder if it's a good idea (from a performance point of view) to use this.

2010/12/30 Andreas Baldeau :

...

instance Ord TypeRep where    compare t1 t2 =        compare            (unsafePerformIO (typeRepKey t1))            (unsafePerformIO (typeRepKey t2))

...

typeRepKey :: TypeRep -> IO Int typeRepKey (TypeRep (Key i) _ _) = return i

So the question is, if ghc could transform this to simply compare the keys throwing away unsafePerformIO and return.