Check out http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/HscMain and the notes at the top of http://darcs.haskell.org/ghc/compiler/coreSyn/CorePrep.lhs Beyond that I'm happy to help Simon | -----Original Message----- | From: haskell-cafe-bounces@haskell.org [mailto:haskell-cafe- | bounces@haskell.org] On Behalf Of Tom Ellis | Sent: 14 March 2013 20:05 | To: Haskell Cafe | Subject: [Haskell-cafe] Where's the case? or The difference between simpl and | prep | | The -ddump-simpl output below doesn't contain a case corresponding to the | seq in sum', but the -ddump-prep does. Isn't the output from simpl the | input to prep? If so, where does the case reappear from? If not, how are | simpl and prep related? | | It seems to have something to do with "Str=DmdType SS" but I don't | understand. This seems to come from the IdInfo on the Id which is the | binder "Test.sum'" but [1] says that this information is optional so it | seems strange that such crucial information would be encoded there. | | Thanks, | | Tom | | [1] http://www.haskell.org/ghc/docs/7.6.2/html/libraries/ghc- | 7.6.2/IdInfo.html#t:IdInfo | | | % cat Test.hs | module Test where | | sum' :: [Integer] -> Integer -> Integer | sum' [] n = n | sum' (x:xs) n = n `seq` sum' xs (n + x) | % ghc -fforce-recomp -ddump-simpl -O2 Test.hs | [1 of 1] Compiling Test ( Test.hs, Test.o ) | | ==================== Tidy Core ==================== | Result size = 14 | | Rec { | Test.sum' [Occ=LoopBreaker] | :: [GHC.Integer.Type.Integer] | -> GHC.Integer.Type.Integer -> GHC.Integer.Type.Integer | [GblId, Arity=2, Caf=NoCafRefs, Str=DmdType SS] | Test.sum' = | \ (ds_daw :: [GHC.Integer.Type.Integer]) | (n_a9J :: GHC.Integer.Type.Integer) -> | case ds_daw of _ { | [] -> n_a9J; | : x_a9K xs_a9L -> | Test.sum' xs_a9L (GHC.Integer.Type.plusInteger n_a9J x_a9K) | } | end Rec } | | | | % ghc -fforce-recomp -ddump-prep -O2 Test.hs | [1 of 1] Compiling Test ( Test.hs, Test.o ) | | ==================== CorePrep ==================== | Result size = 17 | | Rec { | Test.sum' [Occ=LoopBreaker] | :: [GHC.Integer.Type.Integer] | -> GHC.Integer.Type.Integer -> GHC.Integer.Type.Integer | [GblId, Arity=2, Caf=NoCafRefs, Str=DmdType SS, Unf=OtherCon []] | Test.sum' = | \ (ds_saQ :: [GHC.Integer.Type.Integer]) | (n_saS :: GHC.Integer.Type.Integer) -> | case ds_saQ of _ { | [] -> n_saS; | : x_saW xs_saV -> | case GHC.Integer.Type.plusInteger n_saS x_saW | of sat_saZ { __DEFAULT -> | Test.sum' xs_saV sat_saZ | } | } | end Rec } | | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe@haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe