#8774: Transitivity of Auto-Specialization -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Resolution: | Keywords: Inlining Operating System: Linux | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #5928, #8668, | Differential Rev(s): #8099 | Wiki Page: | -------------------------------------+------------------------------------- Comment (by crockeea): I finally got 7.6 installed, and can reproduce the issue. The problem isn't that a `Foo a` appears, it's that without the SPECIALIZE pragma, there is a function called `Main.$splus` in core that takes/uses dictionaries, even though the type is monomorphic: {{{ Main.$splus :: Foo.Foo (Foo.Qux GHC.Types.Int) -> Foo.Foo (Foo.Qux GHC.Types.Int) -> Foo.Foo (Foo.Qux GHC.Types.Int) [GblId, Arity=2, Str=DmdType SS, Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=2, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [30 30] 110 20}] Main.$splus = \ (ds_dJ0 :: Foo.Foo (Foo.Qux GHC.Types.Int)) (ds1_dJ1 :: Foo.Foo (Foo.Qux GHC.Types.Int)) -> case ds_dJ0 of _ { Foo.Bar v1_aH6 -> case ds1_dJ1 of _ { Foo.Bar v2_aH7 -> case (Foo.$fNumQux_$c+ @ GHC.Types.Int GHC.Num.$fNumInt Data.Vector.Unboxed.Base.$fUnboxInt v1_aH6 v2_aH7) }}} Replying to [comment:10 erikd]:
Even with ghc 7.6, this seems to specialize correctly:
{{{ cabal exec -- ghc -fforce-recomp -ddump-simpl -dsuppress-idinfo main.hs 2>&1 | grep Foo ... @ (Foo.Qux GHC.Types.Int) @ (Foo.Foo (Foo.Qux GHC.Types.Int)) (Foo.$WBar @ (Foo.Qux GHC.Types.Int)) ... }}}
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8774#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler