#13867: Silly definitions remain after SpecConstr -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Consider this {{{ f x xs = let g y = case y of [] -> 0 (a:as) -> g as in g (x:xs) }}} Compile with -O2 and we get this {{{ f = \ (@ t_axv) (@ a_axw) ($dNum_axx :: Num a_axw) (x_amR :: t_axv) (xs_amS :: [t_axv]) -> let { lvl_sxV [Dmd=<S,U>] :: a_axw [LclId, Str=DmdType] lvl_sxV = fromInteger @ a_axw $dNum_axx Foo.f1 } in letrec { $sg_syr [Occ=LoopBreaker] :: t_axv -> [t_axv] -> a_axw [LclId, Arity=2, Str=DmdType <L,U><L,U>] $sg_syr = \ _ [Occ=Dead] (sc1_syq :: [t_axv]) -> g_sxS sc1_syq; g_sxS [Occ=LoopBreaker] :: [t_axv] -> a_axw [LclId, Arity=1, Str=DmdType <S,1*U>] g_sxS = \ (y_amU :: [t_axv]) -> case y_amU of _ [Occ=Dead] { [] -> lvl_sxV; : a1_amV as_amW -> g_sxS as_amW }; } in $sg_syr x_amR xs_amS }}} Look at that stupid `$sg_syr` function. It should jolly well be inlined at its only call site. But it isn't because it's a loop breaker? Why is it a loop breaker? Because earlier there was a RULE for `g` that mentioned `$sg`. This is stupid. It's not killing us but it is obviously wrong. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13867> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler