#4301: Optimisations give bad core for foldl' (flip seq) () -------------------------------------+------------------------------------- Reporter: | Owner: daniel.is.fischer | Status: new Type: bug | Milestone: 7.10.1 Priority: low | Version: 6.12.3 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: Runtime | Related Tickets: performance bug | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by thomie): * cc: dfeuer (added) * difficulty: => Unknown Comment: `foldl'` doesn't seem to get inlined with HEAD. I don't know if this ticket is still relevant. {{{ $ cat test.hs module Foo where import Data.List foo :: [a] -> () foo = foldl' (flip seq) () $ ghc-7.9.20141125 -ddump-simpl -dsuppress-all -fforce-recomp -O test.hs ... foo1 foo1 = \ @ a_aua x_auY y_auZ -> case y_auZ of _ { __DEFAULT -> x_auY } foo foo = \ @ a_aua -> foldl' (foo1) () }}} With 7.8.3: {{{ $ ghc-7.8.3 -ddump-simpl -dsuppress-all -fforce-recomp -O test.hs ... Rec { foo1 foo1 = \ @ a_avy w_sP6 -> case case w_sP6 of _ { [] -> (); : x_aOm xs_aOn -> case x_aOm of _ { __DEFAULT -> case foo1 xs_aOn of _ { (# #) -> () } } } of _ { () -> (##) } end Rec } foo foo = \ @ a_avy w_sPd -> case foo1 w_sPd of _ { (# #) -> () } }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/4301#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler