Re: [GHC] #9279: Local wrapper function remains in final program; result = extra closure allocation

#9279: Local wrapper function remains in final program; result = extra closure allocation -------------------------------------+------------------------------------- Reporter: simonmar | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: LateLamLift Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Krzysztof Gogolewski ): In [changeset:"448b77b93b369745e9bfbc8b46a5b87bb73dd379/ghc" 448b77b9/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="448b77b93b369745e9bfbc8b46a5b87bb73dd379" Add RubbishLit for absent bindings of UnliftedRep Summary: Trac #9279 reminded us that the worker wrapper transformation copes really badly with absent unlifted boxed bindings. As `Note [Absent errors]` in WwLib.hs points out, we can't just use `absentError` for unlifted bindings because there is no bottom to hide the error in. So instead, we synthesise a new `RubbishLit` of type `forall (a :: TYPE 'UnliftedRep). a`, which code-gen may subsitute for any boxed value. We choose `()`, so that there is a good chance that the program crashes instead instead of leading to corrupt data, should absence analysis have been too optimistic (#11126). Reviewers: simonpj, hvr, goldfire, bgamari, simonmar Reviewed By: simonpj Subscribers: osa1, rwbarton, carter GHC Trac Issues: #15627, #9279, #4306, #11126 Differential Revision: https://phabricator.haskell.org/D5153 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9279#comment:23 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler