#12545: Compilation time/space regression in GHC 8.0/8.1 (search in type-level lists and -O) -------------------------------------+------------------------------------- Reporter: | Owner: (none) mikhail.vorozhtsov | Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Inlining Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): See [https://mail.haskell.org/pipermail/ghc-devs/2017-May/014277.html this ghc-devs thread], and [https://mail.haskell.org/pipermail/ghc- devs/2017-June/014278.html this one]. There seem to be several issues: * Why does the small change identified by Ryan have such a huge effect? We need insight. * The change that Richard made to `CoreOpt.simple_opt_expr` actually fixed an outright bug. But it's ''still'' wrong now. See Trac #13798. * The fuss that is caused by this `map/coerce` rule is out of all proportion to its importance. We should think of a better way. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12545#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler