It is very likely that issue 17386 is the issue. With {-# OPTIONS_GHC -Wno-overlapping-patterns -Wno-incomplete-patterns -Wno-incomplete-uni-patterns -Wno-incomplete-record-updates #-}
my module(s) compile very quickly. I'll wait and see if GHC 9 does better before I try to create a smaller case (and now I at least have a workaround). Sebastian Graf <sgraf1...@gmail.com> writes: > Hi, > > I'm not sure I see all the context of the conversation, but it is entirely > possible that code with many local constraints regresses the pattern-match > checker (which is accounted to Desugaring in the profile emitted by -v2), > I'm afraid. That simply has to do with the fact that we now actually care > about them, previously they were mostly discarded. > > I'd be glad if you submitted a relatively isolated reproducer of what is > fast with 8.8 and slow with 8.10 (even better 9.0). > I hope that things have improved since we fixed > https://gitlab.haskell.org/ghc/ghc/-/issues/17836, which is part of 9.0 but > not of 8.10. > > Cheers, > Sebastian > > Am Mo., 15. Feb. 2021 um 19:04 Uhr schrieb Troels Henriksen < > at...@sigkill.dk>: > >> Carter Schonwald <carter.schonw...@gmail.com> writes: >> >> > Ccing ghc devs since that’s a better forum perhaps >> > Crazy theory: >> > >> > this is a regression due the the partial changes to pattern matching >> > coverage checking in 8.10 that finished / landed in ghc 9 >> > >> > Why: >> > Desugaring is when pattern/ case statement translation happens I think? >> > And the only obvious “big thing” is that you have some huge , albeit sane >> > for a compiler, pattern matching >> > >> > I’d first check if the new ghc 9 release doesn’t have that regression in >> > build time that you experienced. And if it does file a ticket. >> > >> > I may be totally wrong, but that seems like a decent likelihood ! >> >> You may be right! Another module that regressed is also mainly >> characterised by large-but-not-insane case expressions: >> >> https://github.com/diku-dk/futhark/blob/d0839412bdd11884d75a1494dd5de5191833f39e/src/Futhark/Optimise/Simplify/Rules.hs >> >> I'll try to split these modules up a little bit (I should have done so a >> while ago anyway) and maybe that will make the picture even clearer. >> >> -- >> \ Troels >> /\ Henriksen >> _______________________________________________ >> ghc-devs mailing list >> ghc-devs@haskell.org >> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs >> -- \ Troels /\ Henriksen _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs