#15019: Fix performance regressions from #14737 -------------------------------------+------------------------------------- Reporter: tdammers | Owner: tdammers Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #14737 | Differential Rev(s): phab:D4568 Wiki Page: | -------------------------------------+------------------------------------- Comment (by tdammers): Looking at one of the regressions, T9010, I set up a trap to catch only those coercions that are found to be equal by `eqType`, but don't match on `isReflCo`. And they're all the same: `(State# RealWorld -> (# State# RealWorld, () #), State# RealWorld -> (# State# RealWorld, () #))`. So this one looks like it would be relatively easy to detect. Unfortunately, the other one, T12707, paints a different picture; here, the matches look like these: {{{ (forall a. K1 R Bool a -> [String] -> [String], forall a. K1 R Bool a -> [String] -> [String]) }}} {{{ (forall a. M1 S ('MetaSel ('Just "foo3Field08") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (K1 R (Maybe Bool)) a -> [String] -> [String], forall a. M1 S ('MetaSel ('Just "foo3Field08") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe Bool)) a -> [String] -> [String]) }}} {{{ (forall a. (:*:) (((S1 ('MetaSel ('Just "foo0Field00") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 String) :*: S1 ('MetaSel ('Just "foo0Field01") 'NoSourceUnpackedness 'SourceStrict 'DecidedUnpack) (Rec0 Int)) :*: (S1 ('MetaSel ('Just "foo0Field02") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 [Int]) :*: (S1 ('MetaSel ('Just "foo0Field03") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe Bool)) :*: S1 ('MetaSel ('Just "foo0Field04") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Bool)))) :*: ((S1 ('MetaSel ('Just "foo0Field05") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 String) :*: S1 ('MetaSel ('Just "foo0Field06") 'NoSourceUnpackedness 'SourceStrict 'DecidedUnpack) (Rec0 Int)) :*: (S1 ('MetaSel ('Just "foo0Field07") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 [Int]) :*: (S1 ('MetaSel ('Just "foo0Field08") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe Bool)) :*: S1 ('MetaSel ('Just "foo0Field09") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Bool))))) (((S1 ('MetaSel ('Just "foo0Field10") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 String) :*: S1 ('MetaSel ('Just "foo0Field11") 'NoSourceUnpackedness 'SourceStrict 'DecidedUnpack) (Rec0 Int)) :*: (S1 ('MetaSel ('Just "foo0Field12") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 [Int]) :*: (S1 ('MetaSel ('Just "foo0Field13") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe Bool)) :*: S1 ('MetaSel ('Just "foo0Field14") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Bool)))) :*: ((S1 ('MetaSel ('Just "foo0Field15") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 String) :*: S1 ('MetaSel ('Just "foo0Field16") 'NoSourceUnpackedness 'SourceStrict 'DecidedUnpack) (Rec0 Int)) :*: (S1 ('MetaSel ('Just "foo0Field17") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 [Int]) :*: (S1 ('MetaSel ('Just "foo0Field18") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe Bool)) :*: S1 ('MetaSel ('Just "foo0Field19") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Bool))))) a -> [String] -> [String], forall a. (:*:) (((S1 ('MetaSel ('Just "foo0Field00") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 String) :*: S1 ('MetaSel ('Just "foo0Field01") 'NoSourceUnpackedness 'SourceStrict 'DecidedUnpack) (Rec0 Int)) :*: (S1 ('MetaSel ('Just "foo0Field02") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 [Int]) :*: (S1 ('MetaSel ('Just "foo0Field03") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe Bool)) :*: S1 ('MetaSel ('Just "foo0Field04") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Bool)))) :*: ((S1 ('MetaSel ('Just "foo0Field05") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 String) :*: S1 ('MetaSel ('Just "foo0Field06") 'NoSourceUnpackedness 'SourceStrict 'DecidedUnpack) (Rec0 Int)) :*: (S1 ('MetaSel ('Just "foo0Field07") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 [Int]) :*: (S1 ('MetaSel ('Just "foo0Field08") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe Bool)) :*: S1 ('MetaSel ('Just "foo0Field09") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Bool))))) (((S1 ('MetaSel ('Just "foo0Field10") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 String) :*: S1 ('MetaSel ('Just "foo0Field11") 'NoSourceUnpackedness 'SourceStrict 'DecidedUnpack) (Rec0 Int)) :*: (S1 ('MetaSel ('Just "foo0Field12") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 [Int]) :*: (S1 ('MetaSel ('Just "foo0Field13") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe Bool)) :*: S1 ('MetaSel ('Just "foo0Field14") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Bool)))) :*: ((S1 ('MetaSel ('Just "foo0Field15") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 String) :*: S1 ('MetaSel ('Just "foo0Field16") 'NoSourceUnpackedness 'SourceStrict 'DecidedUnpack) (Rec0 Int)) :*: (S1 ('MetaSel ('Just "foo0Field17") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 [Int]) :*: (S1 ('MetaSel ('Just "foo0Field18") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (Maybe Bool)) :*: S1 ('MetaSel ('Just "foo0Field19") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Bool))))) a -> [String] -> [String]) }}} Further digging, however, reveals that these are all `Sym` coercions, so I think I can figure out a faster way to detect these. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15019#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler