Re: [GHC] #9233: Compiler performance regression

#9233: Compiler performance regression ---------------------------------+------------------------------------ Reporter: augustss | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Windows | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: ---------------------------------+------------------------------------ Comment (by rwbarton): I profiled GHC and ran it on Lennart's sample code. It spent quite a lot of time, 23.4% in `coercionKind.go`. Further investigation seemed to indicate that most of that time was spent in the `TyConAppCo` case, when called from `coercionRole`. I made the Functor and Applicative (and other) instances of `Pair` lazy in the pair, trying to avoid traversing the entire coercion when we only need the outermost type constructor. It did speed up the compilation significantly, from 25 seconds to 18 seconds: {{{ # current HEAD <> # with lazy Pair instances <> }}} However, it had almost no effect on compile allocations for any program in nofib. Perhaps the bad behavior is triggered by large list or record literals. There must be other regressions, since 7.6.3 takes only 9 seconds on my system. Also, I note that the object files produced by 7.8 or HEAD for Flags and Options are about 25% larger than those produced by 7.6.3. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9233#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler