#12506: Compile time regression in GHC 8. -------------------------------------+------------------------------------- Reporter: deech | Owner: bgamari Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: 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 bgamari): The issue here seems to be the `Tree` module. With `-O1` compilation takes four minutes with much of the time being spent in the simplifier. However, deech said that his real concern was the compilation time with `-O0`. The culprit here appears to be desugaring, which takes over 10 seconds of the 30 second total compilation time (with a profiled compiler). Looking into the profile, it seems that the culprit is `simpleOptPgm`. In particular, it appears that the majority of desugaring time is spent in `optCoercion` called from the `Cast` branch of `simple_opt_expr.go`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12506#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler