#15164: Slowdown in ghc compile times from GHC 8.0.2 to GHC 8.2.1 when doing Called arity analysis -------------------------------------+------------------------------------- Reporter: flip101 | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.6.1 Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Compile-time (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Hello, I have this program that compiles against packages of stack LTS-9.21. When i compile with GHC 8.0.2 (version of LTS-9.21) the compiling is fast. 72.01user 34.61system 0:52.98elapsed 201%CPU (0avgtext+0avgdata 600684maxresident)k When i upgrade to LTS-11.9 compiling gets slow. To test if it was a problem with new package or GHC (ghc gives some new packages too) i ran: /usr/bin/time stack build --compiler ghc-8.2.1 --ghc-options="-v3 -j4 -O2 -fexcess-precision -optc-O3 -optc-ffast-math -rtsopts=none -no-rtsopts- suggestions" with the old package of LTS-9.21 but with the newer GHC 8.2.1 compiler. Now the compile times are much higher: 2481.26user 663.66system 35:38.82elapsed 147%CPU (0avgtext+0avgdata 674732maxresident)k I already took out parts of the grammar to get it even to compile. When i have the full grammar i can let my laptop compile 24 hours and it's still busy. I was not sure how to further reduce the code. Maybe when a lot of effort i can cut out a few lines here and there. So i uploaded the entire project here https://github.com/flip111/parser-calledarityanalysis i already took out a lot of code. If anyone has suggestions on how to further reduce the code i can try. Because i had debug info on (-v3 flag) i saw it was stuck for a long time at "Called arity analysis" I prioritize this bug high because i think the slowdown is very problematic. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15164 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler