Slowdown in ghc compile times from GHC 8.0.2 to GHC 8.2.1 when doing Called arity analysis
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.