#12545: Compilation time/space regression in GHC 8.0/8.1 (search in type-level lists and -O) -------------------------------------+------------------------------------- Reporter: | Owner: (none) mikhail.vorozhtsov | Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Inlining 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 RyanGlScott): Found it. The other culprit is commit 1722fa106e10e63160bb2322e2ccb830fd5b9ab3 (Fix #11230.): {{{ Commit ae86eb9f72fa7220fe47ac54d6d21395691c1308 (Fix tcTyClTyVars to handle SigTvs) ----- $ time ghc4/inplace/bin/ghc-stage2 -fforce-recomp -O -c -Rghc-timing TypeList.hs Regression.hs <<ghc: 68211633024 bytes, 4916 GCs, 73233972/211211872 avg/max bytes residency (20 samples), 571M in use, 0.001 INIT (0.001 elapsed), 28.299 MUT (28.320 elapsed), 4.831 GC (4.828 elapsed) :ghc>> real 0m33.216s user 0m33.040s sys 0m0.176s Commit 1722fa106e10e63160bb2322e2ccb830fd5b9ab3 (Fix #11230.) ----- $ time ghc4/inplace/bin/ghc-stage2 -fforce-recomp -O -c -Rghc-timing TypeList.hs Regression.hs <<ghc: 161224532608 bytes, 8789 GCs, 195013385/460659576 avg/max bytes residency (37 samples), 1272M in use, 0.001 INIT (0.001 elapsed), 66.710 MUT (66.753 elapsed), 18.669 GC (18.660 elapsed) :ghc>> real 1m25.494s user 1m25.252s sys 0m0.260s }}} What's alarming is that that commit is so small! There must be something interesting happening there... -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12545#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler