#13745: Investigate compile-time regressions in regex-tdfa-1.2.2 -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- hvr [[https://mail.haskell.org/pipermail/ghc- devs/2017-May/014208.html|points out]] that GHC 8.2 takes significantly longer to compile `regex-tdfa-1.2.2` than 8.0.2. Interestingly, it seems that compiler allocations fell dramatically while compilation time rose. {{{ GHC 8.0.2: <<ghc: 89544610040 bytes, 2301 GCs, 189183965/391103872 avg/max bytes residency (29 samples), 1075M in use, 0.001 INIT (0.001 elapsed), 55.747 MUT (61.520 elapsed), 23.276 GC (23.278 elapsed) :ghc>> GHC 8.2.1: <<ghc: 115210990008 bytes, 6383 GCs, 116487828/234031864 avg/max bytes residency (77 samples), 670M in use, 0.001 INIT (0.000 elapsed), 64.154 MUT (68.262 elapsed), 37.114 GC (37.077 elapsed) :ghc>> }}} == Reproducing == {{{ $ cabal unpack regex-tdfa-1.2.2 $ cd regex-tdfa-1.2.2 $ cabal install --only-dependencies $ cabal configure $ cabal build $ time ghc -idist/build/autogen -O2 Text/Regex/TDFA.hs \ -XMagicHash -XFlexibleInstances -XMultiParamTypeClasses \ -XRecursiveDo -XBangPatterns -XRankNTypes -XUnboxedTuples \ -XFlexibleContexts -XUnliftedFFITypes }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13745> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler