[GHC] #5642: Deriving Generic of a big type takes a long time and lots of space

[GHC]

#5642: Deriving Generic of a big type takes a long time and lots of space
-------------------------------------+-------------------------------------
        Reporter:  basvandijk        |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.3
      Resolution:                    |             Keywords:  deriving-
                                     |  perf, Generics
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:  T5642
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 The profile compiling `Data400.hs` from the repo given in comment:33 looks
 like this,
 {{{
         Wed Apr 27 23:26 2016 Time and Allocation Profiling Report
 (Final)

            ghc +RTS -hc -p -RTS
 -B/opt/exp/ghc/roots/profiled/lib/ghc-8.1.20160222 Data400.hs -fforce-
 recomp

         total time  =        5.12 secs   (5118 ticks @ 1000 us, 1
 processor)
         total alloc = 7,708,824,224 bytes  (excludes profiling overheads)

 COST CENTRE     MODULE       %time %alloc

 canEvVar        TcCanonical   41.0   45.8
 zonkTopDecls    TcRnDriver    17.4   25.3
 CorePrep        HscMain        6.4    7.5
 SimplTopBinds   SimplCore      5.9    2.6
 CoreTidy        HscMain        5.5    5.6
 Simplify        SimplCore      4.2    0.0
 deSugar         HscMain        3.6    1.7
 tc_rn_src_decls TcRnDriver     3.2    2.9
 solve_loop      TcInteract     2.5    0.7
 OccAnal         SimplCore      1.6    0.2
 pprNativeCode   AsmCodeGen     1.1    1.3
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5642#comment:34>
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