[GHC] #9630: compile-time performance regression (probably due to Generics)

[GHC]

#9630: compile-time performance regression (probably due to Generics)
-------------------------------------+-------------------------------------
       Reporter:  hvr                |                   Owner:  simonpj
           Type:  bug                |                  Status:  new
       Priority:  normal             |               Milestone:  7.10.1
      Component:  Compiler           |                 Version:  7.9
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Unknown            |         Type of failure:  Compile-
     Blocked By:                     |  time performance bug
Related Tickets:  #9583              |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
 This is a continuation of #9583

 Compiling latest Cabal from Git's `Language.Haskell.Extension` module
 shows a significant performance regression with respect to GHC 7.8.3:

 {{{
 $ uname -a
 Linux duo 3.17.0-031700rc6-generic #201409211935 SMP Sun Sep 21 23:37:11
 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

 $ git describe
 cabal-install_merged-1912-g7161e4c

 ########################################################################################

 $ /opt/ghc/7.8.3/bin/ghc --version
 The Glorious Glasgow Haskell Compilation System, version 7.8.3

 $ /opt/ghc/7.8.3/bin/ghc -Rghc-timing -O -c Language/Haskell/Extension.hs
 <<ghc: 5228751760 bytes, 543 GCs, 34135677/114940864 avg/max bytes
 residency (14 samples), 273M in use, 0.00 INIT (0.03 elapsed), 4.96 MUT
 (5.28 elapsed), 3.26 GC (3.47 elapsed) :ghc>>

 ########################################################################################

 $ /opt/ghc/head/bin/ghc --version
 The Glorious Glasgow Haskell Compilation System, version 7.9.20140923

 $ /opt/ghc/head/bin/ghc -Rghc-timing -O -c Language/Haskell/Extension.hs
 <<ghc: 125917854120 bytes, 3181 GCs, 349136895/833496072 avg/max bytes
 residency (30 samples), 2096M in use, 0.001 INIT (0.001 elapsed), 133.003
 MUT (142.730 elapsed), 73.241 GC (78.234 elapsed) :ghc>>
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9630>
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