[GHC] #13930: Cabal configure regresses in space/time

[GHC]

#13930: Cabal configure regresses in space/time
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        Reporter:  bgamari           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13982            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 My apologies, Simon: I believe I was mistaken when I said this required
 profiling to reproduce.

 This can be reproduced with current GHC `master` with,
 {{{
 $ git clone git://github.com/haskell/cabal
 $ cd cabal
 $ ghc-pkg unregister Cabal
 $ cabal install Cabal/ --allow-newer
 $ cabal install cabal-install/ --allow-newer --only-dependencies
 $ cd cabal-install
 $ cabal build
 }}}

 The `unregister Cabal` bit is necessary for some GHC versions due to Cabal
 bug [[https://github.com/haskell/cabal/issues/4509|#4509]].

 For the record, a quick profile reveals that most of the allocations seem
 to be coming from `Distribution.ParseUtils` and
 `Distribution.Compat.ReadP` (both in `Cabal`).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13930#comment:7>
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