[GHC] #13253: Exponential compilation time with RWST & ReaderT stack with `-02`

[GHC]

#13253: Exponential compilation time with RWST & ReaderT stack with `-02`
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        Reporter:  phadej            |                Owner:  dfeuer
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             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:                    |
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Comment (by mpickering):

 Reverting 1722fa106e10e63160bb2322e2ccb830fd5b9ab3 improves the situation
 somewhat but -DBIG is still quite a bit slower.

 Pre-revert
 12s without -DBIG
 1m12 with -DBIG

 Post-revert
 8s without -DBIG
 28s with -DBIG

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13253#comment:12>
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