[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):

 The reason why `-O2` is needed is because an extra pass of the simplifer
 is ran after the `-fliberate-case` pass. If you don't run this extra pass,
 there are lots of uninlined calls to `c<*>` left over.

 The core running with `-O` is here. Starting on about line 950 you can see
 all the nested calls to `<*>` which have been duplicated.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13253#comment:16>
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