[GHC] #1168: Optimisation sometimes decreases sharing in IO code

[GHC]

#1168: Optimisation sometimes decreases sharing in IO code
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        Reporter:  simonmar          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  ⊥
       Component:  Compiler          |              Version:  6.6
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime           |            Test Case:
  performance bug                    |  nofib/spectral/calendar
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 See #11677 for another example

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1168#comment:22>
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