[GHC] #11365: Worse performance with -O

[GHC]

#11365: Worse performance with -O
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        Reporter:                    |                Owner:
  facundo.dominguez                  |
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:
      Resolution:                    |             Keywords:  optimization
                                     |  performance concurrency
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by rwbarton):

 The "state hack" seems to be responsible here. Without `-O`, the argument
 to `replicateM_` is shared and therefore the expensive computation occurs
 only once. With `-O`, `replicateM_` is inlined and then due to the "state
 hack" GHC thinks it is okay to duplicate the expensive computation.

 Try building with `-fno-state-hack`. I made other small adjustments to the
 program in testing; you may also need `-fno-full-laziness`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11365#comment:1>
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