[GHC] #15519: Minor code refactoring leads to drastic performance degradation

[GHC]

#15519: Minor code refactoring leads to drastic performance degradation
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        Reporter:  danilo2           |                Owner:  (none)
            Type:  bug               |               Status:  infoneeded
        Priority:  highest           |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by danilo2):

 @simonpj I removed Criterion as dependency here and get the same results.
 Compile it and pass the resulting eecutable a number - `0`, `1` or `2` to
 execute `test0`, `test1` or `test2` respectively.

 https://github.com/wdanilo/ghc-bug-peg-
 optimization/blob/master/src/Main.hs

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15519#comment:8>
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