[GHC] #14754: -O1 changes result at runtime

[GHC]

#14754: -O1 changes result at runtime
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        Reporter:  Bodigrim          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:
       Component:  Compiler          |              Version:  8.4.1-alpha1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Bodigrim):

 macOS High Sierra 10.13.3

 I encountered the issue, because it affects build of `arithmoi` on Travis,
 so it should be reproducible on Ubuntu too.

 GHC 8.2.2 is fine.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14754#comment:2>
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