[GHC] #7944: GHC goes into an apparently infinite loop at -O2

[GHC]

#7944: GHC goes into an apparently infinite loop at -O2
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        Reporter:  bos               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.9
      Resolution:                    |             Keywords:  SpecConstr
Operating System:  Unknown/Multiple  |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #5550 #8852       |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I just tried compiling the programs in comment:5 and comment:8 with GHC
 8.2.1 and HEAD, and neither went into an infinite loop. I'm not sure
 OtToMH what commit fixed this (wild guess:
 8674883c137401873fd53a6963acd33af651c2af ?), but we should find it and add
 a regression test for it so that this stays fixed.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7944#comment:12>
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