[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:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.9
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash                              |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #5550 #8852       |  Differential Revisions:
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Comment (by amosrobinson):

 Hmm. So I thought in this case, the is_too_recursive check should stop
 specialisation after a few runs.
 The counting of recursive constructors is only going down through
 applications though: I wonder whether it needs to handle lets, cases, etc?
 https://github.com/ghc/ghc/blob/master/compiler/specialise/SpecConstr.hs#L1807

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7944#comment:10>
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