[GHC] #8623: Strange slowness when using async library with FFI callbacks

[GHC]

#8623: Strange slowness when using async library with FFI callbacks
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       Reporter:              |             Owner:  simonmar
  JohnWiegley                 |            Status:  new
           Type:  bug         |         Milestone:  7.8.1
       Priority:  normal      |           Version:  7.6.3
      Component:  Runtime     |  Operating System:  MacOS X
  System                      |   Type of failure:  Runtime performance bug
       Keywords:              |         Test Case:
   Architecture:              |          Blocking:
  Unknown/Multiple            |
     Difficulty:  Unknown     |
     Blocked By:              |
Related Tickets:              |
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 I've attached a Haskell and a C file, when compiled as such:

     ghc -DSPEED_BUG=0 -threaded -O2 -main-is SpeedTest SpeedTest.hs
 SpeedTestC.c

 You should find that with 7.4.2, 7.6.3 or a recent build of 7.8, building
 with SPEED_BUG=0 produces an executable that takes more than a second to
 run, while building with SPEED_BUG=1 runs very quickly.  I've also
 attached the Core for both scenarios.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8623>
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