[GHC] #11666: Severe performance degradation in GHC 8.0.1 compared to GHC 7.10.x

[GHC]

#11666: Severe performance degradation in GHC 8.0.1 compared to GHC 7.10.x
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        Reporter:  mrkkrp            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1-rc2
      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 goldfire):

 Just to be clear: the slowdown is primarily at runtime, not compile time,
 correct? We're aware of and working on a few compile-time regressions
 (though none that should be this bad), but if this is at runtime, it may
 be a newly-discovered problem.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11666#comment:6>
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