[GHC] #7450: Regression in optimisation time of functions with many patterns (6.12 to 7.4)?

[GHC]

#7450: Regression in optimisation time of functions with many patterns (6.12 to
7.4)?
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        Reporter:  iustin            |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.6.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by bgamari):

 I think I finally found it (after struggling for far too long wondering
 why the profiles were so useless, eventually finding that I misspelled
 `OPTIONS_GHC`). `Specialise(pair_fvs)` shows up very strongly in the
 profile. Still trying to reason through what is happening.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7450#comment:14>
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