[GHC] #13873: Adding a SPECIALIZE at a callsite in Main.hs is causing a regression

[GHC]

#13873: Adding a SPECIALIZE at a callsite in Main.hs is causing a regression
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        Reporter:  jberryman         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.2
       Component:  Compiler          |              Version:  8.2.1-rc2
      Resolution:                    |             Keywords:  Specialise
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by simonpj):

 * keywords:   => Specialise


Comment:

 As I understand it, you are saying that

 * adding a SPECIALISE pragma with 8.2 made the the code runs 2x slower

 Whereas adding the same pragma with 8.0 made the code run 3x faster.  (But
 still not as fast as the slowest version with 8.2.)

 But it's the bulleted point that is mysterious.  Ben please do
 investigate.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13873#comment:2>
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