[GHC] #2439: Missed optimisation with dictionaries and loops

[GHC]

#2439: Missed optimisation with dictionaries and loops
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        Reporter:  rl                |                   Owner:  simonpj
            Type:  bug               |                  Status:  new
        Priority:  lowest            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  6.9
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by simonpj):

 You don't give an actual example, and my brain is too small to reconstruct
 the code you have in mind.

 Still, I do agree that wrapping a single value in a data type carries an
 indirection cost.  We could make GHC strict in non-single-method
 dictionaries; indeed that's the way it's supposed to work right now.  But
 someone needs to actually try it out, benchmark etc.

 In short, I'm in no hurry to make this change.

 Meanwhile, it's a crime that you have to fake this stuff up.  The more
 concrete your examples of what you can't do type-securely, the more likely
 someone is to fix them.  At the moment I am clueless.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2439#comment:24>
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