[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:  7.6.2                  
   Component:  Compiler          |     Version:  6.9                    
    Keywords:                    |          Os:  Unknown/Multiple       
Architecture:  Unknown/Multiple  |     Failure:  Runtime performance bug
  Difficulty:  Unknown           |    Testcase:                         
   Blockedby:                    |    Blocking:                         
     Related:                    |  
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Comment(by simonpj):

 The `-fdicts-strict` flag exists but it has had no love for years, and I
 doubt it works right.

 One obstacle is that at the moment we implement a ''single-method'' type
 class with a newtype rather than a data type. We don't want to make that
 strict, lest we force the method rather than the dictionary.

 I rather think we sould remove the special case, so that all dictionaries
 are data types; then we could be uniformly strict.  But we should do some
 bemchmarking to check that nothing slows down.

 Just awaiting someone with a bit of time and benchmarking bandwidth...

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2439#comment:17>
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