[GHC] #9344: takeWhile does not participate in list fusion

[GHC]

#9344: takeWhile does not participate in list fusion
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              Reporter:  dfeuer      |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:              |           Version:  7.8.3
  libraries/base                     |          Keywords:
            Resolution:              |  Operating System:  Unknown/Multiple
Differential Revisions:              |   Type of failure:  Runtime
          Architecture:              |  performance bug
  Unknown/Multiple                   |         Test Case:
            Difficulty:  Unknown     |          Blocking:
            Blocked By:              |
       Related Tickets:              |
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Comment (by nomeata):

 > As for speed, if I'm not very much mistaken it takes a lot of slowness
 and/or a good number of mispredicted branches to make up for the cache
 effects that excessive allocation will have when combined with non-trivial
 code, so I believe that should probably be a secondary concern.

 True, and I’m not worried about that; I’m worried about the short-
 circuting of `takeWhile`: Does it properly stop the producer from
 calculating the rest of the list or not. From looking at the code I
 believe it does, though.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9344#comment:3>
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