[GHC] #9291: Don't reconstruct sum types if the type subtly changes

[GHC]

#9291: Don't reconstruct sum types if the type subtly changes
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        Reporter:  schyler  |            Owner:
            Type:  feature  |           Status:  new
  request                   |        Milestone:
        Priority:  normal   |          Version:  7.8.2
       Component:           |         Keywords:
  Compiler                  |     Architecture:  Unknown/Multiple
      Resolution:           |       Difficulty:  Moderate (less than a day)
Operating System:           |       Blocked By:
  Unknown/Multiple          |  Related Tickets:
 Type of failure:           |
  None/Unknown              |
       Test Case:           |
        Blocking:           |
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Comment (by nomeata):

 >  I would be less interested in the cost of the operation as much as I
 would be interested in the possibility that the CSE could merge multiple
 branches, which means loops can be tighter. Your idea is absolutely
 glorious.

 If you worry about small resulting code, then doing the transformation in
 STG (which is untyped) might be feasible.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9291#comment:11>
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