[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 rwbarton):

 Replying to [comment:8 schyler]:
 > @rwbarton, does that still make it simple for the CSE to eliminate extra
 branches?

 Good question. I don't think it would get CSEd at the Core level, but
 hopefully it would in a later pass (STG or Cmm).

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9291#comment:12>
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