[GHC] #10124: Simple case analyses generate too many branches

[GHC]

#10124: Simple case analyses generate too many branches
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        Reporter:  bgamari           |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.8.4
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #6135, #9661      |  Differential Revisions:
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Comment (by bgamari):

 nomeata, indeed LLVM transforms the C analogue to the example given here
 into only 9 instructions.

 I'd agree that it seems better to avoid breaking up the case expression to
 begin with.

 This weekend I focused on giving the user the ability to write the
 branchless implementation explicitly by fixing #9661. It would be nice to
 have a story for how we could transform cases into branch-less form
 without user intervention, although I'm not sure how to know when this
 transform will pay off.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10124#comment:9>
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