[GHC] #5344: CSE should look through coercions

[GHC]

#5344: CSE should look through coercions
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        Reporter:  reinerp           |                Owner:  simonpj
            Type:  feature request   |               Status:  closed
        Priority:  normal            |            Milestone:  ⊥
       Component:  Compiler          |              Version:  7.0.3
      Resolution:  duplicate         |             Keywords:  cse
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by rwbarton):

 Hah, you confused me by writing this comment before updating #9291 :)

 This example seems easier than the original example in #9291 though, since
 `f` can be expressed using a cast as a well-typed program in the current
 Core language. All else being equal, it seems better to do the CSE earlier
 rather than later, though I'm not sure whether it makes an actual
 difference in practice.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5344#comment:5>
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