[GHC] #13236: Improve floating for join points

[GHC]

#13236: Improve floating for join points
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        Reporter:  simonpj           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  JoinPoints
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Question 2: I'm not saying that we never have a candidate MFE that has a
 join point as a free var.

 I AM saying that in that situation we should not float the MFE.  How could
 it possibly be beneficial?  Floating is mainly to get things outside a
 value lambda -- but that's invalid there's a free join point.  Or to top
 level; ditto.  Case closed.

 Can you give an example where let-binding an MFE (as a join point of
 course) with a free variable is beneficial?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13236#comment:3>
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