[GHC] #11770: Demand analysis: Wrong one-shot annotation due to fixed-point iteration

[GHC]

#11770: Demand analysis: Wrong one-shot annotation due to fixed-point iteration
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        Reporter:  nomeata           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
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 nomeata):

 > Get rid of all one-shot setting in the demand analyser, letting the
 occurrence analyser do the work. The demand analyser would then annotate
 only demand info.

 But would that not mean that useful one-shot information determined by the
 demand analyzer will not be reflected here, and hence not used in later
 passes, e.g. by the simplifier when trying to to floating a let into a
 lambda?

 > I'm suspicious of that updOneShotInfo which keeps one-shot info if it
 was there before.

 Note that due to the magic `oneShot` function, there might be one-shot
 info worth preserving.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11770#comment:3>
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