[GHC] #7994: Make foldl into a good consumer

[GHC]

#7994: Make foldl into a good consumer
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        Reporter:  simonpj           |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by nomeata):

 > (Or, a variant: Do that initialisation, but also do local fixed-
 pointing, starting from the stored values, so that when an inner let is
 re-analysed, but nothing has changed, then there is only one iteration.)

 Ah, so that is what `ae_virigin` is all about... doing the same trick in
 my code helps in keeping compilation times down; but I must be introducing
 bugs somewhere; compiled with my code GHC itself goes into infinite loops
 – but that is a problem for another day.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7994#comment:6>
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