[GHC] #10414: Buggy behavior with threaded runtime (-N1 working, -N2 getting into <<loop>>)

[GHC]

#10414: Buggy behavior with threaded runtime (-N1 working, -N2 getting into
<<loop>>)
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        Reporter:  exio4             |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by rwbarton):

 Inlining `concat` and `concatMap` made no difference, the program still
 loops and a `\s` thunk is still generated inside "`main_mygo`". This
 happens for any combination of the `-fkill-absence` and `-fkill-one-shot`
 flags, and in every version I tested (the 7.7 commit adding cardinality
 analysis, 7.8.4, 7.10.1 and HEAD).

 I then tried removing the `SingleEntry` case as Simon suggested in
 comment:9 and that did generate a `\u` thunk instead and the program no
 longer <<loop>>s.

 So, one conclusion is that `-fkill-absence`/`-fkill-one-shot` don't fully
 disable cardinality analysis like they are expected to.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10414#comment:18>
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