[GHC] #10613: Mechanism for checking that we only enter single-entry thunks once

[GHC]

#10613: Mechanism for checking that we only enter single-entry thunks once
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        Reporter:  bgamari           |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by nomeata):

 > Why not emit some update code into a single entry thunk that updates the
 thunk with something that will explode if it is entered again? That seems
 a lot easier than allocating indirctions.

 Right, that would be sufficient to detect thunks that are wrongly marked
 single-entry. But we also want to learn about thunks that are ''not''
 marked single-entry, but should be.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10613#comment:9>
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