[GHC] #11158: Combine exprIsTrivial and cpe_ExprIsTrivial

[GHC]

#11158: Combine exprIsTrivial and cpe_ExprIsTrivial
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        Reporter:  simonpj           |                Owner:
            Type:  task              |               Status:  infoneeded
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1656
       Wiki Page:                    |
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Comment (by nomeata):

 >  (Trying to set NoCafInfo on all the extra floats I am generating here,
 and rebuilding the libraries. Will report back.)

 That did the trick. No more crashes. I conclude that having a data
 constructor closure mentioned in the SRT is bad.

 But it is not everz occurence that causes problems: With the libraries
 built so that all new floats have `NoCafInfo`, and then building my test
 program to include the floated `()` closure or `GHC.Base.Nothing_closure`
 in the SRT does *not* crash. So there must be further conditions required
 for such an entry in the SRT causing a crash.


 Maybe with this analysis Simon Marlow can without too much effort shed
 more light on the issue.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11158#comment:19>
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