[GHC] #15696: Derived Ord instance for enumerations with more than 8 elements seems to be incorrect

[GHC]

#15696: Derived Ord instance for enumerations with more than 8 elements seems to be
incorrect
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        Reporter:  mrkkrp            |                Owner:  osa1
            Type:  bug               |               Status:  patch
        Priority:  highest           |            Milestone:  8.6.2
       Component:  Compiler          |              Version:  8.6.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14677, #15155    |  Differential Rev(s):  Phab:D5196,
       Wiki Page:                    |  Phab:D5201, Phab:D5226
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Comment (by osa1):

 Just an update before I forget where I had left: the performance
 regression in `wip/T15696` is fixed by any of these:

 - Revert change in `app_ok` general case, don't give case binders
 `evaldUnfolding` in `simplAlts` (first suggestion in comment:77)
 - Revert change in `app_ok` general case, disable binder swapping of case
 bidners and scrutinee.

 Both validate, but I don't have nofib results yet.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15696#comment:82>
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