[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:  (none)
            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:                    |  Differential Rev(s):  Phab:D5196
       Wiki Page:                    |
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Comment (by dfeuer):

 What I've been suggesting is that even when we don't statically know if
 it's been evaluated or tagged, we should surely be using tag bits when we
 find them. It looks like an oversight that we haven't done so in the past,
 and I foresee substantial benefits to fixing that. Perhaps we can win back
 more performance than we lose.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15696#comment:39>
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