[GHC] #14768: -O1 changes result at runtime, duplicating __DEFAULT case

[GHC]

#14768: -O1 changes result at runtime, duplicating __DEFAULT case
-------------------------------------+-------------------------------------
        Reporter:  Bodigrim          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.4.1-alpha3
      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):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by RyanGlScott):

 In case it's useful, I've attached a variation of `Sieve.hs` without a
 `vector` dependency.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14768#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler