[GHC] #11555: catch _|_ breaks at -O1

[GHC]

#11555: catch _|_ breaks at -O1
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        Reporter:  slyfox            |                Owner:
            Type:  bug               |               Status:  merge
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.0.1-rc2
      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:D1973
       Wiki Page:                    |
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Changes (by bgamari):

 * status:  patch => merge


Comment:

 Need to merge 4c3a0a4a,  30ee9102,
 c937f424e4acd61d1c558e8fe9b47e7d580fdbd8, and
 a1c4230e15cbf897b97903c8a1199a1cc91efd26 to `ghc-8.0`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11555#comment:21>
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