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

[GHC]

#11555: catch _|_ breaks at -O1
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        Reporter:  slyfox            |                Owner:
            Type:  bug               |               Status:  new
        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):
       Wiki Page:                    |
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Comment (by NeilMitchell):

 Given the attached Test.hs, I run:

 {{{
 ghc --make Test.hs -outputdir old -O1 -o test_old && test_old
 ghc --make Test.hs -outputdir new -O1 -DNEW -o test_new && test_new
 }}}

 The first prints SUCCESS (the catch worked, using {{{safeCatch1}}}). The
 second prints FAILURE (the catch failed, using {{{safeCatch2}}}). All
 tests carried out with GHC 8.0.0.20160205 on Windows.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11555#comment:14>
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