[GHC] #8131: T7571 with WAY=llvm fails, but not WAY=optllvm

[GHC]

#8131: T7571 with WAY=llvm fails, but not WAY=optllvm
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        Reporter:  thoughtpolice              |            Owner:  rwbarton
            Type:  bug                        |           Status:  new
        Priority:  high                       |        Milestone:
       Component:  Compiler                   |          Version:  7.7
      Resolution:                             |         Keywords:
Operating System:  Unknown/Multiple           |     Architecture:
 Type of failure:  None/Unknown               |  Unknown/Multiple
       Test Case:  llvm/should_compile/T8131  |       Difficulty:  Unknown
        Blocking:                             |       Blocked By:
                                              |  Related Tickets:
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Comment (by rwbarton):

 I have also updated the tests, but the `T8131` `should_fail` test isn't
 working for me: `make TEST=T8131 WAY=llvm` is skipping the test, for some
 reason. It works (and the test fails, of course) if I change
 `compile_fail` to `compile`. Any idea what is going on?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8131#comment:5>
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