[GHC] #15449: Nondeterministic Failure on aarch64 with -jn, n > 1

[GHC]

#15449: Nondeterministic Failure on aarch64 with -jn, n > 1
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        Reporter:  tmobile           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  aarch64
 Type of failure:  Compile-time      |            Test Case:
  crash or panic                     |
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 Quite alright; you had me excited that this ticket might have an easy
 resolution afterall.

 However, given that this is only failing on LLVM/AArch64 it does sound
 like this is likely an `-fllvm` code generation bug. Doing a careful audit
 of the code generator's barriers sounds like the best way forward. This is
 likely wrong on LLVM/x86 as well, but the bug doesn't manifest due to the
 architecture's strong memory model.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15449#comment:7>
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