[GHC] #10433: Fix load/store barriers in pre-ARMv7 builds

[GHC]

#10433: Fix load/store barriers in pre-ARMv7 builds
-------------------------------------+-------------------------------------
              Reporter:              |             Owner:  simonmar
  thoughtpolice                      |            Status:  new
                  Type:  bug         |         Milestone:  7.12.1
              Priority:  high        |           Version:
             Component:  Runtime     |  Operating System:  Unknown/Multiple
  System                             |   Type of failure:  None/Unknown
              Keywords:              |        Blocked By:
          Architecture:  arm         |   Related Tickets:  #10244
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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 As pointed out in #10244 and Phab:D894, the fix we committed for this
 problem isn't 100% correct - from
 753b156dc6b0c38b106c390952750fb800bf27e7:

 {{{
 #elif arm_HOST_ARCH && defined(arm_HOST_ARCH_PRE_ARMv7)
     // TODO FIXME: This case probably isn't totally correct - just because
 we
     // use a pre-ARMv7 toolchain (e.g. to target an old Android device),
 doesn't
     // mean the binary won't run on a newer ARMv7 system - in which case
 it
     // needs a proper barrier. So we should rethink this
     //  - Reid
     __asm__ __volatile__ ("" : : : "memory");
 }}}

 This is a reminder to fix this.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10433>
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