[GHC] #8561: Clang/iOS: __builtin___clear_cache doesn't exist in clang, use __clear_cache instead

[GHC]

#8561: Clang/iOS: __builtin___clear_cache doesn't exist in clang, use
__clear_cache instead
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        Reporter:  lukexi            |            Owner:
            Type:  bug               |           Status:  new
        Priority:  high              |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Other             |     Architecture:  Unknown/Multiple
 Type of failure:  Building GHC      |       Difficulty:  Easy (less than 1
  failed                             |  hour)
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by carter):

 heatsink is likely to follow up on this, but GCC 4.2  lacks the builtin
 clear cache primitive, and thus any OS X system with XCode < 5 has a GCC
 old enough that builtin___clear_cache shoudn't be used.

 (at least if we want to support working at all on older OS X systems,
 which i think is worth doing)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8561#comment:4>
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