[GHC] #8323: explore ways to possibly use more tag bits in x86_64 pointers

[GHC]

#8323: explore ways to possibly use more tag bits in x86_64 pointers
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       Reporter:  carter            |             Owner:
           Type:  task              |            Status:  new
       Priority:  normal            |         Milestone:
      Component:  Compiler          |           Version:  7.6.3
       Keywords:                    |  Operating System:  Unknown/Multiple
   Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
     Difficulty:  Unknown           |         Test Case:
     Blocked By:                    |          Blocking:
Related Tickets:                    |
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 on x86_64, pointers only use 48 bits!
 currently we use 3bits for tagging / arity etc info on x86_64, we should
 explore more uses!

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8323>
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