[GHC] #15642: Improve the worst case performance of weak pointers

[GHC]

#15642: Improve the worst case performance of weak pointers
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Runtime System    |              Version:  8.6.1-beta1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonmar):

 Taking a bit in the info pointer for this seems like a very high cost. We
 only have one spare bit (on 32-bit), and furthermore using that bit has a
 runtime cost because we'd have to mask it everywhere.  Doesn't seem worth
 it to me.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15642#comment:4>
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