[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 dfeuer):

 Oh, and the hash table can just point to the first weak for each key and
 we can chain them up. We just need to skip over any manually finalized
 ones when we traverse.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15642#comment:11>
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