[GHC] #15665: Break up the stable pointer table

[GHC]

#15665: Break up the stable pointer table
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by osa1):

 I don't understand comment:1. What do you mean by "compress the free
 list"?
 What do you mean by "untag stored pointers"?

 I think the only problem would be that currently free slots in stable ptr
 table
 hold offset of the next free slot. So allocating a new stable pointer
 (assuming
 we have space in the table) is as simple as `stable_ptr_free  =
 (spEntry*)(stable_ptr_free->addr);`. If we switch to an array-list
 representation this operation will be more expensive, we'll have to
 traverse
 the chain of arrays until we find the array with the next empty slot.

 If the array-list representation will fix the table copying on GC I think
 this
 may worth it though.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15665#comment:2>
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