[GHC] #8923: Add SmallArray# type

[GHC]

#8923: Add SmallArray# type
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        Reporter:  tibbe             |            Owner:  tibbe
            Type:  feature request   |           Status:  patch
        Priority:  normal            |        Milestone:  7.10.1
       Component:  Compiler          |          Version:  7.9
      Resolution:                    |         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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Comment (by Johan Tibell <johan.tibell@…>):

 In [changeset:"90329b6cc183b3cd05956ae6bdeb6ac6951549c2/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="90329b6cc183b3cd05956ae6bdeb6ac6951549c2"
 Add SmallArray# and SmallMutableArray# types

 These array types are smaller than Array# and MutableArray# and are
 faster when the array size is small, as they don't have the overhead
 of a card table. Having no card table reduces the closure size with 2
 words in the typical small array case and leads to less work when
 updating or GC:ing the array.

 Reduces both the runtime and memory allocation by 8.8% on my insert
 benchmark for the HashMap type in the unordered-containers package,
 which makes use of lots of small arrays. With tuned GC settings
 (i.e. `+RTS -A6M`) the runtime reduction is 15%.

 Fixes #8923.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8923#comment:9>
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