[GHC] #8638: Optimize by demoting "denormalized" Integers (i.e. J# -> S#)

[GHC]

#8638: Optimize by demoting "denormalized" Integers (i.e. J# -> S#)
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        Reporter:  hvr                      |            Owner:  hvr
            Type:  feature request          |           Status:  infoneeded
        Priority:  normal                   |        Milestone:  7.8.1
       Component:  libraries (other)        |          Version:  7.7
      Resolution:                           |         Keywords:  integer-
Operating System:  Unknown/Multiple         |  gmp
 Type of failure:  Runtime performance bug  |     Architecture:
       Test Case:                           |  Unknown/Multiple
        Blocking:                           |       Difficulty:  Unknown
                                            |       Blocked By:
                                            |  Related Tickets:
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Changes (by simonpj):

 * status:  patch => infoneeded


Comment:

 Interesting.  In general it seems like a good idea.  Although making the
 test has a cost, if you get a win, it's a big win.

 I'd first like to know why `mandel` started allocating nearly 50% more
 store.  (I use `-ticky` for answering this kind of question.)  Maybe
 investigating that will show how the patch can be improved further.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8638#comment:3>
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