[GHC] #8742: Reuse scavenge_small_bitmap

[GHC]

#8742: Reuse scavenge_small_bitmap
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        Reporter:  Tarrasch          |            Owner:
            Type:  task              |           Status:  new
        Priority:  lowest            |        Milestone:  7.10.1
       Component:  Runtime System    |          Version:  7.6.3
      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 Tarrasch):

 Unfortunately, the output object files did differ. I even did `objdump
 --source rts/dist/build/sm/Scav.o` and saw that the assembly output
 actually was different before and after the patch.

 I would guess that gcc isn't smart enough to in-line a usage like this:
 `my_var = inline_function(..., my_var, ...)`. It probably doesn't realize
 that there's no need to save `my_var` in a temporary.

 Should we abandon this ticket or is it worth merging anyway? I don't have
 any good judgement here since I'm not sure how hot this code is.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8742#comment:6>
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