[GHC] #14727: Unboxed sum performance surprisingly poor

[GHC]

#14727: Unboxed sum performance surprisingly poor
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  UnboxedSums
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 osa1):

 I'd make sure `lookup` is inlined, in which case allocations should be
 reduced.

 OTOH you use one more register to return two values in `lookup#` instead
 of one as before so that may make some things worse.

 It'd be helpful to see benchmark code's Cmm for both versions (with
 `lookup` inlined in the unboxed sums version).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14727#comment:1>
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