[GHC] #10677: slightly silly assembly for testing whether a Word# is 0##

[GHC]

#10677: slightly silly assembly for testing whether a Word# is 0##
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        Reporter:  rwbarton          |                   Owner:
            Type:  bug               |                  Status:  closed
        Priority:  low               |               Milestone:
       Component:  Compiler          |                 Version:  7.11
  (CodeGen)                          |
      Resolution:  fixed             |                Keywords:  newcomer
Operating System:  Unknown/Multiple  |            Architecture:  x86_64
 Type of failure:  Runtime           |  (amd64)
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #10750            |  Differential Revisions:  Phab:D1137
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Comment (by nomeata):

 This causes a `+ 15.08%` runtime regression in fannkuch-redux:

 https://perf.haskell.org/ghc/#graph/nofib/time/fannkuch-
 redux;hl=92f35cd9829db7555397aa3dc8cd243d17694fee

 This is a bit strange... is this just a possible reordering of basic
 blocks?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10677#comment:9>
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