[GHC] #10521: Wrong results in strict Word8 storage on x64

[GHC]

#10521: Wrong results in strict Word8 storage on x64
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        Reporter:  VincentBerthoux2  |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  highest           |               Milestone:  7.10.2
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:  x86_64
 Type of failure:  Incorrect result  |  (amd64)
  at runtime                         |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by simonpj):

 Reid you are a marvel, thank you.

 My instinct is to "account for registers" overlapping.  After all, if Cmm
 optimisations don't know that two registers are the same, all manner of
 bad things can happen, perhaps not limited to `CmmSink`.  Is this just the
 Eq instance for `CmmReg`?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10521#comment:7>
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