[GHC] #13442: Add a coercion/cast operator to CMM

[GHC]

#13442: Add a coercion/cast operator to CMM
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        Reporter:  erikd             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by rwbarton):

 It should be
 {{{
     d = D_[Sp - WDS(1)];
 }}}

 `Sp(-1)` is already a memory access ("the value at `Sp - WDS(1)`").

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13442#comment:11>
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