[GHC] #7684: cgrun071 segfaults

[GHC]

#7684: cgrun071 segfaults
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        Reporter:  tibbe          |            Owner:
            Type:  bug            |           Status:  infoneeded
        Priority:  normal         |        Milestone:  7.8.1
       Component:  Compiler       |          Version:  7.7
      Resolution:                 |         Keywords:
Operating System:  MacOS X        |     Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash  |       Difficulty:  Unknown
       Test Case:  cgrun071       |       Blocked By:
        Blocking:                 |  Related Tickets:
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Comment (by tibbe):

 Replying to [comment:42 simonmar]:
 > Well, one bug is that in `emitPopCntCall` we don't cast the argument to
 the correct width.  The `-dcmm-lint` should catch it, because the argument
 width isn't the same as the primop is expecting, but the Cmm linter
 doesn't check the arguments of prim calls (that's another bug).

 How would one cast the argument in the `emitPopCntCall`?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7684#comment:44>
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