[GHC] #7684: cgrun071 segfaults

[GHC]

#7684: cgrun071 segfaults
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        Reporter:  tibbe          |            Owner:
            Type:  bug            |           Status:  merge
        Priority:  normal         |        Milestone:  7.8.1
       Component:  Compiler       |          Version:  7.7
      Resolution:  fixed          |         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 simonmar):

 So I think this fix is ok - it avoids the question of whether the ABI
 requires the caller to sign/zero-extend or not.  My suggestion to cast the
 argument was based on the type of `hs_popcnt8` taking an `HsInt8`, but I
 see that wasn't what you intended.

 FWIW I think gcc probably should be zero-extending in the caller, not the
 callee, for an 8-bit argument (i.e. gcc 4.2 is correct, 4.9 is wrong).
 This is what we assume in GHC.  I couldn't see anything about this in the
 ABI spec, but there's a gcc bug open:
 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46942

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7684#comment:57>
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