[GHC] #8834: 64-bit windows cabal.exe segfaults in GC

[GHC]

#8834: 64-bit windows cabal.exe segfaults in GC
----------------------------------+----------------------------------
        Reporter:  awson          |            Owner:
            Type:  bug            |           Status:  patch
        Priority:  highest        |        Milestone:  7.8.1
       Component:  Compiler       |          Version:  7.8.1-rc2
      Resolution:                 |         Keywords:
Operating System:  Windows        |     Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash  |       Difficulty:  Unknown
       Test Case:                 |       Blocked By:
        Blocking:                 |  Related Tickets:
----------------------------------+----------------------------------

Comment (by jstolarek):

 Replying to [comment:12 awson]:
 > @simonmar, unreverting `isTrivial` brokes things again.

 So this works:

 {{{
 isTrivial :: CmmExpr -> Bool
 isTrivial (CmmReg _) = True
 isTrivial _          = False
 }}}

 but this doesn't:

 {{{
 isTrivial :: CmmExpr -> Bool
 isTrivial (CmmReg (CmmLocal _)) = True
 isTrivial _                     = False
 }}}

 ? I know this is slightly different from your patch (it ignores literals
 which I believe are irrelevant here). Again, would be nice to see
 differences in Cmm between the two.

 simonmar: could you tell us whether the call to `newCAF` clobbers `R1` ?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8834#comment:14>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler