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

[GHC]

#8834: 64-bit windows cabal.exe segfaults in GC
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        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:
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Comment (by simonmar):

 It's looking more likely that there is a bug related to caller-saves
 registers somewhere else, and the change to `isTrivial` tickles it by
 making `CmmSink` more eager to inline `GlobalReg`s.  This is affecting
 Win64 because that platform has a different C calling convention, with
 different caller-saves registers.

 So either we have a bad optimisation (probably in `CmmSink`), or the
 specification for what is a caller-saves reg on Win64 is wrong
 (`includes/stg/MachRegs.h`).

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8834#comment:18>
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