[GHC] #9303: O2: (GHC version 7.8.3 for x86_64-unknown-linux): allocateRegsAndSpill: Cannot read from uninitialized register %vI_s1Mp

[GHC]

#9303: O2: (GHC version 7.8.3 for x86_64-unknown-linux): allocateRegsAndSpill:
Cannot read from uninitialized register %vI_s1Mp
----------------------------------+---------------------------------------
       Reporter:  slyfox          |             Owner:
           Type:  bug             |            Status:  new
       Priority:  normal          |         Milestone:
      Component:  Compiler (NCG)  |           Version:  7.8.3
       Keywords:                  |  Operating System:  Unknown/Multiple
   Architecture:  x86_64 (amd64)  |   Type of failure:  Compile-time crash
     Difficulty:  Unknown         |         Test Case:
     Blocked By:                  |          Blocking:
Related Tickets:                  |
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 {{{
 ghc --make -O2 M.hs
 [1 of 1] Compiling M                ( M.hs, M.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 7.8.3 for x86_64-unknown-linux):
         allocateRegsAndSpill: Cannot read from uninitialized register
     %vI_s1Mp

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

 As in #9155 bug was caught on '''wx''' package in the same module.
 I didn't try to trim it down to minimal sample.

 No external modules required.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9303>
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