[GHC] #9155: O2: allocateRegsAndSpill: Cannot read from uninitialized register %vI_s154O (GHC version 7.8.2 for x86_64-unknown-linux)

[GHC]

#9155: O2: allocateRegsAndSpill: Cannot read from uninitialized register %vI_s154O
(GHC version 7.8.2 for x86_64-unknown-linux)
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        Reporter:  slyfox            |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.8.2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by slyfox):

 -HEAD has the same disease:
 {{{
 [sf] ~/dev/git/ghc:inplace/bin/ghc-stage2 --make -O2 /tmp/M.hs
 [1 of 1] Compiling M                ( /tmp/M.hs, /tmp/M.o )
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 7.9.20140531 for x86_64-unknown-linux):
         RegAlloc.Liveness.computeLivenss
     SCCs aren't in reverse dependent order
     bad blockId c1cG
 ...
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9155#comment:2>
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