[GHC] #12944: ghc master (8.1.20161206) panics with assertion failure with devel2 flavor and -O

[GHC]

#12944: ghc master (8.1.20161206) panics with assertion failure with devel2 flavor
and -O
-------------------------------------+-------------------------------------
        Reporter:  pacak             |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
  (CodeGen)                          |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by bgamari):

 * priority:  normal => highest
 * component:  Compiler => Compiler (CodeGen)
 * milestone:   => 8.2.1


Comment:

 I can also reproduce this with 9bcc4e335b34c00191e8897aa7393c3856e8996f,
 {{{
 $ ghc -O ~/hi.hs
 [1 of 1] Compiling Numeric.Polynomial.Log ( /home/ben/hi.hs,
 /home/ben/hi.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.1.20161207 for x86_64-unknown-linux):
         StgCmmEnv: variable not found
   $dAdditiveGroup_aIP
   local binds for:
   *^
   ^+^
   negateV
   ^-^
   $p1VectorSpace
   $fAdditiveGroupPoly1
   $WIntOfLog
   $fAdditiveGroupIntOfLog_$cnegateV
   $fAdditiveGroupIntOfLog_$c^+^
   $fAdditiveGroupPoly1_$c^-^
   $fAdditiveGroupPoly1_$cnegateV
   $fAdditiveGroupPoly1_$c^+^
   w_s12P
   ww_s12Q
   ww1_s12R
   ww2_s12S
   ww3_s12T
   dt_s12U
   Call stack:
       CallStack (from HasCallStack):
         prettyCurrentCallStack, called at
 compiler/utils/Outputable.hs:1116:58 in ghc:Outputable
         callStackDoc, called at compiler/utils/Outputable.hs:1120:37 in
 ghc:Outputable
         pprPanic, called at compiler/codeGen/StgCmmEnv.hs:137:9 in
 ghc:StgCmmEnv

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

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12944#comment:1>
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