[GHC] #10602: ghc panic: Template variable unbound in rewrite rule when compiling with -O2

[GHC]

#10602: ghc panic: Template variable unbound in rewrite rule when compiling with
-O2
-------------------------------------+-------------------------------------
        Reporter:  pacak             |                   Owner:  bgamari
            Type:  bug               |                  Status:  infoneeded
        Priority:  highest           |               Milestone:  7.10.2
       Component:  Compiler          |                 Version:  7.10.2-rc2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by pacak):

 Step by step manual to reproduce
 {{{

 % tar xf ../ghc-7.10.1.20150630-src.tar.xz
 % cp mk/build.mk.sample build.mk
 % vim mk/build.mk -- uncomment BuildFlavour = perf
 % autoreconf
 % perl boot
 % ./configure && make -j4
 [stuff]
 % ./inplace/bin/ghc-stage2 binlist.hs -O2

 [1 of 1] Compiling Main             ( binlist.hs, binlist.o )
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 7.10.1.20150630 for x86_64-unknown-linux):
         Template variable unbound in rewrite rule
   sg_s5zd
   [sc_s5zb, sc_s5zc, sg_s5zd, sg_s5ze]
   [sc_s5zb, sc_s5zc, sg_s5zd, sg_s5ze]
   [: @ a_a3fj sc_s5zb sc_s5zc]
   [: @ a_a3fj sc_s5z7 sc_s5z8]

 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10602#comment:10>
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