I am seeing this panic while compiling GHC stage2,

ghc-stage1: panic! (the 'impossible' happened)
  (GHC version 8.1.20170124 for x86_64-unknown-linux):
	runtimeRepPrimRep
  typePrimRep (a :: TYPE k0)
  k0
  Call stack:
      ?callStack, called at compiler/utils/Util.hs:1352:50 in ghc:Util
        prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1166:58 in ghc:Outputable
        callStackDoc, called at compiler/utils/Outputable.hs:1170:37 in ghc:Outputable
        pprPanic, called at compiler/simplStg/RepType.hs:360:5 in ghc:RepType

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

<<ghc: 1038844096 bytes, 158 GCs, 21564561/73278928 avg/max bytes residency (8 samples), 148M in use, 0.000 INIT (0.000 elapsed), 1.113 MUT (1.125 elapsed), 0.935 GC (0.940 elapsed) :ghc>>
compiler/ghc.mk:582: recipe for target 'compiler/stage2/build/StgCmmMonad.p_o' failed

This appears to be due to my enabling of profiling. build.mk contains,

BuildFlavour=prof
ifneq "$(BuildFlavour)" ""
include mk/flavours/$(BuildFlavour).mk
endif
HADDOCK_DOCS=YES
compiler_HC_OPTS += -fprof-auto-exported