"RegAllocLinear.getStackSlotFor: out of stack slots" when compiling SHA1.hs in darcs

I got the following error when compiling darcs under win32/cygwin with ghc 6.8.2 and profiling turned on.

$ make VERBOSE=1
ghc -DPACKAGE_NAME=\"darcs\" -DPACKAGE_TARNAME=\"darcs\" -DPACKAGE_VERSION=\"2.0.0pre3\" -DPACKAGE_STRING=\"darcs\ 2.0.0pre3\" -DPACKAGE_BUGREPORT=\"bugs@darcs.net\" -DSTDC_HEADERS=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -Isrc/win32 -cpp  -package regex-compat -package QuickCheck -package mtl -package parsec -package html -package containers -package pretty -O -funbox-strict-fields  -prof -auto-all -Wall -Werror -I. -I./src -i./src -isrc/win32 -Isrc/win32 -DWIN32
-DHAVE_MAPI -no-auto-all -funfolding-use-threshold20 -c src/SHA1.lhs
ghc.exe: panic! (the 'impossible' happened)
  (GHC version 6.8.2 for i386-unknown-mingw32):
        RegAllocLinear.getStackSlotFor: out of stack slots

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

make: *** [src/SHA1.o] Error 1

Context for the darcs version I tried to compile is attached.