ghc: panic! (the 'impossible' happened). RegAllocLinear.getStackSlotFor: out of stack slots, try -fregs-graph

Linking dist/build/SymmetricTest/SymmetricTest ...
[1 of 4] Compiling Codec.Utils      ( Codec/Utils.hs, dist/build/SHA1Test/SHA1Test-tmp/Codec/Utils.o )
[2 of 4] Compiling Data.Digest.SHA1 ( Data/Digest/SHA1.hs, dist/build/SHA1Test/SHA1Test-tmp/Data/Digest/SHA1.o )
[3 of 4] Compiling Codec.Text.Raw   ( Codec/Text/Raw.hs, dist/build/SHA1Test/SHA1Test-tmp/Codec/Text/Raw.o )
[4 of 4] Compiling Main             ( SHA1Test.hs, dist/build/SHA1Test/SHA1Test-tmp/Main.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 6.10.2 for i386-unknown-linux):
	RegAllocLinear.getStackSlotFor: out of stack slots, try -fregs-graph

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

(Crypto 4.1.0)