compiling truncate :: Float -> Int with -O2 panics ghc

bash-3.2$ cat Bug.hs
{-# OPTIONS -fglasgow-exts -O2 #-}
module Bug (tst) where
tst :: Float -> Bool
tst x = truncate x > (0::Int)

bash-3.2$ ghc Bug.hs
ghc.exe: panic! (the 'impossible' happened)
  (GHC version 6.8.1.20071102 for i386-unknown-mingw32):
	narrowTo
Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

Same results reported on linux.

Trac metadata

Trac field	Value
Version	6.8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	conal@conal.net
Operating system	Unknown
Architecture	Unknown