Pointer equality woes

cas.hs

import Data.CAS
import Data.IORef

test1 = do ref <- newIORef 0
           let old = 0
               new = (old+1)
           casIORef ref old new

test2 = do let old = 0
           ref <- newIORef old
           let new = (old+1)
           casIORef ref old new

main = (print =<< test1) >> (print =<< test2)

{- Unboxing from optimizations affects the semantics:

afoltzer@mbp scratch$ ghc -fforce-recomp --make -O0 cas.hs && ./cas
[1 of 1] Compiling Main             ( cas.hs, cas.o )
Linking cas ...
(False,0)
(True,0)
afoltzer@mbp scratch$ ghc -fforce-recomp --make -O1 cas.hs && ./cas
[1 of 1] Compiling Main             ( cas.hs, cas.o )
Linking cas ...
(True,0)
(True,0)

-}