catch _|_ breaks at -O1

Discovered on xmonad-0.12 test failure. Happens on today's -HEAD and ghc-8.0.1-rc1,-rc2

Short example is (needs only base):

-- cat F.hs
module F where

import qualified Control.Exception as C
import System.IO.Unsafe
import qualified Data.List as L

abort :: String -> a
abort x = error $ "xmonad: StackSet: " ++ x

prop_abort x = unsafePerformIO $ C.catch (abort "fail")
                                         (\(C.SomeException e) ->
                                           return $ "xmonad: StackSet: fail" `L.isPrefixOf` show e )
   where
     _ = x :: Int

Session 1 [ok]:

$ ghci F.hs

GHCi, version 8.0.0.20160204: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling F                ( F.hs, interpreted )
Ok, modules loaded: F.

*F> prop_abort 1
True

Session 2 [fails]:

$ ghci -O1 -fobject-code F.hs

GHCi, version 8.0.0.20160204: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling F                ( F.hs, F.o )
Ok, modules loaded: F.

Prelude F> prop_abort 1
*** Exception: xmonad: StackSet: fail
CallStack (from HasCallStack):
  error, called at F.hs:9:11 in main:F

I would expect exception to be caught on both cases. Is it unreasonable expectation in light of unsafePerformIO?

Trac metadata

Trac field	Value
Version	8.0.1-rc2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	simonpj
Operating system
Architecture