[GHC] #3983: -O2 makes exception disappear

[GHC]

#3983: -O2 makes exception disappear
---------------------------------+------------------------------------------
    Reporter:  benjamin_scarlet  |       Owner:                        
        Type:  bug               |      Status:  new                   
    Priority:  normal            |   Component:  Compiler              
     Version:  6.12.1            |    Keywords:  exception optimization
          Os:  Unknown/Multiple  |    Testcase:                        
Architecture:  x86_64 (amd64)    |     Failure:  None/Unknown          
---------------------------------+------------------------------------------
 In this example, an exception throw/catch seems not to happen when
 optimization is turned on. The behavior seems to be quite finicky.
 Collapsing the code into fewer than the three given modules seems either
 to make the bug go away or to produce a "internal error: PAP object
 entered!" message. Other seemingly innocuous changes produce similar
 results.

 On both Linux and MacOS, this program produces "False" with no
 optimization flags to ghc, or "True" with -O2.

 On 6.10.4 on Linux, it produces "False" with or without -O2.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3983>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler