[GHC] #3207: readMutVar# is inlined/duplicated

[GHC]

#3207: readMutVar# is inlined/duplicated
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    Reporter:  simonmar          |        Owner:                  
        Type:  bug               |       Status:  new             
    Priority:  normal            |    Milestone:  6.12.1          
   Component:  Compiler          |      Version:  6.10.2          
    Severity:  normal            |   Resolution:                  
    Keywords:                    |   Difficulty:  Unknown         
    Testcase:                    |           Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |  
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Comment (by j.waldmann):

 I will attach a file (STCheck) that is perhaps related.

 Behaviour is: when using ghc-6.10.2 and STRef.Lazy, it enters a <<loop>>
 (in ghci, it just hangs, prompt never returns).
 When compiled with ghc-6.8.3, it prints the expected answer (1).

 With ghc-6.10.2 and STRef.Strict, it works.

 With ghc-6.10.2 and replacing readSTRef/writeSTRef (end of program)
 by modifySTRef, it works as well.

 (This actually cost me several hours to isolate.
 The "cache" function is from a real program.)

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3207#comment:3>
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