[GHC] #6156: Optimiser bug on linux-powerpc

[GHC]

#6156: Optimiser bug on linux-powerpc
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  Reporter:  erikd                        |          Owner:  igloo  
      Type:  bug                          |         Status:  new    
  Priority:  normal                       |      Milestone:  7.6.1  
 Component:  Compiler                     |        Version:  7.4.1  
Resolution:                               |       Keywords:         
        Os:  Linux                        |   Architecture:  powerpc
   Failure:  Incorrect result at runtime  |     Difficulty:  Unknown
  Testcase:                               |      Blockedby:         
  Blocking:                               |        Related:         
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Comment(by simonmar):

 Replying to [comment:38 erikd]:

 > foreign import ccall "c_printInt64" printInt64 :: CLLong -> IO ()

 Add "unsafe" here to make the generated code simpler.

 > main :: IO ()
 > main = do
 >     printInt64 input
 >     putStrLn (showHex input "")

 suggest getting rid of the `putStrLn`, again to make things simpler.

 > and compiled without optimisation I get:
 >
 > {{{
 > 1a2a3a4a5a6a7a8a
 > 1a2a3a4a5a6a7a8a
 > }}}
 >
 > and with optimisation I get:
 >
 > {{{
 > 7a8a
 > 1a2a3a4a5a6a7a8a
 > }}}
 >
 > which is weird in that the FFI version is incorrect, but only when
 optimisation is off.

 Did you mean to say ''on'' here?

 > This suggests that its actually a problem with the way 64 bit values are
 passed to functions.

 Yes, probably.

 So now you have a very simple example that generates incorrect code and
 doesn't call any library functions, the bug must be somewhere in the
 generated code for this module.  Compile it with -S and eyeball the
 assembly code.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6156#comment:39>
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