[GHC] #12433: GHCi produces incorrect results when evaluating with compiled code

[GHC]

#12433: GHCi produces incorrect results when evaluating with compiled code
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        Reporter:  diatchki          |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  ghci, dynamic
                                     |  linking, compiled code
Operating System:  Linux             |         Architecture:  x86_64
 Type of failure:  Incorrect result  |  (amd64)
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by rwbarton):

 I think it's `genSwitch` that is at fault here. It calculates the operand
 adjusted for the start of the jump table with `getSomeReg`, but that
 doesn't mean it is entitled to clobber the returned `reg` later, after `--
 HACK: On x86_64 binutils<2.17 is only able to generate...`.

 Here is a single-module reproducer that does not involve the GC. It should
 be compiled with `-dynamic` (or `-fPIC`) and `-O`.
 {{{#!hs
 f :: Int -> IO ()
 f p = case p of
   0 -> return ()
   1 -> return ()
   2 -> return ()
   3 -> return ()
   4 -> return ()
   10 -> return ()
   11 -> return ()
   _ -> print p
 {-# NOINLINE f #-}

 main = f 8
 }}}
 I had to use a value that falls into the default case, as GHC creates an
 unfolding for a scrutinee that has been successfully matched against a
 numeric literal and then I couldn't find any way to get the generated code
 to refer to the original scrutinee.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12433#comment:5>
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