[GHC] #1658: CSE changes semantics

[GHC]

#1658: CSE changes semantics
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  Reporter:  guest     |          Owner:          
      Type:  bug       |         Status:  new     
  Priority:  normal    |      Milestone:          
 Component:  Compiler  |        Version:  6.7     
  Severity:  normal    |       Keywords:          
Difficulty:  Unknown   |             Os:  Multiple
  Testcase:            |   Architecture:  Multiple
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Create file:

 main = print $ 1/0 - 1/0

 Compile with -O0, it outputs: NaN

 Compile with -O1, it outputs: 0.0

 Compile with -O1 -fno-cse, it outputs: NaN

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1658>
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