[GHC] #5615: ghc produces poor code for `div` with constant powers of 2.

[GHC]

#5615: ghc produces poor code for `div` with constant powers of 2.
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    Reporter:  Lennart           |       Owner:              
        Type:  bug               |      Status:  new         
    Priority:  normal            |   Component:  Compiler    
     Version:  7.2.1             |    Keywords:              
    Testcase:                    |   Blockedby:              
          Os:  Unknown/Multiple  |    Blocking:              
Architecture:  x86               |     Failure:  None/Unknown
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 The code for Int {{{(div x c)}}} where {{{c}}} is a constant of the form
 2^n^ should be implemented with an arithmetic right shift, currently it's
 a call to a function.  This optimization should be done for all signed
 types.

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5615>
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