[GHC] #7902: Add support for byte endianness swapping exposed as a primops

[GHC]

#7902: Add support for byte endianness swapping exposed as a primops
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    Reporter:  tab               |       Owner:                  
        Type:  feature request   |      Status:  patch           
    Priority:  normal            |   Milestone:                  
   Component:  Compiler          |     Version:  7.7             
    Keywords:  bswap endianness  |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Changes (by igloo):

  * difficulty:  => Unknown


Comment:

 Attaching patches for GHC here is best, yes. And providing tests too is
 even better, thanks!

 I haven't tried them, but these look OK to me, except that I think it
 would be worth making a helper function to factor out the common code in
 the LLVM backend, as you suggested.

 If you'd like to propose exposing the change via the core libraries, then
 please see http://www.haskell.org/haskellwiki/Library_submissions for
 details of the process. I'm not sure how best to do it, though: If it goes
 into `Bits` then you'll need to give an implementation for `Integer`, and
 in theory could need to give one for a hypothetical `Word13` type. Even
 `Int` and `Word` aren't guaranteed to be a multiple of 8 bits.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7902#comment:7>
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