[GHC] #9736: Constant folding rules are wrong for GHCJS

[GHC]

#9736: Constant folding rules are wrong for GHCJS
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              Reporter:  luite       |            Owner:  luite
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  7.10.1
             Component:  Compiler    |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by luite):

 Ah my intention was just to verify that the changes in GHCJS, which are
 based on 7.8, are still correct in the latest HEAD and then attach the
 patch here.

 One issue likely affects other cross compilers: `shiftRightLogical`
 truncates the value to `Word`size, which is wrong if the host word size is
 different from the target.

 https://github.com/ghc/ghc/blob/f1090855d9b8d33b3194364dcca0683d89049f03/compiler/prelude/PrelRules.lhs#L373

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9736#comment:2>
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