[GHC] #10829: Simplification in the RHS of rules

[GHC]

#10829: Simplification in the RHS of rules
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        Reporter:  afarmer           |                   Owner:
            Type:  bug               |                  Status:  patch
        Priority:  high              |               Milestone:  7.10.3
       Component:  Compiler          |                 Version:  7.10.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #10528            |  Differential Revisions:  Phab:D1246
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Comment (by simonpj):

 I'd be rather surprised if anything optimises worse after this change.
 It's only a question of whether the optimisation happens before or after
 the rule is fired.

 I've been wrong before, and a smoke test would be good.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10829#comment:15>
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