[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 bgamari):

 Someone correct me if I'm wrong but it seems like this change carries a
 bit of risk: Could this not result in a failure in optimization in a
 library with incorrect phasing annotations? We should definitely check
 this against Stackage or some similar smoke-test to ensure that libraries
 with incorrect phasing aren't adversely affected by this change as I don't
 have much confidence that such a regression would appear in nofib (as
 we've already seen in the case of `text`).

 Also, have we looked for Core changes that might explain the regressions
 seen in comment:6? The runtime regressions shown look as though they may
 be real; it would be nice to have at least some idea of what is happening
 here.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10829#comment:14>
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