[GHC] #5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12 (MonoLocalBinds)

[GHC]

#5113: Huge performance regression of 7.0.2, 7.0.3 and HEAD over 7.0.1 and 6.12
(MonoLocalBinds)
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        Reporter:                    |                   Owner:
  daniel.is.fischer                  |                  Status:  closed
            Type:  bug               |               Milestone:
        Priority:  normal            |                 Version:  7.0.3
       Component:  Compiler          |                Keywords:
      Resolution:  fixed             |  performance, MonoLocalBinds
Operating System:  Linux             |            Architecture:  x86
 Type of failure:  Runtime           |               Test Case:
  performance bug                    |  perf/should_run/T5113
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by simonpj):

 The new `substExprS` was dropping rules and specialisations, which is
 terribly wrong.

 So I backed out and fixed #10527 another way; see the commit comments.

 I'm getting a small number of apparently-unrelated validate failures, but
 I figure it's better to push this so that Ben can try it out.

 Simon

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5113#comment:12>
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