[GHC] #10858: Smaller generated Ord instances

[GHC]

#10858: Smaller generated Ord instances
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        Reporter:  nomeata           |                   Owner:
            Type:  task              |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #9557             |  Differential Revisions:
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Comment (by simonpj):

 That `Note` looks plausible but ONLY if you recursively use `(<)` in the
 implementation of `(<)`.  But in the code you give above for `Ord` on
 `ImportDecl` we seem to call `compare` recursively when implementing
 `(<)`.  So we are taking the hit described in the `Note`, but blowing up
 the code much more than necessary!

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10858#comment:11>
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