[GHC] #10422: reorder in nativeCodeGen too slow

[GHC]

#10422: reorder in nativeCodeGen too slow
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              Reporter:  nomeata     |             Owner:  nomeata
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.10.1
  (CodeGen)                          |  Operating System:  Unknown/Multiple
              Keywords:              |   Type of failure:  None/Unknown
          Architecture:              |        Blocked By:
  Unknown/Multiple                   |   Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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 When working on #10397 and after fixing the bottleneck in
 `elimCommonBlocks` I noticed that `reorder` was taking most of the time.
 Bad lazy linked lists.

 I have a fix, will put it on Phabricator for validation shortly

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10422>
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