[GHC] #13570: CoreFVs patch makes n-body slower

[GHC]

#13570: CoreFVs patch makes n-body slower
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           Reporter:  simonpj        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 This commit
 {{{
 commit 751996e90a964026a3f86853338f10c82db6b610
 Author: Simon Peyton Jones <simonpj at microsoft.com>
 Date:   Fri Apr 7 17:10:07 2017 +0100

     Kill off complications in CoreFVs
 }}}
 makes `n-body` in nofib go 25% slower.  See
 [https://perf.haskell.org/ghc/#revision/751996e90a964026a3f86853338f10c82db6b610
 perf results page].

 Investigate.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13570>
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