[GHC] #14068: Loopification using join points

[GHC]

#14068: Loopification using join points
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        Reporter:  nomeata           |                Owner:  nomeata
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  JoinPoints
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13966 #14067     |  Differential Rev(s):  Phab:D3811
  #14827                             |
       Wiki Page:                    |
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Comment (by nomeata):

 Just had a brief look, just to remind myself of the issues here, and
 compared the Core of `x2n1`. With `-O`, I see loopification happening
 (yay!) and no allocation changes (expected). But with `-O -fspec-constr`,
 I see the big increase that is also reported by perf.haskell.org.

 It might just be an unwanted side effect of me trying preventing inlining
 of loopification, and might go away when I release this break – but then
 other things happen. Well, I should test that hypothesis.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14068#comment:25>
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