[GHC] #14152: Float exit paths out of recursive functions

[GHC]

#14152: Float exit paths out of recursive functions
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:  JoinPoints
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14137 #10918     |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by nomeata):

 Inlining the exit join points in the `"final"` simplifier iteration is not
 a clear win:

 {{{
 Nofib runtimes
 Benchmark name                  previous        change          now
 nofib/time/VS                   0.372           + 16.13%        0.432
 seconds
 nofib/time/cryptarithm1         0.503           + 4.17%         0.524
 seconds
 nofib/time/k-nucleotide         5.558           - 7.72%         5.129
 seconds
 }}}

 my theory is that floating exit paths out of tight loops makes tight loops
 very small which is beneficial for *mumble mumble* weird hardware reasons.

 (I know, someone needs to look at the code instead of speculating…)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14152#comment:18>
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