[GHC] #11781: Improve common sub-expression

[GHC]

#11781: Improve common sub-expression
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        Reporter:  simonpj           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2074
       Wiki Page:                    |
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Comment (by simonpj):

 New performance results are in from
 [https://perf.haskell.org/ghc/#revision/e05b00ef8e05e58e93e0559e4499a830bc51b9f4
 GHC speed]
 {{{

     nofib/time/cryptarithm1     0.421    - 4.04%        0.404   seconds
     tests/alloc/T9020   723162856       + 17.86%        852298336
 bytes
     tests/alloc/T9872b  4754051528       - 3.24%        4600233488
 bytes
     tests/alloc/T9872c  4452756568       - 3.28%        4306667256
 bytes

   Interestingly, `T9020` (long sequence of `return()` commands) was
 improved by your previous commit.
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11781#comment:1>
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