[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):

 Well that's remarkable.   A 17% change compiler allocation is huge.

 Oh hang on.  Maybe the program being compiled is changing size!  Try
 `-dshow-passes` before and after.

 Or, to put it another way, does a ''stage1'' compiler show the same
 difference in allocation?  Do you see what I mean?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11781#comment:2>
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