[GHC] #15019: Fix performance regressions from #14737

[GHC]

#15019: Fix performance regressions from #14737
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        Reporter:  tdammers          |                Owner:  tdammers
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14737            |  Differential Rev(s):  phab:D4568
       Wiki Page:                    |
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Comment (by tdammers):

 Improvements should be evident from the changes in the tests, but here
 they are:

 - T5321FD:
   - Before: 415136648
   - After: 367567168 (down 11.5%)
 - T9020:
   - Before: 423163832
   - #14737: 562206104 (up 32.9%)
   - After: 392559256 (down 7.2% from Before)
 - T12425:
   - Before: 134780272
   - #14737: 141952368 (up 5.3%)
   - After: 130646336 (down 3.1% from Before)

 None of the other test cases show any regressions, including the test
 added for #14737.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15019#comment:17>
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