[GHC] #15519: Minor code refactoring leads to drastic performance degradation

[GHC]

#15519: Minor code refactoring leads to drastic performance degradation
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        Reporter:  danilo2           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by danilo2):

 Ok, I've got one more important notice.

 If I put the `NOINLINE` pragma on the `runTokenParser` function, the
 `test0` is working 14 times slower. And this is interesting because
 `runTokenParser` does a simple pattern matching and then evaluates the
 `Text.span` function. So the `Text.span` (mapping a function to 100000
 Chars) takes a tiny fraction of time of this computation.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15519#comment:4>
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