[GHC] #11735: Optimize coercionKind

[GHC]

#11735: Optimize coercionKind
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        Reporter:  goldfire          |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by tdammers):

 Replying to [comment:59 simonpj]:
 > So the allocations are really close.  Where does the extra time go?
 >
 > Can you show mutator and GC times?  Maybe residency, and hence GC time,
 is higher?  Perhaps just an accident of the moments at which major GC
 happens.  What happens if you use use just one generation?

 I've done a run with `-s`, which gives us:

 {{{
 --- ./cases/Grammar.hs ---
 4eb140f564: 12.31 sec, max res. 257,842,544
 8ac966971e: 12.70 sec, max res. 425,496,520
 8a6aa5030d: 12.31 sec, max res. 254,680,256
 --- ./cases/test_rules2.hs ---
 4eb140f564: 1.11 sec, max res. 84,030,624
 8ac966971e: 1.14 sec, max res. 81,325,072
 8a6aa5030d: 1.09 sec, max res. 56,322,200
 }}}

 So it looks like your hunch was about right: in the Grammar.hs case, max
 residency almost doubles in `8ac...`, but `8a6` then gets us back to
 normal; for the test_rules2.hs case, we see only improvement.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11735#comment:69>
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