[GHC] #14683: Slow compile times for Happy-generated source

[GHC]

#14683: Slow compile times for Happy-generated source
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        Reporter:  harpocrates       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.2.2
      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):

 Further profiling result:

 {{{
 COST CENTRE         MODULE   SRC
 %time %alloc

 coercionKind        Coercion compiler/types/Coercion.hs:1707:3-7
 87.5   88.7
 CoreTidy            HscMain  compiler/main/HscMain.hs:1253:27-67
 3.1    3.3
 simplCast-addCoerce Simplify compiler/simplCore/Simplify.hs:1225:53-71
 2.8    2.8
 simplCast           Simplify compiler/simplCore/Simplify.hs:871:62-87
 2.1    1.5
 Stg2Stg             HscMain  compiler/main/HscMain.hs:1489:12-44
 1.6    1.9
 }}}

 In other words, we're spending close to 90% time and alloc on the
 `coercionKind` function.

 alexbiehl mentioned that #11735 might be related, in the sense that
 possible optimizations mentioned there could solve this performance
 problem here.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14683#comment:15>
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