[GHC] #11735: Optimize coercionKind

[GHC]

#11735: Optimize coercionKind
-------------------------------------+-------------------------------------
        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:                    |
-------------------------------------+-------------------------------------

Comment (by tdammers):

 Refactoring `coercionRoleKinds` / `coercionRole` gives us another
 performance boost:

 {{{
         Wed Jan 24 17:17 2018 Time and Allocation Profiling Report
 (Final)

            ghc-stage2 +RTS -p -RTS -B/home/tobias/well-
 typed/devel/ghc/inplace/lib Grammar.hs -ddump-stg -ddump-simpl -ddump-to-
 file -fforce-recomp

         total time  =       24.18 secs   (24176 ticks @ 1000 us, 1
 processor)
         total alloc = 29,250,375,752 bytes  (excludes profiling overheads)

 COST CENTRE           MODULE     SRC
 %time %alloc

 CoreTidy              HscMain    compiler/main/HscMain.hs:1253:27-67
 24.8   28.5
 Stg2Stg               HscMain    compiler/main/HscMain.hs:1489:12-44
 20.1   24.2
 simplCast             Simplify   compiler/simplCore/Simplify.hs:871:62-87
 18.6   15.9
 tc_rn_src_decls       TcRnDriver
 compiler/typecheck/TcRnDriver.hs:(494,4)-(556,7)      8.1    6.9
 addCoerce-pushCoTyArg Simplify
 compiler/simplCore/Simplify.hs:(1236,12)-(1237,72)    7.3    6.4
 subst_ty              TyCoRep    compiler/types/TyCoRep.hs:2225:28-32
 4.2    5.1
 preprocessFile        GhcMake
 compiler/main/GhcMake.hs:(2416,1)-(2443,37)           1.4    0.0
 coercionKind          Coercion   compiler/types/Coercion.hs:1707:3-7
 1.4    3.0
 zonkTopDecls          TcRnDriver
 compiler/typecheck/TcRnDriver.hs:(445,16)-(446,43)    1.3    1.1
 simplExprF1-Lam       Simplify   compiler/simplCore/Simplify.hs:896:5-39
 1.0    1.1
 }}}

 Now on to the 25% spent on CoreTidy.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11735#comment:12>
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