[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):

 Status:

 - Thing 1: Getting rid of non-linearity in coercionKind for the ForallCo
 case. Done.
 - Thing 2: Attacking non-linearity in coercionKindRole on NthCo's. I think
 this part is also more or less done, but I haven't seen anything on phab
 yet.
 - Thing 3: Fixing performance issues with `simplCast` / `SimplCore`. Moved
 to #14737, I believe @goldfire is still working on this.
 - Thing 4: Investigating `CoreTidy`. Moved to #14738, however it seems
 that the problem no longer manifests on GHC HEAD.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11735#comment:70>
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