[GHC] #14737: Improve performance of Simplify.simplCast

[GHC]

#14737: Improve performance of Simplify.simplCast
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        Reporter:  tdammers          |                Owner:  goldfire
            Type:  bug               |               Status:  patch
        Priority:  highest           |            Milestone:  8.6.1
       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:  #11735 #14683     |  Differential Rev(s):  Phab:D4385
       Wiki Page:                    |  Phab:D4568
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"d92c7556501a4cdeb7d269c4624992c94d9b3b8b/ghc" d92c755/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="d92c7556501a4cdeb7d269c4624992c94d9b3b8b"
 Fix performance regressions from #14737

 See #15019. When removing an unnecessary type equality check in #14737,
 several regression tests failed. The cause was that some coercions that
 are actually Refl coercions weren't passed in as such, which made the
 equality check needlessly complex (Refl coercions can be discarded in
 this particular check immediately, without inspecting the types at all).

 We fix that, and get additional performance improvements for free.

 Reviewers: goldfire, bgamari, simonpj

 Reviewed By: bgamari, simonpj

 Subscribers: simonpj, thomie, carter

 Differential Revision: https://phabricator.haskell.org/D4635
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14737#comment:31>
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