[GHC] #14254: The Binary instance for TypeRep smells a bit expensive

[GHC]

#14254: The Binary instance for TypeRep smells a bit expensive
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:  Typeable
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14337            |  Differential Rev(s):  Phab:D3998,
       Wiki Page:                    |  Phab:D4082, Phab:D4085
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Comment (by David Feuer <David.Feuer@…>):

 In [changeset:"bc761ad9c65c7aa62d38db39c59a6c0ae59c8ab8/ghc" bc761ad/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="bc761ad9c65c7aa62d38db39c59a6c0ae59c8ab8"
 Cache TypeRep kinds aggressively

 Cache `TypeRep k` in each `TrApp` or `TrTyCon` constructor of
 `TypeRep (a :: k)`. This makes `typeRepKind` cheap.

 With this change, we won't need any special effort to deserialize
 typereps efficiently. The downside, of course, is that we make
 `TypeRep`s slightly larger.

 Reviewers: austin, hvr, bgamari, simonpj

 Reviewed By: bgamari, simonpj

 Subscribers: carter, simonpj, rwbarton, thomie

 GHC Trac Issues: #14254

 Differential Revision: https://phabricator.haskell.org/D4085
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14254#comment:17>
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