[GHC] #12367: Commit adding instances to GHC.Generics regression compiler performance

[GHC]

#12367: Commit adding instances to GHC.Generics regression compiler performance
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:  Generics
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2411
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"ed4809813fa51524ae73a4475afe33018a67f87d/ghc"
 ed480981/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="ed4809813fa51524ae73a4475afe33018a67f87d"
 InstEnv: Ensure that instance visibility check is lazy

 Previously instIsVisible had completely broken the laziness of
 lookupInstEnv' since it would examine is_dfun_name to check the name of
 the defining module (to know whether it is an interactive module). This
 resulted in the visibility check drawing in an interface file
 unnecessarily. This contributed to the unnecessary regression in
 compiler allocations reported in #12367.

 Test Plan: Validate, check nofib changes

 Reviewers: simonpj, ezyang, austin

 Reviewed By: ezyang

 Subscribers: thomie, ezyang

 Differential Revision: https://phabricator.haskell.org/D2411

 GHC Trac Issues: #12367
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12367#comment:20>
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