[GHC] #9630: compile-time performance regression (probably due to Generics)

[GHC]

#9630: compile-time performance regression (probably due to Generics)
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        Reporter:  hvr               |                Owner:  dfeuer
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.9
      Resolution:                    |             Keywords:  deriving-
                                     |  perf, Generics
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9583, #10293,    |  Differential Rev(s):
  #13059, #10818                     |
       Wiki Page:                    |
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Comment (by dfeuer):

 Commit 2b74bd9d8b4c6b20f3e8d9ada12e7db645cc3c19 (Stop the specialiser
 generating loopy code) had a big positive impact here. My test case (as
 yet unpublished) compiles over twice as quickly. Edward's (when the
 specialization is cross-module) compiles something like one and a half
 times as quickly, and the unused method no longer hurts it (in fact it
 helps it slightly; perhaps the single-method class optimization burns a
 little time). So it looks pretty likely that this bug is squashed. I'll
 try to check a few more things before adding a test case and calling it
 done. I suspect it's still worth looking into the doubled constraint
 solving that came up in comment:55, but perhaps that should be a separate
 (lower priority) ticket.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9630#comment:61>
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