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

[GHC]

#9630: compile-time performance regression (probably due to Generics)
-------------------------------------+-------------------------------------
        Reporter:  hvr               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.4.1
       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:                    |
-------------------------------------+-------------------------------------
Changes (by dfeuer):

 * cc: dfeuer (added)
 * related:  #9583, #10293, #13059 => #9583, #10293, #13059, #10818


Comment:

 It appears that much or all of the regression in the original example
 occurred in b9e49d3e9580e13d89efd1f779cb76f610e0d6e0. Before, I get

 {{{
 dfeuer at squirrel:~/src/cabal> ~/src/ghc-iproute-before/inplace/bin/ghc-
 stage2 -Rghc-timing -O -c Cabal/Language/Haskell/Extension.hs
 <<ghc: 5795390224 bytes, 640 GCs, 37133197/104324936 avg/max bytes
 residency (16 samples), 248M in use, 0.001 INIT (0.001 elapsed), 3.981 MUT
 (4.258 elapsed), 2.622 GC (2.639 elapsed) :ghc>>
 }}}

 After,
 {{{
 dfeuer at squirrel:~/src/cabal> ~/src/ghc-iproute-after/inplace/bin/ghc-
 stage2 -Rghc-timing -O -c Cabal/Language/Haskell/Extension.hs
 <<ghc: 126972407680 bytes, 3337 GCs, 340164097/914871104 avg/max bytes
 residency (36 samples), 2652M in use, 0.001 INIT (0.001 elapsed), 82.951
 MUT (118.315 elapsed), 52.254 GC (52.317 elapsed) :ghc>>
 }}}

 Jeepers!

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9630#comment:40>
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