[GHC] #10800: vector-0.11 compile time increased substantially with 7.10.1

[GHC]

#10800: vector-0.11 compile time increased substantially with 7.10.1
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by erikd):

 Much like for [comment:12 comment 12], set myself up so I could build the
 vector test suite with ghc versions 7.8.4, 7.10.3 and 8.0.0.20160316 and
 then with each compiler ran `cabal clean && time cabal test` a number of
 times with each.

 This is the result of a single run, but is representative of this test:

 {{{
 Compiler      real          user           sys
 7.8.4       1m38.167s     2m03.336s      0m43.800s
 7.10.3      8m59.597s    11m40.756s      5m37.828s
 8.0.0       0m45.165s     1m0.148s       0m23.744s
 }}}

 The 8.0 compiler has not only fixed the compile regression from 7.8 to
 7.10, its actually about twice as fast as 7.8.

 Just as validation I also timed the runtime of the test suites compiled by
 each of the three compile and there didn't seem to be any measurable
 difference in run time performance.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10800#comment:16>
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