[GHC] #15304: Huge increase of compile time and memory use from 8.0.2 to 8.2.2 or 8.4.2

[GHC]

#15304: Huge increase of compile time and memory use from 8.0.2 to 8.2.2 or 8.4.2
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        Reporter:  NathanWaivio      |                Owner:  tdammers
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by monoidal):

 Based on comment:6, I attached a bit smaller version without dependency on
 random.

 On my machine:

 * `ghc-8.0.2 -O -c Cl3.hs -fforce-recomp` takes 2 secs
 * `ghc-8.2.1 -O -c Cl3.hs -fforce-recomp` takes 57 secs
 * `ghc-8.4.3 -O -c Cl3.hs -fforce-recomp` takes 95 secs

 If I don't add `-O`, every version takes 2 secs.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15304#comment:10>
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