[GHC] #13253: Exponential compilation time with RWST & ReaderT stack with `-02`

[GHC]

#13253: Exponential compilation time with RWST & ReaderT stack with `-02`
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        Reporter:  phadej            |                Owner:  bgamari, osa1
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15630            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by tdammers):

 A quick test suggests that the patch from comment:24 makes things better,
 but not by the amount we would expect from actually solving the excessive
 inlining / Core blowup issue. On my machine, compilation time between GHC
 8.4.2 and HEAD with the patch applied goes down from 2:00 minutes to 1:45
 approximately; significantly faster, but not the orders-of-magnitude
 improvement we would expect from a proper fix.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13253#comment:36>
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