[GHC] #14974: 2-fold memory usage regression GHC 8.2.2 -> GHC 8.4.1 compiling `mmark` package

[GHC]

#14974: 2-fold memory usage regression GHC 8.2.2 -> GHC 8.4.1 compiling `mmark`
package
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        Reporter:  hvr               |                Owner:  davide
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.1
      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 simonpj):

 Interesting questions

 * Do we get more or better specialisations from `SpecConstr`?
 * Do any of the library benchmarks run faster?

 Maybe invite the author to give insight, once you have characterised
 better what is happening.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14974#comment:8>
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