[GHC] #13426: compile-time memory-usage regression for DynFlags between GHC 8.0 and GHC 8.2

[GHC]

#13426: compile-time memory-usage regression for DynFlags between GHC 8.0 and GHC
8.2
-------------------------------------+-------------------------------------
        Reporter:  hvr               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      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):  Phab:D3399,
       Wiki Page:                    |  Phab:D3400, Phab:D3421
-------------------------------------+-------------------------------------

Comment (by bgamari):

 dfeuer will need to comment on what specifically "some cases" refers to,
 but the patch in comment:42 removes some `seq`s which don't appear to be
 necessary to prevent thunk leaks. I would expect that this did have a
 positive impact on compiler speed, but in practice this effect
 [[https://perf.haskell.org/ghc/#revision/2088d0be17dccfa91a4759bdbb20faae77c8dbed|appears]]
 to be too small to measure.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13426#comment:44>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler