[GHC] #15703: Significant compilation time blowup when refactoring singletons-heavy code

[GHC]

#15703: Significant compilation time blowup when refactoring singletons-heavy code
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.6.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15725            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 I tried compiling this program using the experimental Phab:D4766 (`Zap
 coercions when not building with -dcore-lint`) branch:

 {{{
 $ time ~/Software/ghc3/inplace/bin/ghc-stage2 -O0 -fforce-recomp Lib.hs
 [1 of 2] Compiling Lib2             ( Lib2.hs, Lib2.o )
 [2 of 2] Compiling Lib              ( Lib.hs, Lib.o )

 real    0m0.497s
 user    0m0.460s
 sys     0m0.028s

 $ time ~/Software/ghc3/inplace/bin/ghc-stage2 -O1 -fforce-recomp Lib.hs
 [1 of 2] Compiling Lib2             ( Lib2.hs, Lib2.o )
 [2 of 2] Compiling Lib              ( Lib.hs, Lib.o )

 real    0m17.164s
 user    0m16.980s
 sys     0m0.200s
 }}}

 This looks promising! Perhaps this really is a duplicate of #8095 in
 disguise?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15703#comment:8>
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