[GHC] #13639: Skylighting package compilation is glacial

[GHC]

#13639: Skylighting package compilation is glacial
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:  dfeuer
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       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:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by niteria):

 This package has 123 modules which contain nothing else than a giant
 multi-kilobyte `String`. See
 https://hackage.haskell.org/package/skylighting-0.3.3.1/src/src/Skylighting/Syntax/Jsp.hs
 for example.

 With `-g` (DWARF) on `ghc-8.0.2`  it appears to lead to ~40m compile
 times. I have a strong suspicion that we end up generating debugging
 information for each of these `(:)` cells, which is bound to be slow with
 4 million of these total and the nesting levels of 10k.
 I may be wrong because #11095 was supposed to improve it and I'm running
 with
 https://git.haskell.org/ghc.git/commitdiff/29122312cc7b8f9890eb53f92d76ecdd8ded24ee
 already.

 I will try to confirm if the problem persists on HEAD.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13639#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler