[GHC] #14161: Performance Problems on AST Dump

[GHC]

#14161: Performance Problems on AST Dump
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        Reporter:  h4ck3rm1k3        |                Owner:  dfeuer
            Type:  bug               |               Status:  new
        Priority:  low               |            Milestone:  8.2.2
       Component:  Compiler          |              Version:  8.3
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by dfeuer):

 Actually, that's only one piece of the puzzle. Another major problem is
 that when `showAstData` is called in `HscMain`, its (`String`) result is
 converted to an `SDoc` using `text`. In order to even think about
 rendering that result, `Pretty` calculates its length. This forces the
 entire dump to be built in memory as a `String`. I don't have enough
 memory to do that on my system!

 I'm working on a patch to make `showAstData` produce a `Doc` right from
 the start rather than a `String`. Initial experiments suggest that this
 has a much better chance of working. One question: when should one produce
 a `Doc` and when should one produce an `SDoc`? I'm pretty unclear on that
 bit.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14161#comment:3>
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