[GHC] #13344: Core string literal patch regresses compiler performance considerably

[GHC]

#13344: Core string literal patch regresses compiler performance considerably
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        Reporter:  bgamari           |                Owner:  bgamari
            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):
       Wiki Page:                    |
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Comment (by rwbarton):

 > Consequently, we came up with a few ideas for instead reducing the cost
 of the now-larger interface files. Happily, this effort may also have
 helpful effects beyond string literals. The gist is that we want make
 interface file deserialisation more lazy. Reid is working on a patch.

 This patch is Phab:D3269.

 > Back to comment:16. Let's assume that this string-CSE thing makes no
 difference. Then all my questions in comment:16 remain. I just want to be
 sure that we are fixing the right problem!

 I think it will make some substantial difference, but I suspect there is
 still something else going on. When your CSE fix is ready (I assume it is
 a simple change), I will try comparing

 * the commit before the top-level string patch, with

 * the top-level string patch plus your fix to CSE

 by doing a `validate --build-only` with detailed tracking of where time is
 being spent.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13344#comment:19>
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