[GHC] #5631: Compilation slowdown from 7.0.x to 7.2.x

[GHC]

#5631: Compilation slowdown from 7.0.x to 7.2.x
---------------------------------+------------------------------------------
    Reporter:  bjpop             |       Owner:                              
        Type:  bug               |      Status:  new                         
    Priority:  normal            |   Component:  Compiler                    
     Version:  7.2.1             |    Keywords:                              
    Testcase:                    |   Blockedby:                              
          Os:  Unknown/Multiple  |    Blocking:                              
Architecture:  Unknown/Multiple  |     Failure:  Compile-time performance bug
---------------------------------+------------------------------------------
 Compile time performance for GHC appears to have slowed down significantly
 for the package:

    http://hackage.haskell.org/package/language-python

 Time to compile the package:

    - GHC 7.0.4: 3m57s
    - GHC 7.2.1: 49m22s
    - GHC 7.2.2: 49m56s

 The culprits are the Happy generated modules:

    Language.Python.Version3.Parser.Parser
    Language.Python.Version2.Parser.Parser

 GHC uses up to 700MB of memory compiling these files (my machine has 2GB
 of RAM and it does not appear to be thrashing during the compilation).

 All versions of GHC in this ticket were downloaded as binary packages from
 the ghc website.

 System:

 OS X 10.7.2
 1.4 GHz Intel Core 2 Duo
 2GB RAM
 GCC 4.2.1

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5631>
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