id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
5631	Compilation slowdown from 7.0.x to 7.2.x	bjpop	igloo	"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"	bug	closed	highest	7.4.1	Compiler	7.2.1	fixed			Unknown/Multiple	Unknown/Multiple	Compile-time performance bug	Unknown	perf/compiler/T5631