[Haskell-cafe] GHC optimizer consuming memory

[Edward Z. Yang]

Hello Mike,

I cannot reproduce using GHC HEAD (though it seems to hang on GHC 7.0.3),
so my guess is the bug has been fixed.

cvs-ghc, any guesses which patch this might have been?

Cheers,
Edward

Excerpts from mike frai's message of Sat Apr 30 14:50:17 -0400 2011:
> Hi,
> 
> While using Michael Snoyman's persistent package, I discovered that a
> certain bit of code generated from it made the GHC optimizer consume a
> ridiculous amount of memory (ie. only when using the "-O" flag). I
> know very little about the GHC compiler and Michael Snoyman
> recommended I post my findings here to see what others thought.
> 
> I've done what I can to extract the code generated from the persistent
> package and simplify/strip it down to the bare minimum of what's
> needed to cause this issue. You can find it in the attachment
> FromTest.hs. From my testing, removing five fields from Rec and the
> equivalent from the fromValue function - the memory consumption drops
> dramatically and I am able to compile.
> 
> For your convenience, I've also attached FromTest.out, which is the
> output I get when compiling FromTest.hs using "ghc -O -v3". This is
> just the output up to the point it starts consuming a lot of memory.
> I've never seen anything after this point because my system slows down
> to a crawl (due to swapping) and I end up killing the process.
> 
> Please let me know what you guys think or if you need any more
> information about this. Thanks,
> - Mike