While running the following I get an error:

$ ./emscripten.py demo.ll /home/chris/v8-trunk/d8
intertyper.js:393: TypeError: Cannot read property 'tokens' of undefined
        params: parseParamTokens(item.tokens[2].item.tokens),
                                                ^

The full demo.ll file is here: https://gist.github.com/914021

Steps to reproduce (if desired). demo.hs:

main = putStrLn "Hello, World!"

Build:

/opt/ghc7/bin/ghc -fllvm -keep-llvm-files demo.hs -fforce-recomp  # outputs demo.ll

I suspect this is probably not a bug in emscripten, as GHC may use some novel extensions to support its calling conventions and such. I don't really know anything about LLVM or how GHC uses it. I suppose it's worth posting; if other Haskellers try this they will get the same problem, undoubtedly.