[MLton] Shootout Revived

[Stephen Weeks]

> Not sure if everyone knows this but the Great Language Shootout is up and 
> running again..
> 
> http://shootout.alioth.debian.org/index.php

Yeah, I saw that.  Brent (who has revived it) was nice enough to send
mail to some of the language maintainers.

> For the last few weeks the rankings were
> 
> gcc mlton, smlnj, ... ocaml
> 
> the ocaml hackers not to be underestimated  submited some changes and now 
> the rankings are
> 
> gcc, ocaml, mlton, smlnj, .....

The main change was getting one of the OCaml benchmarks working.  The
completely missing score was the only reason OCaml was as low as it
was.

> In particular the fibo benchmark seems a bit suboptimal. I imagine
> you could get a small speed up by doing a range test rather than
> using pattern matching, unless the mlton match compiler is being
> much smarter than I imagine.

Yeah, that speeds it up by a few percent (maybe 5%).

> Also, there's also the trick of using Word32 rather than Int to 
> avoid the overflow trapping which Ocaml doesn't do anyway...

For whatever reason, that doesn't seem to help at all.  In fact, in my
tests it hurts.

In any case, I don't think either of those explains why MLton is so
much slower.  It is likely something with our calling convention.

Brent gave me commit access, so I checked in the range change for
fibo.mlton.  If any of y'all improve any of the other benchmarks, let
me know and I'll check in the new version.