[MLton] Multicore CPU's and MLton

[Stephen Weeks]

> Anway, I was wondering is there any quick and dirty way for MLton to 
> take advantage of that extra core...
...
> Is there maybe some way to at least pipe-line the compilaition process, 
> such that the frontend is in one thread spit outing code for the rest of 
> the backend to compile and optimize.

Things don't get easily parallelizable until the code generator, which
does a lot more local stuff than earlier passes.  Since native code
generation takes a big chunk of compile time (~50% for a self
compile), this could help some.  Even easier would be to parallelize
the calls to gcc when using the C codegen.  As the C codegen is even
slower than the native codegen, parallelization there could help even
more.  But then we already have a native codegen for x86, so this only
really helps on other platforms that are going multicore where we
don't have a native codegen.