Future of D on alternate platforms

[Frustrated]

How difficult is it to port D code to future projects on
alternate platforms(mainly coming from win) and, if needed be, a
compiler for those platforms?

At this point, I'm wondering how difficult code I'm writing for
windows will be to port to, say, the iOS, mac, arm, and more
likely, embedded systems such as the tigerSharc, etc.

I've heard many times the LLVM compiler mentioned in the forums
and it seems to be able to compile D code to any platform the
compiler supports(but somehow independent of D... maybe it
compiles it to an intermediate language?).

My goal at this point is to use D on windows to create some
algorithmic software and then potentially port it to some
embedded system with minimal rewrite of the core code. e.g., I
don't want to have to rewrite the algorithms in C and use the
compiler tools for that system. If that was the case there is
little reason to use D in the first place.

Obviously there is no magic compiler that will do it all. I'm
curious though as to the possibility. In 2 years could one expect
D to be more widely used on other systems? I see people already
getting D started on ARM and iOS so it seems feasible that in the
near future it would be relatively easy to port the
code(obviously there are functional differences due to the OS but
I'm talking about the cpu issues at this point).