Hitchikers Guide to Porting Phobos / D Runtime to other architectures

[Dwhatever]

> For LDC with an ARM backend, you only need to compile with 
> -march= and/or -mcpu= if you wish to compile for bare-metal.
>
> The version strings are listed here 
> (http://dlang.org/version.html).  So if I understand your 
> objective, you would only need...
>
> else version(ARM_Thumb) // or version(ARM) if targeting 
> Cortex-A and the like
> {
>    ...
> }
>
> And it may actually need to look more like...
> version(X86)
> {
>     version(Windows)
>     { }
>     else version(Linux)
>     { }
>     else
>     { }
> }
> else version(ARM_Thumb)
> {
>     ...
> }
>
> of course the hard part is filling in the (...).
>
> What CPU/MCU are you targeting?  Are you building for 
> bare-metal?

Yes, for bare metal, no OS, nothing.

I think I have to specify my target architecture and CPU 
otherwise the compiler cannot know that I'm cross compiling for 
ARM. -march= -mcpu= will not work for me.

I'm trying to compile a simple stand alone object file.

class TestClass
{
     ubyte member;

     this(ubyte m) { member = m; }
     ubyte Get() { return member; }
};


extern(C) void main()
{
     // stack class
    scope test = new TestClass(0);

    // simple inline asm test
    __asm("mov r0,#1;
           mov r1,#2", "~{r0,r1}");
}

This test should be simple enough I thought but it turned out 
that to compile and link this, D requires almost everything from 
the runtime.

So the challenge is, compile and link the simple code above 
targeting ARM using LDC, no OS allowed.