I originally tagged this issue against 3.6 just because that's what I was attempting to build. But I'm not super concerned about what release these changes actually land in, I can always backport it to my own builds (and at my own risk).

Even though I'm super interested in seeing these changes done, I'm not sure I'm the right person to do the heavy lifting on this. I don't know if the seemingly undocumented (?) Windows ARM64 ABI matches the well-documented Linux AArch64 ABI, for example. If it does match, that would make porting the asm bits pretty straightforward (mostly just translating GNU assembler AT&T syntax to MASM, I suppose). I could do that. But if it doesn't match then I'd probably need to dig into ARM architecture manuals. Someone else could likely do it in their sleep.