Vulkan Subpass support?

I’m experimenting vulkan subpasses as it should give a performance uplift on mobile platforms. However a renderpass with multiple subpasses is not officially supported yet, I was wondering when this will be available?
Another thing is subpasses would need “SubpassInput, SubpassLoad” in shader, but they are not supported in HLSL based on currently compilation process, I got ompilation error for this, what do I need to do if I want to support them?