How does an HDL address the limitation of software compilers at the software-hardware boundary?

By scope, I mean that the compiler can really only see as far as the source code it is compiling. In something like an OS--especially a non-microkernel--an awful lot ends up having to be read and written across the boundary, and in an unsafe context.

Oh I see. You were talking about a compiler for software talking to hardware. Well, I don't see why talking to hardware is any different to talking to a CPU or main memory or a disk.

Not so much "talking" as directly reading/writing memory outside of your source scope that is also mutated by other chips--like a DMA buffer.

Or for a traditional kernel, reading/writing directly into the address space of a user process. Wouldn't have to worry so much about race conditions there since the process could be suspended, but there is still an opportunity to fudge the indexing.

It looks like something that just gets complied to VHDL and friends? Is there some way to make the description available to user code/GHC? Now that would be interesting.