[PATCH] [ARM/AArch64] Add ACLE special register intrinsics (10.1)

[Bradley Smith]

Hm, I hadn't seen read_register and write_register, it almost looks like what I want, however it seems that it's used specifically for named registers that map to a backend register (and uses CopyFromReg on them). The issue with this is that none of these special registers are real registers in the backend, they just get encoded to immediate field(s).

I however hadn't considered that use of metadata to pass strings through the IR (like read/write_register do) was an acceptable way of doing things. So I might be able to create my own similar intrinsics that use this method of passing the special register string straight through.

Tim, I avoided doing more analysis than I did in the frontend simply because you'd need to get the the point of using the backend SysRegMappers in the frontend, which seemed like the wrong thing to do. That said, if I take the above approach I could easily do this analysis at the lowering stage, which would allow for proper diagnostics. (Assuming emitting these diagnostics in the backend rather than frontend is acceptable?)

http://reviews.llvm.org/D6247