[llvm] [AArch64][SME] Implement the SME ABI (ZA state management) in Machine IR (PR #149062)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm commented:

This is mainly a high level structural review, because I've yet to properly check the finer details of the emit... functions (although I'm guessing they're mostly taken from the existing implementation?).

What I've seen does look very nice.

https://github.com/llvm/llvm-project/pull/149062