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

[Gaëtan Bossu via llvm-commits]

gbossu wrote:

> I'm happy for this to be the starting point to evolve from.

Same here, so please go ahead if that makes your stack of changes easier to manage :) With my limited SME and ZA management knowledge, I cannot comment on whether this new pass is the right approach or how much it's better than the previous approach, so I'll trust @paulwalker-arm and @sdesmalen-arm on that. What I can say is that the changes do make sense to me, and this is a great starting point to enabling better ZA "stack management".

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