[clang] [llvm] Reapply "[AArch64][SVE] Improve fixed-length addressing modes. (#130263)" (PR #130625)

[Ricardo Jesus via llvm-commits]

rj-jesus wrote:

Hi @paulwalker-arm, thanks again for your suggestion. I think the only node missing was `MemIntrinsicSDNode`, which seemingly was considered after `isa<MemSDNode>(Root)` in the original code (although I'm not sure it was reachable). I've moved it before the main `MemSDNode` path to avoid hitting the unreachable.

As far as I could tell, the only `MemIntrinsicSDNode` nodes that the function handles are for `Intrinsic::aarch64_sve_st2`, `st3` and `st4`, so `getMemoryVT()` should be okay to use, I believe. We could also move these intrinsics to the last switch statement and avoid having that dedicated path. I'm not sure what approach is preferable, so I've kept the original code, but please let me know if you'd like me to make that change.

Please let me know if you have any other comments!

https://github.com/llvm/llvm-project/pull/130625