[llvm] [LFI][AArch64] Add rewrites for memory accesses (PR #195167)

[Peter Smith via llvm-commits]

https://github.com/smithp35 commented:

GitHub is giving me an internal error when I try to leave more comments. It doesn't seem to affect my colleagues so there may be some odd state in its system.

A couple more comments that I can express here (hopefully these won't end up as duplicates):
Line 400 
I suggest adding writeback
// Case 2: Pre-index load/store, with writeback.

Line 432
Is it possible that XM1 could be SP? All the other code paths return false in this situation.  

https://github.com/llvm/llvm-project/pull/195167