[llvm] [AArch64] Lower alias mask to a whilewr (PR #100769)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

Can you add tests into llvm/test/CodeGen/AArch64 that show examples of how these should be generated? They should ideally be as minimal as possible, not the full loops.

https://github.com/llvm/llvm-project/pull/100769