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

[Sam Tebbs via llvm-commits]

SamTebbs33 wrote:

> 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.

Ah good idea. I've added tests without the surrounding loop structure.

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