[llvm] [AArch64] Merge scaled and unscaled narrow zero stores (PR #136705)

[David Green via llvm-commits]

davemgreen wrote:

> Can you explain a bit more? Doesn't the new offset always end up being less than or equal to the offset in the first instruction?

Yeah I just wanted to make sure there were not any problems - especially with unscaled and scaled representing the offsets differently with negative offsets and whatnot. We've had them go wrong in the past. This patch doesn't touch them directly but so I think they should be OK, but it's good to make sure they are tested around the extremes.

https://github.com/llvm/llvm-project/pull/136705