[llvm] [AArch64] Reland merge index address with large offset into base address (PR #79951)

[David Green via llvm-commits]

davemgreen wrote:

Thanks. Do you know if the issue from #76202 is still present, or what it might have been caused by? It sounded like a mis-compile.

https://github.com/llvm/llvm-project/pull/79951