[llvm] [AArch64] Mark neon.stN intrinsics as writeonly (PR #145289)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

Seems fine; the intrinsics are supposed to have the same memory semantics as normal IR operations.  (We currently don't provide "volatile" variants.  You can use inline asm if you really need that for some strange reason.)

Please add a regression test of some sort to track that we've added this marking.

https://github.com/llvm/llvm-project/pull/145289