[llvm] [AArch64] Emit ST<OP> instruction when the return value has no use. (PR #72887)

[via llvm-commits]

gonzalobg wrote:

I agree with Kyrill. Replacing LDADD with STADD is unsound unless the implementation of the acquire-fence also changes to fence stores, which would break the atomics ABI. I'll capture this in the bug, and will close it. Thank you both for entertaining the idea though.

https://github.com/llvm/llvm-project/pull/72887