[llvm] [AArch64] Fold COPY(y:gpr, DUP(x:fpr, i)) -> UMOV(y:gpr, x:fpr, i) (PR #89017)

[Amara Emerson via llvm-commits]

aemerson wrote:

I'm pragmatic about incremental solutions, but first have you looked at examining users of instructions in RBS? Even if it works top down there's nothing stopping you from peeking at uses.

https://github.com/llvm/llvm-project/pull/89017