[llvm] [LLVM][AArch64][SVE] Mark DUP immediate instructions with isAsCheapAsAMove. (PR #133945)

[David Sherwood via llvm-commits]

david-arm wrote:

This does seem like a sensible patch, but can it also have unwanted side-effects? For example, MachineLICM is often incredibly aggressive and likes to hoist invariants as far away from the original loop as it possibly can. When you throw intervening function calls in to the mix, could it lead to more fills and spills? I guess it depends upon the ABI and whether or not it's a level playing field, i.e. if SVE and NEON are treated equally then at least it's no different to marking NEON dups as cheap as a move.

https://github.com/llvm/llvm-project/pull/133945