[clang] [AArch64][SME] Remove immediate argument restriction for svldr and svstr (PR #68565)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

This patch seems sort of contradictory to me.  You're encouraging users to pass a non-constant slice_offset, presumably because we expect the backend to optimize it... but at the same time, you're special-casing constant slice_offsets because you don't expect the backend to optimize it.  What do you actually expect the backend to do in practice?

I don't see any backend tests involving a non-zero slice_offset?

We currently have some code in getMemVTFromNode() in AArch64ISelDAGToDAG.cpp that handles sme_ldr/sme_str.  Is that code currently reachable?  If it is reachable, does it need to be adjusted for this change?

https://github.com/llvm/llvm-project/pull/68565