[llvm] [RISCVGatherScatterLowering] Support vp_gather and vp_scatter (PR #73612)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

> > > It seems Roger favor a new patch. https://discourse.llvm.org/t/rfc-improved-vplan-native-path/73152/4 When the patch landing, we will have vp_gather/vp_scatter to trigger this patch.
> > 
> > 
> > We had something like this patch in our downstream, but we got a lot better results doing it in the vectorizer with SCEV information like what's in the BSC vectorizer.
> > @alexey-bataev @nikolaypanchenko
> 
> Thanks for the information. Could I ask is there plan to upstream the vp stride intrinsic generations in vectorizer?

Yes, we have a plan to fully upstream our vectorier (with some changes, of course, to meet the requirements of the upstream implementation)

https://github.com/llvm/llvm-project/pull/73612