Fix incorrect codegen for SVE GatherVector*With*Offsets*

[SwapnilGaikwad]

Equivalent to #119712 for gathers where offsets are incorrectly treated as indices which is leading to incorrect code being emitted.

Discussed here.

@dotnet/arm64-contrib @a74nh @tannergooding @EgorBo

[a74nh]

The isLoadingBytes is a little ugly. Alternative would be to split the switch cases. But, then it'd duplicate the code underneath isLoadingBytes. So, I'm happy

This is similar enough to #119712 that I feel we need both in .NET11 if possible.

So, LGTM.

[EgorBo]

@tannergooding could you please take a quick look if your feedback was addressed

[SwapnilGaikwad]

The isLoadingBytes is a little ugly. Alternative would be to split the switch cases. But, then it'd duplicate the code underneath isLoadingBytes.

Updated compares to use intrinsics only instead of the instructions and intrinsics for better clarity.

[EgorBo]

@SwapnilGaikwad could you please file a manual backport to release/10.0 branch with changes from #119712 and this PR combined?

[SwapnilGaikwad]

@SwapnilGaikwad could you please file a manual backport to release/10.0 branch with changes from #119712 and this PR combined?

Hey @EgorBo , not sure how to do that. Would that be a different PR with changes combined?

[EgorBo]

@SwapnilGaikwad could you please file a manual backport to release/10.0 branch with changes from #119712 and this PR combined?

Hey @EgorBo , not sure how to do that. Would that be a different PR with changes combined?

Yes. Our backport bot doesn't know how to combine changes from two PRs and since the approval process for backports is not simple for RC2/GA, it's better to file just one PR with both

[EgorBo]

I think you can just cherry-pick two commits or just extract them as patches and apply to your release/5.0 branch

e.g.

https://github.com/dotnet/runtime/pull/119712.patch
https://github.com/dotnet/runtime/pull/119853.patch

[SwapnilGaikwad]

I think you can just cherry-pick two commits or just extract them as patches and apply to your release/5.0 branch

e.g.

https://github.com/dotnet/runtime/pull/119712.patch https://github.com/dotnet/runtime/pull/119853.patch

Combined these changes with scatters in #119959.