[llvm] IR: Allow vector type in atomic load and store (PR #117625)

[James Y Knight via llvm-commits]

jyknight wrote:

I'm a little confused by the steps being taken here.

Can we have this fallback via cast to integer by default on _all_ platforms, at the same time as making it legal? (That's how floats were handled, e.g.). We shouldn't have this work only on some platforms, but not others.

https://github.com/llvm/llvm-project/pull/117625