[llvm] [SelectionDAG] Preserve cache hint metadata through DAGCombiner (PR #225954)

[Yonah Goldberg via llvm-commits]

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YonahGoldberg wrote:

I don't think that's really necessary. The test shows that if the smaller loads have mixed metadata then the merged load doesn't carry the metadata, and same for the stores. I think it's fine to do that in the same test.

https://github.com/llvm/llvm-project/pull/225954