[llvm] [clang] [InstCombine] Infer disjoint flag on Or instructions. (PR #72912)

[Craig Topper via cfe-commits]

topperc wrote:

> Also you'll want to do this inside SimplifyDemanded to reuse existing KnownBits information.

Do we do that for other flags already? I based this off Add/Sub.

https://github.com/llvm/llvm-project/pull/72912