[llvm] [InstCombine] Add assume-based optimizations for equality and AMDGPU ballot patterns (PR #160670)

[Sameer Sahasrabuddhe via llvm-commits]

https://github.com/ssahasra requested changes to this pull request.

If github had a reject button, I would have used that for sure. Please arrange an internal review of the process involved in the making of this change.

https://github.com/llvm/llvm-project/pull/160670