[llvm] [SimplifyCFG][Attributes] Preserve some non-equal attrs when intersecting (PR #111014)

[via llvm-commits]

goldsteinn wrote:

> Not willing to take this if it doesn't have an effect.
> 
> The `readnone` problem should be resolved by replacing it with `readonly writeonly`, which will also address this pain point in many other places, not just here.

Yeah that would help elsewhere.
Any thoughts on adding memoryeffects to params?

https://github.com/llvm/llvm-project/pull/111014