[llvm] [IR][Attributes] Take "best" from Callbase/Call Function when getting attributes (PR #112985)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Can you please check the compile-time impact?

Our general convention is to let the CB attribute take precedence over the Callee attribute, as long as it exists. I don't think doing an actual intersection (thus requiring to always look up *both* attributes) is going to be practically useful, as we shouldn't place worse call-site attributes in the first place.

https://github.com/llvm/llvm-project/pull/112985