[llvm] [IPO] Added attributor for identifying invariant loads (PR #141800)

[Shilei Tian via llvm-commits]

shiltian wrote:

> Also, do we want to add some mechanism for declaring that ptr(4) and ptr(6) are all definitionally constant and use it here?

No, this file is target agnostic so all target related stuff can be here. If anything target related needed, it has to go through TTI hook.

https://github.com/llvm/llvm-project/pull/141800