[llvm] [Reland][IPO] Added attributor for identifying invariant loads (PR #146584)

[Shilei Tian via llvm-commits]

shiltian wrote:

Can you avoid mentioning people in the description or please don't forget to remove the mentioning part when the PR is merged; otherwise if the mentioning is included in the commit message, people will get emails from all over the world.

https://github.com/llvm/llvm-project/pull/146584