[llvm] [MachineLICM] Give opportunity to analyze physregs for invariance. (PR #84779)

[Andrzej Warzyński via llvm-commits]

banach-space wrote:

Thanks for preparing this 🙏🏻 

> @sjoerdmeijer @FreddyLeaf any other comments?

This unblocks some nice improvements for us in MLIR. Given that there's always a delay between MLIR and IREE (which is where ultimately we need this), could this be merged before the end of the week? 

https://github.com/llvm/llvm-project/pull/84779