[llvm] [MachineLICM] Improve register pressure estimation. (PR #118615)

[Mikhail Gudim via llvm-commits]

mgudim wrote:

> Any tests and/or numbers to support this patch?

In https://github.com/llvm/llvm-project/pull/90819 we exercise LICM in new ways. While examining one of degradations that I saw, I discovered this.

I'll try to get perf numbers soon. And add a test.

https://github.com/llvm/llvm-project/pull/118615