[llvm] [MLGO] Count LR Evictions Rather than Relying on Cascade (PR #124440)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

I've had to add state to the eviction advisor with a new `mutable` member. I did this following the precedent for the `CachedFeatures` member, but not sure if it's the ideal approach. This approach shouldn't violate any assumptions (like a `MachineFunctionPass` only maintaining state within functions). The alternative is not marking all these methods as `const` (which in the MLRegalloc Eviction Advisor they already effectively aren't due to caching).

https://github.com/llvm/llvm-project/pull/124440