[llvm] [MCSched] Allow tuning LoadLatency/MispredictPenalty (PR #203139)

[Tomer Shafir via llvm-commits]

tomershafir wrote:

I think it would be great that the options could apply across targets, and I think `MCSchedModel` is a natural place for them. We had the intention to contribute a similar option for `MispredictPenalty` tuning on AArch64. I think an approach like https://github.com/llvm/llvm-project/pull/195638 can work. 

As part of the work on that patch I also encountered the divergence pitfall, but it doesnt seem straightforward to achieve on top of the current TableGen infra for sched models, which describes all of the information using public static structs. I think it may not be too critical, and we can compromise so divergent callers would have to be fixed on a need basis.

https://github.com/llvm/llvm-project/pull/203139