[llvm] [MachineLICM] Use `RegisterClassInfo::getRegPressureSetLimit` (PR #119826)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

> I've reverted this in [eeac0ff](https://github.com/llvm/llvm-project/commit/eeac0ffaf46cf9f9b0f680b9940cc4b68a0286d8), because it causes a very large compile-time regression, see https://llvm-compile-time-tracker.com/compare.php?from=e3e26dc41a6ad78c35a1a723cd77f5db8599797d&to=b4e17d4a314ed87ff6b40b4b05397d4b25b6636a&stat=instructions:u.
> 
> If you need a test case for analysis, a good one is probably k.cc from kimwitu++, which regresses by more than 6%.

Thanks for reporting, I have no surprise about compile-time increase. I was going to make `RegisterClassInfo` a pass in https://github.com/llvm/llvm-project/pull/120690 and this will reduce compile-time.
Anyway, I will revisit this after https://github.com/llvm/llvm-project/pull/120690 as you have reverted it.

https://github.com/llvm/llvm-project/pull/119826