[llvm] [MachinePipeliner] Limit the number of stores in BB (PR #154940)

[via llvm-commits]

aankit-ca wrote:

> TODO: Add some comments and tests
> 
> @aankit-ca Could you please run your benchmark with this change? I believe this is the simplest solution for #150262. If you're okay with it, I'd like to proceed with this approach. Here are some notes:
> 
> * I have confirmed that this patch resolves the specific case raised in [hexagon compiler runs "forever" on matrix-spec-types at O2 #150262](https://github.com/llvm/llvm-project/issues/150262), but this change may reduce optimization opportunities for other cases.
> * The default value of `SwpMaxNumStores` is arbitrary. Please let me know if you have any preferences.
> * If we're very lucky, this might also improve compilation time in other cases, without causing any performance regressions.
> 
> Thanks in advance!

Thanks for looking into this issue @kasuga-fj . I'm on a vacation right now and will be back on Sep 2. I'll verify this once I'm back!

https://github.com/llvm/llvm-project/pull/154940