[llvm] [RISCV] Add load/store clustering in post machine schedule (PR #111504)

[Alex Bradbury via llvm-commits]

asb wrote:

> > > > createGenericSchedLive
> > > 
> > > 
> > > I think the reason is you are using pre-ra scheduler here.
> > 
> > 
> > Thank you - the problem was indeed me being too eager with copy and paste and failing to switch to `createGenericSchedPostRA`. Now I've done that though, I see zero codegen changes within the in-tree unit tests.
> 
> Thanks! I will ask @BoyaoWang430 to add some MIR tests. And thanks in advance if you can help to evaluate/review this PR. :-)

Thanks! And more generally, any note you have on how/if it affects codegen on external codebases very welcome. e.g. is this something that kicks in a lot in real-world code but we just don't trigger in our tests, or is it fairly rare it makes a difference (but of course worth addressing for the cases it helps)

https://github.com/llvm/llvm-project/pull/111504