[llvm] [RISCV] Use LD_RV32/SD_RV32 for spills and reloads when Zilsd is enabled (PR #153595)

[Craig Topper via llvm-commits]

topperc wrote:

> > Can we do better by also using zilsd with unaligned scalar memory? I don't know if we know the alignment of the spill slot here, but if it's 8 or more we should also be able to use zilsd regardless.
> 
> I've added support for this now. I have also added a test case where we use `PseudoRV32ZdinxLD/SD` even when the `Zdinx` extension is not enabled. That's the reason I had to remove the assert that was there in the initial commits. Can we maybe introduce another Pseudo for the non `Zdinx` case?

The P extension also needs GPRPair. I don't see a reason to have multiple pseudos. We should just update the name.

https://github.com/llvm/llvm-project/pull/153595