[llvm] [RISCV] Only convert volatile i64 load/store to Zilsd in SelectionDAG. (PR #169529)

[Sam Elliott via llvm-commits]

lenary wrote:

Can we hold off on this? I'm not super happy with the idea of splitting up the i64 operations just to attempt to pair them later in the pipeline.

I don't think we've investigated other ways to avoid the additional moves.

I'll work on a patch today to increase the allocation priority of GPRPairs (And their equivalents).

I do see that we're always going to have a problem with i64s passed in the nth argument, where n is odd. There's likely no escaping that, unfortunately.

I still owe you numbers on how bad the additional moves are in real-world code. I don't think I'll get to that this week. I don't know if you got numbers of your own on that.

https://github.com/llvm/llvm-project/pull/169529