[llvm] [RISCV] Add register allocation hints for lui/auipc+addi fusion. (PR #123860)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

Have you tried https://github.com/llvm/llvm-project/pull/77461 yet? I don't mean my solution is better, but it seems to save the logic to decide whether the pair can be fused. I can rework it if you like.

https://github.com/llvm/llvm-project/pull/123860