[llvm] [RISCV] Generate MIPS load/store pair instructions (PR #124717)

[Craig Topper via llvm-commits]

topperc wrote:

> A thought: The lowering path can be:
> 
> 1. Merge two consecutive load/stores into **pseudo** load/store pair instructions no matter what the offsets are.
> 2. Expand these pseudos in `RISCVExpandPseudo` by checking if their offsets are valid.
> 
> In this way, other vendor pair extensions like THead's can also benefit from this pass.

Why couldn't we check the offsets in this pass?

https://github.com/llvm/llvm-project/pull/124717