[llvm] [GISel][AArch64][AMDGPU][RISCV] Canonicalize (sub X, C) -> (add X, -C) (PR #114309)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> I've reverted the patch in [cff2199](https://github.com/llvm/llvm-project/commit/cff2199e0f0e54177997ecf9571ba874231cefe4). Can you let me know if your CI recovers.
> 

I wouldn't consider this to be a reason to revert. Just fix the fallbacks separately 


https://github.com/llvm/llvm-project/pull/114309