[clang] [CIR] Implement cir.cmp3way Operation (PR #186294)

[Yeongu Choe via cfe-commits]

YeonguChoe wrote:

@erichkeane

Oh no.. I spent several days on it. I updated codes and I think it will work. In that PR, it seems like there is additional attribute other than `strong` and `partial` specified in the documentation.

If that PR is going to be merged soon and mine is going to be discarded,
Can you please assign me task to work on? It is the second time overlapping on task.

Any task from medium to hard difficulty would be rewarding to me.

https://github.com/llvm/llvm-project/pull/186294