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

[Erich Keane via cfe-commits]

erichkeane 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.

I don't really know the progress on that one/likelihood of it being merged, but it is ahead of this one.  I'm sorry this ended up poorly/you keep getting stuck on this sorta thing.  @andykaylor should be able to help you out with a task, but he's on vacation today/monday.

In the meantime, there are a handful of `builtins` that need to be done.  They are perhaps a 'medium' difficulty at best, but hopefully will still be rewarding/hold you over (and get a win!).

`__builtin_fpclassify`
`__builtin_signbit`
`__builtin_flt_rounds`
`__builtin_set_flt_rounds`
`_setjmp`

IIRC, I looked at all of these and they are not implemented in the incubator, so they'll need some architecting/work to figure out how we should lower these.

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