[llvm] [SelectOpt] Add handling for not conditions. (PR #92517)

[David Green via llvm-commits]

davemgreen wrote:

Thanks

> Just wanted to quickly check the reason instcombine isn't doing canonicalisations for these cases. I guess it's because the limited scope that instcombine has, so it won't trigger, is that right?

It will be because `select x, true, y` is treated as `or x, y` (but poison blocking), and it does not want to break that canonical form.

https://github.com/llvm/llvm-project/pull/92517