[llvm] [InstCombine] Factorise add/sub and max/min using distributivity (PR #101507)

[Jorge Botto via llvm-commits]

jf-botto wrote:

> > > The alive proof sometimes times out. I have to add `noundef` to certain variables to make it not time out more consistently. Given how min/max/add preserve undef, I believe these optimisations to be correct when undef values are passed through.
> > 
> > 
> > Try replacing all the i32s with i8. That usually helps with timeouts.
> 
> In this case even `i4` times out: https://alive2.llvm.org/ce/z/UPjvkJ

It works for individual tests.

> Two of the proofs are buggy: https://alive2.llvm.org/ce/z/Xz2-Vq (`src5` -> `tgt5` and `src6` -> `tgt6`).

Thank you. Just noticed that. Will fix it.

https://github.com/llvm/llvm-project/pull/101507