[InstCombine] Y - ~X --> X + Y + 1 fold (PR42457)

Summary:
I *think* we'd want this new variant, because we obviously
have better handling for `add` as compared to `sub`/`not`.

https://rise4fun.com/Alive/WMn

Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=42457 | PR42457 ]]

Reviewers: spatel, nikic, huihuiz, efriedma

Reviewed By: spatel

Subscribers: RKSimon, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63992

llvm-svn: 365011