[InstCombine] (Y + ~X) + 1 --> Y - X fold (PR42459)

Summary:
To be noted, this pattern is not unhandled by instcombine per-se,
it is somehow does end up being folded when one runs opt -O3,
but not if it's just -instcombine. Regardless, that fold is
indirect, depends on some other folds, and is thus blind
when there are extra uses.

This does address the regression being exposed in D63992.

https://godbolt.org/z/7DGltU
https://rise4fun.com/Alive/EPO0

Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=42459 | PR42459 ]]

Reviewers: spatel, nikic, huihuiz

Reviewed By: spatel

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63993

llvm-svn: 364792