[NFC][InstCombine] Tests for x s> x & (-1 >> y) to x s> (-1 >> y) fold.

https://bugs.llvm.org/show_bug.cgi?id=38123
https://rise4fun.com/Alive/I3O

This pattern is not commutative!
We must make sure not to fold the commuted version!

llvm-svn: 337104