[llvm] [DAGCombiner] Set shift flags during visit. (PR #91239)

[Craig Topper via llvm-commits]

topperc wrote:

I'm a bit surprised this code works. Shouldn't the new node have tried to CSE with the original node? I thought that would intersect the flags causing the new flags to be dropped.

https://github.com/llvm/llvm-project/pull/91239