[InstCombine] Remove canonicalization for (X & C1) | C2 --> (X | C2) & (C1|C2) when...

[InstCombine] Remove canonicalization for (X & C1) | C2 --> (X | C2) & (C1|C2) when C1 & C2 have common bits.

It turns out that SimplifyDemandedInstructionBits will get called earlier and remove bits from C1 first. Effectively doing (X & (C1&C2)) | C2. So by the time it got to this check there could be no common bits.

I think the DAGCombiner has the same check but its check can be executed because it handles demanded bits later. I'll look at it next.

llvm-svn: 299384