[X86] Add a few new test cases for shrunkblend combine

One of them shows a missed opportunity to use SimplifyDemandedBits on the condition when its used by multiple vselects.

The other is a case we shouldn't optimize because the condition has a non-vselect use.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@324630 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed