[InstCombine] add test for missing vector icmp fold

Also, add a scalar test to demonstrate one of the intermediate folds that
is necessary to accomplish the existing, multi-step test. And simplify
the vector tests to only check the final piece of that multi-step transform.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278995 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed