Type MVT::i1 became legal in KNL, but store operation can't be narrowed to this type,
since the size of VT (1 bit) is not equal to its actual store size(8 bits).
Added a test provided by David (dag@cray.com)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226805 91177308-0d34-0410-b5e6-96231b3b80d8
