[X86] Various vXi1 insertion improvements.

Add missing patterns for inserting v1i1 into a zero vector. Use insert_subvector to zero upper bits before inserting an element into a vXi1 vector. Replace kshift based isel pattern with insert_subvector based pattern now that code that caused the pattern has been fixed to emit insert_subvector.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323173 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed