the LowerPartSet(). It didn't handle the situation correctly when
the low, high argument values are in reverse order (low > high)
with 'Val' type is i32 (a corner case).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63386 91177308-0d34-0410-b5e6-96231b3b80d8