by xoring the high-bit. This fails if the source operand is a vector because we need to negate
each of the elements in the vector.
Fix rdar://12281066 PR13813.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163802 91177308-0d34-0410-b5e6-96231b3b80d8