Improve test robustness

Improve test robustness in preparation of coming commits:
- Avoid undefs which may get propagated too much.
- Remove several pointless add 0, instructions

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231307 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed