value is zero.
This allows optmizations to kick in more easily.
Fix some test cases so that they remain meaningful (i.e., not completely dead
coded) when optimizations apply.
<rdar://problem/14096009> superfluous multiply by high part of zero-extended
value.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184222 91177308-0d34-0410-b5e6-96231b3b80d8