atementblock cuts. However, this (1) cuts not only after but before-and-after
 (which prevents certain rewrites because the input operators are unknown),
 and (2) is statement-centric which potentially prevents the cut right after 
 the problematic operation.
 
 TODO: Cleanup runtime to never access individual statements of potentially
 split statements blocks again (for consistency). However, currently it is
 only used in places (e.g., parfor optimizer) that are not directly affected.</div>
</li>
</ul>
</d