A SCEV is not low-cost just because you can divide it by a power of 2. We need to also
check what we are dividing to make sure it too is not a high-code expansion. This helps
to not expand the exit value of certain loops, helping not to bloat the code.
The change in no-iv-rewrite.ll is reverting to back before rL194116, and looks a lot like
the other tests in replace-loop-exit-folds.ll.