> useless basic blocks that haven't been optimized away. Is this to be
> expected?

I believe this should not happen but it's hard to say without looking at a complete dump. Could
you post full Cmm dump + a minimial working example that generates that?

> On a related note, doesn't Cmm support fall-through branches?

Cmm program is represented as a graph with each node (a block of code) having explicit list of
successors. Having fall-throughs in Cmm would require storing blocks linearily with a guarantee
that their order will not change. Note that fall-throughs are present in the generated assembly.