Sat Jul 3 12:55:55 CEST 2010

Simple IIR compilation: slow + fast state memory

The no-brain solution is:

- Load state slow -> fast
- Iterate over input & output, updating fast state
- Store state fast -> slow

This is just a "subsampling" conversion of an IIR filter from sample
to block based ops.

If I recall, this is mostly there: query the SSA form for "Z"