Back when I was hacking on the iPod Linux project (alternative OS for classic iPods) there was a guy (normalperson) working on optimising the FLAC decoder to ru

Back when I was hacking on the iPod Linux project (alternative OS for classic iPods) there was a guy (normalperson) working on optimising the FLAC decoder to run as efficiently as possible on the SoC's ARM7TDMI. IIRC he used Duff's device to squeeze a small amount of juice out of various tight loops. Then again, we were using an ancient version of GCC which didn't have great optimisation for ARM. Sorry, I've just realised this doesn't really answer your question.