What is the smallest, simplest CPU that GCC can compile for?

GCC supports Moxie (originally ggx), a little architecture invented by Anthony Green for experimentation.

You, too, can follow the steps he took to invent your own small simple CPU and port GCC to it.

Moxie is a great target because it was designed specifically to be an ideal target for GCC. I am the author and would be happy to answer any questions. green at moxielogic dot com