Any and all of the above. Although the VideoCore in the Pi is particularly interesting because it's responsible for the early stages of the Pi's boot process (

Any and all of the above. Although the VideoCore in the Pi is particularly interesting because it's responsible for the early stages of the Pi's boot process (the ARM cores are actually turned off when you initially apply power). Right now, that's all a big Broadcom-proprietary binary chunk; good compilers would be the first step towards freeing that code.