Hi all, I've implemented a stack based or zero operand CPU, including GCC/gdb toolchain, eCos operating system support, simulator, HDL implementation, etc.
I'm boldly assuming that a fair number of people on this list might find this a little bit fascinating. It's all open source of course: http://www.opencores.org/projects.cgi/web/zpu/overview - the ZPU has 11 instructions, the rest is implemented using microcode(yields small CPU + small code size). - the only registers are SP and PC - 16 or 32 bit datapath - GCC is very much oriented towards all sorts of register based CPU's. I settled on exposing stack slots as CPU registers + some other tricks. GCC generates very decent code(80% of codesize to ARM thumb). - Cygwin binaries + GCC source code available(of course) - ++ -- Øyvind Harboe http://www.zylin.com - eCos ARM & FPGA developer kit
