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

Question

In terms of instruction set and simplicity of emulation. I would like to implement a virtual CPU and figured why not emulate an existing one, so to be able to compile C code to it.

Another route is to search for backends to single instruction set architectures: https://stackoverflow.com/questions/3711443/minimal-instruction-set-to-solve-any-problem-with-a-computer-program People seem to have done a clang backend for subleq: https://stackoverflow.com/questions/3711443/minimal-instruction-set-to-solve-any-problem-with-a-computer-program/38523869#38523869 — Ciro Santilli Путлер Капут 六四事, Sep 08 '17 at 07:08

score 23 · Accepted Answer · answered Feb 01 '11 at 21:14

23

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

answered Feb 01 '11 at 21:14

Anthony Green

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Is there reference documentation about the architecture and instructions set? – Tamás Szelei Feb 02 '11 at 14:48
What there is exists at http://moxielogic.org/wiki ... although it will take me a bit to undo damage from the wiki vandals. Check back soon. – Anthony Green Feb 02 '11 at 17:11
Can Moxie architecture be used in a closed source commercial project (think inclusion of it's emulator in a video game)? On your site I didn't find a license that clearly specifies that. – ezolotko Jan 04 '16 at 22:31
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Hi @ezolotko. Thanks for asking. The answer is, in general, yes. I'll try to update the docs/website soon, but please contact me directly at green AT moxielogic.com. Thanks again. – Anthony Green Jan 06 '16 at 03:10

score 6 · Answer 2 · answered Jan 27 '11 at 21:49

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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.

answered Jan 27 '11 at 21:49

ephemient

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score 5 · Answer 3 · answered Jan 27 '11 at 21:41

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ZPU (an FPGA targeted 32bit processor) is very small.

answered Jan 27 '11 at 21:41

Yann Ramin

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score 2 · Answer 4 · answered Apr 13 '13 at 16:56

This probably isn't an uncommon question; I'd hope that most CPU/machine simulation toolkits would include a simple example implementation, but some don't.

I haven't worked with it, but Knuth's MMIX architecture (wikipedia) looks interesting. Like Moxie, it was created to "illustrate machine-level aspects of programming" and is simpler than real machines. It's supported by GCC and there appear to be multiple existing simulators that could be used as a reference in your efforts.

score 2 · Answer 5 · answered Jan 27 '11 at 15:16

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Possibly the AVR ATTiny45 or similar AVR chip.

answered Jan 27 '11 at 15:16

Cory

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score 1 · Answer 6 · answered Jan 27 '11 at 18:50

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Maybe something from the Ti MSP430 series.

answered Jan 27 '11 at 18:50

Aaron Altman

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score 1 · Answer 7 · answered Jan 23 '19 at 17:19

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MIPS I (one of the targets of GCC) is a surprisingly easy-to-emulate 32-bit platform. Here is an short and simple emulator which can load and run a statically linked Linux MIPS I executable: https://github.com/pts/pts-mips-emulator

answered Jan 23 '19 at 17:19

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

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