Massive work in progress.
('LMC Simulator' executable icon by Professor Magnus Bordewich, University of Durham, overlayed on LLVM logo. Temporary, maybe.)
Little Man Computer (LMC) is an incredibly simple instruction set, used for teaching, that gives a model of a computer
in the Von Neumann Architecture. It was first introduced by Dr. Stuart Madnick of M.I.T. in 1965. This program provides
a compiler back-end to translate LLVM's IR to LMC. So, in theory, any language compilable to IR can be compiled to LMC.
This project focuses on compiling C to
LMC. Here is a list of the instructions. (Note: there
are two main conventions for instruction mnemonics I've seen. I am using the ones listed on Wikipedia.)
The purpose of this project is mainly for entertainment. It is quite ridiculous that C could compile to this simple and (functionally) useless language. Also, this would have made homework at school and my first year university project far easier.
This project includes two standalone packages: lmc which allows the construction, analysis, and optimisation of LMC
programs, and compiler which will take LLIR and compile it to (unoptimised) LMC instructions. (The lmc package can
then be used to optimise it.)
Once the project is at a suitable level of completeness I will include a CLI tool to compile and optimise code from
inputs. For now, there is a program in compiler/testing/compiler.go that gives an incredibly simple example of how
this tool may look. It does compilation and optimisation.
The compiler is really simple. I mean, extremely basic. It performs rudimentary pattern matching on IR instructions, converts them to LMC instructions, producing some of the worst LMC in existence, before optimising it.
LMC typically has a limit of 100 mailboxes, however this is not observed or worried about in this project. Mainly because I can't be bothered to include that limitation, and my excuse is I am treating it as RAM; a program does not know ahead of time how large its target device's RAM will be, so neither does this compiler.
An overview and examples of the lmc package.
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An overview and examples of the compiler package. For details of optimisation algorithms included
see lmc/optimisation/OPTIMISTAION.md
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compiler/lmc.h contains some very useful macros and builtin functions. These functions are
marked extern and when pattern matched are, essentially, drop-in replaced by some LMC instructions. There are two
types that are recommended to be used when creating a program: number_t and bool_t.
Also included in this header file is the entry point to any LMC program, void _lmc(void).
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