A very simple brainfuck compiler for apple silicon (m1) macs, written in python. Inspired by a hilarious post I read on scalable, resilient brainfuck I decided to finally get around with playing with arm64 (AArch64) assembly on my new Apple Silicon MacBook Air 💻. I haven't touched assembly in over a decade, but this was a lot of fun! Brainfuck is a very simple language that is technically Turing complete but it's very easy to implement.
There are two steps: a compilation step and an assembly step. To compile some brainfuck
source code simply supply it as an argument to bfc.py:
$ ./bfc.py "++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++."
note the use of quotes "" to ensure the shell does not misinterpret the >< characters.
This will generate some raw arm64 assembly in a file named output.s and that's basically
the entire point of this project. Please do peruse the contents of output.s
In order to actually run this, you'll need to
assemble the instructions into a real binary using the included assemble.sh script:
$ ./assemble.sh output.s
this will generate a binary which can be executed directly:
$ ./output
Hello World!
This was mainly an exercise for myself so it's not the greatest implementation. The biggest drawback is probably that the stack sized allocated is only 16 cells, which is probably not enough for some of the bigger brainfuck programs. However, this could be easily raised in theory.
Also, I only ever tested this on my MacBook Air 2020 (M1), so your milage may vary. I
think in principle it could run under linux on a raspberry pi 3/4 with some minor tweaks
in assemble.sh (namely not linking to libSystem). It should not work on any x86 PC.
Other than that there are definitely some low hanging fruit for optimization, I'll leave that as a treat for myself. Maybe one day I'll have a full compiler/interpreter in arm64 assembly!
Most of my understanding was gleaned by compiling small trivial C programs with clang and reading the disassembled binary. However, there were a number of references I relied on that I'd like to list out below:
- https://modexp.wordpress.com/2018/10/30/arm64-assembly/
- https://en.wikipedia.org/wiki/Brainfuck (duh)
- https://github.com/below/HelloSilicon
- https://chromium.googlesource.com/chromiumos/docs/+/master/constants/syscalls.md#arm-32_bit_EABI
Creative Commons Zero, which is as close to public domain as we can get.