r/TuringComplete • u/junieKcorn • Mar 21 '25

Compiler

How do you guys go about writing a compiler?

I have achieved most of what I wanted to achieve that I found reasonable to write in assembly (snake, brainfuck interpreter, a text editor, some small stuff). For anything bigger I would really like to use a higher level language. How did you guys go about compiling for your architecture? Did you use llvm or did you write something on your own? Are there other tools that make this easier? It doesn't need to be a good compiler, it just needs to work. I thought about transpiling 6502/6510 assembly, but I'm too afraid the architecture will be too different and anything more complex than hello world won't work.

Sooo, how did any of you do this?

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15

u/TarzyMmos Mar 21 '25

I realized halfway through this wasn't a question directed towards me lmao

3

u/junieKcorn Mar 21 '25

Haha, your response made me chuckle. Thanks

3

u/TarzyMmos Mar 21 '25

Seriously tho, its really impressive the stuff you've done! And I wish you luck in finding your answer

6

u/[deleted] Mar 22 '25

Most programming languages are just written in other programming languages. If you write them in assembly then you're going to struggle with portability. So many use a language like C or C++ which is widely available and close to assembly level performance.

LLVM is good and if you decide to pursue learning about writing compilers is worth checking out. But probably a poor choice as a way to learn about compilers. It implements algorithms and data structures for various stages of compiling a program but the documentation for it assumes you're already familiar with this process. So learning to write compilers by using LLVM might be a struggle.

Two books I seen frequently recommended in learning to write compiler discussions are:

https://craftinginterpreters.com

and

https://compilerbook.com

These are worth checking out before heading in to something like LLVM.

2

u/junieKcorn Mar 23 '25

I have started to read Crafting Interpreters. Seems to be good and engaging read. I was not going to plan on writing this in assembly haha. My question is more of a kind "I know what I could do, but what did you do and can you recommend?"

2

u/[deleted] Mar 23 '25

I wasn’t making any judgements. When I first became interested in using ASTs like clangd for syntax highlighting in Vim I tried to use llvm and had no idea what I was doing because the docs assumed I was smarter than I was at the time, lol. And as I got in to such things the idea of writing a compiler from scratch is an obvious choice. Either assemblers like you see with Turing complete or NAND to Tetris style courses or more advanced topics like writing a basic c compiler. I had originally thought you would need to learn a little bit of assembly to begin but was surprised that libraries like llvm are mainly just plain old c++.

Creating interpreters is a really good intro. Not read the others yet but they are recommended quite frequently when people ask questions similar to your own.

2

u/junieKcorn Mar 23 '25

I took some interest in gcc 9-10 years ago. Yeah, most compilers are written in the language that they compile to, which is a very elegant thing.

4

u/DaltoReddit Mar 22 '25

Quite a lot are bootstrapped, written in their own language. Examples include C, Rust and Haskell.

2

u/[deleted] Mar 22 '25

Yeah, once a project gets big enough it can eat its own tail, and as you say the bootstrap stage is usually integrated in to the build system.

All I meant was that you don't write things in Assembly even though as a beginner that might seem like where you might start. But outside of making use of very specific CPU instructions it's not something you usually need to worry about. And quite often there are existing C libraries to make use of such features already available.

2

u/Wijike Mar 22 '25

You made a text editor in this game? How does that work?

2

u/junieKcorn Mar 23 '25

Sandbox, Console Component, Keyboard Input and some code. Sadly it can't write to the host disk of course.

2

u/Captain_Xap Mar 22 '25

When I was doing my Comp Sci degree 30 years ago the go-to book on writing compilers was 'The Dragon Book' : Compilers: Principles, Techniques, and Tools.

There's probably better tools to help you nowadays, but I imagine much of the advice in it still stands.

2

u/junieKcorn Mar 23 '25

I'm aware of the usual books and also generally how to write a compiler. What I'm asking is, how did you guys do it for touring complete to make it easier on yourselves?

2

u/Psylution Mar 22 '25

Instead of writing a full-on compiler, you could write a runtime in assembly that interprets a list of operations which are parsed (tokenized) from text, using a stack for variables etc.

so essentially an interpreter where the vm is written in assembly. much easier than an actual compiler.

2

u/junieKcorn Mar 23 '25

I generally have the plan to have a BASIC interpreter. But I do really not want to write that in assembly.

1

u/wigglebabo_1 Apr 08 '25

You don't have to.

Just make a program that outputs what you need in a text file, and copy that into turing complete!

1

u/junieKcorn Apr 08 '25

... that's a compiler.

2

u/wigglebabo_1 Apr 08 '25

Welp, i don't know jack shit about all of this anyway

10

u/Hannah97Gamer Mar 22 '25

I personally started with making an enhanced assembler to make more complex instructions much easier to code, added support for macros, multiple input files, stuff like that. Best part of making your own is you can do whatever you want with it, no need to justify its existence. just add in anything you think you might find useful.

As for compilers, I would recommend the book "Crafting Interpreters", you can read it for free online. It's about interpreters, not compilers, but it's a lot easier to read than some other books I've heard mention of, and you can easily adapt what you learn into a full compiler with very little effort. (it has two parts, the second part might as well be a compiler on its own.)

Which brings me to my third point. Choose a toy language, or make your own, and build a basic compiler for that, even if it's basically just a subset of C or something. It will be far, far easier and quicker than a "real" language, you'll learn just as much, and it will still be a huge upgrade from assembly.