QBE – Compiler Back End

by smartmic • 3 months ago

97 28 3 months ago

superdisk3• 3 months ago

Cool project, and FWIW it's like one Claude prompt to add MIPS support to this. I did that and then was able to compile my little custom language to the N64.

ursuscamp• 3 months ago

Truly amazing times. Just doing things has never been easier, and it has really reinvigorated me.

vintagedave• 3 months ago

I did that

Can you contribute it? I don't see it listed as an official backend.

kouosi• 3 months ago

Can you contribute it? I don't see it listed as an official backend.

I don't think anyone wants AI generated contribution to QBE (neither do I).

superdisk3• 3 months ago

As the other commenter said, I don't think contributing it would be that useful, since QBE is a rather zen-garden project and I don't think the author would accept slop. Also he could just generate it with a prompt himself :P

It's certainly fun as a toy though!

Rochus3• 3 months ago

it's like one Claude prompt to add MIPS support to this

Can you provide the code somewhere? Is it complete? Does it really work? I have a hard time to believe that an LLM really can generate a complete and working backend for a target architecture with "one prompt". From my experience with such tools, by the end of the day it takes longer until it covers all edge cases and actually works than when writing it myself.

Tiberium2• 3 months ago

They absolutely can for simpler cases like this, especially recent GPT 5.x models are amazing at such lower-level compiler work.

superdisk3• 3 months ago

The backend is only ~1300 lines. QBE is a super simple project which is why adding a backend to it worked so well. I just pointed Claude at the existing RISC-V backend for reference and it whipped up the MIPS one. It really does work, though there might be bugs I didn't run into. I compiled an Amiga MOD player, written in my language, to the N64 and it worked fine, if that gives you an idea of how stress tested it was. IIRC it runs about 5x slower than GCC-generated code.

https://gist.github.com/SuperDisk/1aa50263a773143c82a39d4771...

graemeg• 3 months ago

Do you know if there is ongoing work to support x86_64 on Windows?

Willyboar• 2 months ago

Yes, windows support already merged to main so it will be in 1.3

lucrbvi• 3 months ago

I really like QBE but I hope they will make it a true library because I don't want to launch a subprocess to compile a program.

heavensteeth• 3 months ago

This is exactly my gripe unfortunately, it feels like needless fragility. IIRC the author has said they believe it wouldn't be too difficult to patch QBE to work as a library, but from what I've seen the code is somewhat terse and eccentric.

fuhsnn2• 3 months ago

There is a library conversion fork: https://github.com/sgraham/sqbe.

IMO when the intended usage is AOT with an external assembler, which is another subprocess, text-based IO is actually the more natural approach.

mamcx• 3 months ago

Tangentially: Is there a Rust alternative similar to this?

sparky4pro• 3 months ago

There are at least 2 Go libraries written in Go, based on QBE. One is used by this project: https://github.com/xplshn/gbc

duped• 2 months ago

Why not? Processes are cheaper than you might think. GCC invokes several as an example.

rurban• 2 months ago

Because this concept only works for offline compilers, but not for dynamic languages. It's about 100x slower.

I'm just converting the call to an external assembler in my compiler rcc to assemble the bytes directly. No need for strings and external files. The cost of the external call is outrageous.

Tiberium2• 3 months ago

Also relevant: https://git.sr.ht/~mcf/cproc is a C compiler on top of QBE

anthk2• 2 months ago

For 32 bit support there's cparser which is very close to cproc.

anthk2• 3 months ago

A, c9x among codemadness, cool people, among gopher://bitreich.org

https://codemadness.org/git/

Tons of these tools I use are from these guys (among 2f30). Small, predictable, usable, such as pointtools and catpoint. Sfeed for RSS, scc for gopher and so on, and smu for markdown from git repos > html.

sylware• 3 months ago

Combined with cproc, I get 70% of gcc -O2, for a small fraction of the code... and a plain and simple C coded compiler.

cestith• 3 months ago

Related, there’s Blaise which is a new Object Pascal that uses QBE as its backend.

https://news.ycombinator.com/item?id=48058644

There’s also cproc which has a few HN posts about it.

https://news.ycombinator.com/item?id=24076603 https://news.ycombinator.com/item?id=28242024 https://news.ycombinator.com/item?id=32466098 https://news.ycombinator.com/item?id=25273918

fweimer• 3 months ago

IR description here: https://c9x.me/git/qbe.git/tree/doc/il.txt

It looks like it doesn't have native support for identifying GC roots, so it's either conservative GC or explicit stack management. I would really like to see something that is (mostly) memory-safe and has string-as-bytes. It's a bit wild that people use Chez Scheme as a target IR for lack of better options.

stevefolta• 3 months ago

Looks like a new 1.3 release is coming very soon.

I love QBE, but it does have its limitations: - It handles the ABIs for passing and returning structures in registers, but only with superfluous copies to and from the stack. - Can't generate debug info for data. This is probably due to lack of assembler support and/or complexity in the DWARF format. - The line number debug info directives are currently undocumented and don't support inlined functions.

But it's smol, effective, and it doesn't make you deal with phi nodes!

QBE – Compiler Back End

Related Stories