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Life & fun · November 5, 2025

Cj–tiny no-deps JIT in C for x86-64 and ARM64

Hey y’all! About 7 years ago, I had this idea to write a JIT with an autogenerated backend for x86 based on the ISA specs. I sketched something out and then just kinda let it sit. I picked it up again a few weeks ago and made a complete-ish backend for both x86 and ARM64. It has no dependencies, the backends are completely autogenerated (by horrible, horrible JS scripts), and I built a small abstraciton layer for things like functions prologues etc. It’s super duper early and will probably break on your machine, but it’s good enough to compile some cool examples (look at the examples…

Cj–tiny no-deps JIT in C for x86-64 and ARM64 launched on November 5, 2025 with 21 votes, #602 of 9,795 launches that month and more than 90% of that year's launches.

Visit github.com ↗Alternativestop 6% of November 2025

In plain words

Cj is a lightweight JIT compiler written in C that generates machine code for x86-64 and ARM64 processors. It features autogenerated backends derived directly from ISA specifications and includes no external dependencies. Designed for developers experimenting with compilation techniques, the project is in early stages but includes functional examples such as a minimal language implementation. The backends are produced through automated JavaScript scripts, with an abstraction layer handling function prologues and similar low-level details.

written from the facts on this page · September 2026

From the sources

a simple x86/arm jit framework for c. Contribute to hellerve-pl-experiments/cj development by creating an account on GitHub.

is a small JIT framework written in C, with x86 and arm64 backends. the backends are autogenerated (check out codegen ). x86 uses asmdb as a data source, arm64 uses a handgenerated file from mra_tools . register definitions are hand-crafted. the rest is handwritten and basically trivial in the grand scheme of jit compilation. examples, tests, and codegen docs contain some llm-generation, so peruse at your own peril. because i wanted to understand the isa for both processor architectures and it seemed like a fun project. # dev build make dev # "prod" build make all # install (don't) make install basic usage #include "ctx.h" #include "op.h" int main ( void ) { // Create JIT context cj_ctx *…from github.com

In the maker’s words, at launch

Hey y’all! About 7 years ago, I had this idea to write a JIT with an autogenerated backend for x86 based on the ISA specs. I sketched something out and then just kinda let it sit. I picked it up again a few weeks ago and made a complete-ish backend for both x86 and ARM64. It has no dependencies, the backends are…

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