Langcraft

The LLVM target for Minecraft you've never wanted

Langcraft is a code generator targeting Minecraft Data Packs. It can currently run a fairly substantial set of bitcode files without issue. The project has a built-in command interpreter for debugging that supports breakpoints (ish) and inspecting register/memory values. All generated datapacks can be run in a real Minecraft Java Edition 1.16+ world in under 5 minutes.

(See also Wasmcraft2 for the spiritual successor to this project, which is faster and more reliable)

Usage

cargo run -- --arg1 --arg2 ./path/to/llvm/bitcode.bc

Valid arguments are:

• --help: Display usage and available options
• --out=path/to/dir/: Specify the directory the datapack files should be placed in (default is ./out)
• --run: Run the command interpreter on the generated code
• --trace-bbs: Insert a print command at the beginning of each LLVM basic block

To use the generated datapack in Minecraft:

1. Copy the entire output folder (./out by default) to the datapacks/ directory of a Minecraft world (using a superflat void world is recommended)
2. Run /function setup:setup. This only has to be done the first time a Langcraft datapack is used in a world.
3. Run /function rust:run
4. If the datapack is modified while the world is open, run /reload and then go back to step 3.

Rust code must be built as follows:

• Release mode
• panic=abort
• #![no_std]
• #![no_main]
• Have a main function with #[no_mangle]
• Use i686-unknown-linux

rust_interp is a Rust project already configured to generate the proper bitcode. The interpreter binary target as shown in the demo can be built with:

sh compile_rust.sh

And the file to use will be:

rust_interp/target/i686-unknown-linux-gnu/release/deps/interpreter-SOMEHEXSTRING.bc

Any other language capable of generating LLVM bitcode can be used, as long as it can be built for a bare-metal 32-bit target. For a clang example see compile_c.sh.

Note that the latest nightly versions of rustc now use LLVM 11, which Langcraft cannot parse (yet). You can set an earlier version to use for a directory with:

rustup override set nightly-2020-08-23

Demo

A video of a Langcraft-compiled interpreter can be seen here.

License

Licensed under either of

• MIT License
• Apache License, Version 2.0