inkwell

Inkwell(s)

It’s a New Kind of Wrapper for Exposing LLVM (Safely)

Inkwell aims to help you pen your own programming languages by safely wrapping llvm-sys. It provides a more strongly typed interface than the underlying LLVM C API so that certain types of errors can be caught at compile time instead of at LLVM’s runtime. This means we are trying to replicate LLVM IR’s strong typing as closely as possible. The ultimate goal is to make LLVM safer from the rust end and a bit easier to learn (via documentation) and use.

Requirements

• Rust 1.85+
• One of LLVM 12-23

Usage

You’ll need to point your Cargo.toml to use a single LLVM version feature flag corresponding to your LLVM version as such:

[dependencies]
inkwell = { version = "0.10.0", features = ["llvm23-1"] }

Supported versions: LLVM 12-23 mapping to a cargo feature flag llvmM-N where M and N correspond to the LLVM major and minor version, e.g. llvm18-1 for LLVM 18.1.x.

Please be aware that we may make breaking changes on master from time to time since we are pre-v1.0.0, in compliance with semver. Please prefer a crates.io release whenever possible!

Documentation

Documentation is automatically deployed here based on master. These docs are not yet 100% complete and only show the latest supported LLVM version due to a rustdoc issue. See #2 for more info.

Examples

Tari’s llvm-sys example written in safe code¹ with Inkwell:

use inkwell::builder::Builder;
use inkwell::context::Context;
use inkwell::execution_engine::{ExecutionEngine, JitFunction};
use inkwell::module::Module;
use inkwell::support::LLVMString;
use inkwell::OptimizationLevel;

use std::error::Error;

/// Convenience type alias for the `sum` function.
///
/// Calling this is innately `unsafe` because there's no guarantee it doesn't
/// do `unsafe` operations internally.
type SumFunc = unsafe extern "C" fn(u64, u64, u64) -> u64;

struct CodeGen<'ctx> {
    context: &'ctx Context,
    module: Module<'ctx>,
    builder: Builder<'ctx>,
}

impl<'ctx> CodeGen<'ctx> {
    fn compile_sum(&self) -> Option<()> {
        let i64_type = self.context.i64_type();
        let fn_type = i64_type.fn_type(&[i64_type.into(), i64_type.into(), i64_type.into()], false);
        let function = self.module.add_function("sum", fn_type, None);
        let basic_block = self.context.append_basic_block(function, "entry");

        self.builder.position_at_end(basic_block);

        let x = function.get_nth_param(0)?.into_int_value();
        let y = function.get_nth_param(1)?.into_int_value();
        let z = function.get_nth_param(2)?.into_int_value();

        let sum = self.builder.build_int_add(x, y, "sum").unwrap();
        let sum = self.builder.build_int_add(sum, z, "sum").unwrap();

        self.builder.build_return(Some(&sum)).unwrap();

        Some(())
    }

    /// Hands the finished module to a JIT engine, which owns it from now on.
    fn into_execution_engine(self) -> Result<ExecutionEngine<'ctx>, LLVMString> {
        self.module.create_jit_execution_engine(OptimizationLevel::None)
    }
}

fn main() -> Result<(), Box<dyn Error>> {
    let context = Context::create();
    let codegen = CodeGen {
        context: &context,
        module: context.create_module("sum"),
        builder: context.create_builder(),
    };

    codegen.compile_sum().ok_or("Unable to build `sum`")?;

    let execution_engine = codegen.into_execution_engine()?;
    let sum: JitFunction<SumFunc> = unsafe { execution_engine.get_function("sum")? };

    let x = 1u64;
    let y = 2u64;
    let z = 3u64;

    unsafe {
        println!("{} + {} + {} = {}", x, y, z, sum.call(x, y, z));
        assert_eq!(sum.call(x, y, z), x + y + z);
    }

    Ok(())
}

¹ There are two uses of unsafe in this example because the actual act of compiling and executing code on the fly is innately unsafe. For one, there is no way of verifying we are calling get_function() with the right function signature. It is also unsafe to call the function we get because there’s no guarantee the code itself doesn’t do unsafe things internally (the same reason you need unsafe when calling into C).

LLVM’s Kaleidoscope Tutorial

Can be found in the examples directory.

Alternative Crate(s)

• llvm-ir

Contributing

Check out our Contributing Guide