Melior

Melior is the MLIR bindings for Rust. It aims to provide a simple, safe, and complete API for MLIR with a reasonably sane ownership model represented by the type system in Rust.

This crate is a wrapper of the MLIR C API.

Examples

Building a function to add integers

use melior::{
    Context,
    dialect::{arith, DialectRegistry, func},
    ir::{*, attribute::{StringAttribute, TypeAttribute}, r#type::FunctionType},
    utility::register_all_dialects,
};

let registry = DialectRegistry::new();
register_all_dialects(&registry);

let context = Context::new();
context.append_dialect_registry(&registry);
context.load_all_available_dialects();

let location = Location::unknown(&context);
let module = Module::new(location);

let index_type = Type::index(&context);

module.body().append_operation(func::func(
    &context,
    StringAttribute::new(&context, "add"),
    TypeAttribute::new(FunctionType::new(&context, &[index_type, index_type], &[index_type]).into()),
    {
        let block = Block::new(&[(index_type, location), (index_type, location)]);

        let sum = block.append_operation(arith::addi(
            block.argument(0).unwrap().into(),
            block.argument(1).unwrap().into(),
            location
        ));

        block.append_operation(func::r#return(&[sum.result(0).unwrap().into()], location));

        let region = Region::new();
        region.append_block(block);
        region
    },
    &[],
    location,
));

assert!(module.as_operation().verify());

Install

cargo add melior

Dependencies

LLVM/MLIR 16 needs to be installed on your system. On Linux and macOS, you can install it via Homebrew.

brew install llvm@16

Documentation

On GitHub Pages.

Contribution

Contribution is welcome! But, Melior is still in the alpha stage as well as the MLIR C API. Note that the API is unstable and can have breaking changes in the future.

Technical notes

• We always use &T for MLIR objects instead of &mut T to mitigate the intricacy of representing a loose ownership model of the MLIR C API in Rust.
• Only UTF-8 is supported as string encoding.
  • Most string conversion between Rust and C is cached internally.

Naming conventions

• Mlir<X> objects are named <X> if they have no destructor. Otherwise, they are named <X> for owned objects and <X>Ref for borrowed references.
• mlir<X>Create functions are renamed as <X>::new.
• mlir<X>Get<Y> functions are renamed as follows:
  • If the resulting objects refer to &self, they are named <X>::as_<Y>.
  • Otherwise, they are named just <X>::<Y> and may have arguments, such as position indices.

Safety

Although Melior aims to be completely type safe, some part of the current API is not.

• Access to operations, types, or attributes that belong to dialects not loaded in contexts can lead to runtime errors or segmentation faults in the worst case.
  • Fix plan: Load all dialects by default on creation of contexts, and provide unsafe constructors of contexts for advanced users.
• IR object references returned from functions that move ownership of arguments might get invalidated later.
  • This is because we need to borrow &self rather than &mut self to return such references.
  • e.g. Region::append_block()
  • Fix plan: Use dynamic check, such as RefCell, for the objects.

References

• The raw C binding generation depends on femtomc/mlir-sys.
• The overall design is inspired by TheDan64/inkwell.

License

Apache 2.0