rust/compiler/rustc_codegen_cranelift/docs/usage.md

Usage

rustc_codegen_cranelift can be used as a near-drop-in replacement for cargo build or cargo run for existing projects.

Assuming $cg_clif_dir is the directory you cloned this repo into and you followed the instructions (prepare.sh and build.sh or test.sh).

Cargo

In the directory with your project (where you can do the usual cargo build), run:

$ $cg_clif_dir/build/cargo.sh build

This will build your project with rustc_codegen_cranelift instead of the usual LLVM backend.

Rustc

You should prefer using the Cargo method.

$ $cg_clif_dir/build/bin/cg_clif my_crate.rs

Jit mode

In jit mode cg_clif will immediately execute your code without creating an executable file.

This requires all dependencies to be available as dynamic library. The jit mode will probably need cargo integration to make this possible.

$ $cg_clif_dir/build/cargo.sh jit

or

$ $cg_clif_dir/build/bin/cg_clif -Cllvm-args=mode=jit -Cprefer-dynamic my_crate.rs

There is also an experimental lazy jit mode. In this mode functions are only compiled once they are first called. It currently does not work with multi-threaded programs. When a not yet compiled function is called from another thread than the main thread, you will get an ICE.

$ $cg_clif_dir/build/cargo.sh lazy-jit

Shell

These are a few functions that allow you to easily run rust code from the shell using cg_clif as jit.

function jit_naked() {
    echo "$@" | $cg_clif_dir/build/bin/cg_clif - -Cllvm-args=mode=jit -Cprefer-dynamic
}

function jit() {
    jit_naked "fn main() { $@ }"
}

function jit_calc() {
    jit 'println!("0x{:x}", ' $@ ');';
}