1# Usage
2
3rustc_codegen_cranelift can be used as a near-drop-in replacement for `cargo build` or `cargo run` for existing projects.
4
5Assuming `$cg_clif_dir` is the directory you cloned this repo into and you followed the instructions (`y.rs prepare` and `y.rs build` or `test.sh`).
6
7## Cargo
8
9In the directory with your project (where you can do the usual `cargo build`), run:
10
11```bash
12$ $cg_clif_dir/build/cargo build
13```
14
15This will build your project with rustc_codegen_cranelift instead of the usual LLVM backend.
16
17## Rustc
18
19> You should prefer using the Cargo method.
20
21```bash
22$ $cg_clif_dir/build/bin/cg_clif my_crate.rs
23```
24
25## Jit mode
26
27> ⚠⚠⚠ The JIT mode is highly experimental. It may be slower than AOT compilation due to lack of incremental compilation. It may also be hard to setup if you have cargo dependencies. ⚠⚠⚠
28
29In jit mode cg_clif will immediately execute your code without creating an executable file.
30
31> This requires all dependencies to be available as dynamic library.
32> The jit mode will probably need cargo integration to make this possible.
33
34```bash
35$ $cg_clif_dir/build/cargo jit
36```
37
38or
39
40```bash
41$ $cg_clif_dir/build/bin/cg_clif -Zunstable-features -Cllvm-args=mode=jit -Cprefer-dynamic my_crate.rs
42```
43
44There is also an experimental lazy jit mode. In this mode functions are only compiled once they are
45first called.
46
47```bash
48$ $cg_clif_dir/build/cargo lazy-jit
49```
50
51## Shell
52
53These are a few functions that allow you to easily run rust code from the shell using cg_clif as jit.
54
55```bash
56function jit_naked() {
57    echo "$@" | $cg_clif_dir/build/bin/cg_clif - -Zunstable-features -Cllvm-args=mode=jit -Cprefer-dynamic
58}
59
60function jit() {
61    jit_naked "fn main() { $@ }"
62}
63
64function jit_calc() {
65    jit 'println!("0x{:x}", ' $@ ');';
66}
67```
68