| # Crunchy |
| |
| The crunchy unroller - deterministically unroll constant loops. For number |
| "crunching". |
| |
| The Rust optimizer will unroll constant loops that don't use the loop variable, |
| like this: |
| |
| ```rust |
| for _ in 0..100 { |
| println!("Hello!"); |
| } |
| ``` |
| |
| However, using the loop variable will cause it to never unroll the loop. This is |
| unfortunate because it means that you can't constant-fold the loop variable, and |
| if you end up stomping on the registers it will have to do a load for each |
| iteration. This crate ensures that your code is unrolled and const-folded. It |
| only works on literals, unfortunately, but there's a work-around: |
| |
| ```rust |
| debug_assert_eq!(MY_CONSTANT, 100); |
| unroll! { |
| for i in 0..100 { |
| println!("Iteration {}", i); |
| } |
| } |
| ``` |
| |
| This means that your tests will catch if you redefine the constant. |
| |
| To default maximum number of loops to unroll is `64`, but that can be easily increased using the cargo features: |
| |
| * `limit_128` |
| * `limit_256` |
| * `limit_512` |
| * `limit_1024` |
| * `limit_2048` |
