crunchy 0.1.0

Crunchy unroller: deterministically unroll constant loops

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:

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:

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.