Crate unroll

An attribute-like procedural macro for unrolling for loops with integer literal bounds.

This crate provides the [unroll_for_loops] attribute-like macro that can be applied to functions containing for-loops with integer bounds. This macro looks for loops to unroll and unrolls them at compile time.

Usage

Just add #[unroll_for_loops] above the function whose for loops you would like to unroll. Currently all for loops with integer literal bounds will be unrolled, although this macro currently can’t see inside complex code (e.g. for loops within closures).

Example

The following function computes a matrix-vector product and returns the result as an array. Both of the inner for-loops are unrolled when #[unroll_for_loops] is applied.

use unroll::unroll_for_loops;

#[unroll_for_loops]
fn mtx_vec_mul(mtx: &[[f64; 5]; 5], vec: &[f64; 5]) -> [f64; 5] {
    let mut out = [0.0; 5];
    for col in 0..5 {
        for row in 0..5 {
            out[row] += mtx[col][row] * vec[col];
        }
    }
    out
}

Attribute Macros

• unroll_for_loops
  Attribute used to unroll for loops found inside a function block.