Shorten precomputed_sine_table

[orottier]

let table: Vec<f32> = (0..TABLE_LENGTH_USIZE)
    .map(|x| ((x as f32) * 2.0 * PI * (1. / (TABLE_LENGTH_F32))).sin())
    .collect();

This computes the full sine wave from t=0 to t=2PI.
We can use the symmetries of the sine wave to store only the part of t=0 to t=PI/2 and derive the other ranges from it:
https://www.electronics-notes.com/images/waveform-sine-wave-02.png

This will reduce the general memory usage so we can utilize the caches for other things which may improve the libs performance

[b-ma]

This could also introduce some if/else branching in loops which might not be that good for perfs no?

[orottier]

Good point, so I put some effort in a branchless version for tables with a power-of-two size: https://godbolt.org/z/9Yhs6hPoh
I'm no assembly hero, but I think we can see it is branchless because there are no labels and jump instructions present.