Optimze break patterns

bench.rs

use criterion::{criterion_group, criterion_main, Criterion};

fn r1(len: usize) -> usize {
    let mut random = len as u32;
    let mut gen_u32 = || {
        random ^= random << 13;
        random ^= random >> 17;
        random ^= random << 5;
        random
    };
    let mut gen_usize = || {
        if usize::BITS <= 32 {
            gen_u32() as usize
        } else {
            (((gen_u32() as u64) << 32) | (gen_u32() as u64)) as usize
        }
    };
    gen_usize()
}

fn r2(len: usize) -> usize {
    let mut seed = len;
    let mut gen_usize = || {
        if usize::BITS <= 32 {
            // Pseudorandom number generator from the "Xorshift RNGs" paper by George Marsaglia.
            let mut r = seed as u32;
            r ^= r << 13;
            r ^= r >> 17;
            r ^= r << 5;
            seed = r as usize;
            seed
        } else {
            // Pseudorandom number generator from the "wyrand"(https://github.com/wangyi-fudan/wyhash) by Wang Yi.
            seed = seed.wrapping_add(0xa0761d6478bd642fu64 as usize);
            let r = (seed as u128).wrapping_mul((seed as u64 ^ 0xe7037ed1a0b428dbu64) as u128);
            ((r as u64) ^ (r >> 64) as u64) as usize
        }
    };
    gen_usize()
}

pub fn criterion_benchmark(c: &mut Criterion) {
    let mut count1 = 0usize;
    let mut count2 = 0usize;
    let mut t1 = || {
        count1 += 1;
        r1(count1)
    };
    let mut t2 = || {
        count2 += 1;
        r2(count2)
    };
    c.bench_function("old", |b| b.iter(|| t1()));
    c.bench_function("new", |b| b.iter(|| t2()));
}

criterion_group!(benches, criterion_benchmark);
criterion_main!(benches);