https://github.com/rust-lang/rust/pull/37573

bench_copy_from_slice.rs

#![feature(test)]

extern crate test;

macro_rules! unroll_10 {
    { $x: block } => {
        $x $x $x $x $x $x $x $x $x $x
    }
}

#[inline(always)]
fn do_bench_u8(b: &mut test::Bencher, from: usize, to: usize) {
    let src = [2u8, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53,
      59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103];
    b.iter(|| {
        for _ in 0..10 {
            let mut dst = [0_u8; 27];
            let mut i = 0;
            unroll_10! {{
                let f = test::black_box(from);
                let t = test::black_box(to);
                (&mut dst[f+i..t+i]).copy_from_slice(&src[f+i..t+i]);
                i = i + 1;
            }};
            test::black_box(dst);
        }
    });
}

#[inline(always)]
fn do_bench_u32(b: &mut test::Bencher, from: usize, to: usize) {
    let src = [2u32, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53,
      59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103];
    b.iter(|| {
        for _ in 0..10 {
            let mut dst = [0_u32; 27];
            let mut i = 0;
            unroll_10! {{
                let f = test::black_box(from);
                let t = test::black_box(to);
                (&mut dst[f+i..t+i]).copy_from_slice(&src[f+i..t+i]);
                i = i + 1;
            }};
            test::black_box(dst);
        }
    });
}

#[bench]
fn bench_copy_u8_slice_01_x100(b: &mut test::Bencher) {
    do_bench_u8(b, 1, 2);
}

#[bench]
fn bench_copy_u8_slice_02_x100(b: &mut test::Bencher) {
    do_bench_u8(b, 1, 3);
}

#[bench]
fn bench_copy_u8_slice_03_x100(b: &mut test::Bencher) {
    do_bench_u8(b, 1, 4);
}

#[bench]
fn bench_copy_u8_slice_04_x100(b: &mut test::Bencher) {
    do_bench_u8(b, 1, 5);
}

#[bench]
fn bench_copy_u8_slice_06_x100(b: &mut test::Bencher) {
    do_bench_u8(b, 1, 7);
}

#[bench]
fn bench_copy_u8_slice_08_x100(b: &mut test::Bencher) {
    do_bench_u8(b, 1, 9);
}

#[bench]
fn bench_copy_u8_slice_16_x100(b: &mut test::Bencher) {
    do_bench_u8(b, 1, 17);
}

#[bench]
fn bench_copy_u32_slice_01_x100(b: &mut test::Bencher) {
    do_bench_u32(b, 1, 2);
}

#[bench]
fn bench_copy_u32_slice_02_x100(b: &mut test::Bencher) {
    do_bench_u32(b, 1, 3);
}

#[bench]
fn bench_copy_u32_slice_03_x100(b: &mut test::Bencher) {
    do_bench_u32(b, 1, 4);
}

#[bench]
fn bench_copy_u32_slice_04_x100(b: &mut test::Bencher) {
    do_bench_u32(b, 1, 5);
}

#[bench]
fn bench_copy_u32_slice_06_x100(b: &mut test::Bencher) {
    do_bench_u32(b, 1, 7);
}

#[bench]
fn bench_copy_u32_slice_08_x100(b: &mut test::Bencher) {
    do_bench_u32(b, 1, 9);
}

#[bench]
fn bench_copy_u32_slice_16_x100(b: &mut test::Bencher) {
    do_bench_u32(b, 1, 17);
}