mozilla/rust — pull request #8121 by thestinger (2013-07-30 05:56:47+00:00)
Title: implement pointer arithmetic with GEP

Closes #8118, #7136

~~~rust
extern mod extra;

use std::vec;
use std::ptr;

fn bench_from_elem(b: &mut extra::test::BenchHarness) {
do b.iter {
let v: ~[u8] = vec::from_elem(1024, 0u8);
}
}

fn bench_set_memory(b: &mut extra::test::BenchHarness) {
do b.iter {
let mut v: ~[u8] = vec::with_capacity(1024);
unsafe {
let vp = vec::raw::to_mut_ptr(v);
ptr::set_memory(vp, 0, 1024);
vec::raw::set_len(&mut v, 1024);
}
}
}

fn bench_vec_repeat(b: &mut extra::test::BenchHarness) {
do b.iter {
let v: ~[u8] = ~[0u8, ..1024];
}
}
~~~

Before:

test bench_from_elem ... bench: 415 ns/iter (+/- 17)
test bench_set_memory ... bench: 85 ns/iter (+/- 4)
test bench_vec_repeat ... bench: 83 ns/iter (+/- 3)

After:

test bench_from_elem ... bench: 84 ns/iter (+/- 2)
test bench_set_memory ... bench: 84 ns/iter (+/- 5)
test bench_vec_repeat ... bench: 84 ns/iter (+/- 3)