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implement pointer arithmetic with GEP

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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)
This commit is contained in:
Daniel Micay 2013-07-30 00:33:52 -04:00
parent e94e4d51ca
commit ef870d37a5
19 changed files with 131 additions and 80 deletions
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7
src/libstd/unstable/intrinsics.rs
View file

@ -321,6 +321,13 @@ extern "rust-intrinsic" {
/// Get the address of the `__morestack` stack growth function.
pub fn morestack_addr() -> *();
/// Adjust a pointer by an offset.
///
/// This is implemented as an intrinsic to avoid converting to and from an
/// integer, since the conversion would throw away aliasing information.
#[cfg(not(stage0))]
pub fn offset<T>(dst: *T, offset: int) -> *T;
/// Equivalent to the `llvm.memcpy.p0i8.0i8.i32` intrinsic, with a size of
/// `count` * `size_of::<T>()` and an alignment of `min_align_of::<T>()`
pub fn memcpy32<T>(dst: *mut T, src: *T, count: u32);