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ptr: optimize {swap,replace,read}_ptr #7670

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ptr: optimize {swap,replace,read}_ptr #7670

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12 changes: 6 additions & 6 deletions src/libstd/ptr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ use cast;
use option::{Option, Some, None};
use sys;
use unstable::intrinsics;
use util::swap;

#[cfg(not(test))] use cmp::{Eq, Ord};
use uint;
Expand Down Expand Up @@ -177,9 +178,9 @@ pub unsafe fn swap_ptr<T>(x: *mut T, y: *mut T) {
let t: *mut T = &mut tmp;

// Perform the swap
copy_memory(t, x, 1);
copy_memory(x, y, 1);
copy_memory(y, t, 1);
copy_nonoverlapping_memory(t, x, 1);
copy_memory(x, y, 1); // `x` and `y` may overlap
copy_nonoverlapping_memory(y, t, 1);

// y and t now point to the same thing, but we need to completely forget `tmp`
// because it's no longer relevant.
Expand All @@ -192,7 +193,7 @@ pub unsafe fn swap_ptr<T>(x: *mut T, y: *mut T) {
*/
#[inline]
pub unsafe fn replace_ptr<T>(dest: *mut T, mut src: T) -> T {
swap_ptr(dest, &mut src);
swap(cast::transmute(dest), &mut src); // cannot overlap
src
}

Expand All @@ -202,8 +203,7 @@ pub unsafe fn replace_ptr<T>(dest: *mut T, mut src: T) -> T {
#[inline(always)]
pub unsafe fn read_ptr<T>(src: *mut T) -> T {
let mut tmp: T = intrinsics::uninit();
let t: *mut T = &mut tmp;
copy_memory(t, src, 1);
copy_nonoverlapping_memory(&mut tmp, src, 1);
tmp
}

Expand Down