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copy tail bytes better for aligned types

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This commit is contained in:
Djzin 2017-05-27 14:29:41 +01:00
parent fcc970aca5
commit c6307a2fa5
1 changed files with 21 additions and 0 deletions
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21
src/libcore/mem.rs
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@ -479,6 +479,27 @@ pub fn swap<T>(x: &mut T, y: &mut T) {
ptr::copy_nonoverlapping(t, y.offset(i), block_size);
i += block_size as isize;
}
// Swap remaining bytes 8 at a time if x & y are properly aligned
if align_of::<T>() % 8 == 0 {
while i + 8 <= len as isize {
let t = *(x.offset(i) as *mut u64);
*(x.offset(i) as *mut u64) = *(y.offset(i) as *mut u64);
*(y.offset(i) as *mut u64) = t;
i += 8;
}
}
// Swap remaining bytes 4 at a time if x & y are properly aligned
if align_of::<T>() % 4 == 0 {
while i + 4 <= len as isize {
let t = *(x.offset(i) as *mut u32);
*(x.offset(i) as *mut u32) = *(y.offset(i) as *mut u32);
*(y.offset(i) as *mut u32) = t;
i += 4;
}
}
if i < len {
// Swap any remaining bytes
let mut t: UnalignedBlock = uninitialized();