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better respect alignment for copying tail

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This commit is contained in:
Djzin 2017-05-27 16:39:51 +01:00
parent 74751358e6
commit d4d3f53468
1 changed files with 37 additions and 25 deletions
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62
src/libcore/mem.rs
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@ -532,35 +532,47 @@ pub fn swap<T>(x: &mut T, y: &mut T) {
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
// Swap any remaining bytes, using aligned types to copy
// where appropriate (this information is lost by conversion
// to *mut u8, so restore it manually here)
let mut t: UnalignedBlock = uninitialized();
let t = &mut t as *mut _ as *mut u8;
let rem = (len - i) as usize;
ptr::copy_nonoverlapping(x.offset(i), t, rem);
ptr::copy_nonoverlapping(y.offset(i), x.offset(i), rem);
ptr::copy_nonoverlapping(t, y.offset(i), rem);
if align_of::<T>() % 8 == 0 && len % 8 == 0 {
let t = &mut t as *mut _ as *mut u64;
let x = x.offset(i) as *mut u64;
let y = y.offset(i) as *mut u64;
ptr::copy_nonoverlapping(x, t, rem / 8);
ptr::copy_nonoverlapping(y, x, rem / 8);
ptr::copy_nonoverlapping(t, y, rem / 8);
} else if align_of::<T>() % 4 == 0 && len % 4 == 0 {
let t = &mut t as *mut _ as *mut u32;
let x = x.offset(i) as *mut u32;
let y = y.offset(i) as *mut u32;
ptr::copy_nonoverlapping(x, t, rem / 4);
ptr::copy_nonoverlapping(y, x, rem / 4);
ptr::copy_nonoverlapping(t, y, rem / 4);
} else if align_of::<T>() % 2 == 0 && len % 2 == 0 {
let t = &mut t as *mut _ as *mut u16;
let x = x.offset(i) as *mut u16;
let y = y.offset(i) as *mut u16;
ptr::copy_nonoverlapping(x, t, rem / 2);
ptr::copy_nonoverlapping(y, x, rem / 2);
ptr::copy_nonoverlapping(t, y, rem / 2);
} else {
let t = &mut t as *mut _ as *mut u8;
let x = x.offset(i);
let y = y.offset(i);
ptr::copy_nonoverlapping(x, t, rem);
ptr::copy_nonoverlapping(y, x, rem);
ptr::copy_nonoverlapping(t, y, rem);
}
}
}
}