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Use split_at in slice's ToOwned::clone_into

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It appears to codegen slightly more efficiently with `split_at` taking
two slices at once, rather than slicing across different calls.
This commit is contained in:
Josh Stone 2020-03-20 15:28:26 -07:00
parent 6dee5f1126
commit e8339e820b
1 changed files with 6 additions and 6 deletions
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12
src/liballoc/slice.rs
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@ -733,14 +733,14 @@ impl<T: Clone> ToOwned for [T] {
fn clone_into(&self, target: &mut Vec<T>) {
// drop anything in target that will not be overwritten
target.truncate(self.len());
let len = target.len();
// reuse the contained values' allocations/resources.
target.clone_from_slice(&self[..len]);
// target.len <= self.len due to the truncate above, so the
// slice here is always in-bounds.
target.extend_from_slice(&self[len..]);
// slices here are always in-bounds.
let (init, tail) = self.split_at(target.len());
// reuse the contained values' allocations/resources.
target.clone_from_slice(init);
target.extend_from_slice(tail);
}
}