1// Set the length of the vec when the `SetLenOnDrop` value goes out of scope.
2//
3// The idea is: The length field in SetLenOnDrop is a local variable
4// that the optimizer will see does not alias with any stores through the Vec's data
5// pointer. This is a workaround for alias analysis issue #32155
6pub(super) struct SetLenOnDrop<'a> {
7 len: &'a mut usize,
8 local_len: usize,
9}
10
11impl<'a> SetLenOnDrop<'a> {
12 #[inline(always)]
13 pub(super) fn new(len: &'a mut usize) -> Self {
14 SetLenOnDrop {
15 local_len: *len,
16 len,
17 }
18 }
19
20 #[inline(always)]
21 pub(super) fn increment_len(&mut self, increment: usize) {
22 self.local_len += increment;
23 }
24}
25
26impl Drop for SetLenOnDrop<'_> {
27 #[inline(always)]
28 fn drop(&mut self) {
29 *self.len = self.local_len;
30 }
31}
32