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Rollup merge of #54851 - alexcrichton:revert-optimize, r=sfackler

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Fix a regression in 1.30 by reverting #53564

Investigation on #54477 revealed https://github.com/rust-lang/rust/pull/53564 as the culprit in the regression for that crate. I've reproduced the regression with the [detailed test cases provided](https://github.com/rust-lang/rust/issues/54477#issuecomment-427398456). While we figure out how to fix the regression this commit reverts the current culprit.
This commit is contained in:
Pietro Albini 2018-10-05 22:33:21 +02:00 committed by GitHub
commit 402c69950b
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1 changed files with 5 additions and 47 deletions
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52
src/liballoc/collections/vec_deque.rs
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@ -19,7 +19,6 @@
use core::cmp::Ordering; use core::cmp::Ordering;
use core::fmt; use core::fmt;
use core::isize;
use core::iter::{repeat, FromIterator, FusedIterator}; use core::iter::{repeat, FromIterator, FusedIterator};
use core::mem; use core::mem;
use core::ops::Bound::{Excluded, Included, Unbounded}; use core::ops::Bound::{Excluded, Included, Unbounded};
@ -203,33 +202,6 @@ impl<T> VecDeque<T> {
len); len);
} }
/// Copies all values from `src` to the back of `self`, wrapping around if needed.
///
/// # Safety
///
/// The capacity must be sufficient to hold self.len() + src.len() elements.
/// If so, this function never panics.
#[inline]
unsafe fn copy_slice(&mut self, src: &[T]) {
/// This is guaranteed by `RawVec`.
debug_assert!(self.capacity() <= isize::MAX as usize);
let expected_new_len = self.len() + src.len();
debug_assert!(self.capacity() >= expected_new_len);
let dst_high_ptr = self.ptr().add(self.head);
let dst_high_len = self.cap() - self.head;
let split = cmp::min(src.len(), dst_high_len);
let (src_high, src_low) = src.split_at(split);
ptr::copy_nonoverlapping(src_high.as_ptr(), dst_high_ptr, src_high.len());
ptr::copy_nonoverlapping(src_low.as_ptr(), self.ptr(), src_low.len());
self.head = self.wrap_add(self.head, src.len());
debug_assert!(self.len() == expected_new_len);
}
/// Copies a potentially wrapping block of memory len long from src to dest. /// Copies a potentially wrapping block of memory len long from src to dest.
/// (abs(dst - src) + len) must be no larger than cap() (There must be at /// (abs(dst - src) + len) must be no larger than cap() (There must be at
/// most one continuous overlapping region between src and dest). /// most one continuous overlapping region between src and dest).
@ -1052,7 +1024,7 @@ impl<T> VecDeque<T> {
iter: Iter { iter: Iter {
tail: drain_tail, tail: drain_tail,
head: drain_head, head: drain_head,
ring: unsafe { self.buffer_as_slice() }, ring: unsafe { self.buffer_as_mut_slice() },
}, },
} }
} }
@ -1862,22 +1834,8 @@ impl<T> VecDeque<T> {
#[inline] #[inline]
#[stable(feature = "append", since = "1.4.0")] #[stable(feature = "append", since = "1.4.0")]
pub fn append(&mut self, other: &mut Self) { pub fn append(&mut self, other: &mut Self) {
unsafe { // naive impl
// Guarantees there is space in `self` for `other`. self.extend(other.drain(..));
self.reserve(other.len());
{
let (src_high, src_low) = other.as_slices();
// This is only safe because copy_slice never panics when capacity is sufficient.
self.copy_slice(src_low);
self.copy_slice(src_high);
}
// Some values now exist in both `other` and `self` but are made inaccessible
// in`other`.
other.tail = other.head;
}
} }
/// Retains only the elements specified by the predicate. /// Retains only the elements specified by the predicate.
@ -2635,8 +2593,8 @@ impl<T> From<VecDeque<T>> for Vec<T> {
let mut right_offset = 0; let mut right_offset = 0;
for i in left_edge..right_edge { for i in left_edge..right_edge {
right_offset = (i - left_edge) % (cap - right_edge); right_offset = (i - left_edge) % (cap - right_edge);
let src = right_edge + right_offset; let src: isize = (right_edge + right_offset) as isize;
ptr::swap(buf.add(i), buf.add(src)); ptr::swap(buf.add(i), buf.offset(src));
} }
let n_ops = right_edge - left_edge; let n_ops = right_edge - left_edge;
left_edge += n_ops; left_edge += n_ops;