New upstream version 1.44.1+dfsg1

[rustc.git] / src / liballoc / slice.rs

diff --git a/src/liballoc/slice.rs b/src/liballoc/slice.rs
index 7b83658fca60d03ad6e54c63ed6665adc5c262ec..53477288b59ee8a89d39bb2bbbd5eceb0730ea8e 100644 (file)
--- a/src/liballoc/slice.rs
+++ b/src/liballoc/slice.rs
@@ -90,7 +90,6 @@ use core::borrow::{Borrow, BorrowMut};
 use core::cmp::Ordering::{self, Less};
 use core::mem::{self, size_of};
 use core::ptr;
-use core::{u16, u32, u8};
 
 use crate::borrow::ToOwned;
 use crate::boxed::Box;
@@ -141,12 +140,14 @@ mod hack {
     use crate::string::ToString;
     use crate::vec::Vec;
 
+    // We shouldn't add inline attribute to this since this is used in
+    // `vec!` macro mostly and causes perf regression. See #71204 for
+    // discussion and perf results.
     pub fn into_vec<T>(b: Box<[T]>) -> Vec<T> {
         unsafe {
             let len = b.len();
             let b = Box::into_raw(b);
-            let xs = Vec::from_raw_parts(b as *mut T, len, len);
-            xs
+            Vec::from_raw_parts(b as *mut T, len, len)
         }
     }
 
@@ -166,7 +167,7 @@ mod hack {
 impl<T> [T] {
     /// Sorts the slice.
     ///
-    /// This sort is stable (i.e., does not reorder equal elements) and `O(n log n)` worst-case.
+    /// This sort is stable (i.e., does not reorder equal elements) and `O(n * log(n))` worst-case.
     ///
     /// When applicable, unstable sorting is preferred because it is generally faster than stable
     /// sorting and it doesn't allocate auxiliary memory.
@@ -201,7 +202,7 @@ impl<T> [T] {
 
     /// Sorts the slice with a comparator function.
     ///
-    /// This sort is stable (i.e., does not reorder equal elements) and `O(n log n)` worst-case.
+    /// This sort is stable (i.e., does not reorder equal elements) and `O(n * log(n))` worst-case.
     ///
     /// The comparator function must define a total ordering for the elements in the slice. If
     /// the ordering is not total, the order of the elements is unspecified. An order is a
@@ -255,7 +256,7 @@ impl<T> [T] {
 
     /// Sorts the slice with a key extraction function.
     ///
-    /// This sort is stable (i.e., does not reorder equal elements) and `O(m n log(m n))`
+    /// This sort is stable (i.e., does not reorder equal elements) and `O(m * n * log(n))`
     /// worst-case, where the key function is `O(m)`.
     ///
     /// For expensive key functions (e.g. functions that are not simple property accesses or
@@ -298,7 +299,7 @@ impl<T> [T] {
     ///
     /// During sorting, the key function is called only once per element.
     ///
-    /// This sort is stable (i.e., does not reorder equal elements) and `O(m n + n log n)`
+    /// This sort is stable (i.e., does not reorder equal elements) and `O(m * n + n * log(n))`
     /// worst-case, where the key function is `O(m)`.
     ///
     /// For simple key functions (e.g., functions that are property accesses or
@@ -433,7 +434,7 @@ impl<T> [T] {
     ///
     /// ```should_panic
     /// // this will panic at runtime
-    /// b"0123456789abcdef".repeat(usize::max_value());
+    /// b"0123456789abcdef".repeat(usize::MAX);
     /// ```
     #[stable(feature = "repeat_generic_slice", since = "1.40.0")]
     pub fn repeat(&self, n: usize) -> Vec<T>
@@ -735,14 +736,14 @@ 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);
     }
 }
 
@@ -936,7 +937,7 @@ where
 /// 1. for every `i` in `1..runs.len()`: `runs[i - 1].len > runs[i].len`
 /// 2. for every `i` in `2..runs.len()`: `runs[i - 2].len > runs[i - 1].len + runs[i].len`
 ///
-/// The invariants ensure that the total running time is `O(n log n)` worst-case.
+/// The invariants ensure that the total running time is `O(n * log(n))` worst-case.
 fn merge_sort<T, F>(v: &mut [T], mut is_less: F)
 where
     F: FnMut(&T, &T) -> bool,