From 93e587b81791bdd943117b19ade708c9f7193325 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emilio=20Cobos=20=C3=81lvarez?= <emilio@crisal.io>
Date: Wed, 4 May 2022 17:32:42 +0200
Subject: [PATCH] slice: #[inline] a couple iterator methods.

The one I care about and actually saw in the wild not getting inlined is
clone(). We ended up doing a whole function call for something that just
copies two pointers.

I ended up marking as_slice / as_ref as well because make_slice is
inline(always) itself, and is also the kind of think that can kill
performance in hot loops if you expect it to get inlined. But happy to
undo those.
---
 library/core/src/slice/iter.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/library/core/src/slice/iter.rs b/library/core/src/slice/iter.rs
index 98dd1521d0e85..415ed6203f4f5 100644
--- a/library/core/src/slice/iter.rs
+++ b/library/core/src/slice/iter.rs
@@ -127,6 +127,7 @@ impl<'a, T> Iter<'a, T> {
     /// ```
     #[must_use]
     #[stable(feature = "iter_to_slice", since = "1.4.0")]
+    #[inline]
     pub fn as_slice(&self) -> &'a [T] {
         self.make_slice()
     }
@@ -146,6 +147,7 @@ iterator! {struct Iter -> *const T, &'a T, const, {/* no mut */}, {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Clone for Iter<'_, T> {
+    #[inline]
     fn clone(&self) -> Self {
         Iter { ptr: self.ptr, end: self.end, _marker: self._marker }
     }
@@ -153,6 +155,7 @@ impl<T> Clone for Iter<'_, T> {
 
 #[stable(feature = "slice_iter_as_ref", since = "1.13.0")]
 impl<T> AsRef<[T]> for Iter<'_, T> {
+    #[inline]
     fn as_ref(&self) -> &[T] {
         self.as_slice()
     }
@@ -303,6 +306,7 @@ impl<'a, T> IterMut<'a, T> {
     /// ```
     #[must_use]
     #[stable(feature = "slice_iter_mut_as_slice", since = "1.53.0")]
+    #[inline]
     pub fn as_slice(&self) -> &[T] {
         self.make_slice()
     }
@@ -310,6 +314,7 @@ impl<'a, T> IterMut<'a, T> {
 
 #[stable(feature = "slice_iter_mut_as_slice", since = "1.53.0")]
 impl<T> AsRef<[T]> for IterMut<'_, T> {
+    #[inline]
     fn as_ref(&self) -> &[T] {
         self.as_slice()
     }