Use non-overlapping swap for inner heapsort loop

Voultapher · Voultapher · commit 54391983486d · 2024-09-04T19:54:46.000+02:00
This regresses binary-size slightly for normal builds, but the important
release_lto_thin_opt_level_s config sees a small improvement in
binary-size and a larger types such as string and 1k see 2-3% run-time
improvements with this change.
diff --git a/library/core/src/slice/sort/unstable/heapsort.rs b/library/core/src/slice/sort/unstable/heapsort.rs
@@ -69,9 +69,7 @@ where
                 break;
             }
 
-            // Swap `node` with the greater child, move one step down, and continue sifting. This
-            // could be ptr::swap_nonoverlapping but that adds a significant amount of binary-size.
-            ptr::swap(v_base.add(node), v_base.add(child));
+            ptr::swap_nonoverlapping(v_base.add(node), v_base.add(child), 1);
         }
 
         node = child;

Original file line number	Diff line number	Diff line change
`@@ -69,9 +69,7 @@ where`
`69`	`69`	`break;`
`70`	`70`	`}`
`71`	`71`
`72`		- // Swap `node` with the greater child, move one step down, and continue sifting. This
`73`		`- // could be ptr::swap_nonoverlapping but that adds a significant amount of binary-size.`
`74`		`- ptr::swap(v_base.add(node), v_base.add(child));`
	`72`	`+ ptr::swap_nonoverlapping(v_base.add(node), v_base.add(child), 1);`
`75`	`73`	`}`
`76`	`74`
`77`	`75`	`node = child;`