Avoid OrderBy.ToArray/ToList overheads for length 1 (dotnet#99639)

We already special-case length 0. That can trivially be extended to length 1.
davidwrighton · Aug 20, 2024 · 2203250 · 2203250
1 parent 3a6b292
commit 2203250
Showing 1 changed file with 7 additions and 3 deletions.
diff --git a/src/libraries/System.Linq/src/System/Linq/OrderedEnumerable.SpeedOpt.cs b/src/libraries/System.Linq/src/System/Linq/OrderedEnumerable.SpeedOpt.cs
@@ -15,7 +15,7 @@ private abstract partial class OrderedIterator<TElement>
             public override TElement[] ToArray()
             {
                 TElement[] buffer = _source.ToArray();
-                if (buffer.Length == 0)
+                if (buffer.Length <= 1)
                 {
                     return buffer;
                 }
@@ -29,11 +29,15 @@ public override List<TElement> ToList()
             {
                 TElement[] buffer = _source.ToArray();
 
-                List<TElement> list = new();
-                if (buffer.Length > 0)
+                List<TElement> list = new(buffer.Length);
+                if (buffer.Length >= 2)
                 {
                     Fill(buffer, SetCountAndGetSpan(list, buffer.Length));
                 }
+                else if (buffer.Length == 1)
+                {
+                    list.Add(buffer[0]);
+                }
 
                 return list;
             }