Further optimize SegmentedArray<T> indexer for net5.0

sharwell · Feb 21, 2021 · 15e1fd3 · 15e1fd3
1 parent da87848
commit 15e1fd3
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Showing 2 changed files with 22 additions and 4 deletions.
diff --git a/src/Dependencies/Collections/SegmentedArray`1.cs b/src/Dependencies/Collections/SegmentedArray`1.cs
@@ -7,6 +7,7 @@
 using System.Collections.Generic;
 using System.Reflection.Emit;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using Microsoft.CodeAnalysis.Collections.Internal;
 
 namespace Microsoft.CodeAnalysis.Collections
@@ -118,7 +119,28 @@ public ref T this[int index]
             [MethodImpl(SegmentedArrayHelper.FastPathMethodImplOptions)]
             get
             {
+#if NET
+                if (typeof(T).IsValueType)
+                {
+                    // Direct indexing is faster because it avoids more null checks
+                    return ref _items[index >> SegmentShift][index & OffsetMask];
+                }
+                else
+                {
+                    // Operate on a local copy of the structure since this method uses unsafe operations based on
+                    // validation at the start of the method.
+                    var self = this;
+
+                    // MemoryMarshal.GetArrayDataReference is faster because it avoids array variance checks
+                    if ((uint)index >= (uint)self.Length)
+                        ThrowHelper.ThrowIndexOutOfRangeException();
+
+                    var segment = Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(self._items), index >> SegmentShift);
+                    return ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(segment), index & OffsetMask);
+                }
+#else
                 return ref _items[index >> SegmentShift][index & OffsetMask];
+#endif
             }
         }
 

diff --git a/src/Dependencies/Collections/SegmentedList`1.cs b/src/Dependencies/Collections/SegmentedList`1.cs
@@ -1049,11 +1049,7 @@ public void Sort(Comparison<T> comparison)
 
             if (_size > 1)
             {
-#if NET
-                _items.AsSpan(0, _size).Sort(comparison);
-#else
                 SegmentedArray.Sort<T>(_items, 0, _size, Comparer<T>.Create(comparison));
-#endif
             }
             _version++;
         }