Use Span<T>.Fill implementation for Array.Fill

src/libraries/System.Collections/src/System/Collections/BitArray.cs

@@ -51,7 +51,7 @@ public BitArray(int length, bool defaultValue)
 
             if (defaultValue)
             {
-                m_array.AsSpan().Fill(-1);
+                Array.Fill(m_array, -1);
 
                 // clear high bit values in the last int
                 Div32Rem(length, out int extraBits);

src/libraries/System.Private.CoreLib/src/System/Array.cs

@@ -785,10 +785,8 @@ public static void Fill<T>(T[] array, T value)
                 ThrowHelper.ThrowArgumentNullException(ExceptionArgument.array);
             }
 
-            for (int i = 0; i < array.Length; i++)
-            {
-                array[i] = value;
-            }
+            var span = new Span<T>(ref MemoryMarshal.GetArrayDataReference(array), array.Length);
+            span.Fill(value);
         }
 
         public static void Fill<T>(T[] array, T value, int startIndex, int count)
@@ -808,10 +806,9 @@ public static void Fill<T>(T[] array, T value, int startIndex, int count)
                 ThrowHelper.ThrowCountArgumentOutOfRange_ArgumentOutOfRange_Count();
             }
 
-            for (int i = startIndex; i < startIndex + count; i++)
-            {
-                array[i] = value;
-            }
+            ref T first = ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(array), startIndex);
+            var span = new Span<T>(ref first, count);
+            span.Fill(value);
         }
 
         public static T? Find<T>(T[] array, Predicate<T> match)

src/libraries/System.Private.Xml/src/System/Xml/Core/XmlTextWriter.cs

@@ -144,7 +144,7 @@ private enum Token
         private static char[] CreateDefaultIndentChars()
         {
             var result = new char[IndentArrayLength];
-            result.AsSpan().Fill(DefaultIndentChar);
+            Array.Fill(result, DefaultIndentChar);
             return result;
         }