diff --git a/src/coreclr/tools/Common/Compiler/DependencyAnalysis/ObjectDataBuilder.cs b/src/coreclr/tools/Common/Compiler/DependencyAnalysis/ObjectDataBuilder.cs
index b5128ff27fb1f..53e4671b57a58 100644
--- a/src/coreclr/tools/Common/Compiler/DependencyAnalysis/ObjectDataBuilder.cs
+++ b/src/coreclr/tools/Common/Compiler/DependencyAnalysis/ObjectDataBuilder.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Buffers.Binary;
 using System.Collections.Generic;
 using Internal.TypeSystem;
 
@@ -85,42 +86,27 @@ public void EmitByte(byte emit)
 
         public void EmitShort(short emit)
         {
-            EmitByte((byte)(emit & 0xFF));
-            EmitByte((byte)((emit >> 8) & 0xFF));
+            BinaryPrimitives.WriteInt16LittleEndian(_data.AppendSpan(sizeof(short)), emit);
         }
 
         public void EmitUShort(ushort emit)
         {
-            EmitByte((byte)(emit & 0xFF));
-            EmitByte((byte)((emit >> 8) & 0xFF));
+            BinaryPrimitives.WriteUInt16LittleEndian(_data.AppendSpan(sizeof(ushort)), emit);
         }
 
         public void EmitInt(int emit)
         {
-            EmitByte((byte)(emit & 0xFF));
-            EmitByte((byte)((emit >> 8) & 0xFF));
-            EmitByte((byte)((emit >> 16) & 0xFF));
-            EmitByte((byte)((emit >> 24) & 0xFF));
+            BinaryPrimitives.WriteInt32LittleEndian(_data.AppendSpan(sizeof(int)), emit);
         }
 
         public void EmitUInt(uint emit)
         {
-            EmitByte((byte)(emit & 0xFF));
-            EmitByte((byte)((emit >> 8) & 0xFF));
-            EmitByte((byte)((emit >> 16) & 0xFF));
-            EmitByte((byte)((emit >> 24) & 0xFF));
+            BinaryPrimitives.WriteUInt32LittleEndian(_data.AppendSpan(sizeof(uint)), emit);
         }
 
         public void EmitLong(long emit)
         {
-            EmitByte((byte)(emit & 0xFF));
-            EmitByte((byte)((emit >> 8) & 0xFF));
-            EmitByte((byte)((emit >> 16) & 0xFF));
-            EmitByte((byte)((emit >> 24) & 0xFF));
-            EmitByte((byte)((emit >> 32) & 0xFF));
-            EmitByte((byte)((emit >> 40) & 0xFF));
-            EmitByte((byte)((emit >> 48) & 0xFF));
-            EmitByte((byte)((emit >> 56) & 0xFF));
+            BinaryPrimitives.WriteInt64LittleEndian(_data.AppendSpan(sizeof(long)), emit);
         }
 
         public void EmitNaturalInt(int emit)
@@ -245,8 +231,7 @@ public Reservation ReserveShort()
         public void EmitShort(Reservation reservation, short emit)
         {
             int offset = ReturnReservationTicket(reservation);
-            _data[offset] = (byte)(emit & 0xFF);
-            _data[offset + 1] = (byte)((emit >> 8) & 0xFF);
+            BinaryPrimitives.WriteInt16LittleEndian(_data.AsSpan(offset), emit);
         }
 
         public Reservation ReserveInt()
@@ -257,19 +242,13 @@ public Reservation ReserveInt()
         public void EmitInt(Reservation reservation, int emit)
         {
             int offset = ReturnReservationTicket(reservation);
-            _data[offset] = (byte)(emit & 0xFF);
-            _data[offset + 1] = (byte)((emit >> 8) & 0xFF);
-            _data[offset + 2] = (byte)((emit >> 16) & 0xFF);
-            _data[offset + 3] = (byte)((emit >> 24) & 0xFF);
+            BinaryPrimitives.WriteInt32LittleEndian(_data.AsSpan(offset), emit);
         }
 
         public void EmitUInt(Reservation reservation, uint emit)
         {
             int offset = ReturnReservationTicket(reservation);
-            _data[offset] = (byte)(emit & 0xFF);
-            _data[offset + 1] = (byte)((emit >> 8) & 0xFF);
-            _data[offset + 2] = (byte)((emit >> 16) & 0xFF);
-            _data[offset + 3] = (byte)((emit >> 24) & 0xFF);
+            BinaryPrimitives.WriteUInt32LittleEndian(_data.AsSpan(offset), emit);
         }
 
         public void EmitReloc(ISymbolNode symbol, RelocType relocType, int delta = 0)
diff --git a/src/coreclr/tools/Common/System/Collections/Generic/ArrayBuilder.cs b/src/coreclr/tools/Common/System/Collections/Generic/ArrayBuilder.cs
index 32023e27c19fc..0005f54747827 100644
--- a/src/coreclr/tools/Common/System/Collections/Generic/ArrayBuilder.cs
+++ b/src/coreclr/tools/Common/System/Collections/Generic/ArrayBuilder.cs
@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Runtime.CompilerServices;
+
 using Debug = System.Diagnostics.Debug;
 
 namespace System.Collections.Generic
@@ -29,6 +31,19 @@ public void Add(T item)
             _items[_count++] = item;
         }
 
+#if NET
+        public readonly Span<T> AsSpan(int start) => _items.AsSpan(start);
+
+        public Span<T> AppendSpan(int length)
+        {
+            int origCount = _count;
+            EnsureCapacity(origCount + length);
+
+            _count = origCount + length;
+            return _items.AsSpan(origCount, length);
+        }
+#endif
+
         public void Append(T[] newItems)
         {
             Append(newItems, 0, newItems.Length);
@@ -67,32 +82,26 @@ public void EnsureCapacity(int requestedCapacity)
         {
             if (requestedCapacity > ((_items != null) ? _items.Length : 0))
             {
-                int newCount = Math.Max(2 * _count + 1, requestedCapacity);
-                Array.Resize(ref _items, newCount);
+                Grow(requestedCapacity);
             }
         }
 
-        public int Count
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private void Grow(int requestedCapacity)
         {
-            get
-            {
-                return _count;
-            }
+            int newCount = Math.Max(2 * _count + 1, requestedCapacity);
+            Array.Resize(ref _items, newCount);
         }
 
-        public T this[int index]
+        public readonly int Count => _count;
+
+        public readonly T this[int index]
         {
-            get
-            {
-                return _items[index];
-            }
-            set
-            {
-                _items[index] = value;
-            }
+            get => _items[index];
+            set => _items[index] = value;
         }
 
-        public bool Contains(T t)
+        public readonly bool Contains(T t)
         {
             for (int i = 0; i < _count; i++)
             {
@@ -105,7 +114,7 @@ public bool Contains(T t)
             return false;
         }
 
-        public bool Any(Func<T, bool> func)
+        public readonly bool Any(Func<T, bool> func)
         {
             for (int i = 0; i < _count; i++)
             {