diff --git a/src/libraries/System.Private.CoreLib/src/System/Int128.cs b/src/libraries/System.Private.CoreLib/src/System/Int128.cs
index 50dce177e17135..7a6262dcf5be07 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Int128.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Int128.cs
@@ -1290,22 +1290,33 @@ public static Int128 Clamp(Int128 value, Int128 min, Int128 max)
         /// <inheritdoc cref="INumber{TSelf}.CopySign(TSelf, TSelf)" />
         public static Int128 CopySign(Int128 value, Int128 sign)
         {
-            Int128 absValue = value;
-
-            if (IsNegative(absValue))
-            {
-                absValue = -absValue;
-            }
-
-            if (IsPositive(sign))
+#if TARGET_32BIT
+            Int128 t = value;
+            if (Int128.IsPositive(sign))
             {
-                if (IsNegative(absValue))
+                if (Int128.IsNegative(t))
                 {
-                    Math.ThrowNegateTwosCompOverflow();
+                    t = -t;
+                    if (Int128.IsNegative(t))
+                    {
+                        Math.ThrowNegateTwosCompOverflow();
+                    }
                 }
-                return absValue;
+                return t;
             }
-            return -absValue;
+            if (Int128.IsPositive(t))
+            {
+                t = -t;
+            }
+            return t;
+#else
+            // Int128.MinValue == value && 0 <= sign
+            if ((long)value._upper == long.MinValue && value._lower == 0 && (long)sign._upper >= 0)
+            {
+                Math.ThrowNegateTwosCompOverflow();
+            }
+            return value * Math.SignOrOneIfZero((long)value._upper ^ (long)sign._upper);
+#endif
         }
 
         /// <inheritdoc cref="INumber{TSelf}.Max(TSelf, TSelf)" />
diff --git a/src/libraries/System.Private.CoreLib/src/System/Int16.cs b/src/libraries/System.Private.CoreLib/src/System/Int16.cs
index af144fb860c921..24ee8c4a92928b 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Int16.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Int16.cs
@@ -631,24 +631,11 @@ public static short Log2(short value)
         /// <inheritdoc cref="INumber{TSelf}.CopySign(TSelf, TSelf)" />
         public static short CopySign(short value, short sign)
         {
-            short absValue = value;
-
-            if (absValue < 0)
-            {
-                absValue = (short)(-absValue);
-            }
-
-            if (sign >= 0)
+            if (value == short.MinValue && sign >= 0)
             {
-                if (absValue < 0)
-                {
-                    Math.ThrowNegateTwosCompOverflow();
-                }
-
-                return absValue;
+                Math.ThrowNegateTwosCompOverflow();
             }
-
-            return (short)(-absValue);
+            return (short)(value * Math.SignOrOneIfZero(value ^ sign));
         }
 
         /// <inheritdoc cref="INumber{TSelf}.Max(TSelf, TSelf)" />
diff --git a/src/libraries/System.Private.CoreLib/src/System/Int32.cs b/src/libraries/System.Private.CoreLib/src/System/Int32.cs
index 2f91c2c2a59702..717f4c3762f962 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Int32.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Int32.cs
@@ -666,24 +666,11 @@ public static int Log2(int value)
         /// <inheritdoc cref="INumber{TSelf}.CopySign(TSelf, TSelf)" />
         public static int CopySign(int value, int sign)
         {
-            int absValue = value;
-
-            if (absValue < 0)
-            {
-                absValue = -absValue;
-            }
-
-            if (sign >= 0)
+            if (value == int.MinValue && sign >= 0)
             {
-                if (absValue < 0)
-                {
-                    Math.ThrowNegateTwosCompOverflow();
-                }
-
-                return absValue;
+                Math.ThrowNegateTwosCompOverflow();
             }
-
-            return -absValue;
+            return value * Math.SignOrOneIfZero(value ^ sign);
         }
 
         /// <inheritdoc cref="INumber{TSelf}.Max(TSelf, TSelf)" />
diff --git a/src/libraries/System.Private.CoreLib/src/System/Int64.cs b/src/libraries/System.Private.CoreLib/src/System/Int64.cs
index ca170d8c903ed0..254d8a5c38add7 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Int64.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Int64.cs
@@ -661,26 +661,14 @@ public static long Log2(long value)
         public static long Clamp(long value, long min, long max) => Math.Clamp(value, min, max);
 
         /// <inheritdoc cref="INumber{TSelf}.CopySign(TSelf, TSelf)" />
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static long CopySign(long value, long sign)
         {
-            long absValue = value;
-
-            if (absValue < 0)
+            if (value == long.MinValue && sign >= 0)
             {
-                absValue = -absValue;
+                Math.ThrowNegateTwosCompOverflow();
             }
-
-            if (sign >= 0)
-            {
-                if (absValue < 0)
-                {
-                    Math.ThrowNegateTwosCompOverflow();
-                }
-
-                return absValue;
-            }
-
-            return -absValue;
+            return value * Math.SignOrOneIfZero(value ^ sign);
         }
 
         /// <inheritdoc cref="INumber{TSelf}.Max(TSelf, TSelf)" />
diff --git a/src/libraries/System.Private.CoreLib/src/System/IntPtr.cs b/src/libraries/System.Private.CoreLib/src/System/IntPtr.cs
index 3dd33c2c66b82d..0a4c87e5bd8990 100644
--- a/src/libraries/System.Private.CoreLib/src/System/IntPtr.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/IntPtr.cs
@@ -674,24 +674,11 @@ public static nint Log2(nint value)
         /// <inheritdoc cref="INumber{TSelf}.CopySign(TSelf, TSelf)" />
         public static nint CopySign(nint value, nint sign)
         {
-            nint absValue = value;
-
-            if (absValue < 0)
-            {
-                absValue = -absValue;
-            }
-
-            if (sign >= 0)
+            if (value == nint.MinValue && sign >= 0)
             {
-                if (absValue < 0)
-                {
-                    Math.ThrowNegateTwosCompOverflow();
-                }
-
-                return absValue;
+                Math.ThrowNegateTwosCompOverflow();
             }
-
-            return -absValue;
+            return value * Math.SignOrOneIfZero(value ^ sign);
         }
 
         /// <inheritdoc cref="INumber{TSelf}.Max(TSelf, TSelf)" />
diff --git a/src/libraries/System.Private.CoreLib/src/System/Math.cs b/src/libraries/System.Private.CoreLib/src/System/Math.cs
index 7d20cc72202dd1..841ecdc2305bd9 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Math.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Math.cs
@@ -1468,6 +1468,27 @@ public static int Sign(float value)
             throw new ArithmeticException(SR.Arithmetic_NaN);
         }
 
+        // Helper functions for CopySign
+        // >= 0: returns 1
+        // < 0: returns -1
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static int SignOrOneIfZero(int value)
+        {
+            return (value >> (32 - 2)) | 1;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static int SignOrOneIfZero(nint value)
+        {
+            return (int)(value >> (8 * nint.Size - 2)) | 1;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal static int SignOrOneIfZero(long value)
+        {
+            return (int)(value >> (64 - 2)) | 1;
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static decimal Truncate(decimal d)
         {
diff --git a/src/libraries/System.Private.CoreLib/src/System/SByte.cs b/src/libraries/System.Private.CoreLib/src/System/SByte.cs
index fb4734d41b69f6..0d61ff474edd23 100644
--- a/src/libraries/System.Private.CoreLib/src/System/SByte.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/SByte.cs
@@ -592,24 +592,11 @@ public static sbyte Log2(sbyte value)
         /// <inheritdoc cref="INumber{TSelf}.CopySign(TSelf, TSelf)" />
         public static sbyte CopySign(sbyte value, sbyte sign)
         {
-            sbyte absValue = value;
-
-            if (absValue < 0)
-            {
-                absValue = (sbyte)(-absValue);
-            }
-
-            if (sign >= 0)
+            if (value == sbyte.MinValue && sign >= 0)
             {
-                if (absValue < 0)
-                {
-                    Math.ThrowNegateTwosCompOverflow();
-                }
-
-                return absValue;
+                Math.ThrowNegateTwosCompOverflow();
             }
-
-            return (sbyte)(-absValue);
+            return (sbyte)(value * Math.SignOrOneIfZero(value ^ sign));
         }
 
         /// <inheritdoc cref="INumber{TSelf}.Max(TSelf, TSelf)" />