Move reduce sum to numerics

src/ImageSharp/Common/Helpers/Numerics.cs

@@ -5,6 +5,7 @@ using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.Arm;
 using System.Runtime.Intrinsics.X86;
 
 namespace SixLabors.ImageSharp;
@@ -808,6 +809,19 @@ internal static class Numerics
         return Sse2.ConvertToInt32(vsum);
     }
 
+    /// <summary>
+    /// Reduces elements of the vector into one sum.
+    /// </summary>
+    /// <param name="accumulator">The accumulator to reduce.</param>
+    /// <returns>The sum of all elements.</returns>
+    [MethodImpl(InliningOptions.ShortMethod)]
+    public static int ReduceSumArm(Vector128<uint> accumulator)
+    {
+        Vector128<ulong> sum2 = AdvSimd.AddPairwiseWidening(accumulator);
+        Vector64<uint> sum3 = AdvSimd.Add(sum2.GetLower().AsUInt32(), sum2.GetUpper().AsUInt32());
+        return (int)AdvSimd.Extract(sum3, 0);
+    }
+
     /// <summary>
     /// Reduces even elements of the vector into one sum.
     /// </summary>

src/ImageSharp/Formats/Webp/Lossy/LossyUtils.cs

@@ -226,7 +226,7 @@ internal static class LossyUtils
             sum = AccumulateSSE16Neon(a.Slice(y * WebpConstants.Bps), b.Slice(y * WebpConstants.Bps), sum);
         }
 
-        return ReduceSum(sum);
+        return Numerics.ReduceSumArm(sum);
     }
 
     [MethodImpl(InliningOptions.ShortMethod)]
@@ -238,7 +238,7 @@ internal static class LossyUtils
             sum = AccumulateSSE16Neon(a.Slice(y * WebpConstants.Bps), b.Slice(y * WebpConstants.Bps), sum);
         }
 
-        return ReduceSum(sum);
+        return Numerics.ReduceSumArm(sum);
     }
 
     [MethodImpl(InliningOptions.ShortMethod)]
@@ -255,7 +255,8 @@ internal static class LossyUtils
         // pair-wise adds and widen.
         Vector128<uint> sum1 = AdvSimd.AddPairwiseWidening(prod1);
         Vector128<uint> sum2 = AdvSimd.AddPairwiseWidening(prod2);
-        return ReduceSum(AdvSimd.Add(sum1, sum2));
+
+        return Numerics.ReduceSumArm(AdvSimd.Add(sum1, sum2));
     }
 
     // Load all 4x4 pixels into a single Vector128<uint>
@@ -273,14 +274,6 @@ internal static class LossyUtils
         }
     }
 
-    [MethodImpl(InliningOptions.ShortMethod)]
-    private static int ReduceSum(Vector128<uint> sum)
-    {
-        Vector128<ulong> sum2 = AdvSimd.AddPairwiseWidening(sum);
-        Vector64<uint> sum3 = AdvSimd.Add(sum2.GetLower().AsUInt32(), sum2.GetUpper().AsUInt32());
-        return (int)AdvSimd.Extract(sum3, 0);
-    }
-
     [MethodImpl(InliningOptions.ShortMethod)]
     private static Vector128<uint> AccumulateSSE16Neon(Span<byte> a, Span<byte> b, Vector128<uint> sum)
     {