Change arguments of AccumulateSSE16Neon to pointers for better code generation

Author: brianpopow

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

@@ -216,17 +216,18 @@ private static int Vp8_Sse16xN_Avx2(Span<byte> a, Span<byte> b, int numPairs)
     }
 
     [MethodImpl(InliningOptions.ShortMethod)]
-    private static int Vp8_Sse16x16_Neon(Span<byte> a, Span<byte> b)
+    private static unsafe int Vp8_Sse16x16_Neon(Span<byte> a, Span<byte> b)
     {
         Vector128<uint> sum = Vector128<uint>.Zero;
-        ref byte aRef = ref MemoryMarshal.GetReference(a);
-        ref byte bRef = ref MemoryMarshal.GetReference(b);
-        for (int y = 0; y < 16; y++)
+        fixed (byte* aRef = &MemoryMarshal.GetReference(a))
         {
-            sum = AccumulateSSE16Neon(
-                ref Unsafe.Add(ref aRef, y * WebpConstants.Bps),
-                ref Unsafe.Add(ref bRef, y * WebpConstants.Bps),
-                sum);
+            fixed (byte* bRef = &MemoryMarshal.GetReference(b))
+            {
+                for (int y = 0; y < 16; y++)
+                {
+                    sum = AccumulateSSE16Neon(aRef + (y * WebpConstants.Bps), bRef + (y * WebpConstants.Bps), sum);
+                }
+            }
         }
 
 #if NET7_0_OR_GREATER
@@ -237,17 +238,18 @@ ref Unsafe.Add(ref bRef, y * WebpConstants.Bps),
     }
 
     [MethodImpl(InliningOptions.ShortMethod)]
-    private static int Vp8_Sse16x8_Neon(Span<byte> a, Span<byte> b)
+    private static unsafe int Vp8_Sse16x8_Neon(Span<byte> a, Span<byte> b)
     {
         Vector128<uint> sum = Vector128<uint>.Zero;
-        ref byte aRef = ref MemoryMarshal.GetReference(a);
-        ref byte bRef = ref MemoryMarshal.GetReference(b);
-        for (int y = 0; y < 8; y++)
+        fixed (byte* aRef = &MemoryMarshal.GetReference(a))
         {
-            sum = AccumulateSSE16Neon(
-                ref Unsafe.Add(ref aRef, y * WebpConstants.Bps),
-                ref Unsafe.Add(ref bRef, y * WebpConstants.Bps),
-                sum);
+            fixed (byte* bRef = &MemoryMarshal.GetReference(b))
+            {
+                for (int y = 0; y < 8; y++)
+                {
+                    sum = AccumulateSSE16Neon(aRef + (y * WebpConstants.Bps), bRef + (y * WebpConstants.Bps), sum);
+                }
+            }
         }
 
 #if NET7_0_OR_GREATER
@@ -296,10 +298,10 @@ private static unsafe Vector128<uint> Load4x4Neon(Span<byte> src)
     }
 
     [MethodImpl(InliningOptions.ShortMethod)]
-    private static Vector128<uint> AccumulateSSE16Neon(ref byte aRef, ref byte bRef, Vector128<uint> sum)
+    private static unsafe Vector128<uint> AccumulateSSE16Neon(byte* a, byte* b, Vector128<uint> sum)
     {
-        Vector128<byte> a0 = Unsafe.As<byte, Vector128<byte>>(ref aRef);
-        Vector128<byte> b0 = Unsafe.As<byte, Vector128<byte>>(ref bRef);
+        Vector128<byte> a0 = AdvSimd.LoadVector128(a);
+        Vector128<byte> b0 = AdvSimd.LoadVector128(b);
 
         Vector128<byte> absDiff = AdvSimd.AbsoluteDifference(a0, b0);
         Vector64<byte> absDiffLower = absDiff.GetLower();