From 7840665f04a5c1f5cc726082947de973202061c4 Mon Sep 17 00:00:00 2001
From: James Jackson-South <james_south@hotmail.com>
Date: Thu, 15 Aug 2024 20:41:42 +1000
Subject: [PATCH] Don't use FMA for 512

---
 src/ImageSharp/Common/Helpers/Vector512Utilities.cs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/ImageSharp/Common/Helpers/Vector512Utilities.cs b/src/ImageSharp/Common/Helpers/Vector512Utilities.cs
index 3325ad1aeb..8a9ba6aa44 100644
--- a/src/ImageSharp/Common/Helpers/Vector512Utilities.cs
+++ b/src/ImageSharp/Common/Helpers/Vector512Utilities.cs
@@ -138,9 +138,10 @@ internal static class Vector512Utilities
     /// </remarks>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static Vector512<float> MultiplyAddEstimate(Vector512<float> a, Vector512<float> b, Vector512<float> c)
-        => Vector512.Create(
-            Vector256Utilities.MultiplyAddEstimate(a.GetLower(), b.GetLower(), c.GetLower()),
-            Vector256Utilities.MultiplyAddEstimate(a.GetUpper(), b.GetUpper(), c.GetUpper()));
+
+        // Don't actually use FMA as it requires many more instruction to extract the
+        // upper and lower parts of the vector and then recombine them.
+        => (a + b) * c;
 
     [DoesNotReturn]
     private static void ThrowUnreachableException() => throw new UnreachableException();