From 91d768d985cf5dd2eae18bc06b5f3941f015b99d Mon Sep 17 00:00:00 2001
From: SingleAccretion <AccretionMail@yandex.ru>
Date: Fri, 2 Dec 2022 21:36:46 +0300
Subject: [PATCH] Speed up Matrix4x4.CreateScale

---
 .../src/System/Numerics/Matrix4x4.cs          | 46 +++++++++++--------
 1 file changed, 28 insertions(+), 18 deletions(-)

diff --git a/src/libraries/System.Private.CoreLib/src/System/Numerics/Matrix4x4.cs b/src/libraries/System.Private.CoreLib/src/System/Numerics/Matrix4x4.cs
index d0738641a3e2ec..4cbe3d4a93ad7b 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Numerics/Matrix4x4.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Numerics/Matrix4x4.cs
@@ -1202,10 +1202,13 @@ public static Matrix4x4 CreateRotationZ(float radians, Vector3 centerPoint)
         /// <returns>The scaling matrix.</returns>
         public static Matrix4x4 CreateScale(float xScale, float yScale, float zScale)
         {
-            Matrix4x4 result = Identity;
+            Matrix4x4 result = default;
+
             result.M11 = xScale;
             result.M22 = yScale;
             result.M33 = zScale;
+            result.M44 = 1;
+
             return result;
         }
 
@@ -1217,7 +1220,7 @@ public static Matrix4x4 CreateScale(float xScale, float yScale, float zScale)
         /// <returns>The scaling matrix.</returns>
         public static Matrix4x4 CreateScale(float xScale, float yScale, float zScale, Vector3 centerPoint)
         {
-            Matrix4x4 result = Identity;
+            Matrix4x4 result = default;
 
             float tx = centerPoint.X * (1 - xScale);
             float ty = centerPoint.Y * (1 - yScale);
@@ -1226,9 +1229,12 @@ public static Matrix4x4 CreateScale(float xScale, float yScale, float zScale, Ve
             result.M11 = xScale;
             result.M22 = yScale;
             result.M33 = zScale;
+            result.M44 = 1;
+
             result.M41 = tx;
             result.M42 = ty;
             result.M43 = tz;
+
             return result;
         }
 
@@ -1237,10 +1243,13 @@ public static Matrix4x4 CreateScale(float xScale, float yScale, float zScale, Ve
         /// <returns>The scaling matrix.</returns>
         public static Matrix4x4 CreateScale(Vector3 scales)
         {
-            Matrix4x4 result = Identity;
+            Matrix4x4 result = default;
+
             result.M11 = scales.X;
             result.M22 = scales.Y;
             result.M33 = scales.Z;
+            result.M44 = 1;
+
             return result;
         }
 
@@ -1250,18 +1259,19 @@ public static Matrix4x4 CreateScale(Vector3 scales)
         /// <returns>The scaling matrix.</returns>
         public static Matrix4x4 CreateScale(Vector3 scales, Vector3 centerPoint)
         {
-            Matrix4x4 result = Identity;
+            Matrix4x4 result = default;
 
-            float tx = centerPoint.X * (1 - scales.X);
-            float ty = centerPoint.Y * (1 - scales.Y);
-            float tz = centerPoint.Z * (1 - scales.Z);
+            Vector3 t = centerPoint * (Vector3.One - scales);
 
             result.M11 = scales.X;
             result.M22 = scales.Y;
             result.M33 = scales.Z;
-            result.M41 = tx;
-            result.M42 = ty;
-            result.M43 = tz;
+            result.M44 = 1;
+
+            result.M41 = t.X;
+            result.M42 = t.Y;
+            result.M43 = t.Z;
+
             return result;
         }
 
@@ -1270,11 +1280,12 @@ public static Matrix4x4 CreateScale(Vector3 scales, Vector3 centerPoint)
         /// <returns>The scaling matrix.</returns>
         public static Matrix4x4 CreateScale(float scale)
         {
-            Matrix4x4 result = Identity;
+            Matrix4x4 result = default;
 
             result.M11 = scale;
             result.M22 = scale;
             result.M33 = scale;
+            result.M44 = 1;
 
             return result;
         }
@@ -1285,19 +1296,18 @@ public static Matrix4x4 CreateScale(float scale)
         /// <returns>The scaling matrix.</returns>
         public static Matrix4x4 CreateScale(float scale, Vector3 centerPoint)
         {
-            Matrix4x4 result = Identity;
+            Matrix4x4 result = default;
 
-            float tx = centerPoint.X * (1 - scale);
-            float ty = centerPoint.Y * (1 - scale);
-            float tz = centerPoint.Z * (1 - scale);
+            Vector3 t = centerPoint * (Vector3.One - new Vector3(scale));
 
             result.M11 = scale;
             result.M22 = scale;
             result.M33 = scale;
+            result.M44 = 1;
 
-            result.M41 = tx;
-            result.M42 = ty;
-            result.M43 = tz;
+            result.M41 = t.X;
+            result.M42 = t.Y;
+            result.M43 = t.Z;
 
             return result;
         }