Added a test verifying that double negation is not removed for CSEs

src/tests/JIT/opt/CSE/CSEWithDoubleNegation.cs

@@ -0,0 +1,34 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace CSEWithDoubleNegation
+{
+    class DoNotMorphAwayCSEThatRepresentsDoubleNegation
+    {
+        private static int _static = 0;
+
+        static int Main(string[] args)
+        {
+            if (DoubleNeg() != 22)
+            {
+                Console.WriteLine("DoubleNeg() failed to return the expected value of 22");
+                return -1;
+            }
+
+            return 100;
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static int DoubleNeg()
+        {
+            var a = 21;
+            _static = 42;
+
+            return 43 - (0 - (a - _static));
+        }
+    }
+}
+

src/tests/JIT/opt/CSE/CSEWithDoubleNegation.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <CLRTestPriority>1</CLRTestPriority>
+  </PropertyGroup>
+  <PropertyGroup>
+    <DebugType>None</DebugType>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="CSEWithDoubleNegation.cs" />
+  </ItemGroup>
+</Project>