JIT: Don't fold NEG(NEG(X)) to X when NEG(x) is a CSE candidate (#57478)

src/coreclr/jit/morph.cpp

@@ -13114,13 +13114,17 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac)
         case GT_NEG:
             // Remove double negation/not.
             // Note: this is not a safe tranformation if "tree" is a CSE candidate.
-            // Consider for example the following expression: NEG(NEG(OP)), where the top-level
+            // Consider for example the following expression: NEG(NEG(OP)), where any
             // NEG is a CSE candidate. Were we to morph this to just OP, CSE would fail to find
             // the original NEG in the statement.
-            if (op1->OperIs(oper) && opts.OptimizationEnabled() && !gtIsActiveCSE_Candidate(tree))
+            if (op1->OperIs(oper) && opts.OptimizationEnabled() && !gtIsActiveCSE_Candidate(tree) &&
+                !gtIsActiveCSE_Candidate(op1))
             {
-                GenTree* child = op1->AsOp()->gtGetOp1();
-                return child;
+                JITDUMP("Remove double negation/not\n")
+                GenTree* op1op1 = op1->gtGetOp1();
+                DEBUG_DESTROY_NODE(tree);
+                DEBUG_DESTROY_NODE(op1);
+                return op1op1;
             }
 
             // Distribute negation over simple multiplication/division expressions

src/tests/JIT/opt/perf/doublenegate/GitHub_57470.cs

@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+//
+// This file is auto-generated.
+// Seed: -1
+//
+using System;
+using System.Runtime.CompilerServices;
+public class TestClass8505
+{
+    static int s_int32_6 = -5;
+    static sbyte s_sbyte_8 = 2;
+    static int s_loopInvariant = 3;
+    public sbyte LeafMethod8()
+    {
+        unchecked
+        {
+            return s_sbyte_8 <<= s_int32_6 >>= s_int32_6 ^ (-2 - (s_int32_6 &= -5)) / (-1 * s_int32_6 * (2 ^ -2)) + 77;
+        }
+    }
+    public void Method0()
+    {
+        unchecked
+        {
+            try
+            {
+            }
+            finally
+            {
+                {
+                    int __loopvar1 = s_loopInvariant, __loopSecondaryVar1_0 = 15 - 4;
+                    do
+                    {
+                    }
+                    while (15 % 4 > LeafMethod8() / 15 + 4);
+                }
+                {
+                }
+            }
+            return;
+        }
+    }
+    public static int Main(string[] args)
+    {
+        TestClass8505 objTestClass8505 = new TestClass8505();
+        objTestClass8505.Method0();
+        return 100;
+    }
+}

src/tests/JIT/opt/perf/doublenegate/GitHub_57470.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <DebugType>None</DebugType>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="GitHub_57470.cs" />
+  </ItemGroup>
+</Project>