JIT: Avoid removing CSE candidates in fgMorphExpandCast (dotnet#106691)

Fix dotnet#106609

src/coreclr/jit/morph.cpp

@@ -451,7 +451,8 @@ GenTree* Compiler::fgMorphExpandCast(GenTreeCast* tree)
     // Because there is no IL instruction conv.r4.un, uint/ulong -> float
     // casts are always imported as CAST(float <- CAST(double <- uint/ulong)).
     // We can eliminate the redundant intermediate cast as an optimization.
-    else if ((dstType == TYP_FLOAT) && (srcType == TYP_DOUBLE) && oper->OperIs(GT_CAST)
+    else if ((dstType == TYP_FLOAT) && (srcType == TYP_DOUBLE) && oper->OperIs(GT_CAST) &&
+             !gtIsActiveCSE_Candidate(tree)
 #ifdef TARGET_ARM
              && !varTypeIsLong(oper->AsCast()->CastOp())
 #endif

src/tests/JIT/Regression/JitBlue/Runtime_106609/Runtime_106609.cs

@@ -0,0 +1,45 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Generated by Fuzzlyn v2.2 on 2024-08-17 17:16:59
+// Run on Arm64 Windows
+// Seed: 18124298882625099135-vectort,vector64,vector128,armadvsimd,armadvsimdarm64,armaes,armarmbase,armarmbasearm64,armcrc32,armcrc32arm64,armdp,armsha1,armsha256
+// Reduced from 129.5 KiB to 0.4 KiB in 00:04:55
+// Hits JIT assert in Release:
+// Assertion failed 'link' in 'Program:Main(Fuzzlyn.ExecutionServer.IRuntime)' during 'Optimize Valnum CSEs' (IL size 39; hash 0xade6b36b; FullOpts)
+// 
+//     File: D:\a\_work\1\s\src\coreclr\jit\optcse.cpp Line: 5295
+// 
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.Arm;
+using Xunit;
+
+public class Runtime_106609
+{
+    [Fact]
+    public static void TestEntrypoint()
+    {
+        if (AdvSimd.IsSupported)
+        {
+            try
+            {
+                Test();
+            }
+            catch
+            {
+            }
+        }
+    }
+
+    public static float[] s_2;
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static void Test()
+    {
+        for (int vr8 = 0; vr8 < 2; vr8++)
+        {
+            var vr9 = Vector64.Create<uint>(0);
+            s_2[0] = (float)(-(-(double)AdvSimd.Extract(vr9, 0)));
+        }
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_106609/Runtime_106609.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <Optimize>True</Optimize>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="$(MSBuildProjectName).cs" />
+  </ItemGroup>
+</Project>