Ensure side effects are preserved for Arm64 (#105963)

Author: tannergooding

src/coreclr/jit/gentree.cpp

@@ -31735,6 +31735,7 @@ GenTree* Compiler::gtFoldExprHWIntrinsic(GenTreeHWIntrinsic* tree)
                         // op3 has side effects, this would require us to append a new statement
                         // to ensure that it isn't lost, which isn't safe to do from the general
                         // purpose handler here. We'll recognize this and mark it in VN instead
+                        break;
                     }
 
                     // op3 has no side effects, so we can return op2 directly

src/tests/JIT/Regression/JitBlue/Runtime_105818/Runtime_105818.cs

@@ -0,0 +1,44 @@
+// 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;
+using System.Numerics;
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.Arm;
+using Xunit;
+
+// Generated by Fuzzlyn v2.2 on 2024-08-01 14:42:46
+// Run on Arm64 MacOS
+// Seed: 17520120436908093806-vectort,vector64,vector128,armadvsimd,armadvsimdarm64,armaes,armarmbase,armarmbasearm64,armcrc32,armcrc32arm64,armdp,armrdm,armrdmarm64,armsha1,armsha256
+// Reduced from 35.4 KiB to 0.6 KiB in 00:00:19
+// Debug: Throws 'System.NullReferenceException'
+// Release: Runs successfully
+
+public class Runtime_105818
+{
+    private static Vector64<long> s_1;
+
+    [Fact]
+    public static void TestEntryPoint()
+    {
+        if (AdvSimd.IsSupported)
+        {
+            Assert.Throws<NullReferenceException>(() => M1());
+        }
+    }
+
+    private static void M1()
+    {
+        var vr2 = Vector64.Create<uint>(4294967295U);
+        var vr3 = Vector64.Create<uint>(0);
+        AdvSimd.BitwiseSelect(vr2, vr3, Vector64.CreateScalar(M2()));
+        System.Console.WriteLine(s_1);
+    }
+
+    private static uint M2()
+    {
+        sbyte[] var0 = default(sbyte[]);
+        return (uint)var0[0];
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_105818/Runtime_105818.csproj

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