[mono][jit] Fix the bblock check in the box+callvirt optimization.

Fixes #95347.

Author: vargaz

src/mono/mono/mini/method-to-ir.c

@@ -9792,12 +9792,11 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
 			//   callvirt instance ISomeIface::Method()
 			// TO
 			//   call SomeStruct::Method()
-			guchar* callvirt_ip;
 			guint32 callvirt_proc_token;
 			if (!((cfg->compile_aot || cfg->compile_llvm) && !mono_class_is_def(klass)) && // we cannot devirtualize in AOT when using generics
 				next_ip < end &&
-				(callvirt_ip = il_read_callvirt (next_ip, end, &callvirt_proc_token)) && 
-				ip_in_bb (cfg, cfg->cbb, callvirt_ip) ) {
+				il_read_callvirt (next_ip, end, &callvirt_proc_token) &&
+				ip_in_bb (cfg, cfg->cbb, next_ip) ) {
 				MonoMethod* iface_method;
 				MonoMethodSignature* iface_method_sig;
 

src/tests/JIT/Regression/JitBlue/Runtime_95347/Runtime_95347.cs

@@ -0,0 +1,16 @@
+// 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 Xunit;
+
+public static class Runtime_95347
+{
+    [Fact]
+    public static int Test()
+    {
+        object? n = "abcd";
+        var s = (n ?? false).ToString();
+        return (s == "abcd") ? 100 : -1;
+    }
+}

src/tests/JIT/Regression/JitBlue/Runtime_95347/Runtime_95347.csproj

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