Implement sizeof() in the interpreter (#115745)

Implements CEE_SIZEOF in the interpreter

Author: kg

src/coreclr/interpreter/compiler.cpp

@@ -3500,6 +3500,16 @@ int InterpCompiler::GenerateCode(CORINFO_METHOD_INFO* methodInfo)
                         m_pLastNewIns->SetDVar(m_pStackPointer[-1].var);
                         m_ip++;
                         break;
+                    case CEE_SIZEOF:
+                    {
+                        CORINFO_CLASS_HANDLE clsHnd = ResolveClassToken(getU4LittleEndian(m_ip + 1));
+                        AddIns(INTOP_LDC_I4);
+                        m_pLastNewIns->data[0] = m_compHnd->getClassSize(clsHnd);
+                        PushStackType(StackTypeI4, NULL);
+                        m_pLastNewIns->SetDVar(m_pStackPointer[-1].var);
+                        m_ip += 5;
+                        break;
+                    }
                     default:
                         assert(0);
                         break;

src/tests/JIT/interpreter/Interpreter.cs

@@ -416,6 +416,9 @@ public static void RunInterpreterTests()
         if (!TestArray())
             Environment.FailFast(null);
 
+        if (!TestSizeof())
+            Environment.FailFast(null);
+
         System.GC.Collect();
     }
 
@@ -945,4 +948,15 @@ public static bool ArrayDouble(int length, double value)
 
         return true;
     }
+
+    public static unsafe bool TestSizeof()
+    {
+        if (sizeof(int) != 4)
+            return false;
+        if (sizeof(double) != 8)
+            return false;
+        if (sizeof(MyStruct) != 4)
+            return false;
+        return true;
+    }
 }