Add a test that we don't fold non-BasicObject

Author: tekknolagi

zjit/src/hir/opt_tests.rs

@@ -9905,4 +9905,34 @@ mod hir_opt_tests {
           Return v52
         ");
     }
+
+    #[test]
+    fn test_dont_fold_load_field_with_primitive_return_type() {
+        eval(r#"
+            S = "abc".freeze
+            def test = S.bytesize
+            test
+        "#);
+        assert_snapshot!(hir_string("test"), @r"
+        fn test@<compiled>:3:
+        bb0():
+          EntryPoint interpreter
+          v1:BasicObject = LoadSelf
+          Jump bb2(v1)
+        bb1(v4:BasicObject):
+          EntryPoint JIT(0)
+          Jump bb2(v4)
+        bb2(v6:BasicObject):
+          PatchPoint SingleRactorMode
+          PatchPoint StableConstantNames(0x1000, S)
+          v20:StringExact[VALUE(0x1008)] = Const Value(VALUE(0x1008))
+          PatchPoint MethodRedefined(String@0x1010, bytesize@0x1018, cme:0x1020)
+          PatchPoint NoSingletonClass(String@0x1010)
+          v24:CInt64 = LoadField v20, :len@0x1048
+          v25:Fixnum = BoxFixnum v24
+          IncrCounter inline_cfunc_optimized_send_count
+          CheckInterrupts
+          Return v25
+        ");
+    }
 }