Revert "Reverts b44fdfa91f05ec5c202a6105fb33caf2144166e7 (see #6819)"

This reverts commit 2b9db5838965388b2e7209f80b27aba7c83a7d27.

src/optimization/dce.ml

@@ -145,7 +145,7 @@ and mark_field dce c cf stat =
 			| Some (c,_) -> mark_field dce c cf stat
 		end else
 			add cf;
-		if not stat then
+		if not stat && is_physical_var_field cf then
 			match c.cl_constructor with
 				| None -> ()
 				| Some ctor -> mark_field dce c ctor false