On Mon, 9 Dec 2024 19:26:53 GMT, Coleen Phillimore <cole...@openjdk.org> wrote:
> The Class.getModifiers() method is implemented as a native method in > java.lang.Class to access a field that we've calculated when creating the > mirror. The field is final after that point. The VM doesn't need it anymore, > so there's no real need for the jdk code to call into the VM to get it. This > moves the field to Java and removes the intrinsic code. I promoted the > compute_modifiers() functions to return int since that's how java.lang.Class > uses the value. It should really be an unsigned short though. > > There's a couple of JMH benchmarks added with this change. One does show > that for array classes for non-bootstrap class loader, this results in one > extra load which in a long loop of just that, is observable. I don't think > this is real life code. The other benchmarks added show no regression. > > Tested with tier1-8. src/java.base/share/classes/java/lang/Class.java line 244: > 242: classLoader = loader; > 243: componentType = arrayComponentType; > 244: modifiers = 0; The comment above about assigning a parameter to the field to prevent the JIT from assuming an incorrect default also should apply to the new `modifiers` field. I think the constructor, which is never called, should also pass in a `dummyModifiers` value rather than using 0 directly ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/22652#discussion_r1880689835
