On Tue, 4 Feb 2025 14:43:51 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.
>
> Coleen Phillimore has updated the pull request incrementally with one
> additional commit since the last revision:
>
> Fix copyright and param name
src/hotspot/share/opto/memnode.cpp line 2458:
> 2456: return TypePtr::NULL_PTR;
> 2457: }
> 2458: // ???
I suspect that we still need this code to support intrinsics like
LibraryCallKit::inline_native_classID() and maybe other users of this field,
but the comment below no longer makes sense.
src/hotspot/share/opto/memnode.cpp line 2459:
> 2457: }
> 2458: // ???
> 2459: // (Folds up the 1st indirection in
> aClassConstant.getModifiers().)
Suggestion:
// Fold up the load of the hidden field
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/22652#discussion_r1943695585
PR Review Comment: https://git.openjdk.org/jdk/pull/22652#discussion_r1943696867
