On Thu, 3 Sep 2026 20:01:19 GMT, Ioi Lam <[email protected]> wrote:
>> `FieldClosure` is used for iterating fields in an object. For Valhalla, it
>> has been enhanced to handle fields that are inside inlined fields. However,
>> the current implementation has two problems:
>>
>> [1] It type casts the address of an inlined field into an `oop` pointer.
>> This is unsafe as many operations, such as getting the header of an `oop`,
>> will not work with such an `oop` pointer:
>>
>> https://github.com/openjdk/jdk/blob/b1f975efa481bd5e20c1b7d58a87d0866df205e6/src/hotspot/share/runtime/fieldDescriptor.cpp#L216
>>
>> [2] The parameter `base_offset` is used in many functions. Its meaning is
>> unclear and inconsistent.
>>
>> https://github.com/openjdk/jdk/blob/b1f975efa481bd5e20c1b7d58a87d0866df205e6/src/hotspot/share/runtime/fieldDescriptor.cpp#L159
>>
>> https://github.com/openjdk/jdk/blob/b1f975efa481bd5e20c1b7d58a87d0866df205e6/src/hotspot/share/oops/instanceKlass.hpp#L99-L101
>>
>> This RFE refactors `FieldClosure` to avoid the above problems.
>> `FieldClosure` now carries information about inlined fields. This
>> information can be used by various field iteration code to simplify their
>> operations. See `FieldClosure::inline_klass()` and
>> `FieldClosure::inline_offset()`.
>>
>> As a result, users of `FieldClosure` and `FieldDescriptor()` no longer need
>> to perform obscure arithmetics with `InlineKlass::payload_offset()`.
>>
>> This RFE also moves a few common operations into utility functions to avoid
>> code duplication.
>>
>> Also:
>> - Fixed a bug in `FlatArrayKlass::oop_print_elements_on()` in the handling
>> of nullable elements.
>>
>> ---------
>> - [x] I confirm that I make this contribution in accordance with the
>> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai).
>
> Ioi Lam has updated the pull request incrementally with two additional
> commits since the last revision:
>
> - @fparain review comments
> - Changed inline_xxx to flat_xxx
src/hotspot/share/cds/aotMapLogger.cpp line 879:
> 877: for (int i = 0; i < _indent + 1; i++) _st->print(" ");
> 878: _st->print_cr(" - [null_marker] @%d %s",
> 879: field_offset_in_obj + vk->null_marker_offset(),
`vk->null_marker_offset()` returns of the offset of the null-marker as an
offset from the beginning of the object for a heap buffered value.
Shouldn't `null_marker_offset_in_payload()` be used instead?
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/32565#discussion_r3960943228
