> `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 with a new target base due to a merge or a rebase. The pull request now contains 14 commits: - Merge branch 'master' into clean-up-flat-field-iteration - @stefank comments - @stefank and @matias9927 comments - fixed whitespaces - Restored ValuePayloadContext::klass() and added test case with abstract value class - clean up: ValuePayloadContext::_klass is used only in asserts - Alternative - @fparain comment: fixed null marker printing, added tests - clean up names with new naming convention (see https://github.com/openjdk/jdk/pull/32673) - Merge branch 'master' into clean-up-flat-field-iteration - ... and 4 more: https://git.openjdk.org/jdk/compare/4ab51270...0b85c347 ------------- Changes: https://git.openjdk.org/jdk/pull/32565/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=32565&range=09 Stats: 849 lines in 19 files changed: 645 ins; 93 del; 111 mod Patch: https://git.openjdk.org/jdk/pull/32565.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/32565/head:pull/32565 PR: https://git.openjdk.org/jdk/pull/32565
