8370880: [lworld] Split ciObjArrayKlass into ciRefArrayKlass and ciFlatArrayKlass #1739

merykitty · 2025-11-15T10:54:41Z

Hi,

This PR splits ciObjArrayKlass into ciRefArrayKlass and ciFlatArrayKlass, aligns the hierarchy with the corresponding types of the VM.

Please kindly review, thanks a lot.

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Issue

JDK-8370880: [lworld] Split ciObjArrayKlass into ciRefArrayKlass and ciFlatArrayKlass (Enhancement - P2)

Reviewers

Tobias Hartmann (@TobiHartmann - Committer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/valhalla.git pull/1739/head:pull/1739
$ git checkout pull/1739

Update a local copy of the PR:
$ git checkout pull/1739
$ git pull https://git.openjdk.org/valhalla.git pull/1739/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1739

View PR using the GUI difftool:
$ git pr show -t 1739

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/valhalla/pull/1739.diff

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bridgekeeper · 2025-11-15T10:55:43Z

👋 Welcome back qamai! A progress list of the required criteria for merging this PR into lworld will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2025-11-15T10:56:57Z

@merykitty This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8370880: [lworld] Split ciObjArrayKlass into ciRefArrayKlass and ciFlatArrayKlass

Reviewed-by: thartmann

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been no new commits pushed to the lworld branch. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you prefer to avoid any potential automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the lworld branch, type /integrate in a new comment.

mlbridge · 2025-11-15T11:01:03Z

Webrevs

merykitty · 2025-11-15T11:02:36Z

There are still a lot of refactoring to be done regarding moving elements from ciArrayKlass to ciObjArrayKlass since now it is the new common ancestor of all arrays of objects.

TobiHartmann

Thank you for working on this, Quan-Anh! Testing looks good except for this:

compiler/valhalla/inlinetypes/TestArrayNullMarkers.java#AVF-nAVF
-XX:+IgnoreUnrecognizedVMOptions -XX:-TieredCompilation -XX:-DoEscapeAnalysis -XX:+AlwaysIncrementalInline

# A fatal error has been detected by the Java Runtime Environment:
#
#  Internal Error (/workspace/open/src/hotspot/share/ci/ciMetadata.hpp:105), pid=418142, tid=418159
#  assert(is_flat_array_klass()) failed: bad cast
#
# JRE version: Java(TM) SE Runtime Environment (26.0) (fastdebug build 26-jep401ea2-2025-11-17-0811237.tobias.hartmann.valhalla2)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 26-jep401ea2-2025-11-17-0811237.tobias.hartmann.valhalla2, mixed mode, compressed oops, compressed class ptrs, g1 gc, linux-amd64)
# Problematic frame:
# V  [libjvm.so+0x1ca876a]  TypeAryPtr::flat_layout_helper() const+0x7a

Current CompileTask:
C2:2887  380 % !b        compiler.valhalla.inlinetypes.TestArrayNullMarkers::main @ 698 (2967 bytes)

Stack: [0x00007f5639cfe000,0x00007f5639dfe000],  sp=0x00007f5639df8240,  free space=1000k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V  [libjvm.so+0x1ca876a]  TypeAryPtr::flat_layout_helper() const+0x7a  (ciMetadata.hpp:105)
V  [libjvm.so+0x102a8a9]  GraphKit::get_layout_helper(Node*, int&)+0x299  (graphKit.cpp:4100)
V  [libjvm.so+0x102cd43]  GraphKit::new_array(Node*, Node*, int, Node**, bool, Node*)+0x43  (graphKit.cpp:4345)
V  [libjvm.so+0x158b712]  LibraryCallKit::inline_newArray(bool, bool)+0x242  (library_call.cpp:4904)
V  [libjvm.so+0x15b2c6a]  LibraryIntrinsic::generate(JVMState*)+0x22a  (library_call.cpp:130)
V  [libjvm.so+0xdbc50f]  Parse::do_call()+0xebf  (doCall.cpp:771)
V  [libjvm.so+0x18fee88]  Parse::do_one_bytecode()+0x4c8  (parse2.cpp:3526)
V  [libjvm.so+0x18e6007]  Parse::do_one_block()+0x357  (parse1.cpp:1703)
V  [libjvm.so+0x18e7300]  Parse::do_all_blocks()+0x130  (parse1.cpp:760)
V  [libjvm.so+0x18eae81]  Parse::Parse(JVMState*, ciMethod*, float)+0xea1  (parse1.cpp:664)
V  [libjvm.so+0x9e1975]  ParseGenerator::generate(JVMState*)+0x135  (callGenerator.cpp:99)
V  [libjvm.so+0x9e6ba3]  CallGenerator::do_late_inline_helper()+0xa03  (callGenerator.cpp:751)
V  [libjvm.so+0xbdc968]  Compile::inline_incrementally_one()+0x1b8  (compile.cpp:2614)
V  [libjvm.so+0xbde0ab]  Compile::inline_incrementally(PhaseIterGVN&)+0x38b  (compile.cpp:2707)
V  [libjvm.so+0xbe0c9e]  Compile::Optimize()+0x47e  (compile.cpp:2843)
V  [libjvm.so+0xbe45c5]  Compile::Compile(ciEnv*, ciMethod*, int, Options, DirectiveSet*)+0x1da5  (compile.cpp:879)
V  [libjvm.so+0x9de490]  C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x4e0  (c2compiler.cpp:149)
V  [libjvm.so+0xbf3e20]  CompileBroker::invoke_compiler_on_method(CompileTask*)+0x780  (compileBroker.cpp:2345)
V  [libjvm.so+0xbf5680]  CompileBroker::compiler_thread_loop()+0x530  (compileBroker.cpp:1989)
V  [libjvm.so+0x118d15b]  JavaThread::thread_main_inner()+0x13b  (javaThread.cpp:772)
V  [libjvm.so+0x1c68ee6]  Thread::call_run()+0xb6  (thread.cpp:243)
V  [libjvm.so+0x1893bc8]  thread_native_entry(Thread*)+0x128  (os_linux.cpp:883)

merykitty · 2025-11-17T14:41:10Z

Thanks for your testing. Unfortunately, the issue cuts pretty deep. We have multiple potential inconsistencies when dealing with _klass such as when trying to obtain a flat TypeAryPtr from a non-flat TypeAryPtr. I think it can be addressed as follow-up issues. To fix the immediate crash, I choose to fix a particular issue, that is we can only compute the _klass if we have klass_is_exact.

This reverts commit be61436.

merykitty · 2025-11-17T16:34:48Z

Too bad it seems pretty hard to walk on the thin line right now. I think it is better to tighten the type system around arrays first.

TobiHartmann · 2025-11-17T19:30:38Z

Right, I think so too, the latest version hits more issues :(

openjdk · 2025-12-18T06:43:14Z

@merykitty this pull request can not be integrated into lworld due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout ciRefArray
git fetch https://git.openjdk.org/valhalla.git lworld
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge lworld"
git push

merykitty · 2025-12-19T03:14:51Z

I think this PR is ready for review again.

TobiHartmann

Looks good to me otherwise. Thanks!

TobiHartmann · 2026-01-05T13:13:05Z

src/hotspot/share/opto/type.cpp

        }
        _is_ptr_to_narrowoop = UseCompressedOops && ::is_reference_type(field_bt);
+      } else if (klass()->is_obj_array_klass()) {
+        _is_ptr_to_narrowoop = UseCompressedOops;


UseCompressedOops is always true here, right? It's checked in line 3685. Also above.

You are right, I have removed those check.

TobiHartmann

Thanks, looks good!

merykitty · 2026-01-06T14:10:02Z

Thanks a lot for your reviews!

/integrate

openjdk · 2026-01-06T14:11:52Z

Going to push as commit 9aff0ae.

openjdk · 2026-01-06T14:12:00Z

@merykitty Pushed as commit 9aff0ae.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

Refactor ciObjArrayKlass to align with the VM type

b401f2f

openjdk bot added the rfr Pull request is ready for review label Nov 15, 2025

TobiHartmann reviewed Nov 17, 2025

View reviewed changes

can only infer klass if exact

be61436

Revert "can only infer klass if exact"

5f01c76

This reverts commit be61436.

merykitty marked this pull request as draft November 17, 2025 16:34

openjdk bot removed the rfr Pull request is ready for review label Nov 17, 2025

openjdk bot added the merge-conflict Pull request has merge conflict with target branch label Dec 18, 2025

Merge branch 'lworld' into ciRefArray

368af08

openjdk bot removed the merge-conflict Pull request has merge conflict with target branch label Dec 18, 2025

merykitty added 2 commits December 18, 2025 23:26

remove redundant changes

b8a652f

wrong value is passed as flat

cddbcb5

merykitty marked this pull request as ready for review December 19, 2025 03:06

openjdk bot added the rfr Pull request is ready for review label Dec 19, 2025

TobiHartmann approved these changes Jan 5, 2026

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label Jan 5, 2026

merykitty added 2 commits January 6, 2026 18:52

Merge branch 'lworld' into ciRefArray

700a2f4

Remove unnecessary UseCompressedOops checks

8e286e8

TobiHartmann approved these changes Jan 6, 2026

View reviewed changes

openjdk bot added the integrated Pull request has been integrated label Jan 6, 2026

openjdk bot closed this Jan 6, 2026

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jan 6, 2026

8370880: [lworld] Split ciObjArrayKlass into ciRefArrayKlass and ciFlatArrayKlass #1739

8370880: [lworld] Split ciObjArrayKlass into ciRefArrayKlass and ciFlatArrayKlass #1739

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