[lworld] RFR: 8370880: [lworld] Split ciObjArrayKlass into ciRefArrayKlass and ciFlatArrayKlass

[Tobias Hartmann]

On Sat, 15 Nov 2025 10:54:41 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

> Hi,
> 
> This PR splits `ciObjArrayKlass` into `ciRefArrayKlass` and `ciFlatArrayKlass`, aligns the hierarchy with the corresponding types of the VM.
> 
> I also had to fix `GraphKit::cast_to_flat_array`, currently it incorrectly assumes that the cast is to an exact type, splitting into `cast_to_flat_array` and `cast_to_flat_array_exact` seems to make it clearer.
> 
> Please kindly review, thanks a lot.

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)

-------------

PR Review: https://git.openjdk.org/valhalla/pull/1739#pullrequestreview-3471990086