Happened once with test/langtools/tools/javac/MethodParameters/LegacyOutputTest/LegacyOutputTest.java and several times with an internal test suite.

# Internal Error (/workspace/open/src/hotspot/share/opto/loopTransform.cpp:2228), pid=781540, tid=787403
# Error: assert(opaq->outcnt() == 1 && opaq->in(1) == limit) failed
#
# JRE version: Java(TM) SE Runtime Environment (20.0) (fastdebug build 20-internal-2022-12-07-2029099.coleen.phillimore.jdk-ks)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 20-internal-2022-12-07-2029099.coleen.phillimore.jdk-ks, mixed mode, sharing, tiered, compressed oops, compressed class ptrs, g1 gc, linux-aarch64)
# Problematic frame:
# V [libjvm.so+0x12a6000] PhaseIdealLoop::do_unroll(IdealLoopTree*, Node_List&, bool)+0x230

Stack: [0x0000fffd3e200000,0x0000fffd3e400000], sp=0x0000fffd3e3f99d0, free space=2022k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x12a6000] PhaseIdealLoop::do_unroll(IdealLoopTree*, Node_List&, bool)+0x230 (loopTransform.cpp:2228)
V [libjvm.so+0x12b0100] IdealLoopTree::iteration_split_impl(PhaseIdealLoop*, Node_List&)+0x530 (loopTransform.cpp:3870)
V [libjvm.so+0x12b02e8] IdealLoopTree::iteration_split(PhaseIdealLoop*, Node_List&)+0x108 (loopTransform.cpp:3906)
V [libjvm.so+0x12b022c] IdealLoopTree::iteration_split(PhaseIdealLoop*, Node_List&)+0x4c (loopTransform.cpp:3890)
V [libjvm.so+0x12dd958] PhaseIdealLoop::build_and_optimize()+0xc64 (loopnode.cpp:4543)
V [libjvm.so+0x9a6e00] PhaseIdealLoop::optimize(PhaseIterGVN&, LoopOptsMode)+0x1e0 (loopnode.hpp:1082)
V [libjvm.so+0x9a29a8] Compile::Optimize()+0xde8 (compile.cpp:2146)
V [libjvm.so+0x9a527c] Compile::Compile(ciEnv*, ciMethod*, int, Options, DirectiveSet*)+0x11cc (compile.cpp:830)
V [libjvm.so+0x7c4578] C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x1b4 (c2compiler.cpp:113)
V [libjvm.so+0x9b1ac4] CompileBroker::invoke_compiler_on_method(CompileTask*)+0xa10 (compileBroker.cpp:2237)
V [libjvm.so+0x9b2528] CompileBroker::compiler_thread_loop()+0x5b8 (compileBroker.cpp:1916)
V [libjvm.so+0xed2350] JavaThread::thread_main_inner()+0x21c (javaThread.cpp:709)
V [libjvm.so+0x17d6548] Thread::call_run()+0xf8 (thread.cpp:224)
V [libjvm.so+0x14eed44] thread_native_entry(Thread*)+0x100 (os_linux.cpp:739)
C [libpthread.so.0+0x7908] start_thread+0x188