Happened once in a personal job.

# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (c:\\sb\\prod\\1676563492\\workspace\\open\\src\\hotspot\\share\\opto\\cfgnode.cpp:439), pid=20508, tid=18308
# assert(status != RegionNode::LoopStatus::NeverIrreducibleEntry) failed: do not set this
#
# JRE version: Java(TM) SE Runtime Environment (21.0) (fastdebug build 21-internal-LTS-2023-02-16-1602470.daniel.jelinski.jdk)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 21-internal-LTS-2023-02-16-1602470.daniel.jelinski.jdk, mixed mode, sharing, tiered, compressed oops, compressed class ptrs, g1 gc, windows-amd64)

From hs_err*.log:

--------------- T H R E A D ---------------

Current thread (0x000001ebe8093700): JavaThread "C2 CompilerThread0" daemon [_thread_in_native, id=18308, stack(0x00000079d3100000,0x00000079d3200000)]


Current CompileTask:
C2: 17281 4480 % ! 4 DigestEchoServer$HttpsProxyTunnel$1::run @ 2 (164 bytes)

Stack: [0x00000079d3100000,0x00000079d3200000]
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [jvm.dll+0xbf8011] os::win32::platform_print_native_stack+0xf1 (os_windows_x86.cpp:236)
V [jvm.dll+0xe701b0] VMError::report+0x10c0 (vmError.cpp:813)
V [jvm.dll+0xe71dee] VMError::report_and_die+0x6ce (vmError.cpp:1593)
V [jvm.dll+0xe72534] VMError::report_and_die+0x64 (vmError.cpp:1352)
V [jvm.dll+0x577307] report_vm_error+0xb7 (debug.cpp:286)
V [jvm.dll+0x457efb] RegionNode::set_loop_status+0x3b (cfgnode.cpp:439)
V [jvm.dll+0xaa56c6] IdealLoopTree::split_fall_in+0x156 (loopnode.cpp:3148)
V [jvm.dll+0xa8cec6] IdealLoopTree::beautify_loops+0xf6 (loopnode.cpp:3441)
V [jvm.dll+0xa8d6b2] IdealLoopTree::beautify_loops+0x8e2 (loopnode.cpp:3505)
V [jvm.dll+0xa8dbbb] PhaseIdealLoop::build_and_optimize+0x4db (loopnode.cpp:4335)
V [jvm.dll+0x519018] PhaseIdealLoop::optimize+0xd8 (loopnode.hpp:1192)
V [jvm.dll+0x50c0a2] Compile::Optimize+0x972 (compile.cpp:2292)
V [jvm.dll+0x50969b] Compile::Compile+0x16bb (compile.cpp:834)
V [jvm.dll+0x427665] C2Compiler::compile_method+0x145 (c2compiler.cpp:116)
V [jvm.dll+0x523b99] CompileBroker::invoke_compiler_on_method+0x849 (compileBroker.cpp:2240)
V [jvm.dll+0x52130d] CompileBroker::compiler_thread_loop+0x23d (compileBroker.cpp:1917)
V [jvm.dll+0x7ef322] JavaThread::thread_main_inner+0x282 (javaThread.cpp:711)
V [jvm.dll+0xde5833] Thread::call_run+0x253 (thread.cpp:229)
V [jvm.dll+0xbf6948] os::win32::thread_native_entry+0xb8 (os_windows.cpp:550)
C [ucrtbase.dll+0x21bb2]
C [KERNEL32.DLL+0x174b4]
C [ntdll.dll+0x526a1]