when running the java/security/MessageDigest/TestDigestIOStream.java test on Linux aarch64 with the fastdebug JVM we saw at least twice this assertion/crash :


#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/linuxaarch64/jdk/src/hotspot/share/opto/phaseX.cpp:1763), pid=359638, tid=359665
# assert(t->meet(t0) == t->remove_speculative()) failed: Not monotonic
#
# JRE version: OpenJDK Runtime Environment (21.0) (fastdebug build 21-internal-adhoc..jdk)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 21-internal-adhoc..jdk, mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-aarch64)
# Problematic frame:
# V [libjvm.so+0x140bab0] PhaseCCP::analyze()+0x320
#

--------------- S U M M A R Y ------------
.....
Host: xyz , AArch64, 16 cores, 61G, Ubuntu 22.04.1 LTS
Time: Tue Jan 10 23:46:43 2023 CET elapsed time: 1022.346197 seconds (0d 0h 17m 2s)

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

Current thread (0x0000ffff7c4cd470): JavaThread "C2 CompilerThread0" daemon [_thread_in_native, id=359665, stack(0x0000ffff3b800000,0x0000ffff3ba00000)]


Current CompileTask:
C2:1022346 11353 ! 4 TestDigestIOStream::testDigestOnOff (838 bytes)

Stack: [0x0000ffff3b800000,0x0000ffff3ba00000], sp=0x0000ffff3b9faa90, free space=2026k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x140bab0] PhaseCCP::analyze()+0x320 (phaseX.cpp:1763)
V [libjvm.so+0x936dec] Compile::Optimize()+0x48c (compile.cpp:2360)
V [libjvm.so+0x938d7c] Compile::Compile(ciEnv*, ciMethod*, int, Options, DirectiveSet*)+0x1464 (compile.cpp:830)
V [libjvm.so+0x787df4] C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x33c (c2compiler.cpp:113)
V [libjvm.so+0x9444bc] CompileBroker::invoke_compiler_on_method(CompileTask*)+0x87c (compileBroker.cpp:2237)
V [libjvm.so+0x944d38] CompileBroker::compiler_thread_loop()+0x358 (compileBroker.cpp:1916)
V [libjvm.so+0xde7ffc] JavaThread::thread_main_inner()+0x204 (javaThread.cpp:710)
V [libjvm.so+0x1741a90] Thread::call_run()+0xf8 (thread.cpp:224)
V [libjvm.so+0x138107c] thread_native_entry(Thread*)+0x104 (os_linux.cpp:739)
C [libc.so.6+0x7d5c8]
Registers:
R0=0x0000ffff83d0a500
R1=0x00000000000006e3
R2=0x0000ffff83d0b4f8
R3=0x0000ffff83d0b4e8
R4=0x0000000000000058
R5=0x0000ffff8455c000
R6=0x0000ffff24f54760
R7=0x0000000000000058
R8=0x0000ffff3b9fa8e8
R9=0x0000000000000000
R10=0x0000000005a116aa
R11=0x0000ffff7c4acff0
R12=0x0000000000000001
R13=0x13ae49e55b5d3045
R14=0x0000000000000000
R15=0x0000ffff240048e8
R16=0x0000ffff841cf660
R17=0x0000ffff84368fc0
R18=0x0000000000000005
R19=0x0000ffff3b9fb9c8
R20=0x0000ffff7c4e6e08
R21=0x0000ffff3b9fab00
R22=0x0000ffff3b9fab78
R23=0x0000ffff84188000
R24=0x0000ffff84188000
R25=0x0000ffff3b9fc570
R26=0x0000ffff7c4e6e28
R27=0x0000ffff7c4e6e28
R28=0x0000ffff28d4bde8
R29=0x0000ffff3b9faa90
R30=0x0000ffff8366ba88

CPU: total 16 (initial active 16) 0x41:0x3:0xd0c:1, fp, asimd, evtstrm, aes, pmull, sha1, sha256, crc32, lse, dcpop
/proc/cpuinfo:
processor : 0
BogoMIPS : 50.00
Features : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm lrcpc dcpop asimddp ssbs
CPU implementer : 0x41
CPU architecture: 8
CPU variant : 0x3
CPU part : 0xd0c
CPU revision : 1
 ......