The attached Java Fuzzer test starts to fail after JDK-8286182 which was just a backout of an RFE (JDK-8284742) which was pushed in b20. However, the Java Fuzzer test does not reproduce with b19. This suggests that a changeset since b20 has either introduced a new bug or has revealed an existing issue. It could also be a duplicate of JDK-8283386 which fails with the same assertion but is very hard to reproduce.

To reproduce:

$ java -Xcomp -XX:CompileOnly=Test Test.java
$ java -Xcomp -XX:CompileOnly=Reduced Reduced.java

#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/opt/mach5/mesos/work_dir/slaves/779adf21-f3e5-4e6a-a889-8cc0f9bc6fbb-S66862/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/e7a5f059-99c2-4c80-b089-a6e1a468a184/runs/f86e41f7-d216-4fe3-8825-70c90f059250/workspace/open/src/hotspot/share/opto/loopnode.cpp:5856), pid=9638, tid=9651
# assert(false) failed: Bad graph detected in build_loop_late
#
# JRE version: Java(TM) SE Runtime Environment (19.0+25) (fastdebug build 19-ea+25-1892)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 19-ea+25-1892, compiled mode, sharing, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0x1498537] PhaseIdealLoop::build_loop_late_post_work(Node*, bool)+0x187
..........
Command Line: -Xcomp -XX:CompileOnly=Test -XX:CompileCommand=quiet --add-modules=ALL-DEFAULT jdk.compiler/com.sun.tools.javac.launcher.Main Test.java
..........
Current CompileTask:
C2: 2281 117 % !b 4 Test::mainTest @ 226 (775 bytes)

Stack: [0x00007fc5b0121000,0x00007fc5b0222000], sp=0x00007fc5b021bf80, free space=1003k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x1498537] PhaseIdealLoop::build_loop_late_post_work(Node*, bool)+0x187
V [libjvm.so+0x1498cf2] PhaseIdealLoop::build_loop_late(VectorSet&, Node_List&, Node_Stack&)+0xb2
V [libjvm.so+0x1499787] PhaseIdealLoop::build_and_optimize()+0x617
V [libjvm.so+0xae252a] PhaseIdealLoop::optimize(PhaseIterGVN&, LoopOptsMode)+0x27a
V [libjvm.so+0xaded57] Compile::Optimize()+0x1027
V [libjvm.so+0xae0ee0] Compile::Compile(ciEnv*, ciMethod*, int, Options, DirectiveSet*)+0x1520
V [libjvm.so+0x8f826a] C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x62a
V [libjvm.so+0xaef9a8] CompileBroker::invoke_compiler_on_method(CompileTask*)+0xbb8
V [libjvm.so+0xaf0998] CompileBroker::compiler_thread_loop()+0x6f8
V [libjvm.so+0x1a6c1ac] JavaThread::thread_main_inner()+0x23c
V [libjvm.so+0x1a77690] Thread::call_run()+0x100
V [libjvm.so+0x1729454] thread_native_entry(Thread*)+0x104