The following test failed in the JDK20 CI:

compiler/loopopts/superword/ProdRed_Double.java

Here's a snippet from the log file:

#section:main
----------messages:(4/486)----------
command: main -XX:+IgnoreUnrecognizedVMOptions -XX:LoopUnrollLimit=250 -XX:CompileThresholdScaling=0.1 -XX:+SuperWordReductions -XX:LoopMaxUnroll=4 compiler.loopopts.superword.ProdRed_Double
reason: User specified action: run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:LoopUnrollLimit=250 -XX:CompileThresholdScaling=0.1 -XX:+SuperWordReductions -XX:LoopMaxUnroll=4 compiler.loopopts.superword.ProdRed_Double
Mode: othervm [/othervm specified]
elapsed time (seconds): 8.905
----------configuration:(0/0)----------
----------System.out:(21/1332)*----------
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=\\loopTransform.cpp:2173
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (c:\\sb\\prod\\1657124970\\workspace\\open\\src\\hotspot\\share\\opto\\loopTransform.cpp:2173), pid=34784, tid=11184
# Error: assert(opaq->outcnt() == 1 && opaq->in(1) == limit) failed
#
# JRE version: Java(TM) SE Runtime Environment (20.0+5) (fastdebug build 20-ea+5-231)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 20-ea+5-231, mixed mode, sharing, compressed oops, compressed class ptrs, g1 gc, windows-amd64)
# Core dump will be written. Default location: C:\\sb\\prod\\1657138250\\testoutput\\test-support\\jtreg_open_test_hotspot_jtreg_tier1_compiler_3\\scratch\\4\\hs_err_pid34784.mdmp
#
# An error report file with more information is saved as:
# C:\\sb\\prod\\1657138250\\testoutput\\test-support\\jtreg_open_test_hotspot_jtreg_tier1_compiler_3\\scratch\\4\\hs_err_pid34784.log
#
# Compiler replay data is saved as:
# C:\\sb\\prod\\1657138250\\testoutput\\test-support\\jtreg_open_test_hotspot_jtreg_tier1_compiler_3\\scratch\\4\\replay_pid34784.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(0/0)----------
----------rerun:(48/5550)*----------


Here's the crashing thread's stack:

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

Current thread (0x000001a2b57cecc0): JavaThread "C2 CompilerThread0" daemon [_thread_in_native, id=11184, stack(0x0000001396800000,0x0000001396900000)]


Current CompileTask:
C2: 1149 287 java.net.URI::<init> (42 bytes)

Stack: [0x0000001396800000,0x0000001396900000]
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [jvm.dll+0xc71ae1] os::platform_print_native_stack+0xf1 (os_windows_x86.cpp:235)
V [jvm.dll+0xecdf54] VMError::report+0x10e4 (vmError.cpp:836)
V [jvm.dll+0xecfa8e] VMError::report_and_die+0x7fe (vmError.cpp:1688)
V [jvm.dll+0xed0214] VMError::report_and_die+0x64 (vmError.cpp:1469)
V [jvm.dll+0x5a97f7] report_vm_error+0xb7 (debug.cpp:284)
V [jvm.dll+0xab8c50] PhaseIdealLoop::do_unroll+0x4c0 (loopTransform.cpp:2173)
V [jvm.dll+0xabfc6a] IdealLoopTree::iteration_split_impl+0x7ca (loopTransform.cpp:3812)
V [jvm.dll+0xabf350] IdealLoopTree::iteration_split+0x160 (loopTransform.cpp:3836)
V [jvm.dll+0xabf21f] IdealLoopTree::iteration_split+0x2f (loopTransform.cpp:3820)
V [jvm.dll+0xabf47c] IdealLoopTree::iteration_split+0x28c (loopTransform.cpp:3852)
V [jvm.dll+0xabf47c] IdealLoopTree::iteration_split+0x28c (loopTransform.cpp:3852)
V [jvm.dll+0xabf47c] IdealLoopTree::iteration_split+0x28c (loopTransform.cpp:3852)
V [jvm.dll+0xabf47c] IdealLoopTree::iteration_split+0x28c (loopTransform.cpp:3852)
V [jvm.dll+0xabf47c] IdealLoopTree::iteration_split+0x28c (loopTransform.cpp:3852)
V [jvm.dll+0xabf47c] IdealLoopTree::iteration_split+0x28c (loopTransform.cpp:3852)
V [jvm.dll+0xacd6e4] PhaseIdealLoop::build_and_optimize+0x1184 (loopnode.cpp:4531)
V [jvm.dll+0x539eca] Compile::Optimize+0x112a (compile.cpp:2408)
V [jvm.dll+0x536c32] Compile::Compile+0x14e2 (compile.cpp:824)
V [jvm.dll+0x459ff5] C2Compiler::compile_method+0x145 (c2compiler.cpp:115)
V [jvm.dll+0x551021] CompileBroker::invoke_compiler_on_method+0x791 (compileBroker.cpp:2314)
V [jvm.dll+0x54e6a9] CompileBroker::compiler_thread_loop+0x279 (compileBroker.cpp:1982)
V [jvm.dll+0x82004f] JavaThread::thread_main_inner+0x29f (javaThread.cpp:694)
V [jvm.dll+0xe45e49] Thread::call_run+0x269 (thread.cpp:229)
V [jvm.dll+0xc70389] thread_native_entry+0xb9 (os_windows.cpp:547)
C [ucrtbase.dll+0x2268a]
C [KERNEL32.DLL+0x17974]
C [ntdll.dll+0x5a0b1]