The following tests failed in the JDK20 CI:

jdk/incubator/vector/Long512VectorTests.java
jdk/incubator/vector/Int512VectorTests.java
jdk/incubator/vector/Float512VectorTests.java
jdk/incubator/vector/Double512VectorTests.java

Here's a snippet from the Long512VectorTests.jtr log file:

test Long512VectorTests.shuffleEqualsLong512VectorTestsSmokeTest(shuffle[i], shuffle[random]): success
test Long512VectorTests.shuffleEqualsLong512VectorTestsSmokeTest(shuffle[i], shuffle[random]): success
test Long512VectorTests.shuffleMiscellaneousLong512VectorTestsSmokeTest(shuffle[random]): success
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=\\assembler_x86.cpp:3195
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (c:\\sb\\prod\\1666171758\\workspace\\open\\src\\hotspot\\cpu\\x86\\assembler_x86.cpp:3195), pid=97300, tid=40888
# Error: assert(VM_Version::supports_avx512vlbw()) failed
#
# JRE version: Java(TM) SE Runtime Environment (20.0+20) (fastdebug build 20-ea+20-1456)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 20-ea+20-1456, mixed mode, sharing, compressed oops, compressed class ptrs, g1 gc, windows-amd64)
# Core dump will be written. Default location: C:\\sb\\prod\\1666180880\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_vector\\scratch\\4\\hs_err_pid97300.mdmp
#
# An error report file with more information is saved as:
# C:\\sb\\prod\\1666180880\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_vector\\scratch\\4\\hs_err_pid97300.log
#
# Compiler replay data is saved as:
# C:\\sb\\prod\\1666180880\\testoutput\\test-support\\jtreg_open_test_jdk_jdk_vector\\scratch\\4\\replay_pid97300.log
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#
----------System.err:(1/56)----------
WARNING: Using incubator modules: jdk.incubator.vector
----------rerun:(48/5516)*----------


Here's the crashing thread's stack:

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

Current thread (0x00000207b4796db0): JavaThread "C2 CompilerThread0" daemon [_thread_in_native, id=40888, stack(0x000000706e900000,0x000000706ea00000)]


Current CompileTask:
C2: 26001 1780 b jdk.incubator.vector.Long512Vector::addIndex (6 bytes)

Stack: [0x000000706e900000,0x000000706ea00000]
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [jvm.dll+0xc08f81] os::win32::platform_print_native_stack+0xf1 (os_windows_x86.cpp:236)
V [jvm.dll+0xe6cb8e] VMError::report+0x10be (vmError.cpp:841)
V [jvm.dll+0xe6e684] VMError::report_and_die+0x644 (vmError.cpp:1700)
V [jvm.dll+0xe6edc4] VMError::report_and_die+0x64 (vmError.cpp:1481)
V [jvm.dll+0x57c4b7] report_vm_error+0xb7 (debug.cpp:285)
V [jvm.dll+0x2a4a3f] Assembler::evmovdqub+0x5f (assembler_x86.cpp:3195)
V [jvm.dll+0xaf0dbc] MacroAssembler::evmovdqub+0x18c (macroAssembler_x86.cpp:2717)
V [jvm.dll+0x41bfa6] C2_MacroAssembler::load_iota_indices+0x2a6 (c2_MacroAssembler_x86.cpp:1713)
V [jvm.dll+0x75ade] loadIotaIndicesNode::emit+0xce (ad_x86.cpp:38225)
V [jvm.dll+0xc171a8] PhaseOutput::scratch_emit_size+0x268 (output.cpp:3352)
V [jvm.dll+0xc17765] PhaseOutput::shorten_branches+0x445 (output.cpp:646)
V [jvm.dll+0xc10d17] PhaseOutput::Output+0x877 (output.cpp:447)
V [jvm.dll+0x50ff49] Compile::Code_Gen+0x379 (compile.cpp:3002)
V [jvm.dll+0x50ec5a] Compile::Compile+0x15da (compile.cpp:865)
V [jvm.dll+0x4353c5] C2Compiler::compile_method+0x145 (c2compiler.cpp:116)
V [jvm.dll+0x5288c4] CompileBroker::invoke_compiler_on_method+0x884 (compileBroker.cpp:2243)
V [jvm.dll+0x5260bd] CompileBroker::compiler_thread_loop+0x23d (compileBroker.cpp:1917)
V [jvm.dll+0x7f26a2] JavaThread::thread_main_inner+0x282 (javaThread.cpp:700)
V [jvm.dll+0xde6f37] Thread::call_run+0x257 (thread.cpp:229)
V [jvm.dll+0xc07898] thread_native_entry+0xb8 (os_windows.cpp:547)
C [ucrtbase.dll+0x1fb80]
C [KERNEL32.DLL+0x84d4]
C [ntdll.dll+0x51791]

This failure mode looks like a regression so I'm starting this bug as a P2.