Intermittent JRuby json issue related to tiered or G1

[Aleksey Shipilev]

On 2/16/21 8:10 PM, Aleksey Shipilev wrote:
> As usual, running with fastdebug builds is the first step here: maybe VM would assert meaningfully,
> and then you can search JIRA for the assert message. My own fastdebug builds are here:
> https://builds.shipilev.net/

Look:

$ export JAVA_HOME=./jdk15-fastdebug/; export PATH=$JAVA_HOME/bin:$PATH
$ while true; do ~/Install/jruby-9.2.14.0/bin/jruby -J-Xmx512m ./test.rb; done
Warming up --------------------------------------
             JSON gem# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc:  SuppressErrorAt=/ifnode.cpp:952
#
# A fatal error has been detected by the Java Runtime Environment:
#
#  Internal Error 
(/home/buildbot/worker/build-jdk15u-linux/build/src/hotspot/share/opto/ifnode.cpp:952), pid=3795216, 
tid=3795432
#  assert(this_bool->_test.is_less() && !fail->_con) failed: incorrect test
#
# JRE version: OpenJDK Runtime Environment (15.0.2) (fastdebug build 
15.0.2-testing+0-builds.shipilev.net-openjdk-jdk15-b50-20210206)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 
15.0.2-testing+0-builds.shipilev.net-openjdk-jdk15-b50-20210206, mixed mode, sharing, tiered, 
compressed oops, g1 gc, linux-amd64)
# Problematic frame:
# V  [libjvm.so+0xbf59ce]  IfNode::fold_compares_helper(ProjNode*, ProjNode*, ProjNode*, 
PhaseIterGVN*)+0x66e
#
# Core dump will be written. Default location: Core dumps may be processed with 
"/usr/share/apport/apport %p %s %c %d %P %E" (or dumping to 
/home/shade/temp/jruby/jruby-issue-6554/core.3795216)
#
# An error report file with more information is saved as:
# /home/shade/temp/jruby/jruby-issue-6554/hs_err_pid3795216.log
#
# Compiler replay data is saved as:
# /home/shade/temp/jruby/jruby-issue-6554/replay_pid3795216.log
#
# If you would like to submit a bug report, please visit:
#   https://bugreport.java.com/bugreport/crash.jsp

------

This reliably reproduces with latest JDK 15 binaries from here:
   https://builds.shipilev.net/openjdk-jdk15/

There is a single hit in JIRA, for the bug that was fixed in JDK 9.

But! Neither JDK 16 nor JDK 17 fastdebug assert, which gives us an opportunity to reverse-bisect 
which change had fixed it.

-- 
Thanks,
-Aleksey