ADDITIONAL SYSTEM INFORMATION :
# JRE version: OpenJDK Runtime Environment (8.0_392) (build 1.8.0_392-internal-fastdebug-b00)
# Java VM: OpenJDK 64-Bit Server VM (25.392-b00-fastdebug compiled mode linux-amd64 compressed oops)
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#

A DESCRIPTION OF THE PROBLEM :
I ran a modified testcase using JDK8u321, I found the JVM crashed under the option -Xcomp

# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/data/jdk8u/hotspot/src/share/vm/opto/compile.cpp:3055), pid=63152, tid=0x00007f980f868700
# assert(proj != NULL || p->_con == TypeFunc::I_O) failed: io may be dropped at an infinite loop
#
# JRE version: OpenJDK Runtime Environment (8.0_392) (build 1.8.0_392-internal-fastdebug-b00)
# Java VM: OpenJDK 64-Bit Server VM (25.392-b00-fastdebug compiled mode linux-amd64 compressed oops)
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# If you would like to submit a bug report, please visit:
# http://bugreport.java.com/bugreport/crash.jsp

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
java -Xcomp StringConcatInfiniteLoop

ACTUAL -
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=/compile.cpp:3055
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/data/jdk8u/hotspot/src/share/vm/opto/compile.cpp:3055), pid=63152, tid=0x00007f980f868700
# assert(proj != NULL || p->_con == TypeFunc::I_O) failed: io may be dropped at an infinite loop
#
# JRE version: OpenJDK Runtime Environment (8.0_392) (build 1.8.0_392-internal-fastdebug-b00)
# Java VM: OpenJDK 64-Bit Server VM (25.392-b00-fastdebug compiled mode linux-amd64 compressed oops)
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /home/repository/bugs/StringConcatInfiniteLoop_09_21_11_42_02/hs_err_pid63152.log
#
# Compiler replay data is saved as:
# /home/repository/bugs/StringConcatInfiniteLoop_09_21_11_42_02/replay_pid63152.log
#
# If you would like to submit a bug report, please visit:
# http://bugreport.java.com/bugreport/crash.jsp
#
Current thread is 140291072231168
Dumping core ...

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FREQUENCY : always