When running the dacapo eclipse benchmark with G1 and on Solaris x64 I get the following failure (every time):

# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc: SuppressErrorAt=/matcher.cpp:1454
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/java/east/u2/ap31282/hotspot-gc-g1-opt-new/src/share/vm/opto/matcher.cpp:1454), pid=5086, tid=17
# Error: assert(C->node_arena()->contains(s->_leaf) || !has_new_node(s->_leaf),"duplicating node that's already been matched")
#
# JRE version: 6.0_04-b12
# Java VM: OpenJDK 64-Bit Server VM (14.0-b09-internal-fastdebug mixed mode solaris-amd64 )
# An error report file with more information is saved as:
# /java/east/u2/ap31282/gc_test_suite_amd64/dacapo/hs_err_pid5086.log
#
# If you would like to submit a bug report, please visit:
# http://java.sun.com/webapps/bugreport/crash.jsp
#

This does not occur on Solaris sparc, sparcv9, or x86, nor it seems to happen without G1 enabled. Here's a command line that will cause it (you of course have to have the dacapo test suite):

java -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -d64 -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -jar dacapo-2006-10.jar -s default eclipse