While investigating bug #4393019 I came across this:

No matching rule for:
--N: o597 If <== o591 o871 o797 <<o598 o599 30 >> P=0.000001, C=-1.000000

   --N: o871 Phi <== o856 o797 o795 o796 <<o620 o597 >> #bool
   IREGI 1 IREGI
   NOTEMP_IREGI 1 NOTEMP_IREGI
   V9LONGREGI 1 V9LONGREGI
   G1REGI 2 G1REGI
   O0REGI 2 O0REGI
   O1REGI 2 O1REGI
   O2REGI 2 O2REGI
   O3REGI 2 O3REGI
   O4REGI 2 O4REGI
   O5REGI 2 O5REGI
   L7REGI 2 L7REGI
   IREGP 101 moveIP
   SP_OR_IREGP 102 moveIP
   NOTEMP_IREGP 103 moveIP
   G1REGP 102 moveIP
   G3REGP 102 moveIP
   G3REGI 2 G3REGI
   G4REGP 102 moveIP
   G5REGP 102 moveIP
   I0REGP 102 moveIP
   O0REGP 102 moveIP
   O1REGP 102 moveIP
   O2REGP 102 moveIP
   O7REGP 102 moveIP
   L7REGP 102 moveIP
   O7REGI 2 O7REGI
   INLINE_CACHE_REGP 102 moveIP
   COMPILER_METHOD_OOP_REGP 102 moveIP
   INTERPRETER_METHOD_OOP_REGP 102 moveIP
   INDIRECT 201 moveIP
   STACKSLOTI 200 regI_to_stkI
   MEMORY 201 INDIRECT

   --N: o797 Bool <== _ o787 <<o871 o829 o597 o391 o368 o620 >> [ne]
   CMPOP 1 CMPOP
   CMPOPU 1 CMPOPU
   CMPOP_REG 1 CMPOP_REG
   CMPOPFL 1 CMPOPFL
   CMPOPFG 1 CMPOPFG

#
# HotSpot Virtual Machine Error, Internal Error
# Please report this error at
# http://java.sun.com/cgi-bin/bugreport.cgi
#
# Fatal: SoftMatchFailure is not allowed except in product
#
# Error ID: /export/azeem/c2-baseline/src/share/vm/opto/matcher.hpp, 303 [ Patched ]
#
# Problematic Thread: prio=5 tid=0xfe1a8 nid=0xb runnable
#
Dumping core....
doit2[8]: 25334 Abort(coredump)

To reproduce
cd /net/sqesvr/export/vsn/GammaBase/Bugs/{BugID}
doit2 <path to JDK1.4>

Starting the CTW at 1000 causes the bug to occur, but at 1100 it does not.