hotspot JIT producing incorrect code -how should I report a bug?

Keith McNeill mcneill at
Tue Jul 8 17:56:29 PDT 2008

Vladimir Kozlov wrote:
> Keith,
> First questions would be what HS version (-version or -Xinternalversion)
> you are using and on what hardware/OS.
java -Xinternalversion
Java HotSpot(TM) Server VM (10.0-b22) for linux-x86 JRE (1.6.0_06-b02), 
built on Mar 25 2008 00:26:44 by "java_re" with gcc 3.2.1-7a (J2SE release)

Note that the problem has occurred on every 1.6 jdk I've tried up to the 
latest 1.6.0_10 beta

The problem does not occur on JDK 1.5
> Then you can create file .hotspot_compiler in the directory where
> VM is running and put the next instruction into it:
> exclude class/subclass method
> where class/subclass is full class name provided by +PrintCompliation,
> for examle, java/lang/String.
> It will exclude JIT compilation of the method so you can verify that
> it causes the problem.
Tried that.  The problem does not happen when the method is excluded 
from JITing using the exclude keyword
> The next question is do you have access to a debug version of Hotspot VM?
No I don't.  But I would be happy to try it.

I'm using x86 linux (ubuntu 8.04) 32bit
> It could print generated assembler for the method.
> We can give it to you so you can try it but we need to know
> hardware (x86/sparc), os (linux, win, solaris), 32 or 64-bits VM
> (-version shows it).
> Thanks,
> Vladimir
> Keith McNeill wrote:
>> Hotspot is producing incorrect code deep in the bowels of our 
>> system.  A simple example doesn't produce the problem.
>> The code in question works as expected until the method is JITted.  
>> Using -XX:+PrintCompliation I can tell that once the method is 
>> compiled the method in question starts behaving incorrectly. I'd 
>> liked the bug to get fixed but I don't have a clue how to give you 
>> guys a reasonable bug report that would have enough information to 
>> enable the bug to be fixed.  I tried producing a simple example of 
>> the problem and that didn't produce the problem (I wasn't too 
>> surprised about that).
>> I could imagine that it would be useful to send you the .class file 
>> in question and the JITted code in question.  Is there anyway to get 
>> hotspot to dump the JITted code?  Or get hotspot to dump some state 
>> that would make it useful?  Is there some other way to get the 
>> information to  the correct people?
>> Thanks,
>> Keith

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