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

[Vladimir Kozlov]

Keith,

First questions would be what HS version (-version or -Xinternalversion)
you are using and on what hardware/OS.

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.

The next question is do you have access to a debug version of Hotspot VM?
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